摘要
Aims Accurate prediction of spatiotemporal variations in carbon and water fluxes of heterogeneous landscape is critical to comprehensively address the effects of climate change and vegetation dynamics on landscape and regional carbon and water cycling.Methods A field study was conducted to characterize the seasonal variations in gas fluxes and explore their relationships with abiotic and biotic factors in a small grassland landscape.Daytime carbon and water fluxes including net ecosystem exchange,gross ecosystem productivity,ecosystem respiration and evapotranspiration(ET)were measured for three types of grassland patches over a growing season using the closed chamber method.The key plant trait variables were measured,based on which community weighted mean(CWM)and functional variance(FDvar)were calculated.Important Findings The results showed that the temporal variations in the carbon and water fluxes were regulated by meteorological,soil and community functional variables.Inclusion of the CWM and FDvar of plant trait measures greatly improved the degree of explanation of the predict models.Specific leaf area and leafδ^(13)C content(Lδ^(13)C)were the most important trait variables in affecting the variations of the gas fluxes.CWMs indices had greater importance than FDvar indices in predicting the variation of the C fluxes but FDvar indices were more important for ET than C fluxes.Our findings demonstrated that mass ratio hypothesis and the complementary effects hypothesis are not mutually exclusive but have different relative importance for different ecosystem processes.Community functional traits played important roles in predicting the spatiotemporal variations of carbon and water fluxes in semiarid grassland.
准确预测异质性景观碳水通量的时空变化,对于综合理解气候变化和植被动态对景观和区域碳水循环的影响至关重要。本研究通过野外观测试验来探究草地斑块碳水通量的季节变化及其与非生物和生物因子之间的关系。在生长季通过密闭同化箱法测定了三个类型草地斑块的日间碳水通量(包括生态系统净交换、总生态系统生产力、生态系统呼吸和蒸散发),同时测定了关键植物性状指标,并计算性状加权平均值和功能分异度。研究结果表明,碳水通量的时间变化受气象因子、土壤因子和群落功能性状的影响。考虑植物功能性状加权平均值和功能分异度可以极大地提高景观尺度碳水通量变异的解释度。比叶面积和叶片δ^(13)C含量是影响气体通量变化的重要性状指标。群落加权平均值对碳通量的预测能力优于功能分异度,而功能分异度对蒸散发的解释度更高。我们的研究结果表明,生物量比假说和互补效应假说互不排斥,但两者对不同的生态系统过程的相对重要性不同,群落功能性状对半干旱草地碳水通量时空变化的机理解释和模型预测具有重要作用。
基金
supported by the National Key Research and Development Program of China(no.2016YFC0501602)
International Partnership Program(no.121311KYSB20170004)of Chinese Academy of Sciences.
