The role of spatiotemporal plant trait variability in model predictions of ecohydrological responses to climate change in a desert shrubland
The role of spatiotemporal plant trait variability in model predictions of ecohydrological responses to climate change in a desert shrubland
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DOI：
10.1016/j.jhydrol.2020.125088
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发表时间：
2020-09
影响因子：
6.4
通讯作者：
Shaoqing Liu;G. Ng
中科院分区：
文献类型：
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作者：
Shaoqing Liu;G. Ng
虽然土壤性质、地形和气候的空间异质性通常被纳入生态水文模型，但植物功能性状的时空变异性通常被忽视。我们研究的目的是评估特征参数变异对模拟生态水文过程的影响。在莫哈韦沙漠沿地形和气候梯度的两个荒漠灌木地，采用模型-数据融合方法对植物功能性状的时空动态参数进行了约束。结果表明：阔叶-常绿-灌木植物功能类型的比叶面积和生根深度估算值存在空间变异性，低海拔地区比叶面积较小，生根深度较深；我们还发现，两个地点的比叶面积估计值随着时间的推移而变化，以响应水分胁迫，但具有不同的敏感性，可能取决于物种和/或气候。特征参数估算的空间变异性大于时间变异性，在准确模拟生态水文过程中发挥更重要的作用，但包括比叶面积的时间变异性进一步改善了季节预测。在代表性浓度路径4.5 （RCP 4.5）和8.5 （RCP 8.5）温室气体排放情景下的未来气候预估强迫模拟中，性状参数的空间变异影响碳通量和水通量的预测，而性状参数的时间变异导致更高的生态功能和水利用效率的预测。在RCP 4.5情景下，较高的水分利用效率改善了生态水文功能，但在RCP 8.5情景下，其缓冲强水胁迫的能力较弱，表明在特征参数时空变化的情况下，对预测生态水文过程的影响取决于气候预估。总体而言，我们的建模结果促使我们进一步以野外为基础研究荒漠灌丛的时间和地下特征变异性，并提出了多个特征的时空组合变异性如何在水分胁迫下支持生态水文功能的问题。
Although spatial heterogeneity of soil properties, topography, and climate is commonly incorporated into ecohydrological models, the spatial and temporal variability in plant functional traits is typically overlooked. The objective of our study is to evaluate the impact of trait parameter variability on modeled ecohydrological processes. We implemented a model-data fusion approach to constrain spatiotemporally dynamic parameters in plant functional traits at two desert shrubland sites located along a topographic and climate gradient in the Mojave Desert. Our results showed that the estimates for specific leaf area and rooting depth for the broadleaf-evergreen-shrub plant-functional-type showed spatial variability, with lower specific leaf area and deeper rooting depth found at the low elevation site. We also found that the specific leaf area estimates changed over time at both sites in response to water stress, but with different sensitivities, possibly depending on species and/or climate. The spatial variability in trait parameter estimates was greater than temporal variability and played a more important role in accurately simulating ecohydrological processes, but including the temporal variability in specific leaf area further improved seasonal predictions. In simulations forced by future climate projections under the Representative Concentration Pathway 4.5 (RCP 4.5) and 8.5 (RCP 8.5) greenhouse gas emissions scenarios, spatial variability in trait parameters impacted predictions of both carbon and water fluxes, while temporal variability in trait parameters resulted in predictions of higher ecological function and water use efficiency. The higher water use efficiency led to improved ecohydrological function in simulations under RCP 4.5, but it showed little capacity for buffering intensive water stresses under the more pessimistic RCP 8.5 scenario, indicating that with spatiotemporally variable trait parameters, the impact on predicted ecohydrological processes depends on the climate projections. Overall, our modeling results prompt further field-based examination of temporal and belowground trait variability in desert shrublands, and they raise the question of how combined spatiotemporal variabilities of multiple traits may support ecohydrological function under water stress.