Seasonal Variation and Controlling Factors of Carbon Balance Over Dry Semi-Humid Cropland in Guanzhong Plain

Abstract

A theoretical basis for optimizing mitigation and adaptation to future climate change can be obtained by determining the carbon balance and its control mechanism in agroecosystems. To better understand summer maize and winter wheat agroecosystems in dry semi-humid carbon balance mechanism, we conducted an in-depth analysis of three-year (2019.6-2022.6) seasonal dynamics of carbon flux and its driving factors in summer maize/winter wheat cropland in the Guanzhong Plain combined with path analysis. The results showed that net radiation (Rn) was the main direct controlling factor of net ecosystem exchange (NEE) in the summer maize growing season (Rn), followed by leaf area index (LAI). Moreover, LAI was the main factor controlling the seasonal variation of NEE in winter wheat growing season, followed by Rn. Furthermore, LAI was the dominant direct driving factor for the total primary production (GPP) in summer maize and winter wheat growing seasons. Also, LAI was the dominant driving factor for the total ecosystem total respiration (TER) in the summer maize season while Rn (indirect effect) and LAI (direct effect) were the main influencing factors of TER in the winter wheat season. The NEE values of the summer maize system, winter wheat system, and summer maize/winter wheat system in the Guanzhong Plain were from 119 to 221, from -601 to -595, and from -433 to -291 gCm-2, respectively (net biological production (NBP); from -709 to -437, from 220 to 303, and from -496 and -260  gCm-2, respectively). Notably, the average carbon emission rate of the summer maize/winter wheat system in the Guanzhong Plain, considering the carbon output at harvest is 386.2  gCm-2 year-1. Therefore, this study may guide assessment of carbon balance of agroecosystems in dry sub-humid regions, and provide a strong reference for achieving carbon neutrality in local agroecosystems.

Keywords: Agroecosystem, Carbon flux, Environmental factor, Leaf area index, Carbon balance.