Dissertations / Theses on the topic 'Seedling survival'

Whitebark pine (WBP) is a keystone species of Rocky Mountain alpine and subalpine areas. A pervasive non-native fungal disease (white pine blister rust), mountain pine beetle infestation, and successional replacement by shade-tolerant competitors following decades of fire exclusion have severely reduced whitebark pine and threaten these high-elevation ecosystems. Land managers are attempting to reverse whitebark pines decline by increasing regeneration of rust-resistant trees while restoring successional processes. Restoration efforts include the planting of whitebark pine seedlings and over 200,000 seedlings have been planted on National Forest, BLM and National Park service lands. In this Rocky Mountain (RM) study, select whitebark pine plantations were surveyed and seedling survival rates and ecological data collected. The purpose of this initial study was to determine overall survival rates for planted whitebark pine seedlings and to identify environmental conditions that have promoted high seedling survival. Data were analyzed at the site, plot and tree level. Microsites created by stumps, rocks and downed logs in close proximity to WBP seedlings greatly enhanced survival, seedling height and seedling growth during the first year after planting. Potential direct solar radiation was inversely related to WBP survival. Wet planting sites were detrimental to seedling survival. Results as to the effect of fire on seedling survival were inconclusive. However for 1st year seedlings it does appear that moderate, mixed or severe burning did result in much higher survival than unburned. To further understand the environmental conditions that affect seedling survival, an experimental planting was designed and monitored using the knowledge gained from the RM study. Seedling survival in this planting was statistically significantly associated with the presence of a microsite. And increased health of seedlings was associated with the presence of beneficial mycorrhizal associates. Only seedling located in burned or unburned whitebark pine communities were colonized with native fungi and colonization was higher for burned than for unburned sites. Whitebark pine seedlings are successfully being planted and it is possible to discern how different environmental conditions are affecting the survival, height, growth and health of planted seedlings.

Subtropical Thicket is the dominant vegetation biome in the Eastern Cape. Little regeneration through seedlings has been observed in Thicket. This is of serious concern, as Thicket has been degraded over large areas of its distribution. An understanding of the seed dynamics is necessary for any restoration project. A number of possible causes for the lack of seedlings were therefore investigated. Study sites were best classified according to the biogeographical regions of the Subtropical Thicket Ecosystem Planning (STEP) project. The seed bank of Thicket is dissimilar to the aboveground vegetation, as it lacks woody species and is dominated by herbs and grasses, making little contribution to the regeneration of Thicket species. An increase in canopy cover resulted in lower soil and air temperatures, as well as light, and an increase in litter depth. Seedling abundance and species richness increases with mean annual rainfall, with woody seedlings being dominant in the higher rainfall areas, and succulent species in the lower rainfall regions. Anemochorous species dominated the germinable seed bank, and zoochorous species were more prevalent underneath the canopy, compared to open areas, an indication of active seed dispersal. No germination was recorded in many Thicket species, and dormancy mechanisms were lacking in many of the species that did germinate. Immersion in hot water increased germination in the hard seeds of Acacia karroo, whereas shade enhanced germination in small seeded Burchellia bubalina. The response of seedlings of four Thicket species with varying distribution to shade and drought was studied. Ptaeroxylon obliquum and Aloe africana are drought tolerant species, whereas Burchellia bubalina and Rhus dentata were intolerant to low soil moisture. All four species were able to grow in deep shade, although Rhus dentata would be classified as a shade avoider, unlike the other three species that are shade tolerant. This results in the four species having different regeneration niches. It was concluded that dispersal and the lack of “safe sites” for seedlings were the main limitations to seedling establishment in Mainland Thicket.

Many studies have reported deficient or intermittent patterns of natural regeneration in temperate deciduous woodland. The present study aimed to assess the relative impact of herbivore-mediated plant mortality on the natural regeneration dynamics of representative tree species (Acer pseudoplatanus, Betula pendula, Fraxinus excelsior, Ilex aquifolium, Sorbus aucuparia, Taxus baccata and Ulmus glabra) in representative temperate deciduous woodland (Shipley Wood and Derwent Gorge, County Durham). Sapling density and the density, spatial association and size distribution of adult tree populations varied significantly between tree species and study sites, reflecting contrasting patterns of current and historical regeneration. Rates of post-dispersal seed predation and seedling herbivory were quantified using field-based 'cafeteria' trials. Rodents were the principal agents responsible for seed predation, whereas seedling herbivory was attributable to a mixed suite of herbivores including invertebrates, rodents and larger mammals. Rates of seed predation and seedling herbivory varied significantly between tree species, most likely reflecting individualistic, trade-off responses to chemical and physical attributes. Fine-scale spatial variation most likely reflected the preferential foraging of rodents beneath protective vegetation cover. There was no consistent evidence to support the hypothesis that dispersed seeds may escape disproportionately high offspring mortality beneath parent plants resulting from increased herbivore activity. Natural seedling density varied significantly between years and between tree species, according to the abundance of viable seeds produced by conspecific adult trees. Although seedling survivorship varied significantly between species, the survivorship of each species was similar between years and between cohorts of the same year. Canopy cover, field layer cover or correlated factors were significant determinants of seed germination and seedling emergence, establishment and survival, according to age- and species-specific tolerances. In relative terms, patterns of natural regeneration were primarily herbivore- limited (Acer and Taxus), microsite-limited (Betula, Fraxinus, Ilex and Ulmus) or limited by herbivores and microsites (Sorbus). The availability of viable seeds may have also limited the recruitment of Ilex, Sorbus, Taxus and Ulmus. Vegetative expansion, mast seeding, seed bank regeneration and repeated, prolonged reproduction may have reduced the actual impact of herbivory on natural regeneration, such that long-lived iteroparous tree species were unlikely to have been critically dependent on current recruitment.

Thesis (MScAgric)--University of Stellenbosch, 2004.<br>ENGLISH ABSTRACT: The influence of chemical seed treatments on the germination, seedling survival and yield of canola (cv. Varola 44) was investigated in a series of incubation studies, glasshouse experiments, as well as field trials in the canola producing areas in the Western Cape Province. Incubation experiments were conducted to compare germination and seedling growth of untreated (control) seed with that of seed treated at different application rates (0.5, 1.0 and 2.0 times the recommended) of Cruiser® and SA-combination (which consists of Thiulin® at 0.5g a.i.; Apron® at 0.0815 g a.i.; Gaucho® at 0.6125 g a.i. and Rovral® at 0.9975 g a.i.). The results indicated that seed treatment (all rates of SA-combination and highest rate of Cruiser) delayed germination and seedling growth, especially if the seed was subjected to the Accelerated Ageing Test. Glasshouse studies with pasteurised soil at different water contents, seed sources (storage periods) and planting depths confirmed the phytotoxic effects of the chemical seed treatments in the absence of soil borne pathogens. From the results it became clear that extreme water conditions (very wet or dry) increased the suppressing effect on germination and seedling growth, but that no phytotoxic reactions occurred in moist (favourable soil water conditions) soil, regardless of application rate of the chemicals used, planting depth and seed source. In a second glasshouse experiment conducted in moist soil (kept at 50% of field water capacity to prevent any toxic effects) from seven different localities that were naturally infested with pathogens, both chemicals proved to be effective where soil borne pathogens (Rhizocfonia so/ani and Pythium spp.) occurred. No clear trend could however be found due to either chemical or application rates used. Finally, field trials were conducted to study the effect of chemical seed treatments on the plant populations and yield of canola planted in different row widths (17 and 34 cm) and seeding rates (3, 5 and 7 kq.ha'). Results showed that treated seeds produced more plants.rn" and yielded more than untreated seeds at Roodebloem Experimental Farm, while the highest seeding rate produced significantly more plants.rn" (Roodebloem and Langgewens Experimental Farms), but not significantly higher yields than the lowest seeding rate at the same locality. Although row width did not have an effect on plant population, yield (Roodebloem 2003) was significantly less at the wider (34 cm) rows. As in earlier experiments, no consistent differences between the two chemicals used were found. These results clearly illustrated both the negative (in the absence of pathogens) and positive (where soil borne pathogens do occur) effects that chemical seed treatments may have on the germination, seedling growth and even yield of canola under local environmental and soil conditions. Because no significant differences were found between the chemicals used, both chemicals should be regarded as efficient. More research, especially under field conditions and with more cultivars, is needed before the registration of a chemical for seed treatment could be considered.<br>AFRIKAANSE OPSOMMING: Die invloed van chemiese saadbehandeling op die ontkieming, saailing oorlewing en opbrengs van canola (cv. Varola 44) is ondersoek in 'n reeks inkubasie studies, glashuis eksperimente en veldproewe in die canolaproduserende gebiede in die Wes Kaap Provinsie. Inkubasie eksperimente is uitgevoer om die ontkieming en saailing groei van onbehandelde (kontrole) saad te vergelyk met dié van saad wat behandel is teen verskillende dosisse (0.5, 1.0 en 2.0 keer die aanbevole) van Cruiser® en SA-kombinasie (wat bestaan uit Thiulin® teen 0.5g a.i.; Apron® teen 0.0815 g a.i.; Gaucho® teen 0.6125 g a.i. en Rovral® teen 0.9975 g a.i.). Die resultate het aangedui dat saadbehandeling (vir alle dosisse van SAkombinasie en die hoogste dosis van Cruiser) ontkieming en saailing groei vertraag, veral wanneer die saad onderwerp was aan die Versnelde Verouderings Toets. Glashuis studies met gepasteuriseerde grond by verskillende waterinhoude, saad bronne (stoor periodes) en plantdieptes, het die fitotoksiese effekte van die chemiese saadbehandelings bevestig in die afwesigheid van grondgedraagde patogene. Vanuit die resultate het dit duidelik geword dat ekstreme water toestande (baie nat of droog) die onderdrukkende effek op ontkieming en saailinggroei verhoog het, maar dat geen fitotoksiese reaksies plaasgevind het in klam (gunstige grondwater toestande) grond nie, ongeag die dosisse of chemikalieë gebruik, plantdiepte en saad bron. In 'n tweede glashuis eksperiment uitgevoer in klam grond (gehou by 50% van veldwaterkapasiteit om toksiese effekte te voorkom) van sewe lokaliteite wat natuurlik besmet was met patogene, was beide chemikalië effektief waar grondgedraagde patogene (Rhizoctonia so/ani en Pythium spp.) voorgekom het. Geen duidelike tendens is egter waargeneem vir enige van die chemikalieë of dosisse nie. Laastens is veldproewe uitgevoer om die effek van chemiese saadbehandelings op plant populasies en opbrengs te bepaal van canola geplant in verskillende rywydtes (17 en 34 cm) en saaidigthede (3, 5 en 7 kg.ha-1). Resultate het aangedui dat behandelde saad meer plante.rn" produseer en 'n groter opbrengs lewer as onbehandelde saad by Roodebloem Eksperimentele Plaas, terwyl die hoogste saaidigtheid betekenisvol meer plante.m" (Roodebloem en Langgewens Eksperimentele Plase), maar nie betekenisvol hoër opbrengste gelewer het as die laagste saaidigtheid by dieselfde lokaliteit nie. AI het rywydte nie 'n effek op plant populasie gehad nie, was opbrengs (Roodebloem 2003) betekenisvol minder by die wyer (34 cm) rye. Soos in vroeëre eksperimente is geen konsekwente verskille tussen die twee chemikalieë gevind nie. Hierdie resultate illustreer duidelik beide negatiewe (in die afwesigheid van grondgedraagde patogene) en positiewe (in die aanwesigheid van grondgedraagde patogene) effekte wat chemiese saadbehandelings op ontkieming, saailing groei en selfs opbrengs van canola onder plaaslike omgewings en grondtoestande kan hê. Omdat geen betekenisvolle verskille tussen die chemikalieë gevind is nie, moet beide chemikalieë as doeltreffend aanvaar word. Meer navorsing, veralonder veldtoestande en met meer kultivars, is egter nodig voordat die registrasie van 'n chemiese middel vir saadbehandeling oorweeg kan word.

A trade-off between seed size and seed number is central in seed ecology, and has been suggested to be related to a trade-off between competition and colonization, as well as to a trade-off between stress tolerance and fecundity. Large seeds endure hazards during establishment, such as shading, drought, litter coverage and competition from other plants, better than do small seeds, due to a larger amount of stored resources in the seed. Small seeds, however, are numerous and small-seeded species are therefore more fecund. Moreover, a pattern with small-seeded species being associated with open habitats and large-seeded species being associated with closed habitats has been reported in the literature. In this thesis I assess effects of seed size on recruitment, and how relationships between seed size and recruitment may relate to habitat conditions. Seed sowing experiments were performed in the field to assess inter- and intra-specific relationships between seed size and recruitment in open and closed habitats (Paper I and II). Seed removal experiments were performed in the field to assess what effects seed predation may have on a relationship between seed size and recruitment (Paper III). A garden experiment was performed based on contests between larger-seeded and smaller-seeded species, in order to examine different models on co-existence of multiple seed size strategies. The results showed that there was a weak positive relationship between seed size and recruitment in the field, and that this relationship was only weakly and inconclusively related to habitat (Paper I and II). Seed removal was negatively related to seed size in closed habitats and unrelated to seed size in open habitats (Paper III). This indicates that any positive relationship between seed size and recruitment may be an effect of higher seed removal in small-seeded species. However, when grown under controlled conditions in a garden experiment, there was a clear advantage of larger-seeded species over smaller-seeded species (Paper IV). This advantage was unaffected by seed density, indicating that there was no competitive advantage of the larger-seeded species. Instead, indirect evidence suggests that larger-seeded species exhibit higher tolerance to stress.<br><p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Accepted.</p><p> </p>

In order to assess the enhancement of seedling survival and growth during drought conditions, five-hundred bare-root seedlings each of Shumard oak (Quercus shumardii Buckl.) and green ash (Fraxinus pennsylvanica Marsh.) were planted each with four soil amendments at a Wildlife Management Area in Lewisville, Texas. The treatments were a mycorrhizal inoculant, mulch fabric, and two superabsorbent gels (TerraSorb® and DRiWATER®). Survival and growth measurements were assessed periodically for two years. Research was conducted on vegetation, soil, and site history for baseline data. Both superabsorbent gels gave significant results for Shumard oak survival, and one increased green ash diameter. For overall growth, significant results were found among DRiWATER®, mycorrhizae, and mulch treatments.

Mestrado em Biologia dos Recursos Vegetais / Instituto Superior de Agronomia / Faculdade de Ciências. Universidade de Lisboa<br>Mediterranean drylands are expected to become drier due to climate change. This may aggravate desertification by increasing dryland susceptibility to land degradation, leading to the loss of biodiversity and ability to provide ecosystem services. In Mediterranean Basin drylands, a large area is occupied by oak woodlands, a semi-natural agro-silvopastoral system called Montado in Portugal. In the drier areas, where Montado seems to act as a buffer against desertification, the dominant tree species is Holm oak (Quercus ilex subsp. rotundifolia), However, in the last decades, a declining trend has been reported for Holm oak woodlands, mostly attributed to unsustainable land management, biotic factors and to an increase in aridity at a regional scale. Also, at a local scale, it has been shown that microclimate conditions driven by topography have a major influence on this species natural regeneration rates. Over the last decades, many (re)afforestation with Holm oak have been implemented to revert Montado’s decline and combat desertification, although not always successful. The aim of this work was to study the effect of macro- and microclimate on Holm oak performance, specifically on acorn germination and first summer seedling survival. Holm oak acorns were collected along a climatic gradient based on long-term precipitation (30 yrs.), resulting in 6 macroclimate provenances. In 2 sites, the driest and the wettest sites of the gradient, areas with contrasting microclimates were selected using Potential Solar Radiation (PSR) as a proxy of microclimate conditions. Holm oak performance was, thus, studied along a macroclimate gradient and in microclimate contrasting conditions. Holm oak acorns from each provenance where characterized biometrically and acorn production evaluated. Germination of acorns and seedling survival were evaluated under greenhouse similar conditions and in the field under contrasting macro- and microclimate conditions. We found that macro- and microclimatic provenance influences acorn size and germination. Drier sites and more exposed areas (higher PSR) had bigger acorns with higher germination. Field conditions did not seem to affect germination but rather the first summer seedling survival. The survival of Holm oak seedlings to the first summer was significantly higher in the wetter site and in less exposed areas than in the drier site and in more exposed areas. This work provides guidelines to increase Holm oak seedling quantity and quality in nurseries to be used in (re)afforestation plans and to improve Holm oak young seedling survival, either by focusing (re)afforestation in microclimatic favorable areas (using remote sensing derived information like PSR), or by providing additional assistance to seedlings growing in drier and/or more exposed areas. In addition, it may also help to better understand Holm oak seedling mortality and/or natural regeneration patterns. Hence, these findings may contribute to improve the success of Holm oak (re)afforestation as a critical restoration tool to combat desertification in Portuguese drylands, and revert Holm oak Montado’s decline, particularly under a climate change scenario<br>N/A

Remote sensing of the environment has become an effective and useful research approach applied across a wide range of scientific and professional disciplines. Generally remote sensing is used to evaluate patterns and processes at broad spatio-temporal scales, such as classifying landscape vegetation patterns or for creating digital surface models, however, there are increasing opportunities to expand the use of remotely sensed information to a wider range of applications at variable spatial and temporal scales. In the field of plant seedling and germination research methods are needed to improve plant establishment and restoration monitoring, particularly in areas that have historically low success rates such as in semi-arid and arid rangeland landscapes. The purpose of this research is to assess the efficacy of remote sensing for tracking seedling height, seedling density, and seedling fate, and determine the biotic causes of seedling mortality in a rangeland revegetation site in northwestern Utah. In Chapter 1, we use 28 time-lapse and motion sensing infrared cameras (Reconyx) to measure seedling density and height in fenced and unfenced plots during the initial four months of seedling establishment and growth. We compare imaged-based measurements of seedling height and density with similar measurements collected in the field and at different daylight hours to determine the accuracy and reliability of remotely sensed measurements. We found that the ideal sample periods for capturing the clearest images were at the time the sun passed zenith and shadows were minimized. Average seedling height was 14% lower in image-based versus field estimates. Seedling density was underestimated by approximately 30% when using cameras. Our study establishes that remote sensing of seedlings using time-lapse cameras is a method for seedling research and monitoring in restoration efforts which merits further research and development. In Chapter 2, we track biotic causes of seedling fate using the methods developed in Chapter 1, and compare seedling survival in fenced and unfenced plots. Fencing led to a four-fold increase in the number of seedlings emerged from the soil. Herbivory and damage caused by trampling and burial resulted in the death of 61.4 % of all unfenced seedlings. Fencing plots increased the probability of seedling survival by seven times. Using cameras to track seedling fate at two restoration sites revealed that small herbivores, including Lepus californicus, Thomomys bottae, and Dipodomys sp. drastically reduced seedling survival during the first year after planting. Effects of herbivores on seedling survival should be taken into consideration when planning revegetation operations, and further research can increase knowledge of how herbivory affects restoration efforts. Using cameras can provide meaningful information to managers and researchers about seedling status and fate.

Wildfires play a significant role in many different elements of Mediterranean forest ecosystems. In recent years, prescribed fires have started being used more often as a fuel reduction tool, and also as silvicultural treatment to help the regeneration and health improvement of stands. Apart from the fact that fire may alter microsite conditions, very little is known about the impact of prescribed burning on natural regeneration or plant species renewal in Mediterranean pine forests. Likewise, knowledge about the influence of seedling predators on post-fire regeneration is still scarce. In this study, we aimed to compare the effects of seedling predation on recruitment in earlier stages after prescribed burnings in three pine stands in Central Spain: a pure stand of Pinus nigra; a mixed stand of Pinus halepensis and Pinus pinaster and a mixed stand P. nigra with P. pinaster. In situ we superficially sowed seeds from two different species. In the sowing experiment, we tested two different seed provenances (drier and more humid spanish regions) for each species. In all, 60 plots (30 burned, 30 unburned) per site, with 10 seeding units per plot and more than 20,000 seeds, were used in the whole study. Seedling predation was evaluated by replicating the seeding units inside and outside a wire cage as protection for rodents and birds. Our results showed that prescribed fires alter initial seedling predation intensity: predation was significantly higher in the seedlings grown in the plots affected by prescribed fire. The individuals sown before the fire passed showed slightly more predation than those sown after fire passage. Provenances did not appear as an important predation drive. Understanding the role of the predation associated with these treatments can help improve Mediterranean pine forest management.

Terrestrial mammals affect numerous aspects of plant demography, colonization, and community structure in Neotropical forests. Granivorous mammals destroy seeds via seed predation and seedlings through herbivory, negatively affecting plant fitness. Mammals can also positively affect plants by dispersing or hoarding seeds. Seed fate outcomes are contingent on the interaction between mammal seed handling strategies and the intrinsic anti-predation defenses possessed by seeds. In field experiments at La Selva Biological Station, I investigated how collared peccaries (Pecari tajacu) and Central American agoutis (Dasyprocta punctata) affect five species of large seeds that have various defenses against predation. Overall, peccaries consumed and killed most non-defended and chemically-defended seeds but they could not destroy seeds with physical defenses. Agoutis killed non-defended and physically-defended seeds, but not seeds with chemical defenses. Using seeds of Mucuna holtonii, I investigated how chemical and structural defenses deter mammal and insect seed predation respectively. I also determined how endosperm removal by invertebrates affects seed germination and seedling biomass. Chemical defenses protected seeds from rodents, but not ungulates that digest seeds via pregastric fermentation. Physical defenses protected seeds from invertebrate seed predators, and removal of endosperm negatively affected both seed germination and seedling growth. To determine how scatter-hoarding by agoutis affects seed escape from seed predators, germination, and seedling growth, I created simulated agouti hoards. I also investigated how mammals affect young seedling survival. Hoarding enhanced seed survival, germination, and seedling growth for most species of seeds. Terrestrial mammals killed some seedlings via seed predation rather than by herbivory. Overall, large mammal activity in La Selva negatively affected seed and seedling survival and this likely influences many aspects of forest dynamics.

There is a concern about the lack of regeneration of riparian hardwood forest communities in the Middle Sheyenne River Watershed of northeastern North Dakota. Natural resource managers and landowners are unsure if herbivory by ungulates or other factors are responsible for a lack of tree seedling regeneration and survival. We focused our research on the role of ungulates and competitive vegetation in seedling survival and growth in demonstration tree planting sites. Landowners utilized exclosures from ungulate browsing and/or grazing, and different forms of vegetation control. The riparian study showed the combination of deer with cattle significantly affected survival of seedlings after three years at p<0.012, and that vegetation competition played less of a role in seedling survival. The upland study found that tree and shrub species in general did not respond significantly in terms of overall growth with treatments such as fabric and glyphosate herbicide to control vegetation competition.

Abstract The restoration of degraded landscapes has become one of our most valuable tools for conservation, however there are many factors which can restrict natural regeneration and impede active restoration attempts. The purpose of this study was to investigate three key processes which commonly limit the establishment of forest tree species into abandoned pasture in tropical forests: i) dispersal limitation, ii) seed predation, and iii) competition from the grass sward. Seed dispersal I identified 59 species of birds that were using the grassland habitat. Through 216 hours of focal tree observations I established that isolated trees in the grassland that had larger canopies, and those that were providing a food source (i.e. flowers or fruit) had significantly higher bird visitation rates and average stay lengths. I found evidence of the “perch effect” as patches of remnant trees encouraged more birds into areas of grassland, and the density of seedlings under tree canopies was significantly positively correlated with bird visitations. 95% of the seedlings found beneath tree canopies in grassland were of a different species to that of the tree canopy above them, demonstrating the dispersal of seeds from elsewhere into these microhabitats. 98% of these seedlings are grassland or forest edge species showing forest core species are still dispersal or microsite limited despite the effect of these trees. Seed predation Removal rates of seeds from experimentally laid out seed piles varied among seed species, the habitat the pile was in, and the predator guild able to access the piles. Preliminary results indicate that these trends are driven by the ecology of the seed predator. Removal of seeds by vertebrates was highest in the core forest, while ant predation was constant across all habitats. Vertebrates removed the larger seeds (Entandrophragma angolense and Sterculia tragacantha) while ants preferred the smaller Celtis gomphophylla and Croton macrostachyus. Overall predation rates in grassland were lower than those in the forest, and the presence of remnant trees did not influence predation rates, a positive sign for regeneration and the survival of seeds dispersed into these areas. Competition from the grass sward While the grass sward provides shade for seedlings of forest tree species it is also a harsh environment for them, as the grass competes with seedlings for water. Removing the grass and covering planted seedlings with artificial shading structures significantly increased both the survival and growth of these seedlings. Recommendations From this study I was able to make recommendations for a low input restoration program at Ngel Nyaki. Planting seedlings in small „islands‟ takes advantage of the natural increase in dispersal of seeds under isolated trees, while low seed predation rates increase the chance of survival of these seeds to germination. Planting these seedlings under shade will lead to increases both their growth rates and their survival. Once the secondary forest develops, under-planting seedlings of core forest trees will introduce them to the system, as the natural establishment of these seeds appears to be limited in the current environment. This study has also served to remind us how little we know about this particular forest-grassland system, and has led to the development of ideas for further investigations into several more aspects of regeneration.

This thesis includes two studies. The first study examined changes in soil characteristics as a result of prolonged conifer dominance in successional aspen-conifer forests. Changing disturbance patterns in aspen-conifer forests appear to be altering successional dynamics that favors conifer expansion in aspen forests. The primary objective of this paper was to identify how increasing conifer dominance that develops in later successional stages alters forest soil characteristics. Soil measurements were collected along a stand composition gradient: aspen dominated, aspen-conifer mix, conifer dominated and open meadow, which includes the range of conditions that exists through the stages of secondary succession in aspen-conifer forests. Soil chemistry, moisture content, respiration, and temperature were measured. There was a consistent trend in which aspen stands demonstrated higher mean soil nutrient concentrations than adjacent meadows, mixed or conifer stands. Soil moisture was significantly higher in aspen stands and meadows in early summer. Soil respiration was significantly higher in aspen stands than conifer stands or meadows throughout the summer. The results indicate that soil resource availability and respiration peak within aspen dominated stands that are present during early succession and then decrease as conifer abundance increases along our stand composition gradient, representative of stand characteristics present in mid to late successional stages. Emerging evidence from other studies suggest that these observed changes in soil characteristics with increasing conifer dominance may have negative feedbacks on aspen growth and vigor. The second study examined the facilitation effect between aspen and subalpine fir establishment. In subalpine forests, conifer species are often found intermixed with broadleaf species. However, few if any studies have explored the existence and influence of facilitation between broadleaf tree species and conifers. We have observed the general establishment of subalpine fir seedlings at the base of aspen trees in a subalpine forest, indicating that a facilitative relationship may exist. To explore the potential facilitative relationship during secondary succession in subalpine forests, subalpine fir seeds were planted across a stand composition gradient (aspen dominated → mixed → conifer dominated stands) at six study sites in the Fishlake National Forest. Seeds were placed during the fall of 2010, at distances of 0 cm and 25 cm in each cardinal direction at the base of mature aspen and subalpine fir trees in each of the three stand types. Seeds were also planted within stand interspaces and in adjacent meadows. Seedling emergence was recorded at the beginning of the summer of 2011 and seedling mortality was recorded in October 2011. Soil moisture content was measured at the position that seeds were placed during the summers of 2009 and 2011. Aspen dominated stands had subalpine fir germination that was on average 11 times greater than mixed or conifer dominated stands. Germination was 2.3 fold greater at the base of aspen trees than fir trees and two fold greater at the base of aspen trees than interspaces. Seedling mortality was lower in aspen stands but was not significantly influenced by position relative to mature trees. Soil moisture was highest in aspen dominated stands, with better soil moisture conditions at the base of aspen trees and in interspaces compared to the base of fir trees. Few if any studies regarding conifer facilitation have provided evidence for facilitation at the germination life stage, rather they focus on seedling survival. However, our study illustrates a strong facilitative interaction in which both aspen dominated stands and aspen trees increase the likelihood of subalpine fir seedling establishment by drastically increasing rates of subalpine fir germination. Because of aspen's primary role in initiating secondary succession through post-disturbance sucker regeneration, and the subsequent dependence of conifers on aspen for establishment, aspen mortality via competition with conifers under longer fire cycles, droughts, or intensive ungulate browsing may result in a loss of aspen-conifer forest communities in some locales.

In the wetter climates associated with the coastal forests of northwestern North America, coarse woody debris (CWD) accumulations in the form of snags, downed boles, and large branches can be large in natural forest ecosystems. Seedlings often regenerate on stumps and downed logs in the understory of old-growth coastal forests. The question remains though, whether CWD is a necessary component for seedling survival and growth in forests managed for commodity production. This study addresses one concern of forest managers: is there an immediate nutritional or moisture supply advantage conferred by CWD for the survival and growth of seedlings in the coastal climate of British Columbia? We compared survival and growth of seedlings planted in decaying wood compared to non-woody humus forms and mineral soil under heavy shade and full light conditions. Low light environments are of particular interest since reports of the strong association between CWD and regeneration has primarily referred to understory seedlings and saplings in old-growth forests.

A região dos morros graníticos de Porto Alegre (Estado do Rio Grande do Sul), inserida no sul do Brasil, apresenta uma cobertura vegetal em forma de mosaico natural de florestas e áreas abertas (savanas ou campos). Neste locais, segundo o clima atual, as formações florestais tendem a avançar sobre a matriz herbácea, principalmente de forma agrupada, formando ilhas de nucleação florestal. Este padrão é mantido por forças seletivas como a precipitação, o fogo e a herbivoria (vertebrados e invertebrados), que incidem de maneira mais intensa sobre as fases iniciais das populações de plantas pioneiras da floresta. As forças atuam de maneira distinta nos diversos hábitats disponíveis para o estabelecimento de plântulas, criando um arranjo espacial em forma de ilhas. Esta tese aborda, no primeiro capítulo, os padrões florísticos e espaciais de ilhas de nucleação florestal em ecótono natural de floresta-savana, segundo as diferentes exposições solares (norte, topo e sul) dominantes do morro Santana, comparando-as, floristicamente, com as bordas de mata. No segundo capítulo, é avaliada, experimentalmente, a sobrevivência de plântulas de guamirim (Myrcia palustris DC.; Myrtaceae) sob a influência de uma seca severa em diferentes hábitats (borda de mata, ilhas de nucleação florestal e matriz herbácea) presentes em três exposições solares (norte, topo e sul). Em ambos os casos, os estudos foram conduzidos no morro Santana (30°03’ S, 51°07’ W), cuja altitude máxima é de 311m acima do nível do mar. Para avaliar os padrões florísticos e espaciais, foram selecionadas vinte oito ilhas de nucleação florestal das várias área de cobertura (entre 5,5 a 904m2) em um mosaico natural de floresta-campo e quatro parcelas na borda da mata de dois tamanhos distintos (121,5 e 243m2). As espécies vegetais foram identificadas, classificadas em síndromes de dispersão e a abundância de indivíduos foi registrada. Os padrões florísticos foram observados através de análise multivariada. As relações entre a área de cobertura e diversidade/riqueza e entre o número de indivíduos e a riqueza foram analisadas por regressão linear. Para avaliar a sobrevivência de M. palustris, foram analisadas as taxas de sobrevivência e de mortalidade, bem como as causas desta mortalidade para esta espécie arbórea florestal generalista. As sobrevivências e causas de morte foram avaliadas mensalmente, durante os primeiros meses de vida desta espécie, em um período de seca severa em três hábitats e dois controles: borda de mata (B), ilhas de nucleação florestal (I) e matriz herbácea (H), além dos controle-interno (CI) e controleexterno (CE) repetidas em três ambientes geomorfológicos (norte, topo e sul). Em cada hábitat foram transplantadas plântulas isoladas e agrupadas (2-4), com o objetivo de avaliar a mortalidade densidade-dependente. Foram registrados 4214 indivíduos (2828 nas ilhas de nucleação e 1386 nas bordas de mata) distribuídos em 38 famílias e 111 espécies. A análise de agrupamento formou três grupos: g1, com ilhas de nucleação florestal mais iniciais dos três ambientes geomorfológicos (predomínio das ilhas do topo); g2, também por ilhas dos três ambientes geomorfológicos (predomínio das ilhas do norte); e g3, com as ilhas mais desenvolvidas dos três ambientes geomorfológicos (predomínio das ilhas do sul) unidas às bordas de mata. A dispersão zoocórica é dominante nas ilhas dos três grupos, ao passo que a dispersão autocórica apresentou um tendência de aumento de g1 para g3 e a dispersão anemocórica, o inverso. Nas mais desenvolvidas, houve maior riqueza e abundância de espécies lenhosas florestais tardias do que em ilhas mais iniciais. Os testes de aleatorização entre os três grupos revelaram que as áreas de cobertura de g3 (344,5m2) e g2 (156m2) são significativamente maiores que g1 (40,9m2) (p = 0,001), o que não ocorreu entre g3 e g2 (p = 0,063). Os valores de diversidade foram diferentes (p = 0,001) entre g1 (1,56) e g2 (2,16) ou g3 (2,97) e, levemente diferentes (p = 0,04) entre g2 e g3. Retirando as bordas de mata, as ilhas das três diferentes exposições solares diferiram (p = 0,02) em relação à riqueza e a abundância do norte e do topo, do norte e do sul, mas não entre o sul e o topo (p = 0,06). A análise de congruência obteve valor máximo (0,72) unindo riqueza e abundância; se acrescidos a eles a área de cobertura, a diversidade e a densidade das ilhas, este valor ainda permanece alto (0,7). A área de cobertura foi o único parâmetro especial que se mostrou correlacionado com riqueza (R2 = 0,676; p < 0,001) e com a diversidade (R2 = 0,49; p < 0,001). Quanto maior o número de indivíduos, maior a riqueza em g1 (R2 g1 = 0,63; p = 0,002), em g2 (R2 g2 = 0,66; p = 0,004), mas não em e g3 (R2 g3 = 0,6; p = 0,07). A falta de significância na correlação em g3 é resultado do baixo número de unidades amostrais neste grupo (6). com a Os resultados com M. palustris revelam que as taxas de sobrevivências médias mensais aumentaram inversamente com a quantidade de precipitação mensal para todos os ambientes (R2 = 0,46; p = 0,006). A curva de sobrevivência decaiu mais abruptamente no topo do que nos demais ambientes geomorfológicos (p < 0,01), sem diferenças entre norte e sul (p = 0,263). Esta mesma curva foi diferente entre todos os hábitats (p < 0,01), resultando numa maior chance de sobrevivência em B, seguida por I e nula em H. As forças seletivas que causam a morte das plântulas são distintas entre os hábitats (p < 0,01): a herbivoria por invertebrado é maior em H; por vertebrado, é maior em I e H; a seca/doença é maior em B; e o fogo, maior em I. A partir destes resultados, são apresentadas as seguintes conclusões: Os padrões florísticos e espaciais do avanço florestal em ilhas de nucleação refletem os processos de sucessão de um estádio mais inicial e simples para um estádio mais “tardio” e complexo, similar a uma borda de mata. Este processo é limitado pela distribuição de micro-hábitats adequados ao estabelecimento das espécies lenhosas florestais de dispersão zoocórica. A sucessão nas ilhas é retroalimentada positivamente, sendo que a chegada e o estabelecimento de novos indivíduos de espécies florestais atrai mais dispersores de sementes, acelerando a sucessão. A composição florística é dependente, também, da localização da ilha em relação às diferentes exposições solares. Para a sobrevivência de plântulas de M. palutris, a precipitação mensal é o parâmetro determinante primário. A distribuição dos hábitats afeta a dinâmica do avanço florestal na medida em que varia, entre eles, a taxa de sobrevivência de plântulas. Mesmo em anos de seca severa, ocorre o avanço da floresta em hábitats mais sombreados presentes no mosaico. Por fim, pode-se concluir que o avanço da floresta sobre a matriz herbácea é um fenômeno vinculado à natureza florística das matas adjacentes. Na matriz da paisagem, há diversos hábitats potencialmente disponíveis que modificam as chances de sobrevivência de plântulas e, portanto, contribuem, de formas diferentes, para a dinâmica da vegetação de comunidades de populações de espécies lenhosas. Entre os hábitats, a matriz herbácea é o hábitat mais inóspito para plântulas destas espécies e a borda da mata, o mais adequado. As ilhas apresentam uma condição intermediária entre os dois primeiros hábitats, sendo as mais desenvolvidas bastante semelhantes às bordas. Os mecanismos que retardam esta dinâmica são, em ordem de importância, a disponibilidade de água (em todos os hábitats), o herbivoria por vertebrado (nas ilhas e matriz herbácea), o fogo (na matriz herbácea) e, por último, a herbivoria por invertebrado (na matriz herbácea).<br>The region of granitic hills of Porto Alegre (State of Rio Grande do Sul) in southern brazilian’s region is contituted by a mosiac of forest and open areas (savannas or grassland). In these sites, according to the actual climate, the conditions are suitable for forest, which should mean that this vegetation type is in expansion, invading the surrounding herbaceous matrix. This expansion shows, mainly, an aggregation pattern by woody thickets of forest nucleation. The maintenance of the pattern is made by selective forces like precipitation, fire and herbivory (vertebrade and invertebrade) which are stronger in a juvenil phases of tree popualations. The selective forces act differently within all habitats available for seedling stablishment, creating a spatial arrangment of woody island. On the first chapter of this study, we analysed the floristic and spatial patterns of thickets island of forest expansion in a natural ecotone of forest-savanna, according to the slope (north, top and south) on Santan hill. It compares the floristic ans spatial patterns of thickets and forest edges in this three slopes. On the second chapter, we evaluated monthly, the seedling suvivorship of guamirim (Myrcia palustris DC.; Myrtaceae) under the influence of a severious drought (2004/2005) within differents habitats (forest edge, thickets and herbaceous matrix) of three slopes (north, top and south), during 15 months, by an experimental approach. In both cases, the study was carried out in Santana hill (30°03’ S, 51°07’ W), with maximum altitude 311m above sea level. In order to evaluate the floristic and spatial patterns, we selected 28 thickets of many cover areas (between 5,5 to 904m2) and four forest edges of two sizes (121,5 e 243m2). All woody individuals (h ³ 1m) were registered. The species, their abundance and dispersal modes were registered too. The floristic patterns were analysed by multivariate analyses. The relationship between cover area and diversity/richness or abundance and richness were analysed by linear regression. For survivorship of M. palutris seedlings, we analysed the survival/mortality rates and the mortality causes for this generalist tree. The survival and mortality causes were tested within three habitats and two controls: forest edge (B), thickets (I), herbaceous matrix (H), innercontrol (CI) and external-control (CE). The habitats were placed in three differents slopes (north, top and south). In all traits, we tranplanted isolated and group seedlings (1-4), to investigate the density-dependent mortality. We registered 4214 individuals (2828 in the thickets and 1386 in edge) amongst 38 botanical families and 111 species. The cluster analyses showed three groups: g1 with initial thickets of three slopes (predominance of top thickets), g2 also with thickets of three slopes (predominance of north thickets) and g3 with more development thickets of three slopes (predominance of south thickets) together with four forest edges. The dispersal by animals was dominant in all three groups. The autochorie dispersal showed an increase trend from g1 to g3, while anemochorie dispersal was in opposite way. The randomization tests indicates that g3 cover area (344,4m2) and g2 (156m2) are bigger (p = 0,001) than g1 (40,9m2) and g3 and g2 are no different (p = 0,063). The diversity (H’) was almost the same, with g3 (2,97) or g2 (2,16) higher (p = 0,001) than g1 (1,56), but g3 and g2 are slightly differents (p = 0,04). Without the forest edges samples, the thickets had differents richness and abundance (p = 0,02) from the north to the top or to the south, but no differences (p = 0,06) form the south to the top. The congruence analyses had maximum value (0,72) joining richness and abundance, however with more area cover, diversity and densitiy together, the value keeps high (0,7). Just one single parameter, cover area, could explain the increase of richness (R2 = 0,676; p < 0,001) and diversity (R2 = 0,49; p < 0,001). With increase number of individuals, increase the richness in g1 (R2 g1 = 0,63; p = 0,002), in g2 (R2 g2 = 0,66; p = 0,004), but not in g3 (R2 g3 = 0,6; p = 0,07). The lack of significance in g3 is related to the few sample units of this group (6). The results with M. palustris seedlings showed a inverse relation (R2 = 0,46; p = 0,006) between the mean mensal mortality (mm) and the the mensal precipitation for all habitats in all slopes. The suvivorship curve decreased more abruptly in the top than north or south (p < 0,01), but not form the south to north (p = 0,263). This curve were also different (p < 0,01) amongst all habitats, which makes the chance of survival be higher in B than I and nule in H. The selective forces that cause seedlings death are distinct amongst the habitats (p < 0,01): by invertebrade herbivory higher in H, by vertebrade herbivory higher in I and, drought/disease higher in B and by fire higher in H. Based on this results, we found this conclusions: The floristic and spatial patterns of forest expansion by woody thickets reflect the successional process that ranges from an initial and simple stage (more pioneer) to an latter and complex stage (less pioneer) similar with the forest edge. This process is limited by micro-habitats distribution which are suitable for forest tree seedlings with dispersal by animals. The successional process within the thickets have a positive feedback, where the arrival and stablishment of new individuals from forest species atract more seed dispersors, accelerating the process. The floristic composition depends also from the thicket slope location. For the survivorship of M. palutris seedling, the mensal precipitation was main determinant parameter. The habitat distribution affects the forest expansion dynamics due the differents suvival rates amongst them. Even with a severious drought, there is forest expansion in the mosaic within more shade habitats. We concluded that the forest expansion over the herbaceous matriz is a phenomena dependent from the surrounding forest edges. Within the mosaic landscape, there are several potencial habitats available wich modified the chances of seedling survival and, therefore, had distinct contributions to communities and popualtion dynmics of woody species. Amongst habitats, the herbaceous matriz is the less suitable for seedlings of this specie, while the forest edge is the most one. The thickets has the intermediate conditions, where the most development are very similar to the edges. The mechanisms wich delay this dynamic, on the decreased importance order, is the water availability (all habitats), the vertebrate herbivore (thickets and herbaceous matrix), the fire (herbaceous matrix) and the invertebrade herbivory (herbaceous matrix).

The aim of this thesis was to study patterns of reproduction of Betula pendula and B. pubescens coll. along an altitudinal, coastal-inland, gradient in northern Sweden. The altitudinal variation was related to the distribution of the birch taxa along the gradient. Six years field data showed a steep decrease of seed germinability of B. pendula towards its altitudinal range limit in the Scandes every year. In contrast, B. pubescens ssp. pubescens showed significant positive correlations between seed germinability and altitude in three of the six years. Furthermore, there was a highly significant positive correlation between seed weight and altitude for B. pubescens coll., but not for B. pendula. Production of viable seeds fluctuated strongly between years in most populations, except in marginal B. pendula populations in the mountain area where it was constantly very low. On average 15 - 41 % of the seeds produced in B. pendula populations above 400 m altitude were attacked by gall midges (Semudobia ssp.). Corresponding values for B. pendula populations below 400 m altitude were 4 - 7 %. In B. pubescens populations, the seeds attacked by Semudobia ssp. never exceeded 3 %. The high frequency of Semudobia attackes in high altitude marginal B. pendula populations was suggested to be due to limited resources for defense against the seed predator. A 3-yr study documented large variations in pollination and seed quality between taxa, high and low altitude populations, and between years. Empty seeds (without embryos) dominated among the sampled seeds in most cases. This proportion was decreased by pollen addition, in both B. pendula and B. pubescens, in mountain populations, but not in coastal populations. The high percentage of empty seeds was therefore suggested to be partly caused by pollen-limitation, but failure of pollen tube penetration - fertilisation, or maternal resource supply could also have had an influence. A laboratory experiment showed increased pollen germination and length of the longest pollen tube per style after increased pollination. The correlations between number and length of pollen tubes per style were however mostly low in natural populations, suggesting low probability of pollen competition in the natural situation. Sowing experiments indicated that differences in initial seedling density between B. pendula and B. pubescens was more affected by interspecific differences in seed quality than by interspecific differences in survival of seedlings after establishment A study of the age structure of a B. pendula stand, planted about 250 m above its natural altitudinal limit, indicated that this birch may reproduce above its recent range limit during temporally warmer periods. It was concluded that the level of accumulated resources in B. pendula in marginal sites in the Scandes would mostly be too low for completion of the reproductive cycle. In contrast, B. pubescens ssp. pubescens is able to accumulate enough rescources for reproduction also at relative high altitudes.<br><p>Diss. (sammanfattning) Umeå : Umeå universitet, 1994, härtill 5 uppsatser.</p><br>digitalisering@umu

Historically, the Kentucky Inner Bluegrass blue ash-oak savanna-woodland was the primary ecosystem of the Inner Bluegrass Region (IBR) of Kentucky. After European settlement, the majority (>99%) of Bluegrass savanna was converted to agricultural and urban land uses. Currently remnant savanna tree species are failing to recruit. Therefore, a long-term restoration ecology project researching competition and disturbance on seedling establishment, survival, and growth has been established at Griffith Woods (the largest remaining savanna in Kentucky) in Harrison Co., KY. Fourteen native hardwood tree species (a total of 6,168 seedlings) have been experimentally planted. Light, soil, surrounding vegetation, and herbivory, factors thought to influence seedling survival, have been initially assessed. Results show that soils differed spatially in P, Ca, Mg, Zn, pH, N percent and soil organic matter percent. Light was significantly reduced by diffusive filtering through vegetation. Vegetation biomass was influenced by pH and Mg. Initial seedling survival was high, but significantly differed by species type, location, and soil pH, Mg, and Zn. This research demonstrates that under a similar range of conditions, native hardwood tree seedling establishment is possible. Therefore, the potential exists to restore Bluegrass savanna-woodland in order to return proper ecological functioning into a degraded landscape.

Western larch (Larix occidentalis Nutt.) is an important component of the montane forest in southeastern British Columbia. It grows in cool-temperate (IDF and ICH zones) and boreal climates (MS zone and, occasionally, ESSF zone). Larch is considered a very shade-intolerant species which can tolerate low light (partial shading) only during the seedling stage (the first 5 growing seasons). Typically, it regenerates after fire in the open on seedbeds exposed by burning. However, to what extent it tolerates low light and how various light environments affect its survival and growth is not known. The objective of our study was to determine the variation in survival and growth of western larch seedlings in relation to light availability and site conditions.

From the Proceedings of the 1988 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 16, 1988, University of Arizona, Tucson, Arizona

Equal numbers of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and Pacific silver fir (Abies amabilis (Doug.) Forbes) seedlings,,were spring planted, in 1981 and 1982, as 1-0 styroplugs on a south-facing high elevation clearcut located on Mount Arrowsmith, Vancouver Island, British Columbia. A number of treatments were applied to determine whether modification of seedling microclimate would increase survival and growth. These treatments included inclining the seedlings to the southwest, provision of shade cards, irrigation, and irrigation and shade cards combined. The highest survival rates, regardless of treatment, were exhibited by Douglas-fir. Approximately 72% and 82% of untreated seedlings, planted in 1981 and 1982 respectively, survived. Survival of seedlings that received treatment ranged from 81% to 95%. Douglas-fir seedlings were able to survive and grow because they were highly drought tolerant. Unirrigated seedlings lowered their osmotic potential by over 1.1 MPa in the course of a growing season in response to declining soil water potentials and consequently were able to maintain turgor. The transpiration rates of these seedlings were never less than 50% of those that were irrigated. Western hemlock, and to an even greater extent, Pacific silver fir seedlings lacked stress avoidance and tolerance mechanisms. Consequently there was very poor survival of both species. Survival rates were significantly increased by shade cards and irrigation but never exceeded 64% in either species. The extent and type of growth in all species was markedly affected by changes in microclimate. Irrigated seedlings developed the largest shoots and the smallest root systems. Shaded seedlings had larger shoots, but generally less roots, than untreated seedlings which had the lowest shoot to root dry mass ratios. A boundary-line analysis model that related seedling stomatal conductance (g[sub s]) to measurements of hourly average solar irradiance, air temperature, vapour pressure deficit and average root zone soil water potential, accounted for over 70% of the variability in g[sub s]. When the number of hours from sunrise was included as an independent variable, over 85% of the variability in g[sub s]could be explained. Measurements of seedling seasonal dry matter accumulation were better correlated with estimates of seedling growing season transpiration than with estimates of average growing season total seedling g[sub s].<br>Land and Food Systems, Faculty of<br>Graduate

A short duration-high intensity grazing trial was conducted in spring of 1985 to determine whether shrub establishment in crested wheatgrass pastures could be enhanced through spring grazing by cattle, or by fertilization of shrub seedlings. Data was collected on diet selection by cattle during spring grazing, and on subsequent shrub growth and survival. Shrubs studied were transplants of sagebrush, Artemisia tridentata, fourwing saltbush, Atriplex canescens, bitterbrush, Purshia tridentata, and one year old bitterbrush seedlings. Cattle did not browse sagebrush or fourwing saltbush transplants, but utilization of bitterbrush transplants and seedlings averaged 15 and 42 percent, respectively. Shrub selection by cattle was unaffected by grazing pressure or fertilization. Fertilization increased growth of sagebrush transplants but had no effect on survival. Trampling of shrubs was greater than anticipated. Trampling reduced growth in sagebrush, and reduced survival of both bitterbrush and sagebrush transplants. Browsing reduced growth of bitterbrush seedlings, but increased growth and survival of bitterbrush transplants. Despite adverse effects from trampling and browsing on some shrubs, the overall effect of spring grazing of crested wheatgrass by cattle was to enhance establishment of fourwing saltbush and bitterbrush transplants. Spring grazing had no measurable effect on establishment of sagebrush transplants or on survival of one year old bitterbrush seedlings.

This report consists of two parts: 1) a review of factors affecting the early growth and survival of indigenous seedlings planted for the purpose of ecological restoration; 2) field trials of different treatments at establishment of planted Coprosma robusta and Phormium tenax on an overburden dump and coastal dunes at Cape Foulwind, Westport, New Zealand. The literature review includes information from New Zealand and international sources. Where little is information is available on indigenous species information from forestry research has been discussed. Little is known about the nutrient requirements of indigenous seedlings in the field. Mycorrhiza may have some importance in restoration, particularly on disturbed ground. Weeds and vertebrates have a major influence on growth and survival, while the effects of invertebrates requires further evaluation. The fertiliser trial showed that cement kiln dust significantly reduced growth compared to the control in some instances. No significant response was observed from blood and bone. It was concluded that insufficient blood and bone was applied. The addition of compost in the planting hole did not have a significant effect on growth or survival. In several analyses there was significantly greater growth and survival in plots receiving weed mat than in plots receiving hand weeding or no weeding. Hand weeding resulted in similar growth, but higher survival, as not weeding. Little difference in growth and survival was detected in the planting density trial. Physical and chemical analysis of the overburden dump soil showed this site to be a poorer medium for growth than the coastal dunes. This was supported in all analyses by significantly less growth on the overburden dump than on the coastal flat.

Thesis (M.S.)--University of Nevada, Reno, 2008.<br>"May, 2008." Includes bibliographical references (leaves 39-44). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2009]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

The effects of phosphorus fertilization on the growth and survival of Liatris pycnostachya, Physostegia virginiana, and Sporobolus heterolepis seedlings were examined in a prairie restoration project. Treatment included fertilizing once at the time of planting. Plant responses were measured on two soil types, Bono (very high phosphorus levels, lower and flatter) and Morley (very low phosphorus levels, on a slight hill with some slope). P fertilization did not increase the growth of any species on either soil type, although results may have been limited by the effects of surrounding plant competition. Only one significant difference in plant growth was observed between fertilized and unfertilized plots; control Liatris pycnostachya and Physostegia virginiana in the Bono soils produced more shoots than fertilized plants of the same species. P- fertilized Liatris pycnostachya in Morley soil had significantly higher survivorship than unfertilized plants. In contrast, P-fertilized Physostegia virginiana in the Bono soil had the significantly lower survivorship than unfertilized plants. For the other species on either soil type, the survivorship was not significantly different. Because P-fertilization produced very limited benefit, and even adverse plant responses in some cases, the recommendation of this study is that P-fertilization should not be applied at the time of planting of prairie restoration projects.<br>Department of Biology

A demanda por projetos de restauração ecológica, com a utilização de técnicas de plantio total, tem aumentado nos últimos anos, com a consequente necessidade de otimização dos insumos para tal atividade que, além de garantir maior sobrevivência das mudas a campo, é essencial para o setor. Assim, as compensações ambientais, geradas pela obra do trecho sul do Rodoanel Mário Covas (São Paulo), proporcionaram uma importante oportunidade de se realizar alguns estudos nessa temática. O objetivo deste trabalho foi avaliar a taxa de sobrevivência e o crescimento inicial (12 meses), de 30 espécies arbóreas nativas, provenientes de mudas acondicionadas em recipientes com 3 volumes distintos (tubetão 290 cm3, tubetinho 56 cm3 e bandeja 9 cm3), com e sem utilização de hidrogel no plantio, e submetidas às mesmas ações de manutenção. As espécies nativas regionais contemplaram todos os grupos sucessionais (pioneira e não pioneiras), pertencentes a 17 famílias botânicas. Como resultados deste trabalho, pode-se concluir que as espécies provenientes do recipiente tubetão obtiveram as menores porcentagens de mortalidade, seguidas de tubetinho e bandeja, entretanto algumas espécies de bandeja mostraram-se com índices de mortalidade menores, se comparadas a outras espécies provenientes de tubetinhos, apresentando assim possibilidades de uso, desde que adotados manejos diferenciados (irrigação pós-plantio e controle de competidores) visando a garantir o aumento da sobrevivência inicial das mudas. O hidrogel não interferiu no estabelecimento e nem no crescimento das mudas nos diferentes recipientes, para o período em que o experimento foi avaliado. Quanto ao desenvolvimento das mudas em crescimento e incremento de altura, pode-se concluir que, uma vez garantido o estabelecimento das mudas, não houve diferenças entre os recipientes, reforçando que, com manejos diferenciados, os custos da restauração poderão ser significativamente reduzidos, para as situações que exijam como metodologia o plantio total na restauração ecológica de uma dada área.<br>The demand for ecological restorations project, using total planting techniques, has increased in recent years, with the consequent optimizations need of inputs for such activity that, besides increasing the seedlings survival in the field, is essential for the sector. Thus, environmental compensation, generated by the work of the southern section of the Rodoanel Mário Covas (São. Paulo), provided a valuable opportunity to conduct some studies in this area. This studys aim was to evaluate the survival rate and early growth (12 months) of 30 native species from plants in containers packed with three separate volumes (290 cm3 tubetão, tubetinho 56 cm3 and bandeja 9 cm3), with and without hydrogels use at planting, and subordinated to the same maintenance actions. The regional native species, contemplated at all successional groups (pioneer and non-pioneer), belonging to 17 botany families. As a result of this work, we can conclude that species from the container tubetão had the lowest percentage of mortality, followed by tubetinho and bandeja, however some bandeja species have come out with lower mortality rates, compared to other species from tubetinhos, thus presenting use opportunities since different management are adopted (irrigation after planting and control of competitors) in order to guarantee the increase of initial survival of seedlings. The hydrogel did not affect the establishment and neither the growth of seedlings in different containers, during the period in which the experiment was evaluated. Concerning the seedlings development in growth and increase in height, one can conclude that once guaranteed the seedlings establishment of, there were no differences between the containers, reinforcing that with different managements, the restoration costs may be significantly reduced for situations that require the total planting as a methodology in ecological restoration of a given area.

The forest product industry is keenly interested in extending the normal planting season, as well as in the comparative field performance of standard nursery bare-root seedlings and containerized rooted cuttings. The effect of seasonal planting dates on survival, above and belowground biomass allocation, water relations, gas exchange attributes and foliar carbon isotope composition (δ13C) of two stock types of slash pine (Pinus elliottii Engelm.) were examined. Slash pine bare-root seedlings (BRS) and containerized rooted cuttings (CRC) were hand planted in September, November, January, March and April in three consecutive planting seasons (2000-2001, 2001-2002 and 2002-2003) on three sites with silt loam topsoils in southwestern Louisiana. First-year mean survival of CRC across all planting dates and sites was consistently high at 96 to 98%, whereas BRS survival was significantly (P < 0.0001) lower at 59 to 81% and highly variable among study sites and dates through three planting seasons. Generally, there was a negative relationship between soil moisture at the time of planting and first-year survival of BRS planted September through March in 2001-2002 and 2002-2003 planting seasons, whereas the opposite was observed only for BRS planted in April 2002 and 2003. Survival of CRC was affected very little by the variation in soil moisture. Containerized rooted cuttings had higher early above and belowground biomass, and height and diameter than did BRS. However, three years after planting the size differences between stock types disappeared or became negligible. Early size differences among trees planted September through March also decreased after three years, although September trees were tallest. Growth of the April-planted trees was poor compared to trees planted in other months. Late-planted April trees had higher δ13C values, and higher water-use efficiency in the first growing season compared to earlier planted trees. Differences in δ13C values among the planting dates disappeared in the second growing season. Net photosynthesis rates did not differ considerably between stock types or among planting dates in the second and third growing seasons. This study indicates that it is possible to extend the planting season to as early as September and as late as March by using CRC.

Markberedning är vanligt förekommande när återbeskogning skall ske efter en avverkning. Vilken metod som väljs styrs av olika faktorer som t ex markfuktighet, humuslagrets tjocklek och mineraljordlagrets djup. I detta arbete studeras ett försök vid SLU: s försökspark i Siljansfors, ca 20 km SV om Mora. Studien omfattar två olika försöksytor, Sf 284 och Sf 287, planterade med gran (Picea abies) år 2004 respektive 2007. Ståndorten är en moränmark, markfuktighetsklassen är frisk och vegetationstypen är blåbär- och lingontyp och är belägen cirka 210 m.ö.h.  Syftet med denna studie är att utvärdera och jämföra tre olika markberedningsmetoder med avseende på överlevnad och höjdtillväxt hos granplantor (Picea abies) under de första åren efter plantering. Vid plantering utan markberedning och utan kemiskt behandlade plantor är risken för en hög avgång på grund av skador orsakade av snytbagge (Hylobius abietis L.) stor de första åren. De markberedningsmetoder som jämfördes var högläggning, fläckmarkberedning och inversmetoden. Dessa tre metoder jämfördes inbördes samt mot att inte markbereda alls. I det totala samlade plantmaterialet var hälften kemiskt behandlat mot snytbagge. Fördelningen kemiskt behandlat och obehandlat plantmaterial var jämt fördelat i alla försök och upprepningar. I studien ingick också en utvärdering av den så kallade ”kanteffekten”, dvs. effekten av att plantorna sattes närmare än, respektive längre än 10 cm från kanten av den anlagda markberedningsytan. I juli 2009 mättes planthöjd och överlevnad på försöksytorna. Resultatet presenteras som medelvärden i form av stapeldiagram. Överlevnadsgraden höjdes med hjälp av markberedning, permetrinbehandling och val av planteringspunkt i förhållande till humuskant.  Det var framför allt högläggning och inversmarkberedning som gynnade plantornas höjdtillväxt.<br>Soil preparation is common when reforestation occurs after harvesting. Which method is chosen is governed by various factors such as soil moisture, humus layer thickness and depth of mineral soil. An experiment was made at SLU's experimental park in Siljansfors, about 20 km SW about Mora. The study comprises two different experimental areas, Sf 284 and Sf 287, where Picea abies was planted in 2004 and 2007 respectively. The soil is a moraine, the soil moisture class is fresh and the vegetation type is blueberry and lingonberry type. The site is located approximately 210 m above sea level. The purpose of this study was to evaluate and compare three different soil preparation methods regarding to survival and height growth of Picea abies during the first years after planting. In the case of planting without soil preparation and without chemically treated plants, the risk of a high mortality due to the damage caused by pine weevil (Hylobius abietis L.) is high during the first years. The soil preparation methods that were compared were mounding, patch scarification and the inverse method. These three methods were compared to each other as well as to no soil preparation at all. In the total aggregate plant material, half were chemically treated against pine weevil. The distribution of chemically treated and untreated plant material was evenly distributed throughout all trials and repeats. The study also included an evaluation of the so-called "edge effect", i.e. the effect of placing the plants closer than, respectively, longer than 10 cm from the edge of the scarified patch. In July 2009, plant height and survival were measured in the experimental areas. The result is presented as averages in the form of bar charts. The survival rate was increased by soil preparation, permetrin treatment and selection of planting point relative to humus edge. It was above all mounding and inverse soil preparation that favored the height of the plants.

This work helps increasing our general understanding of how plants behave under altered hydrological conditions which occur along rivers regulated by hydropower dams. Usually, natural-real environments are highly unpredictable. Consequently, research based on field data becomes challenging and results may contain uncertainty. Here, an experimental design in a greenhouse is developed. Several measured attributes of selected plant species related to germinability, performance and survival were used as indicators of the impact of watering treatments which mimic hydrological regime spilled through hydropower dams. Specifically, direct effect<img src="https://cdncache-a.akamaihd.net/items/it/img/arrow-10x10.png" /><img src="https://cdncache-a.akamaihd.net/items/it/img/arrow-10x10.png" /> of water availability changes, water fluctuation and water flooding, and indirect effect<img src="https://cdncache-a.akamaihd.net/items/it/img/arrow-10x10.png" /> through derived erosion, were tested. Results benefitted from indoors controlled conditions. They showed significant different responses depending on species and hydrological changes. In general, Helianthus annuus was slightly affected. It deal well flooding conditions, and was comparatively more affected by water fluctuation and stress. Carex and Filipendula species showed the highest sensitivities to flow. They hardly germinated under any water treatment (few germinations under flooding for Carex and few under water fluctuation for Filipendula) and performance was very low for germinates. Betula pubescens was in between. Contrarily to Helianthus, it was severely affected by flooding, and also for water fluctuation. It survived water stress better than Helianthus, but looked unhealthy. All species seeds but Helianthus were highly eroded. However, erosion resulting<img src="https://cdncache-a.akamaihd.net/items/it/img/arrow-10x10.png" /> from water fluctuation was relatively higher than from prolonged flooding. Differing responses are the result of morphological and physiological characteristics of the species which enable them to success under certain stressful conditions, such as water scarcity and anoxia. These results objectively inform about tolerance limits of selected species to key hydrological conditions and are useful for riparian areas management and environmental flows designs.

碩士<br>國立臺灣師範大學<br>生命科學研究所<br>101<br>Plant functional traits are usually defined as morphological and physiological traits of plants that may influence their survival, growth, reproduction and fitness. Identifying key functional traits to predict the survival and growth of plants in a given habitat and provides an effective approach to understand the strategies of resource exploitation. Such understand may serve as a basis to construct community assembly rules. In this study, I applied a trait-based approach to compare the survival and growth of seven shade-tolerant species during their seedling stage in the Kenting karst forest. Niche differentiation among seven intermediate and shade-tolerant species and mechanisms of species coexistence were studied. In this study, three questions were addressed. (1) Which environment factors may cause interspecific differences in seedling survival and growth? Do seedling survival and growth vary with light availability and soil depth? (2) Which functional traits are the best predictors to model seedling survival and growth? (3)Are there trade-offs between seedling survival and growth? This study was carried out in the Kenting Karst Forest Dynamics Plot. Seedling censuses were executed every three months during July, 2007 - January, 2013. The survival status and height of seedlings were measured in 144 seedling plots. Proportional hazard mixed models were used to explore the relationships between seedling survival and various functional traits, such as seed mass and specific leaf area. Seedling growth was analyzed by generalized linear mixed models. Our results indicated that seedlings could survived for 185~469 days on average. The survival intervals were significantly influenced by soil depth and light availability during the dry season. In the survival model, the interactions between species and two environmental factors, light availability and soil depth, were significant. Seedling survival was significantly correlated with seed mass, specific leaf area (SLA) and leaf thickness. Meanwhile, relative growth rates of seedling were significantly correlated with SLA and photosynthetic capacity. This study indicated that interspecific variability in seedling survival was critical for these seven species in Kenting karst forest, which may be highly influenced by light availability during the dry season and soil depth. Such results suggested that soil water availability may be the most critical limiting factor in the karst forest.