Livestock grazing strongly affects biodiversity and ecosystem functioning in grasslands. However, it remains unclear how different grazing impact multiple biodiversity, ecosystem multifunctionality (EMF), and their relationship with the interactions of grazing duration, livestock type and climatic factors. Here, we conducted a global synthesis from 104 published studies. Our results showed that light and moderate grazing improved multi-diversity, but heavy grazing significantly decreased multi-diversity and EMF. The grazing-induced decrease of EMF intensified with grazing duration, and the reduction of multi-diversity and EMF under intensive grazing was stronger in more arid climates. The response of EMF increased linearly with that of multi-diversity under all grazing intensities. Moreover, grazing intensity reduced EMF largely via decreasing multi-diversity, whereas a shift of livestock type from small to large size promoted EMF by increasing multi-diversity. This study provides first empirical evidence and new insights into the relationship between multi-diversity and EMF under grazing in global grasslands.
Accurate estimation of N2O emission is one of the primary objectives to project the warming potential. However, the global patterns and main controlling factors of soil N2O emission remain elusive. We compiled a dataset with 6016 field observations from 219 articles and found that the averaged soil N2O emission rate was 1111.8 ± 26.59 µg N m-2 day-1. Soil N2O emission rates were significantly influenced by climatic factors (i.e. mean annual temperature), soil physical and chemical properties (e.g. pH, nitrate, ammonium, and total nitrogen), and microbial traits (microbial biomass nitrogen) at a global scale. The combined direct effects of soil nitrate, ammonium, and total nitrogen (combined standard coefficient = 0.45) accounted for the most variance of global soil N2O emissions (total standard coefficient = 0.84). This study highlights the critical roles of soil nitrogen substrates on N2O emission, which will be helpful to optimize the process-models on soil N2O emissions.