Soil Microbial Metabolic Quotient in Inner Mongolian Grasslands: Patterns and Influence Factors

Abstract

Microbial metabolic quotient (MMQ) is the rate of soil microbial respiration per unit of microbial biomass, and represents the capacity of soil microbes to utilize soil organic matter. Understanding the regional variation and determinants of MMQ can help predict the responses of soil respiration rate to global climate change. Accordingly, we measured and analyzed MMQ-related data (e.g., soil basic respiration rate at 20°C and soil microbial biomass) from 17 grassland sites, which located in meadow steppe, typical steppe, and desert steppe along a 1000-km transect across the Inner Mongolian grasslands, China. Results showed that MMQ varied significantly among the different grassland types (P typical > meadow) and decreased from southwest to northeast (r = − 0.81) with increasing latitude (r = − 0.50), and with increasing mean annual precipitation (r = − 0.69). Precipitation accounted for 56% of the total variation in MMQ, whereas temperature accounted for 26%. MMQ was negatively correlated with precipitation across the Inner Mongolian grasslands. Therefore, climate change, especially in regard to precipitation, may influence soil microbial respiration and soil carbon dynamics through altering MMQ. These results highlighted the importance of spatial patterns in MMQ for accurately evaluating the responses of soil respiration to climate change at regional and global scales.