PRIMARY PRODUCTION AND RAIN USE EFFICIENCY ACROSS A PRECIPITATION GRADIENT ON THE MONGOLIA PLATEAU

TLDR

The response of aboveground net primary production and rain‑use efficiency to precipitation in arid and semiarid ecosystems is key for climate change assessments, yet their patterns in the Eurasian Steppe remain poorly understood. The study examined the spatial and temporal patterns of ANPP and RUE and their driving factors using a long‑term dataset from 21 sites across the Inner Mongolia steppe. By analyzing this dataset, the authors assessed how precipitation, soil nitrogen, and biotic factors influence ANPP and RUE. ANPP increased and its variability declined with higher mean annual precipitation, species richness rose and functional group composition shifted, while RUE increased across ecosystems but decreased within an ecosystem as precipitation rose; these scale‑dependent patterns, driven by interactions among precipitation, soil N, and biotic factors, show that RUE can be enhanced by nitrogen addition and have important implications for climate change impacts and ecosystem management.

Abstract

Understanding how the aboveground net primary production (ANPP) of arid and semiarid ecosystems of the world responds to variations in precipitation is crucial for assessing the impacts of climate change on terrestrial ecosystems. Rain-use efficiency (RUE) is an important measure for acquiring this understanding. However, little is known about the response pattern of RUE for the largest contiguous natural grassland region of the world, the Eurasian Steppe. Here we investigated the spatial and temporal patterns of ANPP and RUE and their key driving factors based on a long-term data set from 21 natural arid and semiarid ecosystem sites across the Inner Mongolia steppe region in northern China. Our results showed that, with increasing mean annual precipitation (MAP), (1) ANPP increased while the interannual variability of ANPP declined, (2) plant species richness increased and the relative abundance of key functional groups shifted predictably, and (3) RUE increased in space across different ecosystems but decreased with increasing annual precipitation within a given ecosystem. These results clearly indicate that the patterns of both ANPP and RUE are scale dependent, and the seemingly conflicting patterns of RUE in space vs. time suggest distinctive underlying mechanisms, involving interactions among precipitation, soil N, and biotic factors. Also, while our results supported the existence of a common maximum RUE, they also indicated that its value could be substantially increased by altering resource availability, such as adding nitrogen. Our findings have important implications for understanding and predicting ecological impacts of global climate change and for management practices in arid and semiarid ecosystems in the Inner Mongolia steppe region and beyond.