As pastagens ocupam a maior parte da área agrícola e contribuem com a segunda e a quinta atividades que compõem o PIB agropecuário brasileiro, a carne e o leite. A crescente utilização da irrigação de pastagens surgiu primordialmente em áreas leiteiras, juntamente com processos que aprimoram a produção, e posteriormente espalhou-se por áreas de gado de corte. Assim surge a necessidade de um manejo adequado da irrigação de pastagens, e é fundamental conhecer sua evapotranspiração, seus limites produtivos e suas caracteristicas nesse processo de intensificação. Portanto, o objetivo deste trabalho foi determinar o consumo de água, os valores do coeficiente de cultura (Kc) e os parâmetros produtivos e biométricos de duas gramíneas tropicais (Panicum maximum cv. Mombaça e Cynodon spp.), em cultivos exclusivos e consorciados em sobressemeadura com aveia preta e azevém. Como objetivos secundários, buscou-se: (i) medir os parâmetros biométricos de altura do dossel forrageiro (ADF) e indice de area foliar (IAF) entre os ciclos identificando o melhor período de corte, (ii) estimar o acúmulo médio de graus dias de desenvolvimento (GDD) nas diferentes estações do ano correlacionando com o crescimento das forrageiras, (iii) estimar o consumo de água das plantas com a sonda FDR Diviner 2000® e correlacionar seus dados com o consumo de água medido em lisímetros de pesagem. O estudo foi realizado na Escola Superior de Agricultura \"Luiz de Queiroz\" (ESALQ/USP) em Piracicaba-SP (Latitude 22°42\'14\"S; Longitude 47°37\'24\"O; Altitude de 569 m). Os experimentos foram conduzidos de março de 2015 a fevereiro de 2017, com delineamento experimental de blocos ao acaso com 4 tratamentos: 1- capim Mombaça em cultivo exclusivo, 2- capim Mombaça em cultivo sobressemeado com aveia e azevém, 3 - Cynodon spp em cultivo exclusivo; 4 - Cynodon spp em cultivo sobressemeado com aveia e azevém. Foram utilizados a aveia preta (Avena strigosa) cv. Embrapa 29 (Garoa) e azevém (Lolium multiflorum) cv. Fepagro São Gabriel. As calibrações dos métodos de lisimetria e da sonda FDR (Diviner 2000®) apresentaram bons ajustes, com altos coeficientes de correlação. Os resultados de consumo de água pelas gramíneas mostraram uma grande variação por período e dentro dos ciclos com grandes consumos de água, obtendo vários valores de Kc maiores que 1. Foram obtidas boas correlações entre crescimento, IAF e acúmulo de graus dias (GDD). Os valores acumulados de evapotranspiração de cultura (Kc) obtidos com o sensor FDR foram maiores que os medidos nos lisímetros. Os resultados detalhados encontram-se no desenvolvimento de cada capítulo deste trabalho. / Pastures represent the largest part of the agricultural area and contribute to the second and fifth activities that make up the Brazilian GPD, meat and milk. The increasing use of pasture irrigation primarily arose in dairy areas, along with processes that improve the production, and subsequently reache areas of beef cattle. Thus, there is a need for an adequate irrigation management, and it is fundamental to know the crop evapotranspiration of pastures, their productive limits and their characteristics in this intensification process. Therefore, this work aimed to determine the crop water consumption, the values of crop coefficient (Kc), and the productive and biometric parameters of two tropical grasses (Panicum maximum cv. \'Mombasa\' and Cynodon spp.) single cropped and intercropped in oversseeding with black oats and ryegrass . As secondary goals, it sought: (i) measuring the biometric parameters of forage canopy height (ADF) and leaf area index (LAI) between the cycles, identifying the best cutting period; (ii) estimating the mean accumulation of degree-days of development (GDD) in the different seasons, correlating them with forage growth; (iii) estimating the crop water consumption with the FDR probe Diviner 2000® and correlating its data with the crop water consumption measured on weighing lysimeters. The study was carried out at the \"Luiz de Queiroz\" College of Agriculture (ESALQ/USP), at Piracicaba, SP (Latitude 22°42\'14\"S; Longitude 47°37\'24\"W; Altitude de 569 m a.s.l.). The experiments were conducted from March 2015 to February 2017, with a randomized complete block design with 4 treatments: 1 - single cropped \'Mombasa guinea grass ; 2- \'Mombasa\' guinea grass intercropped with oats and ryegrass; 3 - single cropped Cynodon spp.; 4 - Cynodon spp. intercropped with oats and ryegrass. The winter forages were black oats (Avena strigosa) cv. Embrapa 29 (Garoa) and ryegrass (Lolium multiflorum) cv. Fepagro São Gabriel. The calibrations of the lysimeters and the FDR probe had good adjustments, with high correlation coefficients. The results obtained of crop water consumption by the grasses showed a great variation by period and inside the growing cycles with great water consumption, often obtaining Kc values above 1. Good correlations were obtained between crop growth, LAI and degrees-days accumulation (GDD). The accumulated values of crop coefficient (Kc) were higher with the FDR sensor than with the lysimeters. The detailed results can be found in the chapters of this work.

A evapotranspiração pode ser responsável por mais da metade da saída de água de uma bacia hidrográfica, sendo uma variável importante para o balanço hídrico e para a estimativa da recarga. Nesse sentido, objetivou-se com este trabalho analisar a evapotranspiração de referência (ETo) e real (ETr) para a região de Jaboticabal-SP, assim como verificar a influência da umidade do solo na evapotranspiração. A variação da evapotranspiração de referência foi estudada a partir da interpretação de dados de uma bateria de seis lisímetros de drenagem (EToLis) e estimativas teóricas por três equações diferentes disponíveis na literatura (Tanque Classe A, Thornthwaite e Penman Monteith FAO 56 utilizando a radiação solar global estimada, observada e todas as variáveis observadas). A evapotranspiração real foi obtida por meio de dados de uma bateria de três lisímetros operando em condições reais de campo e a partir do balanço hídrico seqüencial de Thornthwaite e Mather (1955) utilizando a evapotranspiração de referência obtida pelos três modelos teóricos. Outros três lisímetros receberam irrigações esporádicas e obtiveram-se outros valores de evapotranspiração, a fim de comparar o comportamento da evapotranspiração sob três disponibilidades de água no solo. A análise estatística de correlação indica que as estimativas da ETo por equações teóricas comparadas à EToLis medida em lisímetro de drenagem não apresentaram bons índices de comparação e erro. Admitindo que a operação dos lisímetros não permitiu a determinação da ETo com boa confiabilidade, comparou-se os métodos com a equação de Penman Monteith FAO 56 utilizando todas as variáveis observadas. Observou-se ótima correlação entre a equação de Penman Monteith FAO 56 com os modelos utilizando a radiação solar global observada e estimada e com o Tanque Classe A. No tocante à evapotranspiração real, houve boas correlações entre os valores medidos pelos lisímetros e os valores estimados pelo balanço hídrico de Thornthwaite e Mather. Melhor correlação foi verificada quando se utilizou o valor da CAD calculada em função dos parâmetros físicos do solo. Os valores de ETr obtidos através do balanço hídrico utilizando a ETo estimada por Penman Monteith utilizando a radiação solar global observada apresentou a melhor correlação com os dados lisimétricos. Com relação à variação de umidade do solo, verificou-se um comportamento distinto entre as evapotranspirações observando um aumento da ET de acordo com o aumento do número de irrigações. / The evapotranspiration can be responsible for more than the half of the water that leaves a watershed, being an important variable for the water balance and for estimating the recharge. In this direction, the objective of this study was to analyse the reference (ETo) and actual (ETr) evapotranspiration for the region of Jaboticabal-SP, Brazil, as well as to verify the influence of the soil water content in the evapotranspiration. The variation of the reference evapotranspiration was studied based on data of a battery of six drainage lysimeters (EToLis) and tree different theoretical models were used (Tanque Classe A, Thornthwaite and Penman Monteith FAO 56 using the estimated and observed global solar radiation and all the variables observed). The actual evapotranspiration data were obtained from a battery of three lysimeters operating in real field conditions and from the water balance of Thornthwaite and Mather (1955), using as reference evapotranspiration the values from the three theoretical models. Others three lysimeters received irrigation sporadically and others values of evapotranspiration were measured, in order to compare the behavior of the evapotranspiration under three availabilities soil water content. The statistical correlation analysis indicates that the estimates of ETo from theoretical equations compared to the EToLis measured in lysimeter of draining did not present good indices of comparison and error. Aware that the operation of the lysimeters did not allow the determination of the ETo with good trustworthiness, one compared the methods with the equation of Penman Monteith FAO 56 using all the observed variables. An excellent correlation was observed between the equation of Penman Monteith FAO 56 with the models using observed global solar radiation and estimated and with Tanque Classe A. Regarding actual evapotranspiration, there were good correlations between the values measured for the lysimeters and the estimated values for water balance of Thornthwaite and Mather. The values of ETr through the water balance using the ETo esteem for Penman Monteith using the observed global solar radiation presented the best correlation with the lisimeters data. Regarding to the variation of soil water content, a distinct behavior was verified between the evapotranspirations in accordance with observing an increase of the ET the increase of the irrigation number.

Phenomenological models are presented which predicts transpiration rates (E) of individual leaves of Scaevola plumieri, an indigenous dune pioneer, and Ammophila arenaria, an exotic grass species introduced to stabilise mobile sand. In both cases E is predictably related to atmospheric vapour pressure deficit (VPD). VPD is calculated from measurements of ambient temperature and humidity, hence, where these two environmental variables are known, E can be calculated. Possible physiological reasons for the relationships of E to VPD in both species are discussed. Scaling from measurements of E at the leaf level to the canopy level is achieved by summing the leaf area of the canopy in question. E is predicted for the entire canopy leaf area by extrapolation to this larger leaf area. Predicted transpiration rates of individual shoot within the canopy were tested gravimetrically and shown to be accurate in the case of S. plumieri, but less so in the case of A. arenaria. Using this model, the amount of water used by a known area of sand dune is shown to be less than the rainfall input in the case of S. plumieri in wet and dry years. The water use of A. arenaria exceeds rainfall in the low-rainfall year of 1995, while in 1998 rainfall input is slightly higher than water extraction by the plants. Using a geographic information system (GIS), regional maps (surfaces) of transpiration were calculated from surfaces of mean monthly temperature and mean monthly relative humidity. Monthly surfaces of transpiration were subtracted from the monthly median rainfall to produce a surface of mean monthly water deficit. Areas of water surpluses along the coast correspond with the recorded distribution of both species in the seasons that the plants are most actively growing and reproducing. This suggests that unfavourable water availability during these two species growth periods limit their distributions along the coast. In addition to unfavourable water deficits, additional climatic variables that may be important in limiting the distribution of these two species were investigated using a discriminant function analysis.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The following study quantifies the seasonal and annual distribution of energy balance components (sensible heat fluxes, latent, soil, and net radiation) in this flooded irrigated rice ecosystem in Southern Brazil for three different periods (Fallow 1: 22 July 2003 to 24 November 2003; Rice: 25 November 2003 to 04 April 2004 and Fallow 2: 05 April 2004 to 21 July 2004). In addition, it has been applied the Noah Land Surface Model with the objective of estimating the surface energy fluxes. An important challenge is to implement a new version of Noah Land Surface Model applied to flooded agricultural land called Noah-Paddy. The stabilization of the models has been performed using the atmospheric forcing data obtained from South American Land Data Assimilation System (SALDAS) for the period 22 July 2000 to 21 July 2003. The models were simulated using the observed atmospheric forcing from a micrometeorological tower installed on a flooded irrigated rice paddies located in the city of Paraíso do Sul - RS. The initial conditions were obtained from the last time step of the spin-up experiment performed with atmospheric forcing data of SALDAS. The models results were compared with experimental data for surface energy fluxes. From the simulated results generated by the Noah Land Surface Model, it seems that when the rice crop is flooded, the model does not satisfactorily represents the experimental data. However, using the Noah-Paddy model the components of surface energy balance are more realistic for the system surface-water-atmosphere. The most important contribution performed in this research was to describe the diffent physical processes originated by the presence of a body of water between the soil surface and the atmosphere. This physical system occorr always in flooded agricultural crops in wich the rice paddies field are predominant. / No presente trabalho, quantifica-se a distribuição sazonal e anual das componentes do balanço de energia (fluxos de calor sensível, latente, do solo e saldo de radiação) em um ecossistema de arroz irrigado por inundação localizado no Sul do Brasil para três períodos distintos ao longo do ano (Pousio 1: 22Jul2003 a 24Nov2003; Arroz: 25Nov2003 a 04Abr2004 e Pousio 2: 05Abr2004 a 21Jul2004). Além disso, é utilizado o Modelo de Superfície Noah (Noah LSM) com o objetivo de estimar os fluxos de energia superficiais. Um dos desafios mais importantes é a implementação de uma nova versão do Noah LSM aplicado para áreas agrícolas alagáveis chamado Noah-Paddy. A estabilização dos modelos foi realizada utilizando dados de forçantes atmosféricas do South American Land Data Assimilation System (SALDAS) para o período de 22Jul2000 a 21Jul2003. Os modelos foram executados usando dados de forçantes atmosféricas observados obtidos a partir da torre micrometeorológica instalada sobre uma cultura de arroz irrigado por inundação localizada em Paraíso do Sul - RS. As condições iniciais foram obtidas a partir do último passo de tempo do experimento spin-up realizado com os dados de forçantes atmosféricas do SALDAS. O desempenho dos modelos estudados foi comparado com dados experimentais de fluxos de energia superficiais. A partir dos resultados obtidos pela simulação do Noah LSM verifica-se que, quando a cultura do arroz está irrigada, o modelo não representa satisfatoriamente os dados experimentais. Porém, utilizando o Noah-Paddy as trocas de energia superficiais são representadas de forma mais realísticas para o sistema superfície-água-atmosfera. A contribuição mais importante realizada neste trabalho foi a descrição dos diferentes processos físicos originados pela presença de uma massa de água entre a superfície do solo e a atmosfera. Esse sistema físico ocorre sempre em culturas agrícolas alagadas nas quais as plantações de arroz são predominantes.

It is imperative to understand the strong coupling between the carbon capture process and water use to sustainably manage rangelands. Woody encroachment is undermining rangelands grass production. Evapotranspiration (ET) highlights the links between ecosystem carbon capture process and water use. It forms the biggest flux of the hydrological cycle after precipitation yet it is not well understood. The Grassland and the Albany Thicket (AT) biomes in the Eastern Cape, South Africa, provide an interesting space to study the dynamics in rangelands biomass production and the associated water use. Therefore, the main purpose of this study was to contribute towards management of rangelands by understanding the dynamics in rangeland grass production and water use. To achieve this aim, the impact of Acacia mearnsii, an invasive alien plant, on soil chemical properties and rangelands grass production was investigated. This was achieved by analysing the biophysical attributes of A. mearnsii as they related to grass production. Secondly, selected soil variables that could be used as a prognosis for landscape recovery or deterioration were evaluated. In addition, aboveground grass biomass was measured in areas cleared of A. mearnsii and regression equations were prepared to help model aboveground grass biomass in areas cleared of A. mearnsi. The thesis also explored dynamics in water vapour and energy fluxes in these two biomes using an eddy covariance system. Consequently, water vapour and energy fluxes were evaluated in order to understand landscape water use and energy partitioning in the landscape. The study also tested the application of Penman-Monteith equation based algorithms for estimating ET with micrometeorological techniques used for validation. Pursuant to this, the Penman- Monteith-Leuning (PML) and Penman-Monteith-Palmer (PMP) equations were applied. In addition, some effort was devoted to improving the estimates of ET from the PMP by incorporating a direct soil evaporation component. Finally, the influence of local changes in catchment characteristics on ET was explored through the application of a variant of the Budyko framework and investigating dynamics in the evaporative index as well as applying tests for trends and shifts on ET and rainfall data to detect changes in mean quaternary catchment rainfall and ET. Results revealed that A. mearnsii affected soil chemical properties and impaired grass production in rangelands. Hence, thinning of canopies provided an optimal solution for enhanced landscape water use to sequestrate carbon, provide shade, grazing, and also wood fuel. It was also shown that across sites, ET was water limited since differences between reference ET and actual ET were large. ET was largely sensitive to vapour pressure deficit and surface conductance than to net radiation, indicating that the canopies were strongly coupled with the boundary layer. Rangeland ET was successfully simulated and evaporation from the soil was the dominant flux, hence there is scope for reducing the so-called ‘unproductive’ water use. Further, it was shown that the PML was better able to simulate ET compared to the PMP model as revealed by different model evaluation metrics such as the root mean square error, absolute mean square error and the root mean square observations standard deviation ratio. The incorporation of a soil evaporation component in the PMP model improved estimates of ET as revealed by the root mean square error. The results also indicated that both the catchment parameter (w) and the evaporative index were important in highlighting the impacts of land cover change on ET. It was also shown that, despite changes in the local environment such as catchment characteristics, global forces also affected ET at a local scale. Overall, the study demonstrated that combining remote sensing and ground based observations was important to better understand rangeland grass production and water use dynamics.

Dans un contexte de changement climatique, il est essentiel de prévoir comment les organismes peuvent être affectés dans leurs relations physiques avec l'environnement. Les amphibiens représentent le groupe des vertébrés le plus sensible aux changements environnementaux, en raison d'une perte en eau par évaporation transépidermique (PEET) permanente. Ma thèse vise à mettre en place des approches pour mesurer et modéliser avec précision les surfaces de la peau contribuant à la PEET; établir les lois de transfert d'eau amphibien-environnement; et fournir une meilleure compréhension des réponses physiologiques face au pathogène Batrachochytrium dendrobatidis. Ces expériences ont été réalisées sur des tritons palmés (Lissotriton helveticus) mâles adultes en phase terrestre. Nos résultats suggèrent que L. helveticus ne présente aucune adaptation physiologique pour limiter la PEET, les moyens étant limités à l'expression d'une posture en forme de "$". Une méthode de reconstruction 3D basée sur l'lmagerie par Résonance Magnétique a été utilisée pour générer des géométries 3D des tritons utilisables pour mesurer leur surface, et à des fins de simulation. Nous avons ainsi réalisé une analyse numérique en 3D des PEET, et avons proposé une relation pour estimer cette perte dans une large gamme de conditions climatiques. Enfin, nos résultats supportent l'hypothèse de dysfonctionnement épidermique, suggérant que B. dendrobatidis compromet la capacité des amphibiens à se réhydrater. Ma thèse devrait contribuer à développer de nouvelles approches en sciences des relations eau-amphibiens, et à améliorer nos connaissances sur les effets des changements environnementaux sur les organismes / Ln a context of climate change, it is critical to predict how organisms might be affected in their physical relations with environment. Amphibians are among the vertebrate groups the most affected by ecological changes, because of permanent transepidermal evaporative water loss (TEWL) through their skin. My thesis aims at setting up approaches to measure and model accurately the functional skin surface areas that contribute to TEWL, establishing laws of water transfer between an amphibian and its physical environment, and providing understanding on physiological responses to the skin pathogen Batrachochytrium dendrobatidis. We conducted experiments on adult males of the palmate newt (Lissotriton helveticus) during their terrestrial phase. Our results suggest that L. helveticus did not show any physiological adaptations to restrain TEWL. The ways to reduce TEWL result essentially in the expression of a stereotyped "$"-shaped water-conserving posture. We used a Magnetic Resonance lmaging-based 3D reconstruction method to generate 3D geometries of newt that is suitable for measuring skin surface areas, and for simulation purposes. We successfully performed 3D numerical analysis of TEWL, and proposed an original relationship to estimate TEWL rates in a large range of temperature and humidity. Finally, our results support the epidermal dysfunction hypothesis, which suggests that B. dendrobatidis compromises the ability of amphibians to rehydrate. My thesis would contribute to open new approaches to the science of amphibian water relations, and improve our knowledge of the effects of ecological changes on organisms

Die semiaride Steppe der Inneren Mongolei (China) ist ein gefährdetes Ökosystem. Der Wandel vom traditionellen nomadischen Lebensstil hin zur konventionellen Landwirtschaft überlastet die Steppe und führt zu Degradierung und Desertifikation. Besonders die intensive Beweidung belastet die weiten Grasflächen und mindert deren natürliches Potential Kohlen-stoff (C) im Boden zu speichern. Um den Einfluss unterschiedlicher Beweidungsintensitäten auf die semiaride Steppe zu untersuchen, wurden im Rahmen des Projektes Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate (MAGIM) das Einzugsgebiet des Xilin Flusses in der Inneren Mongolei von 2004 bis 2009 untersucht. Dafür wurden u. a. meteorologische und Eddykovarianz-Messungen an definierten Standorten durchgeführt. Ziel dieser Messungen war es, die Unterschiede im Energiehaushalt und den Kohlendioxid- und Wasserflüssen (CO2- und H2O-Flüsse) für die dominanten Steppenarten und unter verschiedenen Beweidungsintensitäten zu erfassen. Die Schließung der Energiebilanz ergab eine Schließungslücke von 10 – 30% in Abhängigkeit der meteorologischen Bedingungen, wobei die Lücke unter feuchten Bedingungen kleiner ist. Die gemessenen CO2- und H2O-Flüsse sind klein im Vergleich zu Grasländern in den gemäßigten Zonen und reagieren sensitiv auf Veränderungen der Einflussfaktoren. Dabei ist die Evapotranspiration (ET) eng an den eingehenden Niederschlag (P) gekoppelt und über längere Zeiträume wie ein Jahr entspricht ET dem P (ET: 185,7 mm a-1 bis 242 mm a-1; P: 138 mm a-1 bis 332 mm a-1). Die Jahressummen für den Nettoökosystemaustausch (NEE) reichen von -10,7 g C m-2 a-1 (2005) bis -67,5 g C m-2 a-1 (2007) für die unbeweidete Steppe und charakterisieren diese als eine leichte Nettosenke für atmosphärisches CO2. Grundsätzlich zeigt die unbeweidete Steppe eine höherer C-Sequestrierung (maximale C-Sequestrierung im Mittel -0,06 g C m-2 s-1) als die beweidete Steppe (maximale C-Sequestrierung im Mittel -0,02 g C m-2 s-1). Die Messergebnisse zeigen, dass die Steppe unter trockenen Verhältnissen zur CO2-Quelle wird, unter erhöhten Niederschlagsbedingungen zur CO2-Senke und die Beweidung die C-Sequestrierung des Ökosystems unter beiden Bedingungen einschränkt. Im Vergleich der beiden Steppenarten (Leymus chinensis und Stipa grandis) konnte für Leymus chinensis eine höhere Trockentoleranz beobachtet werden. Diese führt zu einer höheren C-Sequestrierung unter trockeneren Verhältnissen. Unabhängig von der Steppenart sind die wichtigsten Einflüsse auf das Ökosystem die Bodenfeuchte, die vom eingehenden P abhängt, die Temperatur (T) und die Beweidung. Diese Faktoren können dabei nicht unabhängig voneinander betrachtet werden. Der Einfluss durch die Beweidung beeinflusst das Ökosystem nachhaltig, wobei die Intensität und die Dauer (Jahre) der Beweidung entscheidend sind, da nicht nur die oberirdische Biomasse reduziert wird, sondern gleichzeitig die Bodeneigenschaften. Um die Sensitivität auf den CO2- und H2O-Austausch der semiariden Steppe über die Messungen hinaus abzuschätzen, wurden Simulationen mit den Modellen BROOK90 und DAILYDAYCENT (DDC) durchgeführt. Beide Modelle konnten gut an die Bedingungen der semiariden Steppe angepasst werden, wobei die Übereinstimmung zwischen der gemessenen und modellierten ET für BROOK90 besser war (r2 = 0,7) als für DDC (r2= 0,34). Beide Modelle konnten gut die Dynamik der ET-Messungen wiedergeben. Die Sensitivitätsanalyse hat gezeigt, dass die Beziehung zwischen P und ET entscheidend für das Ökosystem ist und sich Änderungen in der T nur zum Ende und Beginn der Vegetationsperiode auf den Wasseraustausch auswirken. DDC konnte sehr gut den gemessenen CO2-Austausch simulieren. Die Ergebnisse zeigen die Sensitivität gegenüber den klimatischen Faktoren T, P und der Beweidung. Die CO2-Flüsse werden durch hohe Beweidungsintensitäten so stark minimiert, dass andere Einflussfaktoren dahinter zurücktreten. Bei leichten Beweidungsintensitäten wirkt sich dagegen besonders der P auf die Austauschprozesse aus. Die DDC-Ergebnisse zeigen, dass unter den derzeitigen Bedingungen der bodenorganische Kohlenstoff (SOC) verringert wird, also C aus dem Boden freigesetzt wird. Auch unter unbeweideten Verhältnissen steigt der SOC nicht wieder auf das Ausgangsniveau (von vor der Beweidung) an. Die Ergebnisse zeigten, dass die C-Sequestrierung der Steppe nur erhöht werden kann, wenn der P steigt, die T in einem Optimumbereich (+/- 2°C) bleibt und die Beweidung minimiert wird. Die Messungen und Modellergebnisse zeigen, dass der Niederschlag der limitierende Faktor der semiariden Steppe ist. P bestimmt die Bodenfeuchte, diese wiederum beeinflusst das Pflanzenwachstum und somit den CO2- und H2O-Austausch der Pflanzen. Die Beweidung strapaziert das Ökosystem und reduziert dadurch die CO2- und H2O-Flüsse und verändert die Bodeneigenschaften nachhaltig. Unabhängig von der klimatischen Entwicklung, ist die derzeitige überwiegend hohe Beweidungsintensität der Steppe eine Belastung für das Ökosystem und schränkt das Pflanzenwachstum langfristig ein, was u. a. die Desertifikation begünstigt. / Semiarid grasslands in Inner Mongolia (China) are degrading. The change from the traditional Nomadic lifestyle to conventional agriculture stresses the semiarid grasslands and increases desertification. In particular, intense grazing of the semiarid grasslands reduces their potential of storing carbon (C) in the soil. In the project Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate (MAGIM) a team of scientists researched the catchment area of the Xilin River to investigate impacts of different grazing intensities on semiarid grasslands. Meteorological and eddy covariance measurements took place from 2004 to 2009. The aim of the measurements was to examine the energy balance and the exchange of the carbon dioxide (CO2) and water (H2O) fluxes of the dominant grasslands in Inner Mongolia under different grazing intensities. The energy balance could be closed by 70 – 90% depending on the driving factors. The energy balance shows a smaller gap for moist conditions. The CO2 und H2O fluxes in the study area are much smaller than in temperate grasslands and show a high sensitivity towards the driving factors. Evapotranspiration (ET) is closely connected to the precipitation (P) and over longer periods of a year or more, ET nearly matches P (ET: 185.7 mm a-1 to 242 mm a-1; P: 138 mm a-1 to 332 mm a-1). The annual net ecosystem exchange (NEE) of ungrazed grassland ranges from -10.7 g C m-2 a-1 (2005) to -67.5 g C m-2 a-1 (2007), which makes the grassland a small CO2-sink. Overall, ungrazed grassland shows higher C sequestration (averaged maximum -0.06 g C m-2 s-1) than grazed grassland (averaged maximum -0.02 g C m-2 s-1). The measurements show the semiarid grassland as a CO2-source under dry conditions and as a CO2-sink under moist conditions, while grazing decreases the C sequestration for both climatic conditions. A comparison of the two dominant steppe types (Leymus chinensis and Stipa grandis) showed a higher tolerance for Leymus chinensis under dry conditions, which resulted in higher C sequestration for this vegetation. Besides the steppe type, the main driving factors are P, temperature (T) and grazing. These factors can not only be considered in isolation, but cross correlation needs to get considered as well. Grazing affects the sustainability of the ecosystem, with an increasing impact due to grazing intensity and duration (years). The impact of grazing influences the vegetation directly and shows indirect impacts for the soil properties. Simulations with the models BROOK90 and DAILYDAYCENT (DDC) enable a sensitivity analysis of CO2 and H2O fluxes of the semiarid grassland. Both models performed well, but BROOK90 showed a better fit to observed ET (r2 = 0.7) than DDC (r2= 0.34). Both models simulated the dynamics of the measured ET well. The sensitivity analysis showed a close relationship between P und ET and a smaller impact on ET due to a change in T. DDC performs well in the simulation of CO2 exchange dynamics of the semiarid grassland. The results show for high grazing intensities a decreasing influence of the other driving factors. A change in P has an influence on CO2 and H2O fluxes under low grazing intensities. The results also show a decrease in soil organic carbon (SOC) as grazing intensity increases (under current climatic conditions). An increase in SOC could only be achieved under an increase in P, an optimum T and low grazing intensities. The measurements and results of the simulations indentify P as the main driving factor controlling the CO2 and H2O fluxes in the semiarid grassland. P influences the soil moisture and this influences plant growth, which governs the CO2 and H2O exchange of the vegetation. Grazing decreases the CO2 and H2O exchange and affects the soil properties in the long term. Besides climate change, the current high grazing intensities of the semiarid grassland have a negative impact on the ecosystem, decreasing plant growth and increasing desertification.

Philosophiae Doctor - PhD / The analysis of geologic, hydrologic and hydrogeologic data interpreted to give the characteristics of the Cape Flats aquifer showed the quality of groundwater from the aquifer is suitable for development as a water resource. The conceptual model of the Cape Flats sand shows an unconfined sandy aquifer, grading into semi-confined conditions in some places where thick lenses of clay and peat exists. Recharge rates through the saturated zone of the Cape Flats aquifer have been determined by water table fluctuation (WTF), rainfall-recharge relationship, soil water balance and chloride mass balance methods (CMB). Recharge rates using the WTF vary considerably between wet and dry years and between locations, with a range of 17.3% to 47.5%. Values obtained from empirical rainfall-recharge equation (method 2) agree with those of the WTF. Recharge estimates from the water balance model are comparatively lower but are within the range calculated using empirical method 2 (i.e. 87 - 194 mm or 4 – 21% of MAP). These recharge rates also agree with estimates from the series of other methods applied to sites located in the north-western coast of Western Cape and are comparable to recharge rates obtained elsewhere in the world. / South Africa

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21578号 / 理博第4485号 / 新制||理||1644(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 余田 成男, 教授 秋友 和典, 准教授 石岡 圭一 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

As water demand increases it will become more imperative for golf course superintendents, landscape managers, and other industry professionals to improve water use efficiency in the management of recreational turfgrass. Scheduling irrigation according to actual turfgrass evapotranspiration rates (ETT) is an integral component of efficient irrigation practices. Impracticality of field derived ETT for industry use, however, directs the need of weather station derived reference (predicted) evapotranspiration (ET0). To accurately predict (estimate) ETT of turf and other crops, scientifically derived landscape (crop) coefficients (Kc values) are used in conjunction with mathematical models that incorporate local meteorological data. Research is limited, however, in identifying Kc values and subsequent ET0 for turfgrass species selected and maintained under high intensity recreational practices congruent of golf courses and sports fields in the cool-humid northeast climate. Therefore, objectives of this study were to (i) observe and record ETT of three commonly selected recreational turfgrass species; 'Exacta' Perennial ryegrass (Lollium perenne L.), 'Touchdown' Kentucky bluegrass (Poa pratensis L.), and 'Memorial' Creeping bentgrass (Agrostis stolinifera L.) maintained as golf and sports turf, (ii) analyze the impact various management practices (nitrogen fertility and height of cut) have on ETT, (iii) develop accurate Kc values appropriate for use with the recommended FAO 56 Penman-Monteith mathematical model for accurate ET0 of recreational turf maintained in the cool-humid northeast. Four heights of cut (HOC) and two nitrogen fertility rates (N) were evaluated to determine their impact on turfgrass growth and subsequent water use and ETT of three recreational turfgrass species. Golf turf (creeping bentgrass) maintained at a lower height of cut than sports turf exhibited a smaller leaf area component and a significantly lower (20%) ETT. N applied as slow release (82%) throughout the growing season increased ETT by 5%, particularly with perennial ryegrass sports turf. Taller HOC also increased ETT by 10% due to increased leaf area indices and subsequent decreased resistance to ET. Predicted ET0 according to FAO 56 for all three years of the study (79 observations) captured 71% of ETT. Yearly and monthly calculations suggest less variable (cloudy) weather yielded more accurate ET0. Crop coefficient (Kc) values established in conjunction with FAO 56 ET0 ranged from 0.90 to 1.00 for shorter golf course turf (creeping bentgrass), and 1.15 to 1.25 for taller sports turf (Kentucky bluegrass and perennial ryegrass). Results indicate shorter grass exhibits a lower ETT than taller grass due to various factors, and in the case of industry application, FAO 56 ET0 can accurately estimate ETT of recreational turf in the cool-humid northeast when fitted with appropriate Kc values.