Sun Yuanfeng, Yang Yuanhe, Zhao Xia, Tang Zhiyao, Wang Shaopeng, Fang Jingyun
Institute of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, 100871, China.
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
Sci China Life Sci. 2021 May;64(5):739-751. doi: 10.1007/s11427-020-1837-9. Epub 2020 Nov 17.
Understanding patterns and determinants of net primary productivity (NPP) in global grasslands is ongoing challenges, especially for belowground NPP (BNPP) and its fraction (f). By developing a comprehensive field-based dataset, we revealed that, along with gradients of mean annual precipitation, actual evapotranspiration, and aridity, aboveground NPP (ANPP), BNPP, and total NPP (TNPP) exhibited hump-shaped patterns, whereas f showed an opposite trend. ANPP and TNPP showed positive correlations with mean annual temperature, but f was negatively correlated with it. The relationship between BNPP and climatic factors was considerably weak, indicating that BNPP was relatively stable regardless of the climate conditions. We also observed that the sensitivities of ANPP and BNPP to interannual temperature variability and those of BNPP to interannual precipitation fluctuations exhibited large variations among different study sites, and differed from those at the spatial scale. In contrast, the temporal sensitivities of ANPP to interannual precipitation variability were highly similar across all the individual sites and much smaller than those at the spatial scale. Overall, these results highlight that precipitation, temperature and evapotranspiration all play vital roles in shaping ANPP pattern and its partitioning to belowground and that the patterns of BNPP along climatic gradients do not mirror those of the ANPP.
了解全球草原净初级生产力（NPP）的模式和决定因素是一项持续存在的挑战，尤其是对于地下NPP（BNPP）及其比例（f）而言。通过建立一个基于实地的综合数据集，我们发现，随着年平均降水量、实际蒸散量和干旱程度的梯度变化，地上NPP（ANPP）、BNPP和总NPP（TNPP）呈现出驼峰状模式，而f则呈现相反趋势。ANPP和TNPP与年平均温度呈正相关，但f与之呈负相关。BNPP与气候因子之间的关系相当微弱，这表明无论气候条件如何，BNPP都相对稳定。我们还观察到，不同研究地点的ANPP和BNPP对年际温度变化的敏感性以及BNPP对年际降水波动的敏感性存在很大差异，且与空间尺度上的情况不同。相比之下，所有单个地点的ANPP对年际降水变化的时间敏感性高度相似，且远小于空间尺度上的敏感性。总体而言，这些结果突出表明，降水、温度和蒸散在塑造ANPP模式及其向地下的分配方面都起着至关重要的作用，并且BNPP沿气候梯度的模式与ANPP的模式并不相同。
