Academic literature on the topic 'Trend analyses'

Die Länge der Vegetationsperiode (VP) spielt eine zentrale Rolle für die interannuelle Variation der Kohlenstoffspeicherung terrestrischer Ökosysteme. Die Analyse von Beobachtungsdaten hat gezeigt, dass sich die VP in den letzten Jahrzehnten in den nördlichen Breiten verlängert hat. Dieses Phänomen wurde oft im Zusammenhang mit der globalen Erwärmung diskutiert, da die Phänologie von der Temperatur beeinflusst wird.<br /> <br /> Die Analyse der Pflanzenphänologie in Süddeutschland im 20. Jahrhundert zeigte:<br /> - Die starke Verfrühung der Frühjahrsphasen in dem Jahrzehnt vor 1999 war kein singuläres Ereignis im 20. Jahrhundert. Schon in früheren Dekaden gab es ähnliche Trends. Es konnten Perioden mit unterschiedlichem Trendverhalten identifiziert werden.<br /> - Es gab deutliche Unterschiede in den Trends von frühen und späten Frühjahrsphasen. Die frühen Frühjahrsphasen haben sich stetig verfrüht, mit deutlicher Verfrühung zwischen 1931 und 1948, moderater Verfrühung zwischen 1948 und 1984 und starker Verfrühung zwischen 1984 und 1999. Die späten Frühjahrsphasen hingegen, wechselten ihr Trendverhalten in diesen Perioden von einer Verfrühung zu einer deutlichen Verspätung wieder zu einer starken Verfrühung.<br /> <br /> Dieser Unterschied in der Trendentwicklung zwischen frühen und späten Frühjahrsphasen konnte auch für ganz Deutschland in den Perioden 1951 bis 1984 und 1984 bis 1999 beobachtet werden.<br /> Der bestimmende Einfluss der Temperatur auf die Frühjahrsphasen und ihr modifizierender Einfluss auf die Herbstphasen konnte bestätigt werden. Es zeigt sich jedoch, dass <br /> - die Phänologie bestimmende Funktionen der Temperatur nicht mit einem globalen jährlichen CO2 Signal korreliert waren, welches als Index für die globale Erwärmung verwendet wurde<br /> - ein Index für grossräumige regionale Zirkulationsmuster (NAO-Index) nur zu einem kleinen Teil die beobachtete phänologischen Variabilität erklären konnte.<br /> <br /> Das beobachtete unterschiedliche Trendverhalten zwischen frühen und späten Frühjahrsphasen konnte auf die unterschiedliche Entwicklung von März- und Apriltemperaturen zurückgeführt werden. Während sich die Märztemperaturen im Laufe des 20. Jahrhunderts mit einer zunehmenden Variabilität in den letzten 50 Jahren stetig erhöht haben, haben sich die Apriltemperaturen zwischen dem Ende der 1940er und Mitte der 1980er merklich abgekühlt und dann wieder deutlich erwärmt.<br /> Es wurde geschlussfolgert, dass die Verfrühungen in der Frühjahrsphänologie in den letzten Dekaden Teile multi-dekadischer Fluktuationen sind, welche sich nach Spezies und relevanter saisonaler Temperatur unterscheiden. Aufgrund dieser Fluktuationen konnte kein Zusammenhang mit einem globalen Erwärmungsignal gefunden werden.<br /> Im Durchschnitt haben sich alle betrachteten Frühjahrsphasen zwischen 1951 und 1999 in Naturräumen in Deutschland zwischen 5 und 20 Tagen verfrüht. Ein starker Unterschied in der Verfrühung zwischen frühen und späten Frühjahrsphasen liegt an deren erwähntem unterschiedlichen Verhalten. Die Blattverfärbung hat sich zwischen 1951 und 1999 für alle Spezies verspätet, aber nach 1984 im Durchschnitt verfrüht. Die VP hat sich in Deutschland zwischen 1951 und 1999 um ca. 10 Tage verlängert.<br /> Es ist hauptsächlich die Änderung in den Frühjahrphasen, die zu einer Änderung in der potentiell absorbierten Strahlung (PAS) führt. Darüber hinaus sind es die späten Frühjahrsphasen, die pro Tag Verfrühung stärker profitieren, da die zusätzlichen Tage länger undwärmer sind als dies für die frühen Phasen der Fall ist. Um die relative Änderung in PAS im Vergleich der Spezies abzuschätzen, müssen allerdings auch die Veränderungen in den Herbstphasen berücksichtigt werden.<br /> Der deutliche Unterschied zwischen frühen und späten Frühjahrsphasen konnte durch die Anwendung einer neuen Methode zur Konstruktion von Zeitreihen herausgearbeitet werden. Der neue methodische Ansatz erlaubte die Ableitung verlässlicher 100-jähriger Zeitreihen und die Konstruktion von lokalen kombinierten Zeitreihen, welche die Datenverfügbarkeit für die Modellentwicklung erhöhten.<br /> Ausser analysierten Protokollierungsfehlern wurden mikroklimatische, genetische und Beobachtereinflüsse als Quellen von Unsicherheit in phänologischen Daten identifiziert. Phänologischen Beobachtungen eines Ortes können schätzungsweise 24 Tage um das parametrische Mittel schwanken.Dies unterstützt die 30-Tage Regel für die Detektion von Ausreissern.<br /> Neue Phänologiemodelle, die den Blattaustrieb aus täglichen Temperaturreihen simulieren, wurden entwickelt. Diese Modelle basieren auf einfachen Interaktionen zwischen aktivierenden und hemmenden Substanzen, welche die Entwicklungsstadien einer Pflanze bestimmen. Im Allgemeinen konnten die neuen Modelle die Beobachtungsdaten besser simulieren als die klassischen Modelle.<br /> <br /> Weitere Hauptresultate waren:<br /> - Der Bias der klassischen Modelle, d.h. Überschätzung von frühen und Unterschätzung von späten Beobachtungen, konnte reduziert, aber nicht vollständig eliminiert werden.<br /> - Die besten Modellvarianten für verschiedene Spezies wiesen darauf hin, dass für die späten Frühjahrsphasen die Tageslänge eine wichtigere Rolle spielt als für die frühen Phasen.<br /> - Die Vernalisation spielte gegenüber den Temperaturen kurz vor dem Blattaustrieb nur eine untergeordnete Rolle.<br>The length of the vegetation period (VP) plays a central role for the interannual variation of carbon fixation of terrestrial ecosystems. Observational data analysis has indicated that the length of the VP has increased in the last decades in the northern latitudes mainly due to an advancement of bud burst (BB). This phenomenon has been widely discussed in the context of Global Warming because phenology is correlated to temperatures. <br /> <br /> Analyzing the patterns of spring phenology over the last century in Southern Germany provided two main findings:<br /> - The strong advancement of spring phases especially in the decade before 1999 is not a singular event in the course of the 20th century. Similar trends were also observed in earlier decades. Distinct periods of varying trend behavior for important spring phases could be distinguished.<br /> - Marked differences in trend behavior between the early and late spring phases were detected. Early spring phases changed as regards the magnitude of their negative trends from strong negative trends between 1931 and 1948 to moderate negative trends between 1948 and 1984 and back to strong negative trends between 1984 and 1999. Late spring phases showed a different behavior. Negative trends between 1931 and 1948 are followed by marked positive trends between 1948 and 1984 and then strong negative trends between 1984 and 1999.<br /> This marked difference in trend development between early and late spring phases was also found all over Germany for the two periods 1951 to 1984 and 1984 to 1999.<br /> <br /> The dominating influence of temperature on spring phenology and its modifying effect on autumn phenology was confirmed in this thesis. However,<br /> - temperature functions determining spring phenology were not significantly correlated with a global annual CO2 signal which was taken as a proxy for a Global Warming pattern.<br /> - an index for large scale regional circulation patterns (NAO index) could only to a small part explain the observed phenological variability in spring.<br /> <br /> The observed different trend behavior of early and late spring phases is explained by the differing behavior of mean March and April temperatures. Mean March temperatures have increased on average over the 20th century accompanied by an increasing variation in the last 50 years. April temperatures, however, decreased between the end of the 1940s and the mid-1980s, followed by a marked warming after the mid-1980s. <br /> It can be concluded that the advancement of spring phenology in recent decades are part of multi-decadal fluctuations over the 20th century that vary with the species and the relevant seasonal temperatures. Because of these fluctuations a correlation with an observed Global Warming signal could not be found.<br /> On average all investigated spring phases advanced between 5 and 20 days between 1951 and 1999 for all Natural Regions in Germany. A marked difference be! tween late and early spring phases is due to the above mentioned differing behavior before and after the mid-1980s. Leaf coloring (LC) was delayed between 1951 and 1984 for all tree species. However, after 1984 LC was advanced. Length of the VP increased between 1951 and 1999 for all considered tree species by an average of ten days throughout Germany.<br /> It is predominately the change in spring phases which contributes to a change in the potentially absorbed radiation. Additionally, it is the late spring species that are relatively more favored by an advanced BB because they can additionally exploit longer days and higher temperatures per day advancement. To assess the relative change in potentially absorbed radiation among species, changes in both spring and autumn phenology have to be considered as well as where these changes are located in the year.<br /> For the detection of the marked difference between early and late spring phenology a new time series construction method was developed. This method allowed the derivation of reliable time series that spanned over 100 years and the construction of locally combined time series increasing the available data for model development.<br /> Apart from analyzed protocolling errors, microclimatic site influences, genetic variation and the observers were identified as sources of uncertainty of phenological observational data. It was concluded that 99% of all phenological observations at a certain site will vary within approximately 24 days around the parametric mean. This supports to the proposed 30-day rule to detect outliers. <br /> New phenology models that predict local BB from daily temperature time series were developed. These models were based on simple interactions between inhibitory and promotory agents that are assumed to control the developmental status of a plant. Apart from the fact that, in general, the new models fitted and predicted the observations better than classical models, the main modeling results were: <br /> - The bias of the classical models, i.e. overestimation of early observations and underestimation of late observations, could be reduced but not completely removed. <br /> - The different favored model structures for each species indicated that for the late spring phases photoperiod played a more dominant role than for early spring phases. <br /> - Chilling only plays a subordinate role for spring BB compared to temperatures directly preceding BB.

It seems to be obvious that precipitation has a major impact on greening during the rainy season in semi-arid regions. First results1 imply a strong dependence of NDVI on rainfall. Therefore it will be necessary to consider specific rainfall events besides the known ordinary annual cycle. Based on this fundamental idea, the paper will introduce the development of a rain adjusted vegetation index (RAVI). The index is based on the enhancement of the well-known normalized difference vegetation index (NDVI2) by means of TAMSAT rainfall data and includes a 3-step procedure of determining RAVI. Within the first step both time series were analysed over a period of 29 years to find best cross correlation values between TAMSAT rainfall and NDVI signal itself. The results indicate the strongest correlation for a weighted mean rainfall for a period of three months before the corresponding NDVI value. Based on these results different mathematical models (linear, logarithmic, square root, etc.) are tested to find a functional relation between the NDVI value and the 3-months rainfall period before (0.8). Finally, the resulting NDVI-Rain-Model can be used to determine a spatially individual correction factor to transform every NDVI value into an appropriate rain adjusted vegetation index (RAVI).

The Middle-Late Triassic ∂13Corg trend and the Carnian Pluvial Event C-isotope signature After the Permian/Triassic mass extinction, the Early – lowermost Middle Triassic carbon cycle was extremely unstable (see Figure I for a Triassic Time Scale). The global ∂13Ccarb curve (e.g. Korte et al., 2005) shows a series of large short-term excursions, tentatively associated to a limited biological recovery that characterized this time interval. Carbonate carbon isotopic values seem to stabilize during the Anisian (Middle Triassic), when a Middle – early Late Triassic positive secular trend of 3-4 ‰ begins. This ∂13C rise has been linked to the re-establishment of carbon burial and the re-emergence of coal-swamps (Korte et al., 2005). However, a deeper comprehension of this great ∂13C rise is still necessary: the available data come from carbonates, that reflect the complex marine environment and are very dispersed, then the shape of the curve is not clear. Many questions are open: is the trend really a slow long ∂13C rise or does it rather take place by steps, in one or few short time intervals? If so, which are the causes of these putative steps? Can we observe the same positive shift also in the atmospheric ∂13C? By the end of the Early Carnian (Julian), the ∂13C of carbonates reached already its maximum values of ca. 3.5 ‰ (Korte et al., 2005). However, a short-term climatic episode of late Julian age is documented worldwide at least at tropical latitudes (e.g., Rigo et al., 2007). This episode, known as “Carnian Pluvial Event” or CPE, is characterized by the demise of rimmed carbonate platforms, an increase of coarse terrigenous input, paleosols indicative of a relatively humid climate and a rise of the Carbonate Compensation Depth in the deep Tethys sea. Such characteristics are similar to those of Jurassic and Cretaceous Oceanic Anoxic Events (OAE), that are characterized by significant perturbations of the carbon cycle (Rigo et al., 2007). This work aimed at building a Middle – early Late Triassic ∂13C curve based on terrestrial organic matter (wood, leaves and biomarkers) and testing whether a carbon isotope shift is associated with the CPE. In recent years, researchers have performed C-isotopic analyses of many types of specific structures and compounds exclusively associated with terrestrial land plants, including wood (e.g., Hesselbo et al., 2007), cuticles (e.g., Arens and Jahren, 2000) and pollen (e.g., Jahren, 2004). Plant ∂13C is the result of three fractionation processes of the atmospheric C: 1) fractionation during the photosynthesis, 2) post-photosynthetic fractionation, 3) diagenetic fractionation. Following the Farquhar model (Farquhar et al., 1989), three important factors influence the carbon isotope composition of C3 vascular plant during photosynthesis: 1) physical and biochemical fractionation occurring before and during carboxylation; 2) ecological factors such as water stress (3-6‰ positive shift), nutrients shortage (4‰ negative), light limitation (5-6‰ negative) and temperature (3‰ negative) (Arens et al., 2000); 3) the carbon isotope composition of the atmosphere (∂13Catm). The interplay of these factors produces highly variable carbon-isotope signatures in modern C3 plants and their component parts (wood, cuticles, resin, etc.), with ∂13C values varying from -19‰ to -35‰ (Tipple and Pagani, 2007). Similar variability is to be expected in the fossil record, potentially compromising palaeoclimatic reconstructions based on organic ∂13C. Despite these limitations, Jahren et al.’s (2008) experiments on living plants demonstrate a good correlation in ∂13Catm and ∂13Cplant, and this suggests that carbon isotope values from fossil plants can be used as a proxy for ∂13Catm across a range of pCO2 levels. The study of molecular fossils (biomarkers) is a relatively new frontier for palaeoecology and palaeoclimatology. N-alkanes (normal alkanes; straight-chain saturated hydrocarbons) with chain lengths of C25 - C35 and odd-over-even carbon-number distribution derive from epicuticular waxes of terrestrial higher plants (Peters et al., 2005). These lipids are common in both marine and continental sediments and very resistant to diagenesis. Their C isotope signature has been successfully used to study ∂13C shifts associated with major events such as the P/T mass extinction (Xie et al., 2007) or the Paleocene/Eocene Thermal Maximum (Pagani et al., 2006); to determine the advent of the C4 photosynthetic pathway (Tipple and Pagani, 2007); or to study the relative proportions of C3 and C4 plant material in sediments (Pancost and Boot, 2004, and references therein). ∂13C analysis of n-alkanes partially overcomes issues associate with the large ∂13C range in plants (see above), as they pool together the contribution of Numerous individual plants, and thus have maximum statistical significance. We collected wood, leaves and amber from a number of stratigraphic beds of the Middle - lower Upper Triassic of the Southern Alps (Italy), very rich of plant remains. Wood, leaves and amber were hand picked from disgregated or undisturbed rock, powdered and treated with HCl in order to remove carbonates and pyrite; weighted aliquots of material were analysed for the ∂13Corg. The carbon isotope signatures of separated wood and leaves fragments from the same layers lie in a range of 3-4‰ that is narrower than that expected for modern wood and leaves values (cf. Cernusak et al., 2009), probably due to the loss of some compounds during the diagenesis. Carbon-isotope values of amber vary by 4–5‰, comparable to the range recorded in modern and Cretaceous resins (cf. Stern et al., 2008; Mckellar et al., 2008). Amber seems to better retain the original C-isotope signature (Dal Corso et al., accepted; Roghi et al., in prep.). Moreover, Middle Triassic wood and leaves are offset by ca. 3‰ with respect to Late Triassic ones: Anisian and Ladinian values vary from -27‰ to -23,5‰ ca., instead the Carnian ones show more positive values, from -24‰ to -19,5‰ ca. These data confirm that a ca. 3‰ ∂13Ccarb excursion from Middle to early Late Triassic (Korte et al., 2005) is recorded also by terrestrial organic matter (Dal Corso et al., accepted). Here the first report is presented of a sharp negative ∂13Corg excursion at the onset of the CPE. A ~-4‰ abrupt C isotope excursion is registered by leaf waxes n-alkanes, whereas total organic carbon (TOC) shows a ~-2‰ shift. This shift testifies a rapid injection of CO2 with a light C-isotope composition into the atmosphere. This new dataset confirm the hypothesis that the CPE was a global event. We propose that the C isotope negative shift was triggered by the eruption of the coeval Wrangellia flood basalts with strong consequences for the environments and biosphere (e.g.: demise of carbonate platforms, extinctions and radiations of some of the most important Mesozoic groups).<br>Il Trend isotopico del Carbonio nel Triassico Medio-Superiore e la firma isotopica del “Carnian Pluvial Event” Dopo l’estinzione di massa al limite Permo-Triassico il ciclo del carbonio durante il Triassico Inferiore e il primo Triassico Medio è stato estremamente instabile (vedere figura I per una scala del tempo triassica). La curva del ∂13Ccarb globale (e.g. Korte et al., 2005) mostra una serie di ampie e rapide escursioni dei valori isotopici, probabilmente legate ad un limitato “recovery” biologico. I valori isotopici del carbonio dei carbonati sembra stabilizzarsi durante l’Anisico (Triassico Medio), ove ha inizio un trend secolare positivo del ∂13C pari a circa + 3-4 ‰ che si conclude alla base del Triassico Superiore (Carnico). Questa crescita del ∂13C è stata spiegata con l’aumento del seppellimento di grandi quantità di carbonio organico e il ripristino della deposizione di carbone (Korte VI et al., 2005). Tuttavia, una maggiore comprensione di questo trend isotopico Anisico-Carnico è ancora necessaria: gli isotopiche del carbonio sono stati misurati su carbonati che riflettono un ambiente marino molto complesso e la forma della curva del ∂13C non è chiara poiché i dati sono alquanto dispersi. Molte domande sono ancora aperte: il trend è veramente una lenta e graduale salita dei valori isotopici oppure l’escursione isotopica avviene a gradini, in pochi eventi di breve durata? Possiamo osservare lo stesso trend isotopico in atmosfera? Alla fine del Carnico inferiore il ∂13C dei carbonati raggiunge il suo valore massimo (circa 3.5 ‰, Korte et al., 2005). In questo periodo è stato scoperto un evento climatico, chiamato “Carnian Pluvial Event” (CPE), le cui espressioni biologiche e sedimentologiche sono state documentate globalmente, almeno a paleolatitudini tropicali. Questo episodio è caratterizzato dalla morte delle piattaforme carbonati che orlate nella Tetide Occidentale, l’improvviso ed ingente aumento dell’apporto terrigeno, paleosuoli indicativi di clima relativamente umido e dalla risalita della CCD (Carbonate Compensation Depth) nei bacini profondi della Tetide. Questi connotati rendono il CPE simile agli Eventi Anossici Oceanici (OAE) (Rigo et al., 2007), eventi climatici a scala globale caratterizzati inoltre da una perturbazione del ciclo del carbonio. Questo lavoro ha avuto la finalità di costruire una curva del ∂13C per il Triassico Medio- Superiore basata su analisi di resti fossili vegetali (legni, foglie e biomarker molecolari) e di verificare se una perturbazione del ciclo del carbonio è associata o meno al CPE. Negli ultimi anni l’uso di tessuti fossili di piante superiori, quali legni (e.g. Hesselbo et al., 2007), cuticole (e.g. Arens and Jahren, 2000) a pollini (e..g. Jahren 2004), per misure isotopiche del C organico ha preso via via sempre più piede. La composizione isotopica del carbonio delle piante superiori fossili è il risultato di tre processi di frazionamento a partire dal ∂13C del C atmosferico originale: 1) frazionamento durante la fotosintesi, 2) frazionamento post-fotosintetico, 3) frazionamento “diagenetico”. Secondo il modello di Farquhar (1989), sono tre i fattori principali che controllano il ∂13C delle piante superiori C3 durante la fotosintesi: 1) frazionamento fisico e biochimico prima e durante la carbossilazione; 2) fattori ecologici quali lo stress idrico (che causa uno shift positivo fino al 3-4 ‰), la mancanza di nutrienti (-4 ‰), la limitata esposizione alla luce solare (- 5-6 ‰), la temperatura (- 3 ‰) (Arens et al, 2000); 3) il ∂13C atmosferico. L’interazione di questi fattori ha come conseguenza la grande variabilità di valori che il ∂13C di tessuti di piante superiori attuali C3 (legno, foglie, resine, etc...) può assumere, da -19‰ a -35‰ circa (Tipple e Pagani, 2007). In materiale vegetale fossile una simile variabilità può compromettere e falsare profondamente ricostruzioni paleoclimatiche basate su analisi del ∂13C. Nonostante queste limitazioni, Jahren et al. (2008) hanno dimostrato, con esperimenti in laboratorio ad atmosfera controllata, che esiste un’ottima correlazione tra il ∂13C delle piante a il ∂13C dell’atmosfera in cui queste piante vivono, risultato che rende i resti vegetali fossili potenzialmente degli ottimi proxy per la ricostruzione del ∂13C atmosferico. Lo studio di molecole fossili (biomarker) è relativamente una nuova frontiera nelle paleoecologia e paleoclimatologia. N-alcani (normal-alcani, idrocarburi saturi a catena dritta) con lunghezze comprese fra C25 e C35 a una predominanza di omologhi dispari su pari, derivano dalle cere epicuticolari di piante superiori terrestri (Peters et al., 2005). Questi lipidi sono molto resistenti ai processi diagenetici e molto comuni sia in sedimenti marini che terrestri. Il loro ∂13C è stato usato con successo per studiare perturbazioni isotopiche associate a grandi eventi climatico-biologici del passato, come l’estinzione di massa al limite Permo/Triassico (Xie et al., 2007) o il massimo termico al limite Paleocene/Eocene (Pagani et al., 2006), per definire l’avvento delle piante con via metabolica di tipo C4 (Tipple and Pagani, 2007); o per studiare la proporzione relative di piante C3 e C4 nel passato (Pancost and Boot, 2004). Analisi del ∂13C di n-alcani associati a piante superiori permettono di superare i problemi legati all’alta variabilità del ∂13C di singoli tessuti vegetali poiché le molecole fossili disperse nei sedimenti rappresentano una larga comunità floristica, specialmente se si analizzano sedimenti marini, ed il loro ∂13C costituisce dunque un valore medio che ha un alto valore statistico. Per questa ricerca sono stati campionati legni, foglie e ambre da numerosi livelli del Triassico Medio-Superiore delle Albi Meridionali (Italia), molto ricchi in resti vegetali. Legni, foglie e ambre sono stati saparati manualmente da campioni di roccia integri o sedimenti Late Rethian Norian Carnian ladinian Anisian Olenekian Induan Middle Early TRIASSIC 201.6 204 228 235 241 245 250 251 Fig. I: Triassic Time Scale. Modified after Walker and Geissman, 2009. sciolti, polverizzati e trattati con HCl per rimuovere eventuali tracce di carbonati e pirite; piccole quantità di materiale così trattato sono state dunque analizzate per il ∂13C organico. Il ∂13C di legni e foglie mostra range isotopici tra 3 ‰ e 4 ‰ in ogni singolo livello stratigrafico campionato. Tale range è più limitato rispetto a quanto osservato in legni e foglie recenti (cf. Cernusak et al., 2009), probabilmente perchè durante la diagenesi alcuni composti che costituiscono il legno (cellulosa ed emicellulosa in particolare) vengono rimossi. I valori isotopici dell’ambra, al contrario, variano in un range del 4 ‰, molto simile a quanto misurato in resine recenti e cretaciche (Stern et al., 2008; McKellar et al., 2008). L’ambra dunque sembra conservare meglio l’originale composizione isotopica rispetto ad altri tessuti vegetali fossili (Dal Corso et al., accepted; Roghi et al., in prep.). Legni e foglie del Triassico Medio presentano valori isotopici più negativi di circa il 3 ‰ rispetto al materiale del Carnico (Triassico Superiore): i valori dell’Anisico e del Ladinico variano tra -27 ‰ e -23,5 ‰, mentre quelli del Carnico tra -24 ‰ e -19,5 ‰. Questi dati confermano che l’escursione isotopica secolare, pari a +3 ‰, registrata in carbonati marini e brachiopodi, è stata registrata anche dalle piante superiori terrestri e dunque lo shift isotopico secolare ha interessato il sistema oceani-atmosfera (Dal Corso et al., accepted). Misure del ∂13C della sostanza organica totale (TOC) dei sedimenti, associate ad analisi isotopiche di n-alcani di piante superiori terrestri hanno permesso di scoprire una rapida escursione isotopica negativa associata al Carnian Pluvial Event. In particolare gli n-alcani dispari a catena lunga mostrano uno uno shift del -4 ‰, mentre il TOC uno shift del -2 ‰ circa. Questi dati sono la testimonianza di una rapida iniezione di CO2 con una composizione isotopica “leggera” nell’atmosfera carnica e confermano la natura globale del CPE. Lo scenario che qui si propone per l’interpretazione di questo evento lega indissolubilmente il CPE alla coeva (Furin et al., 2006) eruzione della provincia magmatica di Wrangellia con grandi conseguenze per il clima e la vita (e.g. la morte delle piattaforme carbonatiche e l’estinzioni e la radiazioni di alcuni dei gruppi più importanti nella storia della vita sulla terra).

The value of remote sensing data is particularly evident where an areal monitoring is needed to provide information on the earth's surface development. The use of temporal high resolution time series data allows for detecting short-term changes. In Kogi State in Nigeria different vegetation types can be found. As the major population in this region is living in rural communities with crop farming the existing vegetation is slowly being altered. The expansion of agricultural land causes loss of natural vegetation, especially in the regions close to the rivers which are suitable for crop production. With regard to these facts, two questions can be dealt with covering different aspects of the development of vegetation in the Kogi state, the determination and evaluation of the general development of the vegetation in the study area (trend estimation) and analyses on a short-term behavior of vegetation conditions, which can provide information about seasonal effects in vegetation development. For this purpose, the GIMMS-NDVI data set, provided by the NOAA, provides information on the normalized difference vegetation index (NDVI) in a geometric resolution of approx. 8 km. The temporal resolution of 15 days allows the already described analyses. For the presented analysis data for the period 1981-2012 (31 years) were used. The implemented work flow mainly applies methods of time series analysis. The results show that in addition to the classical seasonal development, artefacts of different vegetation periods (several NDVI maxima) can be found in the data. The trend component of the time series shows a consistently positive development in the entire study area considering the full investigation period of 31 years. However, the results also show that this development has not been continuous and a simple linear modeling of the NDVI increase is only possible to a limited extent. For this reason, the trend modeling was extended by procedures for detecting structural breaks in the time series.

Today, digital development is happening at such a high rate that security is not as prioritized as it should be. When security is prioritized away, there is a high risk that vulnerabilities arise that malicious actors would like to exploit. It can be for accessing sensitive information, financial gain or simply bringing harm. In order for IT-security personnel to be able to more easily prevent and focus efforts on the vulnerabilities that are current today, this study aims to answer the following question: What is the trend of the most prevalent vulnerabilities? What is the trend of product owners with the most vulnerabilities? What is the trend based on the severity linked to the vulnerabilities? What is the trend of the impact on confidentiality, integrity, and accessibility? To answer the questions, a quantitative data analysis was done on the database from the National Vulnerability Database (NVD) together with the dataset from the Common Weakness Enumeration (CWE). The data set from CWE has been used to name and classify the vulnerabilities in NVD. Trends that have been identified in the analysis are as follows: injection, insufficient data authentication and uncontrolled resource consumption are vulnerabilities that have increased percentage every year since 2016. The impact of availability on the reported vulnerabilities declines as a percentage over the years. Vulnerabilities with a high impact on integrity, accessibility and confidentiality has decreased as a percentage.

Thesis: S.M. in Management of Technology, Massachusetts Institute of Technology, Sloan School of Management, 2014.<br>43<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 74-76).<br>This thesis provides a new perspective in trend analysis with the acknowledgement of individuals as carriers of trends and susceptible to influence simultaneously by a trend's perceived significance and by external effects (media, peers, society, etc.), which reshape individuals' trend preferences according to the type, direction, and strength of the stimuli received. Internet trends are considered as elements that carry knowledge that can provoke a shift in actors' behavior, altering their preferences to a new direction because they affect individuals' values and beliefs. If trends can change individuals' behavior and conduct, and later, their preference progression, trends also have the capability to accumulate information on what individuals care about, how their inclinations have changed and towards which new interests they are moving. If products and services have specific aspects that trigger selections of the same products and services by unrelated individuals, this will denote the presence of a unique feature or set of features that acts as a gateway of contact. This work proposes the elaboration of actors' and products' networks to be implemented within Internet systems, to improve current technology that captures and displays users' preference evolution and potential trend formations; since people leave traces of their historic behavior, enabling the observance of relations between their current social and product networks, the newly entered and the ones left behind. Each consecutive preferred product contains information of a new assessment of individuals, expressing further necessities, values, aspirations, and desires. If several individuals point to the same products and services, those similar products and services will be the connection element increasing individuals' level of correlation in relation to the amount of products matched. Moreover, if a trend triggers a new preference, the progression of preferences will contain the sequence of drives and external effects or rather, the record of cultural elements that were involved; information that could be used to forecast the probability of positive reactions towards the trend by other similar individuals who were not following it. Because a trend travels through followers, each follower will be part of a virtual network outlined and materialized by the products and services chosen by them. This thesis suggest the idea that a trend is evidenced through the spontaneous sequence of detection, routing and preference from differentiated actors towards the same product or service, because that concordance shows the existence of a broadly valued aspect and a common-connector element that provokes preference agreements among isolated individuals despite their dissimilarities, allowing Web-based companies to develop and observe social-products networks to understand which trends and features have the potential to be successful, which phenomena are affecting preferences and which remaining users are susceptible to increase the diffusion of the trend..<br>by Ernesto Strazza.<br>S.M. in Management of Technology