环境科学
生态系统呼吸
北方生态系统
初级生产
土壤水分
气孔导度
生态系统
泰加语
含水量
生产力
土壤呼吸
碳循环
土壤碳
植被(病理学)
水文学(农业)
森林生态学
生物气象学
土壤科学
光合作用
生态学
地质学
天蓬
化学
经济
岩土工程
医学
生物化学
病理
宏观经济学
生物
作者
Weimin Ju,Jing M. Chen,T. Andrew Black,Alan G. Barr,Jane Liu,Baozhang Chen
标识
DOI:10.1016/j.agrformet.2006.08.008
摘要
In order to test two hypotheses: (i) that carbon (C) and energy exchanges between terrestrial ecosystems and the atmosphere are closely constrained by soil water availability, and (ii) that vegetation is able to optimize soil water uptake from different soil layers; two model simulations were conducted. The Boreal Ecosystem Productivity Simulator (BEPS) model was run to simulate an aspen forest in Saskatchewan, Canada during the period 1997–2004. In Simulation 1, the effect of soil water availability in different soil layers on stomatal conductance was weighted only by root fraction. In Simulation 2, the influence of soil water availability in different soil layers on stomatal conductance was weighted according to both the root fraction and soil water availability, in order to allow easier access of roots to soil layers containing more water. Comparison against measured fluxes showed that Simulation 2 was an improvement over Simulation 1 in predicting C, water and energy fluxes at different time scales in dry years. In Simulation 1, the daytime C and water fluxes were underestimated during the transition from adequate to insufficient soil water content in the upper layers. In this run, the model captured 92, 79 and 91% of the daily variances in gross primary productivity (GPP), net ecosystem productivity (NEP), and ecosystem respiration (Re) during 1997–2004. In Simulation 2, the daily variances of GPP, NEP, and Re explained by the model increased to 93, 82 and 92%, respectively. In Simulation 1, the annual NEP was considerably underestimated in the dry years and years with dry periods, with a root mean square error (RMSE) of 45 g C m−2 year−1 (n = 8) from 1997 to 2004. In Simulation 2, the RMSE value of simulated annual NEP was reduced to 14 g C m−2 year−1, a relatively small value compared with the average NEP of 157 g C m−2 year−1 during 1997–2004. This suggested that the ability of plant roots to extract water from deep soil layers is critical for the forest to maintain growth when surface layers dried out. Our model results showed that NEP was very sensitive to water conditions at this site. In wet years, heterotrophic respiration was enhanced and NEP was reduced.
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