Response of ecosystem CO2 fluxes to grazing intensities \u2013 a five-year experiment in the Hulunber meadow steppe of China

R R Yan,Philip J Murray,D Y Jin,L J Xu,B H Zhang,S H Lv,Y C Yan,L H Li,B R Chen,X Wang,G X Yang,X P Xin,H J Tang,S Zhao

doi:10.1038/s41598-017-09855-1

Abstract

Grazing is the primary land use in the Hulunber meadow steppe. However, the quantitative effects of grazing on ecosystem carbon dioxide (CO2) fluxes in this zone remain unclear. A controlled experiment was conducted from 2010 to 2014 to study the effects of six stocking rates on CO2 flux, and the results showed that there were significant differences in CO2 fluxes by year, treatment, and month. The effects of light and intermediate grazing remained relatively constant with grazing year, whereas the effects of heavy grazing increased substantially with grazing duration. CO2 flux significantly decreased with increasing grazing intensity and duration, and it was significantly positively correlated with rainfall, soil moisture (SM), the carbon to nitrogen ratio (C/N ratio), soil available phosphorus (SAP), soil NH4+-N, soil NO3−N, aboveground biomass (AGB), coverage, height, and litter and negatively correlated with air temperature, total soil N (TN) and microbial biomass N (MBN). A correspondence analysis showed that the main factors influencing changes in CO2 emissions under grazing were AGB, height, coverage, SM, NH4+-N and NO3−N. Increased rainfall and reduced grazing resulted in greater CO2 emissions. Our study provides important information to improve our understanding of the role of livestock grazing in GHG emissions.

Highlights

The flux of carbon dioxide (CO2) plays a critical role in the carbon (C) cycle of terrestrial ecosystems and is an important index of soil bioactivity, fertility and ventilation[1,2,3]
We examined how the CO2 fluxes were affected by grazing intensity and grazing duration
Related research has provided detailed comparisons of ecosystem CO2 fluxes under different grazing intensities[20, 26, 27], most studies in grasslands are of short duration and may not accurately capture the ecosystem CO2 emissions associated with grazing by animals

Summary

Introduction

The flux of carbon dioxide (CO2) plays a critical role in the carbon (C) cycle of terrestrial ecosystems and is an important index of soil bioactivity, fertility and ventilation[1,2,3]. Grazing animals affect organic matter quantity and quality via several mechanisms, including the return of animal wastes to the soil, alteration of plant productivity and vegetation composition (which govern the quality and amount of plant-leaf–root litter exudates entering the soil), and changes in the activity and composition of soil microbial communities. These changes subsequently affect the rates of nutrient www.nature.com/scientificreports/. Quantifying CO2 emissions and the uptake of different grazing stocking rates is an essential step for understanding the roles of semi-arid temperate grasslands in a context of global climate change

Methods

Results

Conclusion