School of Emergency Management, Xihua University, Chengdu 610039, China.
State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China.
J Environ Manage. 2024 Apr;356:120740. doi: 10.1016/j.jenvman.2024.120740. Epub 2024 Mar 22.
Stomatal conductance (g) and compensatory water uptake (CWU) are crucial processes in land surface models, as they directly influence the exchange of carbon and water fluxes between terrestrial ecosystems and the atmosphere. In this study, we integrated a new stomatal scheme derived from optimal stomatal theory (Medlyn's g model), and an empirical CWU scheme into the Common Land Model (CoLM). Assessing the impacts on modeling gross primary productivity (GPP) and latent flux (LE) through observations obtained from eddy covariance (EC) measurements at three forest sites in China. Our results show that replacing the Ball-Berry's g model (termed BB) with Medlyn's g model (termed MED) did not bring about significant changes (had neutral impacts) in the performance of CoLM simulations at three forest sites. Considering the climate factors of annual mean precipitation to optimize key fitting parameters in g exhibited improvement in model simulations. The average coefficient of determination (R) achieved to 0.65 for GPP and LE at three sites, and the normalized root mean squared error (NRMSE) decreased from 0.83 to 0.77 at those sites. Besides, incorporating CWU into the model improved its performance. The R increased to 0.84 and RMSE decreased to 4.84 μmol m s for GPP, and the R increased to 0.62 and RMSE decreased to 55.64 W m for LE. Therefore, modifying the model process of both contributed more to enhancing the model simulations than relying solely on one of these functions. Our study highlights that the response of plant functional types (PFTs) to water stress can be effectively represented in g models when coupled with biochemical capacity to quantify carbon and water fluxes in forest ecosystems or other ecosystems.
气孔导度（g）和补偿性水分吸收（CWU）是陆面模式中的关键过程，因为它们直接影响陆地生态系统与大气之间碳和水通量的交换。在这项研究中，我们将一个新的气孔方案整合到通用陆面模型（CoLM）中，该方案是从最优气孔理论（Medlyn 的 g 模型）推导而来，同时还整合了一个经验性的 CWU 方案。通过在中国三个森林站点的涡度协方差（EC）测量获得的观测结果，评估了对建模总初级生产力（GPP）和潜热通量（LE）的影响。我们的结果表明，用 Medlyn 的 g 模型（称为 MED）替代 Ball-Berry 的 g 模型（称为 BB），并没有显著改变 CoLM 在三个森林站点的模拟性能（具有中性影响）。考虑到年平均降水量等气候因素来优化 g 中的关键拟合参数，可以提高模型模拟效果。在三个站点，GPP 和 LE 的平均决定系数（R）达到 0.65，归一化均方根误差（NRMSE）从这些站点的 0.83 下降到 0.77。此外，将 CWU 纳入模型也提高了模型性能。GPP 的 R 增加到 0.84，NRMSE 下降到 4.84 μmol m s，LE 的 R 增加到 0.62，NRMSE 下降到 55.64 W m。因此，对模型过程的修改比对其中一个功能的依赖更有助于提高模型模拟效果。我们的研究表明，当将植物功能型（PFTs）对水分胁迫的响应与量化森林生态系统或其他生态系统中碳和水通量的生化能力相结合时，g 模型可以有效地表示。
