基于参数优化的人工灌丛生态系统碳水通量模拟

荒漠草原是陆地生态系统中最为脆弱且受人类干扰较为严重的生态类型之一，精准模拟其碳水通量及对人为干扰的响应，不仅能够揭示其复杂的生态学过程，而且还可为人为生态修复和保护提供决策依据。生态模型能够有效地模拟陆地生态系统的碳水循环过程，但模型众多的参数及其取值的合理性限制了其普遍应用，故探索参数优化是提升生态模型应用的有效途径。利用PEST参数优化方法和涡度相关观测数据对Biome-BGC模型的生理生态参数进行优化，在评估参数优化效果的基础上模拟了1986-2018年宁夏盐池荒漠草原区人工灌丛生态系统的总初级生产力（Gross primary productivity，GPP）和蒸散（Evapotranspiration，ET）。结果表明：（1）参数优化可以改善Biome-BGC模型对荒漠草原区人工灌丛生态系统GPP和ET的模拟效果，参数优化后模拟的GPP和ET均更接近于观测值，其中月尺度的模拟效果更佳；（2）基于PEST的Biome-BGC模型参数优化方法具有较强的普适性，优化后的参数可推广应用于荒漠草原区人工灌丛生态系统长时间序列的GPP和ET模拟；（3）宁夏盐池荒漠草原区人工灌丛生态系统的GPP在1986-2018年呈缓慢上升趋势，增幅为1.47 g C m^-2 a^-1，但ET的年际变化率较大，且无显著变化趋势。

Simulation of carbon and water fluxes of planted shrub ecosystem in desert steppe biome zone based on parameter optimization

Desert steppe is one of the most vulnerable and severely disturbed ecosystems by humans in terrestrial ecosystems. The accurately simulating carbon and water flux of the desert steppe and its response to anthropogenic disturbance can not only reveal its complex ecological process but also provide a decision-making basis for the artificially ecological conservation and restoration. Ecological models can effectively simulate the carbon and water cycle processes of terrestrial ecosystems, but the numerous parameters of the model and the rationality of these values limits their universal application. Therefore, exploring parameter optimization is an effective way to promote the universal application of the ecological models. In this paper, the physiological and ecological parameters of the Biome-BGC model are optimized by using the Parameter ESTimation (PEST) method and data observed by Eddy Covariance. On the basis of evaluating the effect of parameter optimization, gross primary productivity (GPP) and evapotranspiration (ET) of the planted shrub encroachment ecosystem of the desert steppe region in the Yanchi County of Ningxia from 1986 to 2018 were simulated. The results show that:(1) the parameter optimization can improve the simulation effect of the Biome-BGC model on GPP and ET of planted shrub encroachment ecosystems in the desert steppe region. The simulated GPP and ET after parameter optimization are closer to the observed values, and the simulation effect at the monthly scale is better. (2) The parameter optimization method of the Biome-BGC model based on PEST has strong universality, and the optimized parameters can be applied to long-term GPP and ET simulations of the planted shrub encroachment ecosystems in the desert steppe region. (3) The GPP of the planted shrub encroachment ecosystem of desert steppe region in the Yanchi County of Ningxia showed a slow upward trend from 1986 to 2018, with an increase of 1.47 g C m^-2 a^-1, and the interannual variation rate of ET was large, and there was no significant change trend.