Contribution of Climate Change and Grazing on Carbon Dynamics in Central Asian Pasturelands

Chaofan Li,Qifei Han,Wenqiang Xu

doi:10.3390/rs14051210

Abstract

Reducing the uncertainties in carbon balance assessment is essential for better pastureland management in arid areas. Climate forcing data are some of the major uncertainty sources. In this study, a modified Biome-BGC grazing model was driven by an ensemble of reanalysis data of the Climate Forecast System Reanalysis data (CFSR), the European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-Interim), and the Modern-Era Retrospective Analysis for Research and Applications (MERRA), to study the effect of climate change and grazing on the net ecosystem exchange (NEE) of the pasturelands in Central Asia. Afterwards, we evaluated the performance of corresponding climate datasets over four major pastureland types, and quantified the modeling uncertainty induced by climate forcing data. Our results suggest that (1) a significant positive trend in temperature and a negative trend in precipitation were obtained from the three climate datasets. The average precipitation is apparently higher in the CFSR and MERRA data, showing the highest temperature value among the data sets; (2) pasturelands in Central Asia released 2.10 ± 1.60 Pg C in the past 36 years. The highest values were obtained with the CFSR (−1.53 Pg C) and the lowest with the MERRA (−2.35 Pg C) data set; (3) without grazing effects, pasturelands in Central Asia assimilated 0.13 ± 0.06 Pg C from 1981–2014. Grazing activities dominated carbon release (100%), whereas climate changes dominated carbon assimilation (offset 6.22% of all the carbon release). This study offered possible implications to the policy makers and local herdsmen of sustainable management of pastureland and the adaptation of climate change in Central Asia.

Highlights

Occupying about 47% of the global land area, the dryland ecosystem is an essential component to the global carbon cycle [1]
Our results show that the annual net ecosystem exchange (NEE) of Central Asia generally had an increasing trend from 1981–2014, which is in line with some previous studies [13,14,29,30]
This work quantified the temporal and spatial effects and the relative impacts of recent climate change and grazing activities on the NEE for each country or region (Xinjiang), by using the Biome-BGC grazing model forced by three climate datasets (CFSR, ERA-Interim, and Modern-Era Retrospective Analysis for Research and Applications (MERRA))

Summary

Introduction

Occupying about 47% of the global land area, the dryland ecosystem is an essential component to the global carbon cycle [1]. Most of the arid and semiarid regions are facing serious ecosystem degradation that was caused by climate change, as well as human interferences [2]. Carbon dynamics in the dryland ecosystem are sensitive to climatic variability and human activity, yet considerably less is known about the extent of the influence. Biogeochemical models constrained by high-quality, gridded atmospheric variables are essential for simulating the response of carbon and water dynamics to environmental changes at a regional scale [4,5]. Comparing the uncertainties resulting from model schemes and parameterizations, uncertainties caused by the meteorology-driven data need to be further investigated, especially in arid and semi-arid regions, which can deepen our understanding

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Conclusion