Synthesis Research Center of Chinese Ecosystem Research Network, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
Synthesis Research Center of Chinese Ecosystem Research Network, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China.
Sci Total Environ. 2021 May 1;767:144669. doi: 10.1016/j.scitotenv.2020.144669. Epub 2020 Dec 30.
Vegetation productivity dynamics are closely related to climate change, and water availability determines vegetation growth in water-limited ecosystems. Nevertheless, how changes in the interactions between climatic factors and vegetation activity variation regulate the relationship between their trends remains unclear. The Normalized Difference Vegetation Index (NDVI) is an effective proxy of vegetation growth. First, we investigated the NDVI trends, and the results revealed a vegetation activity with weaker greening and greater spatial heterogeneity after an obvious land-cover breakpoint in 1999 compared with that before 1999 in northwest China. Notably, the Loess Plateau greatly led the greenness trends, but the Tibet Plateau showed mean browning after 1999, which implied that the coupling of climate change and vegetation trends varied with spatio-temporal changes. Subsequently, using the Geographical Detector Method (GDM), we quantified and compared the association between climate change and the interannual variability of NDVI in the two stages. Vegetation productivity variation is more closely related to changes in climatic factors after 1999 compared with that before 1999. Precipitation (PPT) and vapor pressure deficit (VPD) are the primary constraints to vegetation growth in both stages. Patterns in NDVI trend increases are consistent with those of increased PPT and decreased VPD and vice versa after 1999. However, the same patterns were not observed before 1999 because of the weak association between climate change and NDVI variation. This implicated a great significance of the association between climate change and changes in vegetation activity for the prediction of potential carbon sequestration due to the shift of dominant factors and their trends under future climate change.
植被生产力动态与气候变化密切相关，而水分可利用性决定了水分限制生态系统中植被的生长。然而，气候因素相互作用的变化如何调节它们趋势之间的关系仍不清楚。归一化差异植被指数（NDVI）是植被生长的有效替代物。首先，我们研究了 NDVI 的趋势，结果表明，与 1999 年之前相比，1999 年之后中国西北地区的植被活动表现出较弱的绿化和更大的空间异质性。值得注意的是，黄土高原极大地引领了绿化趋势，但青藏高原在 1999 年之后呈现出平均变褐的趋势，这意味着气候变化和植被趋势的耦合随着时空变化而变化。随后，我们使用地理探测器方法（GDM）量化并比较了两个阶段气候变化与 NDVI 年际变率之间的关系。与 1999 年之前相比，1999 年之后植被生产力变化与气候因子变化的关系更为密切。降水（PPT）和水汽压亏缺（VPD）是两个阶段植被生长的主要限制因素。1999 年之后，NDVI 趋势增加的模式与 PPT 增加和 VPD 减少的模式一致，反之亦然。然而，在 1999 年之前，由于气候变化与 NDVI 变化之间的弱相关性，并没有观察到相同的模式。这表明，由于未来气候变化下主导因素及其趋势的转变，气候变化与植被活动变化之间的关联对于预测潜在的碳固存具有重要意义。
