Xu Mingjie, Ma Qianhui, Li Shengtong, Yang Fengting, Zhang Tao, Xu Fei, Yang Bin, Zhang Hui, Zhang Shu, Wang Qianyu, Tang Yuanyuan, Wang Huimin
College of Agronomy, Shenyang Agricultural University, Shenyang, China.
Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.
Front Plant Sci. 2023 Mar 1;14:1120202. doi: 10.3389/fpls.2023.1120202. eCollection 2023.
Accurate estimations of forest evapotranspiration (ET) and its components, transpiration (T) and evaporation (E), are important for deep understanding and predicting the responses of forest water cycles to climate change. In this study, the improved Shuttleworth-Wallace model (SWH) was applied to estimate ET, T, and E during 2003-2014 in a subtropical planation, and the modeled results were verified using measurements by the eddy covariance technique, sap flow, and micro-lysimeter method. The study aimed to clarify whether it is feasible and reliable to use the SWH model to estimate and partition ET in forests. In addition, depending on the long-term data, the specific performances in modeling ET under different climatic backgrounds were investigated, and the underlying mechanisms were explored. The results verified that the SWH performed relatively well in the subtropical forest, and the modeled ET, T and E could track the seasonal variations, although overestimations were found in the peak seasons. However, the model was relatively weaker in estimating the interannual variabilities. It performed well in modeling ET in normal years but showed larger model residuals in years with obvious climatic anomalies. In the severe summer-drought (2003) and cold-spring (2005) years, the model greatly overestimated ET. It also overestimated ET in summer since 2010, which may be ascribed to the less dependency of ET on VPD induced by the more humid microclimate in forest accompanied with forest development. For the ET partitioning results, the modeled and measured E and T values were all in reasonable ranges. The possible reasons for underestimations (overestimations) of E and T by measurements (SWH model) were discussed. In this study, the data obtained using different methods and from different scales matched each other and could be cross validated, and the discussion on discrepancies would be beneficial for understanding the advantages and flaws of different methods and could be the basis for optimizing the measurement and model methods. In sum, this study verified that it is feasible to use the SWH model in forests and provided a basis for further improving and optimizing the modeled results under different climate backgrounds.
准确估算森林蒸散量（ET）及其组成部分蒸腾量（T）和蒸发量（E），对于深入理解和预测森林水循环对气候变化的响应至关重要。在本研究中，应用改进的Shuttleworth-Wallace模型（SWH）估算了2003 - 2014年亚热带人工林中的ET、T和E，并利用涡度相关技术、液流和微型蒸渗仪方法的测量数据对模拟结果进行了验证。该研究旨在阐明使用SWH模型估算和划分森林ET是否可行和可靠。此外，基于长期数据，研究了不同气候背景下模拟ET的具体表现，并探讨了其潜在机制。结果验证了SWH在亚热带森林中表现相对较好，模拟的ET、T和E能够跟踪季节变化，尽管在高峰期存在高估现象。然而，该模型在估算年际变异性方面相对较弱。它在正常年份模拟ET表现良好，但在气候异常明显的年份模型残差较大。在严重的夏季干旱（2003年）和寒冷春季（2005年），该模型极大地高估了ET。自2010年以来，它在夏季也高估了ET，这可能归因于随着森林发展，森林微气候湿度增加，ET对水汽压亏缺（VPD）的依赖性降低。对于ET划分结果，模拟和测量的E和T值均在合理范围内。讨论了测量值（SWH模型）低估（高估）E和T的可能原因。在本研究中，使用不同方法和不同尺度获得的数据相互匹配且可交叉验证，对差异的讨论将有助于理解不同方法的优缺点，并可为优化测量和模型方法提供依据。总之，本研究验证了在森林中使用SWH模型是可行的，并为在不同气候背景下进一步改进和优化模拟结果提供了依据。
