School of Urban Planning and Design, Shenzhen Graduate School, Peking University, Shenzhen 518055, China.
School of Urban Planning and Design, Shenzhen Graduate School, Peking University, Shenzhen 518055, China; Key Laboratory of Earth Surface System and Human-Earth Relations, Ministry of Natural Resources of China, Shenzhen Graduate School, Peking University, Shenzhen 518055, China.
Sci Total Environ. 2024 Jan 1;906:167664. doi: 10.1016/j.scitotenv.2023.167664. Epub 2023 Oct 11.
Global vegetation has experienced notable changes in greenness and productivity since the early 1980s. However, the changes in the relationship between productivity and greenness, i.e., the coupling, and its underlying mechanisms, are poorly understood. The Loess Plateau (LP) is one of China's most significant areas for vegetation greening. Yet, it remains poorly documented what changes in the coupling between productivity and greenness are and how environmental and anthropogenic factors affect this coupling in the LP over the past four decades. We investigated the interannual trend of coupling between Gross Primary Productivity (GPP) and Leaf Area Index (LAI), i.e., the GPP-LAI coupling, and its response to climate factors and afforestation in the LP using long-term remote-sensed LAI, GPP and Solar-induced Chlorophyll Fluorescence (SIF). We found a monotonically increasing trend in the GPP-LAI coupling in the LP from 1982 to 2018 (0.0043 yr, p < 0.05), in which the significant trend in the northwest LP was driven by increasing soil water and landcover change, e.g., increased grassland and afforestation. An ensemble of 11 state-of-the-art ecosystem models from the TRENDY project failed to capture the observed monotonically increasing trend of the GPP-LAI coupling in the LP. The consistent projection of a decreasing GPP-LAI coupling in LP during 2019-2100 by 22 Earth System Models (ESMs) under various future scenarios should be treated with caution due to the identified inherent uncertainties in the ecosystem component in ESMs and the notable biases in the simulation of future climate conditions. Our study highlights the need to enhance the key mechanisms that regulate the coupling relationships between photosynthesis and canopy structure in indigenized ecosystem models to accurately estimate the ecosystem change in drylands under global climate change.
自 20 世纪 80 年代初以来，全球植被的绿色度和生产力发生了显著变化。然而，生产力和绿色度之间关系的变化，即耦合及其潜在机制，还了解甚少。黄土高原（LP）是中国最重要的植被绿化区之一。然而，在过去的四十年里，LP 生产力和绿色度之间的耦合变化以及环境和人为因素如何影响这种耦合的情况仍缺乏记录。我们使用长期遥感的叶面积指数（LAI）、总初级生产力（GPP）和太阳诱导叶绿素荧光（SIF），研究了 LP 中 GPP 和 LAI 之间的年际耦合趋势（即 GPP-LAI 耦合）及其对气候因子和造林的响应。我们发现，1982 年至 2018 年，LP 中的 GPP-LAI 耦合呈单调递增趋势（0.0043 yr，p < 0.05），其中 LP 西北部的显著趋势是由土壤水分增加和土地覆盖变化驱动的，例如增加的草地和造林。TRENDY 项目的 11 个最先进的生态系统模型的集合未能捕捉到 LP 中 GPP-LAI 耦合的观测到的单调递增趋势。在各种未来情景下，22 个地球系统模型（ESMs）一致预测 LP 中的 GPP-LAI 耦合在 2019 年至 2100 年期间呈下降趋势，这是由于 ESM 中生态系统组成部分的固有不确定性和对未来气候条件的模拟存在显著偏差，因此应该谨慎对待。我们的研究强调需要增强调节光合作用和冠层结构耦合关系的关键机制，以准确估计全球气候变化下干旱地区的生态系统变化。
