Les forêts boréales stockent de grandes quantités de carbone organique et jouent un rôle important dans le climat planètaire. Le climat est étroitement associé à la surface terrestre à travers les flux de gaz à effet de serre, d’énergie et de vapeur d’eau. Dans la zone de pergélisol sporadique nord-américaine, l’affaissement du sol attribuable au dégel provoque l’expansion de milieux humides sans pergélisol remplaçant des forêts avec pergélisol. Cependant, l’étendue spatiale de ces changements et leurs conséquences sur le climat sont inconnues. Dans cette étude, j’analyse les flux turbulents d’un paysage comprenant des forêts boréales et des milieux humides dans la partie sud de la Taïga des plaines, T.N.-O., Canada. J’associe ces flux avec la modélisation d’empreintes de flux, des données satellite, des données paléoécologiques, et des projections climatiques afin de caractériser l’impact des changements de la couverture terrestre sur les interactions entre la terre et l’atmosphère. Dans la Taïga des plaines, la perte de forêt boréale attribuable au dégel est d’une importance égale à celle due aux feux de forêt. La perte de forêt modifie les flux turbulents d’énergie à travers des changements dans les propriétés aérodynamiques et écophysiologiques de la surface terrestre. L’accroissement de l’albédo cause de petites réductions dans la somme des flux turbulents de chaleur sensible (H) et de chaleur latente (LE)). La diminution de la rugosité et l’augmentation de l’humidité de la surface augmentent toutefois LE tout en réduisant H, ce qui mènerait à une baisse des températures estivales et à une augmentation de l’humidité de l’air, d’après des simulations réalisées à l’aide d’un modèle de la couche limite planétaire. Contrairement à l’effet biophysique de refroidissement du climat régional dû à la perte de couvert forestier, l’expansion des milieux humides et l’augmentation des émissions de méthane (CH4) provoque un réchauffement du climat. L’expansion des milieux humides dans la partie sud de la Taïga des plaines entraîne une augmentation des émissions de 0.034 g CH4 m-2 a-1. Les taux d’absorption de CO2 caractéristiques de ces paysages sont trop faibles pour neutraliser le réchauffement du climat dû aux émissions de CH4 d’ici la fin du 21ème siècle. Tout en dégelant rapidement, ces paysages boréaux restent des puits de CO2, absorbant 74 g CO2 m-2 a-1. L’expansion des milieux humides n’affecte pas les émissions nettes de CO2, les changements de la productivité primaire brute (PPB) et de la respiration de l’écosystème (RE) étant d’une magnitude similaire. Les répercussions négligeables sur les flux nets de CO2 sont largement compensées par les répercussions climatiques directes d’un réchauffement de la température de l’air. Un scénario de réchauffement élevé mène à un accroissement de RE dépassant significativement l’accroissement de PPB. Dans la Taïga des plaines, le dégel du pergélisol a donc des répercussions climatiques qui s’opposent aux plans biophysiques et biogéochimiques. Dans un climat plus chaud, le dégel modifie la façon dont les paysages interagissent avec le climat, ce qui souligne la nécessité d’intégrer les changements dans la couverture terrestre attribuable au dégel dans les modèles du système Terre. / Boreal forests store large amounts of organic carbon and are an important component of the regional and global climate systems. Climate and land surface are closely coupled through the land-atmosphere exchange of greenhouse gases, such as CO2 and CH4, and of energy and water vapor. In lowlands of the North American sporadic permafrost region, thaw-induced surface subsidence leads to expansion of permafrost-free wetlands at the expense of boreal forests underlain by permafrost. However, the spatial extent of these land cover changes and their implications for land-atmosphere interactions are unknown. In this study, I analyze eddy covariance flux measurements from an organic-rich boreal forest-wetland landscape in the southern Taiga Plains, NT, Canada. I combine these measurements with flux footprint modeling, satellite remote sensing data, paleoecological records, and downscaled climate projections to characterize how thaw-induced land cover change affects land-atmosphere interactions and climate. In the Taiga Plains ecozone, thaw-induced boreal forest loss currently transforms the composition and structure of the boreal zone in North America and is of equal importance for tree cover dynamics as wildfire disturbance. Forest loss modifies landatmosphere energy fluxes through changes in aerodynamic and ecophysiological land surface properties. On the one hand, increasing albedo decreases total turbulent energy fluxes (i.e., sensible (H) and latent heat (LE) flux), and on the other hand decreasing surface roughness and increasing wetness enhances LE at the expense of H. The resulting maximum summer air temperatures and humidity would be substantially colder (1-2 C) and wetter (2 mmol mol-1) in a hypothetical permafrost-free wetland landscape, as indicated by planetary boundary layer model simulations. In contrast to the regional biophysical climate cooling impact of thaw-induced land cover change, wetland expansion and related increases in landscape CH4 emissions induce a net global biogeochemical climate warming impact. At the current rate of wetland expansion in the southern Taiga Plains of 0.26 % yr-1, landscape CH4 emissions increase by 0.034 g CH4 m-2 yr-1. Typical rates of long-term net CO2 uptake in these landscapes are too small to neutralize the associated climate warming effect until the end of the 21st century. The rapidly thawing boreal forest-wetland landscape still acts as a net CO2 sink taking up 74 g CO2 m-2 yr-1. Wetland expansion does not affect landscape-level net CO2 uptake as changes in gross primary productivity (GPP) and ecosystem respiration (ER) are of similar magnitude. The negligible thaw-induced effects on net CO2 fluxes are contrasted by larger direct climate change impacts of warming air temperatures and reduced incoming shortwave radiation. For a high warming scenario (RCP8.5), increases in modeled ER outpace the increasing GPP significantly. For a moderate warming scenario (RCP4.5), ER and GPP increase are of similar magnitude. Thaw-induced land cover change in the Taiga Plains causes thus biophysical and biogeochemical climate impacts of opposite sign and at contrasting scales of impacts (regional vs. global). In an increasingly warmer climate, thawing permafrost alters how boreal landscapes interact with climate highlighting the need to incorporate thaw-induced land cover changes into global Earth system models.

As a result of increase in global average surface temperature, abnormalities in different hydroclimatic components such as evapotranspiration, stream flow and precipitation have been experienced. So investigation has to be carried out to assess the hidden abnormality subsisting in the hydroclimatological time series in the form of trend. This thesis broadly consists of following four parts. The first part comprises of a detailed review of various trend detection approaches. Approaches incorporating the effect of serial correlation for trend detection and interesting developments concerning various non parametric approaches are focused explicitly. Recent trends in annual, monthly, and seasonl (winter, pre-monsoon, monsoon and post-monsoon) Tmax and Tmin have been analyzed considering three time slots viz. 1901-2003, 1948-2003 and 1970-2003. For this purpose, time series of Tmax and Tmin of India as a whole and for seven homogeneous regions, viz. Western Himalaya (WH), Northwest (NW), Northeast (NE), North Central (NC), East coast (EC), West coast (WC) and Interior Peninsula (IP) were originally considered. During the last three decades significant upward trend in Tmin is found to be present in all regions considered either at annual or seasonal level. Sequential Mann Kendall test revealed that most of the significant upward trends both in Tmax and Tmin began after 1970. The second part discusses about numerous climate models from both Coupled Model Inter comparison Project-5 and 3 (i.e. CMIP5, CMIP3) and their skills in simulating Indian climate and assessing their performance using various evaluation measures. Performances of climate models were evaluated for whole of India and over all the individual grid points covering India. The newly defined metric symbolized as Skill_All is an intersection of the three metrics i.e. Skill_r, Skill_s and Skill_rmse, is used for overall model evaluation analysis. A notable enhancement of Skill_All for CMIP5 over CMIP3 was found. After overall model evaluation study, Compromise Programming, a distance based decision making technique, was employed to rank the GCMs gridwise. Entropy method was employed to obtain weights of the chosen indicators. Group decision making methodology was used to arrive at a consensus based on the ranking pattern obtained by individual grid points. In the third part, a detailed detection and attribution (D&A) analysis is performed to determine the causes of changes in seasonal Tmax and Tmin during the period 1950-2005. This formal D&A exercise helps in providing better insight (than trend detection analysis) into the nature of the observed seasonal temperature changes. It was noticed that the emergence of observed trend was more pronounced in Tmin compared to Tmax. Although observed changes were not solely associated with one specific causative factor, most of the changes in Tmin are above the bounds of natural internal climate variability. Finally in the fourth part, to understand the climate change impact on the hydrological cycle, a spatiotemporal change detection study of potential evapotranspiration (PET) along with Tmax and Tmin over India has been performed. Climatology patterns for PET confirmed a greater PET rate during the month of March, April, May and June. A significant increasing trend in both Tmax and Tmin (Tmin being more) was observed in more number of grid points compared to PET. Significant positive trends in Tmax, Tmin and PET were observed over most of the grid points in the IP region. Heterogeneities existed in the spatiotemporal variability of PET over all India. This spatio-temporal change detection study would be helpful for present and future water resources management.

Evapotranspiration is a nexus for planetary energy and carbon cycles, as yet poorly constrained. Here I use stable isotopes of oxygen and hydrogen to partition flux of water due to plant transpiration from the direct evaporative flux from soils, water bodies and plant. The study areas, Langat and Kelantan watersheds represent examples of domains dominated by the respective Southwest and Northeast monsoons on the two sides of the main orographic barrier (Titiwangsa mountain range). Mean annual rainfall for the Langat watershed, obtained from 30 years of hydrological data, is 2145 ± 237 mm. Tentatively, 48% of this precipitation returns to the atmosphere via transpiration (T), with 33% partitioned into discharge (Q), 8% into interception (In), and 11% into evaporation (Ed). In the Kelantan watershed, the mean annual rainfall, also based on the 30 year hydrological data, is 2383 ± 120 mm. Similar to Langat, the T accounts for 43% of precipitation (P), 45% is discharged into South China Sea (Q), 12% partitioned into interception (In) and tentatively 0% for evaporation (Ed). Ed for the Langat watershed represents only a small proportion in terms of volumetric significance, up to almost ~11% with strong effect on the isotopic fingerprints of waters associated with the summer Southwest Monsoon (SWM). Note, however, that insignificant Ed for the Kelantan watershed may be an artefact of rain and river water sampling at only coastal downstream portion of the watershed. High humidity (80%) also was recorded for the Malaysian Peninsula watershed. T appropriates about half of all solar energy absorbed by the continents, here ~1000*103 g H2O m-2 yr-1 similar to other tropical regions at 900-1200*103 g H2O m-2 yr-1. The associated carbon fluxes are ~ 1300 g C m-2yr-1, independent of P. Vegetation responses to solar irradiance, via T and photosynthesis reflects the importance of stomatal regulation of the water and carbon fluxes. In order to maintain high transpiration in the tropical region, “constant” water supply is required for continuous pumping of water that delivers nutrients to the plant, suggesting that water and carbon cycle are co-driven by the energy of the sun. The existence of the water conveyor belt may be precondition for nutrient delivery, hence operation of the carbon cycle. Potentially, this may change our perspective on the role that biology plays in the water cycle. In such perspective, the global water cycle is the medium that redistributes the incoming solar energy across the planet, and the anatomical structures of plants then help to optimize the loop of energy transfer via evaporation and precipitation in the hydrologic cycle. The main features of aquatic geochemistry of the Langat and Kelantan rivers inferred from the Principal Component Analysis are controlled by three components that explain 80% and 82% of total variances. These components are reflecting of the geogenic factor with superimposed pollution, the latter particularly pronounced in urbanized sections of the Langat river and dominant in downstream of the Kelantan river. There is no correlation between seasonal variations in major ion chemistry and environmental variables such as precipitation, discharge, temperature or solar activity.

Introduction is focused on analyze green roof like a part of buiding construction, when thesis assembly principles of right proposal green roof layers. Main part describes characteristic properties green roofs at global impact. We get some added values after comparison with classic roof types. Master thesis consists of survey of added values of green roofs in these categories: life cycle assessment, microclima, outdoor climate, water retention. End of thesis devote to psychological effect of green roofs include questionnare about relationship between czech society and green roofs.

Au cours des dernières décennies, une grande variété de pesticides émergents, tels que le chlorantraniliprole (CAP), ont été introduits malgré le manque de connaissance approfondie de leur risque écotoxicologique. Les marais filtrants (TW) sont des technologies écologiques et durables qui ont montré un grand potentiel d’atténuation des polluants agricoles communs, tels que les pesticides dans le ruissellement. L’objectif de cette étude était d’optimiser l’utilisation du marais filtrant sous-surfacique à écoulement horizontal (HSSF) en déterminant: a) l'effet d’un amendement de biochar au substrat et b) la performance de trois espèces de macrophytes (Phragmites australis subsp. americanus, Scirpus cyperinus et Sporobolus michauxianus) dans l'abattement du CAP du ruissellement agricole. L'efficacité d'abattement a été calculée en utilisant la méthode du bilan de masse dans des mésocosmes HSSF matures alimentés avec un ruissellement agricole synthétique contenant du CAP pendant une période d'un mois. Les mésocosmes avec l’ajout de biochar se sont avérés très efficaces dans l’abattement du CAP (90 à 99%) et ils le sont restés tout au long de la période expérimentale. Cette efficacité est probablement due à la grande capacité d’adsorption du biochar, bien que ce mécanisme n’ait pas été directement mesuré. En revanche, l'abattement du CAP dans les mésocosmes plantés sans biochar était faible et limité et il n’y avait pas de différence entre les espèces, bien qu’elles aient eu des différences dans leur biomasse aérienne et leur taux d'évapotranspiration (ET). Cependant, les traitements plantés ont agi comme zone tampon, en atténuant la masse du CAP de l'influent et en la libérant lentement dans l'effluent. Le taux d'ET de Scirpus et Phragmites était plus élevé que celui de Sporobolus, ce qui s’est traduit par un meilleur effet tampon. Cette étude suggère que l'ajout de biochar au substrat HSSF TW est prometteur pour l'atténuation du CAP dans le ruissellement agricole, mais leur efficacité à long terme reste à être étudiée. Malgré tout, les TW devraient être utilisés comme un outil complémentaire, dans le cadre d'actions plus larges visant à réduire la pression des polluants sur les écosystèmes aquatiques. / Over the past decades, a wide variety of emergent pesticides, such as chlorantraniliprole (CAP), have been introduced despite the lack of in-depth knowledge of their ecotoxicological risk. Treatment wetlands (TWs) are environmentally friendly and sustainable technologies that have shown great potential to mitigate common agricultural pollutants, such as pesticides in runoff. The objective of this study was to optimize the use of the horizontal subsurface flow treatment wetlands (HSSF TWs) by determining a) the effect of biochar amendment to the substrate and b) the performance of three species of macrophytes (Phragmites australis subsp. americanus, Scirpus cyperinus and Sporobolus michauxianus) in CAP removal from agricultural runoff. The removal efficiency was calculated using the mass balance method in mature HSSF mesocosms fed with synthetic agricultural runoff containing CAP for a period of one month. Mesocosms with the addition of biochar were very effective in removing CAP (90-99%) and remained so throughout the experimental period. This efficiency is likely due to the high adsorption capacity of biochar, although this mechanism has not been directly measured. In contrast, CAP removal in mesocosms planted without biochar was low and limited and there was no difference between species, although there were differences in their above-ground biomass and their evapotranspiration (ET) rate. However, the planted mesocosms acted as buffer zones, reducing the CAP mass of the influent and slowly releasing it into the discharge. The ET rate of S. cyperinus and P. australis was higher than that of S. michauxianus, resulting in a better buffering effect. This study suggests that adding biochar to the HSSF TW substrate is promising for CAP attenuation in agricultural runoff, but their long-term effectiveness remains to be investigated. Nevertheless, TWs should be used as a complementary tool, as part of wider actions aimed at reducing the pressure of pollutants on aquatic ecosystems.