Academic literature on the topic 'Heather moorlands'

Outbreaks of winter moth, Operophtera brumata L. (Lepidoptera:Geometridae), have recently become common on moorlands in Scotland. This thesis describes the ecology of moorland O. brumata populations, and tests the hypothesis that outbreaks are caused by increased host-plant quality. The principal moorland host, Calluna vulgaris (L.) Hull, common heather, is of low nutritional quality for O. brumata. Experimental nitrogen-enrichment of C. vulgaris enhances O. brumata development, although there is no evidence that outbreaks occur on nitrogen-enriched C. vulgaris in the field. Calluna vulgaris nutritional quality is not significantly affected by growth in carbon dioxide-enriched atmospheres. There is no evidence that moorland O. brumata populations are specialised to feeding on C. vulgaris, and no evidence that synchrony between larval emergence and C. vulgaris budburst affects larval survival and development. Compensatory feeding may enhance the ability of O. brumata to utilise C. vulgaris. Life history and metabolic differences are shown between moorland and non-moorland O. brumata populations. These differences are best explained as physiological adaptations to local climate, and are unlikely to be caused by nutritional specialisation of O. brumata populations to different hosts. Evidence is presented that winter weather conditions strongly affect O. brumata abundance in high-altitude moorland outbreak sites, and that O. brumata escapes from parasitism at such sites. The relative importance of "top-down" factors, such as natural enemies, and "bottom-up" effects, such as host quality, in determining O. brumata abundance is discussed. It is argued that, in high-altitude moorland sites, the interaction between winter weather conditions and the "top-down" effect of natural enemies is a more important determinant of outbreak potential than the "bottom-up" effect of host quality. The effects of future environmental changes on this system are considered.

For roughly the past 200 years land-managers have used the practice of “muirburning” to manipulate the structure of heather (Calluna vulgaris) to create a patchwork of habitat structures able to provide forage and nesting sites for red grouse (Lagopus lagopus scoticus) as well as grazing for sheep (Ovis aries) and red deer (Cervus elaphus). This thesis investigates both the behaviour and impact of management fires in recognition of the need to develop multi-aim land management practices that ensure both continued productivity and protection of biodiversity in the face of climatic and environmental change. Fuel structure and loading are crucial controlling factors on both fire behaviour and impact governing both rate of spread and heat release to the ground surface. A visual obstruction method is developed that estimates total and fine fuel loading as well as the structure of the heather canopy. In order to adequately understand fire impact a dimensional analysis approach is taken to estimating the mass of burnt heather stems. Experiments at a number of spatial and temporal scales relate variation in heather fuel moisture content to stand structure and variation in weather conditions. Monitoring shows moisture contents to be relatively stable temporally, but spatially variable. Periods of extreme low moisture contents in early spring are associated with frozen ground, winter cuticle damage and physiological drought. Such conditions may have contributed to the large number of wildfires in 2003. A replicated plot design was used to investigate the effect of weather conditions and fuel loading on fire behaviour. An empirical approach is taken to fire behaviour modelling with equations describing rate of spread and fireline intensity being developed on the basis of fuel structure descriptors and windspeed. The theoretical negative correlation between fuel bed density and rate of spread is demonstrated to hold true for heather stands, while the impact of heterogeneity in fuel bed structure is also investigated. Redundancy Analysis is used to investigate the influence of multiple predictors on a number of aspects of fire behaviour including: rate of spread, fireline intensity, flame length and ground surface heating. Data from this and previous studies are used to ground-truth a number of fire behaviour prediction systems including BehavePlus and the Canadian Fire Behaviour Prediction System. Finally linkages between fire behaviour, fire severity and heather regeneration are investigated. A number of proxy measures of ‘Immediate Severity’ are tested and used to examine the influence of fires on plant regeneration. The post-fire development of stands is shown to relate primarily to stand age and structure before burning, and to post-fire substrates rather than variation in fire behaviour and severity.

Heather moorlands are of great ecological value and as such are recognised as internationally important habitats. A large proportion of European heather moorland is concentrated within the UK, covering approximately 2-3 million ha" of the UK upland environment. Enhanced levels of N pollution have led to concerns about the eutrophication of many natural and semi-natural ecosystems in the UK, including heather moorland. This study aimed to investigate the response of a moorland ecosystem to artificially enhanced N deposition and the interaction of P with increasing N input. A further aim was to investigate the potential for moorland ecosystem recovery from enhanced N deposition. The research presented within this thesis was part of an ongoing long-term N manipulation experiment established in 1989 on a heather moorland in Wales. This study focussed on a N manipulation experiment established at the site in 1998, where N was added at treatment levels of 0, 10,20,40 and 120kg ha" yr". In addition to this there were Nand P combination treatments, with P added at a rate of 20kg ha" yr". A N recovery experiment was established on the 1998 experimental plots, whereby treatment with N to one half of each plot ceased in 2003, in order to investigate potential for recovery from enhanced N deposition. Cal/una vulgaris growth was stimulated by increasing total N input as was the foliar N concentration. The stimulation of C. vulgaris growth indicates that this species was N limited at ambient levels of deposition. Bryophyte and lichen frequency and cover and bryophyte species diversity were significantly reduced by artificially enhanced N deposition. The foliar N concentration of the dominant moss species Hypnum jutlandicum was elevated with increasing N input. Peat and litter nutrient levels also responded positively to N input, with significant increases in N concentration and exchangeable N. The increase in exchangeable N with N addition demonstrates the increase in bio-available N with enhanced N deposition in moorland ecosystems. The P acquiring enzyme phosphatase and the lignin degrading enzyme phenol oxidase showed no consistent response to N input. The different components within the moorland ecosystem showed varying levels of N, P or N and P co-limitation. The dominant plant species C. vulgaris was clearly N limited at ambient levels of N deposition, as indicated by significant growth stimulation and foliar N accumulation with increased N input. However, P addition did cause a positive growth response in this species, albeit weaker than the response to N input, suggesting a certain degree of Nand P co-limitation. The bryophyte and lichen community were clearly P limited, with P addition significantly increasing bryophyte and lichen frequency and species diversity. Soil microorganisms also displayed some evidence of P limitation as the addition of P, even at ambient N deposition, significantly reduced the activity of phosphatase. The moorland showed little evidence of recovery 2 years after N treatment had ceased. However, there was a significant reduction in litter exchangeable NH4, C. vulgaris total foliar N concentration and C. vulgaris shoot extension. Liverwort cover had increased in those plots where N treatment had ceased. The data from the N recovery experiment suggests that although there was some evidence of recovery, the legacy of N deposition to the experiment may persist for some time. A regional survey in 2005 of moorland sites in Scotland, Wales and the Peak District, was used to investigate whether any of the responses to artificially enhanced N deposition at the N manipulation experiment could be used as bio-indicators of N deposition at a regional scale. Of the bio-indicators tested, litter exchangeable Nand C. vulgaris N:P ratio showed a significant positive association with modelled N deposition. A significant negative association was observed between litter phenol oxidase activity, bryophyte species richness and N deposition. Litter total N concentration and phosphatase activity and C. vulgaris and H. jutlandicum total foliar N concentration did not have a significant association with N deposition. The potential bio-indicators identified are from varying components of the moorland ecosystem (i.e. soil system, bryophytes and C. vulgaris) and consequently may not only provide an indication of ecosystem N status but also overall moorland health in response to varying levels of N deposition.

The utilisation of heather moorland by red grouse Lagopus lagopus scoticus was studied with particular emphasis on the influences of vegetation structure on grouse behaviour at a series of spatial scales, from the choice of location within individual heather stands up to the composition and alignment of territories on the moor. A novel method of measurement and multivariate statistical analysis was developed for quantifying the structure of vegetation dominated by ling heather Calluna vulgaris. The method was assessed in relation to existing subjective classifications. The method revealed that gaps in the canopy of tall heather were utilised by grouse during the daytime in winter. The manner in which grouse exploit the vegetation types available in their territories was determined by radio-tracking a population on a managed grouse moor in north-east Scotland over the course of two years. During autumn and winter, territorial grouse showed a preference for tall heather relative to its availability. In spring, a greater use was made of heterogeneous mixtures of heather and graminoids during the daytime, and, to some extent, of shorter heather during the intensive feeding periods at dawn and dusk. Hens showed a very strong affinity for edge between heather stands in spring, but spent more time on the side offering the greater cover. Broods tended to range in areas with more old heather and more edge than generally available, but within their ranges, they clearly preferred heterogeneous areas. The relationships between vegetation patterns, the composition of territories and the alignment of territory boundaries were investigated using fifteen years' historical data. The relationships varied considerably between years. When the population was declining, heather edge was distributed evenly between territories, but it was distributed unevenly during population increase. In general, territory alignment showed a greater association with vegetation edges than with particular types of vegetation.

This study contributes to the understanding of spatial aspects of plant-herbivore interactions within a grazed grass-shrub mosaic in heather moorland, an internationally important ecosystem dominating much of the Scottish uplands. A three-year field experiment was conducted to observe plant-herbivore interactions between Scottish Blackface sheep and heather-grass mosaics. Modelling tools were used for virtual experiments, thus complementing and extending the field data. The experiment showed the importance of a spatially explicit approach to understanding the interactions. The pattern of use of the vegetation mosaics by sheep was strongly heterogeneous, with spatially limited areas of intensive use intermixed with large areas of extensive use. Foraging and ruminating behaviour showed distinctively different patterns of impact, indicating that multiple processes determined herbivore of vegetation mosaics and their concomitant impacts on the dynamics of the vegetation. Application of a spatial interaction model, previously used in human geography, to the field data revealed that the amount of grass in an area was a good predictor of the local heather defoliation. Heather defoliation was highest near large grass patches and lowest away from small grass patches. The virtual experiment showed further that cognitive aspects of foraging behaviour could play an important role in determining the pattern of use by herbivores. Performance of foraging strategies was strongly affected by the heterogeneity of the vegetation, suggesting that herbivores could adapt their foraging strategies depending on the pattern of vegetation. This study provides new insights into the spatial aspects of plant-herbivore interactions in grass-shrub mosaics and offers a starting point for more detailed investigations. At the same time the results necessitate the increased use of spatially explicit approaches in the management of grazed ecosystems.

Concerns have been raised on the deterioration of heather moorland due to management in the UK. A study was therefore conducted on the impacts of moorland management on the soils and hydrology of a catchment on Dartmoor. Soil moisture was measured gridwise using TDR on 19 occasions. At 23 sites within this grid, physical properties of the topsoil were obtained. At three locations, tensiometer nests were installed, recording soil suction at 10 cm depth intervals. At the catchment scale, stream discharge and rainfall were recorded. Grazing densities within the watershed were estimated and the observed patterns were related to vegetation types. Results from the TDR grid showed that in dry conditions, soil moisture patterns are heterogeneous in contrast to a more uniform pattern in wet periods. A threshold soil moisture content of about 0.60 cm3 cm-3 divides the two conditions. The exponential relationship between average hillslope soil moisture content and stream discharge also revealed the division between wet and dry states. A regression analysis showed that during dry conditions, the vegetation plays a significant role in determining the soil water status. During wet conditions, topography becomes more important. In these conditions, the soil water movement is mainly lateral, whereas in the dry state, this is vertical in the soil profile. Tensiometer data showed that most soil water movement is in the topsoil. Analyses suggested that soil moisture under vegetation classes associated with higher grazing pressures is higher in similar topographic conditions. Soil bulk density is higher and the total porosity is lower near the soil surface. This suggests that less rainfall is required to reach the soil moisture threshold and water will be transported laterally down the slope. A heather burning experiment revealed that the direct effect of temperature is shallow. Soil moisture levels do not change over the course of the burn. However, in dry situations during summer, soil moisture contents under burned plots are higher than under unburned vegetation probably due to reduced transpiration. If this effect is similar at the hillslope scale, when the soil is wetting up, the soil moisture threshold value could be reached at an earlier stage and accelerated lateral water movement could be the result. It can be concluded therefore, that moorland management could accelerate water movement on the hillslopes causing higher discharge peaks in wet periods and consequently low flows in summer. However, the effects are subtle and encouraging vegetation heterogeneity could play a role in buffering water to prevent loss to the stream.