Tiantong National Station of Forest Ecosystem Research, Center for Global Change and Ecological Forecasting, School of Ecological and Environmental Sciences, East China Normal University, Shanghai, China.
Institute of Eco-Chongming, Shanghai, China.
Nat Ecol Evol. 2018 Dec;2(12):1897-1905. doi: 10.1038/s41559-018-0714-0. Epub 2018 Nov 12.
The annual peak growth of vegetation is critical in characterizing the capacity of terrestrial ecosystem productivity and shaping the seasonality of atmospheric CO concentrations. The recent greening of global lands suggests an increasing trend of terrestrial vegetation growth, but whether or not the peak growth has been globally enhanced still remains unclear. Here, we use two global datasets of gross primary productivity (GPP) and a satellite-derived Normalized Difference Vegetation Index (NDVI) to characterize recent changes in annual peak vegetation growth (that is, GPP and NDVI). We demonstrate that the peak in the growth of global vegetation has been linearly increasing during the past three decades. About 65% of the NDVI variation is evenly explained by expanding croplands (21%), rising CO (22%) and intensifying nitrogen deposition (22%). The contribution of expanding croplands to the peak growth trend is substantiated by measurements from eddy-flux towers, sun-induced chlorophyll fluorescence and a global database of plant traits, all of which demonstrate that croplands have a higher photosynthetic capacity than other vegetation types. The large contribution of CO is also supported by a meta-analysis of 466 manipulative experiments and 15 terrestrial biosphere models. Furthermore, we show that the contribution of GPP to the change in annual GPP is less in the tropics than in other regions. These multiple lines of evidence reveal an increasing trend in the peak growth of global vegetation. The findings highlight the important roles of agricultural intensification and atmospheric changes in reshaping the seasonality of global vegetation growth.
植被的年际峰值生长对刻画陆地生态系统生产力的能力以及塑造大气 CO2 浓度的季节性起着关键作用。最近全球陆地的变绿表明陆地植被生长呈增加趋势，但峰值生长是否在全球范围内得到增强仍不清楚。在这里，我们使用两个全球总初级生产力 (GPP) 数据集和一个卫星衍生的归一化差异植被指数 (NDVI) 来刻画植被年际峰值生长（即 GPP 和 NDVI）的近期变化。我们表明，在过去三十年中，全球植被生长的峰值呈线性增加。NDVI 变化的约 65%可以由扩展的耕地（21%）、上升的 CO2（22%）和加剧的氮沉降（22%）得到很好的解释。扩展耕地对峰值生长趋势的贡献得到了涡度通量塔、太阳诱导叶绿素荧光和全球植物性状数据库的测量结果的证实，这些结果都表明耕地的光合作用能力高于其他植被类型。466 个操纵实验和 15 个陆地生物圈模型的荟萃分析也支持 CO2 的巨大贡献。此外，我们表明，GPP 对年际 GPP 变化的贡献在热带地区小于其他地区。这些多重证据揭示了全球植被峰值生长呈增加趋势。研究结果突出了农业集约化和大气变化在重塑全球植被生长季节性方面的重要作用。
