Eco-hydrological processes in arid areas are the focus of many hydrological and water resources studies. However, the hydrological cycle and the ecological system have usually been considered separately in most previo...Eco-hydrological processes in arid areas are the focus of many hydrological and water resources studies. However, the hydrological cycle and the ecological system have usually been considered separately in most previous studies, and the correlation between the two has not been fully understood. Interdisciplinary research on eco-hydrological processes using multidisciplinary knowledge has been insufficient. In order to quantitatively analyze and evaluate the interaction between the ecosystem and the hydrological cycle, a new kind of eco-hydrological model, the ecology module for a grid-based integrated surface and groundwater model(Eco-GISMOD), is proposed with a two-way coupling approach,which combines the ecological model(EPIC) and hydrological model(GISMOD) by considering water exchange in the soil layer. Water interaction between different soil layers is simply described through a generalized physical process in various situations. A special method was used to simulate the water exchange between plants and the soil layer, taking into account precipitation, evapotranspiration, infiltration, soil water replenishment, and root water uptake. In order to evaluate the system performance, the Heihe River Basin in northwestern China was selected for a case study. The results show that forests and crops were generally growing well with sufficient water supply, but water shortages,especially in the summer, inhibited the growth of grass and caused grass degradation. This demonstrates that water requirements and water consumption for different kinds of vegetation can be estimated by considering the water-supply rules of Eco-GISMOD, which will be helpful for the planning and management of water resources in the future.展开更多
The canopy light extinction coefficient （K） is a key factor in affecting ecosystem carbon, water, and energy processes. However, K is assumed as a constant in most biogeochemical models owing to lack of in-site meas...The canopy light extinction coefficient （K） is a key factor in affecting ecosystem carbon, water, and energy processes. However, K is assumed as a constant in most biogeochemical models owing to lack of in-site measurements at diverse terrestrial ecosystems. In this study, by compiling data of K measured at 88 terrestrial ecosystems, we investigated the spatiotemporal variations of this index across main ecosystem types, including grassland, cropland, shrubland, broadleaf forest, and needleleaf forest. Our results indicated that the average K of all biome types during whole growing season was 0.56. However, this value in the peak growing season was 0.49, indicating a certain degree of seasonal variation. In addition, large variations in K exist within and among the plant functional types. Cropland had the highest value of K （0.62）, followed by broadleaf forest （0.59）, shrubland （0.56）, grassland （0.50）, and needleleaf forest （0.45）. No significant spatial correlation was found between K and the major environmental factors, i.e., mean annual precipitation, mean annual temperature, and leaf area index （LAI）. Intra-annually, significant negative correlations between K and seasonal changes in LAI were found in the natural {K=2/π[cosαcosθsina^-1（tanθtanα）＋（1＋cos^2a-cos^2θ^1/2）],a＋θ〉π/2 K=cosαcosθ,α＋θ≤π/2 k K is usually calculated with the Beer Lambert Law （Monsi and Sakei, 1953）：K = - In （Ii/Io） cosθ/（LAIΩ）,（2）ecosystems. In cropland, however, the temporal relation- ship was site-specific. The ecosystem type specific values of K and its temporal relationship with LAI observed in this study may contribute to improved modeling of global biogeochemical cycles.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.91125015)
文摘Eco-hydrological processes in arid areas are the focus of many hydrological and water resources studies. However, the hydrological cycle and the ecological system have usually been considered separately in most previous studies, and the correlation between the two has not been fully understood. Interdisciplinary research on eco-hydrological processes using multidisciplinary knowledge has been insufficient. In order to quantitatively analyze and evaluate the interaction between the ecosystem and the hydrological cycle, a new kind of eco-hydrological model, the ecology module for a grid-based integrated surface and groundwater model(Eco-GISMOD), is proposed with a two-way coupling approach,which combines the ecological model(EPIC) and hydrological model(GISMOD) by considering water exchange in the soil layer. Water interaction between different soil layers is simply described through a generalized physical process in various situations. A special method was used to simulate the water exchange between plants and the soil layer, taking into account precipitation, evapotranspiration, infiltration, soil water replenishment, and root water uptake. In order to evaluate the system performance, the Heihe River Basin in northwestern China was selected for a case study. The results show that forests and crops were generally growing well with sufficient water supply, but water shortages,especially in the summer, inhibited the growth of grass and caused grass degradation. This demonstrates that water requirements and water consumption for different kinds of vegetation can be estimated by considering the water-supply rules of Eco-GISMOD, which will be helpful for the planning and management of water resources in the future.
文摘The canopy light extinction coefficient （K） is a key factor in affecting ecosystem carbon, water, and energy processes. However, K is assumed as a constant in most biogeochemical models owing to lack of in-site measurements at diverse terrestrial ecosystems. In this study, by compiling data of K measured at 88 terrestrial ecosystems, we investigated the spatiotemporal variations of this index across main ecosystem types, including grassland, cropland, shrubland, broadleaf forest, and needleleaf forest. Our results indicated that the average K of all biome types during whole growing season was 0.56. However, this value in the peak growing season was 0.49, indicating a certain degree of seasonal variation. In addition, large variations in K exist within and among the plant functional types. Cropland had the highest value of K （0.62）, followed by broadleaf forest （0.59）, shrubland （0.56）, grassland （0.50）, and needleleaf forest （0.45）. No significant spatial correlation was found between K and the major environmental factors, i.e., mean annual precipitation, mean annual temperature, and leaf area index （LAI）. Intra-annually, significant negative correlations between K and seasonal changes in LAI were found in the natural {K=2/π[cosαcosθsina^-1（tanθtanα）＋（1＋cos^2a-cos^2θ^1/2）],a＋θ〉π/2 K=cosαcosθ,α＋θ≤π/2 k K is usually calculated with the Beer Lambert Law （Monsi and Sakei, 1953）：K = - In （Ii/Io） cosθ/（LAIΩ）,（2）ecosystems. In cropland, however, the temporal relation- ship was site-specific. The ecosystem type specific values of K and its temporal relationship with LAI observed in this study may contribute to improved modeling of global biogeochemical cycles.
