Increased harvested carbon of cropland in China

Abstract

Crop harvested carbon is one of the most important components of the carbon cycle in cropland ecosystems, with a significant impact on the carbon budget of croplands. China is one of the most important crop producers, however, it is still unknown on the spatial and temporal variations of harvested carbon. This study collected statistical data on crop production at the province and county levels in China for all 10 crop types from 1981 to 2020 and analyzed the magnitude and long-term trend of harvested crop carbon. Our results found a substantial increase of harvested carbon in cropland from 0.185 Gt C yr-1 in 1981 to 0.423 Gt C yr-1 in 2020 at a rate of 0.006 Gt C yr-1. The results also highlighted that the average annual carbon sink removal from crop harvesting in China from 1981 to 2020 was 0.32 Gt C yr-1, which was comparable to the net carbon sink of the entire terrestrial ecosystems in China. This study further generated a gridded dataset of harvested carbon from 2001 to 2019 in China by using jointly the statistical crop production and distribution maps of cropland. In addition, a model-data comparison was carried out using the dataset and results from seven state-of-the-art terrestrial ecosystem models, revealing substantial disparities in harvested carbon simulations in China compared to the dataset generated in the study. This study emphasized the increased importance of harvested carbon for estimating cropland carbon budget, and the produced dataset is expected to contribute to carbon budget estimation for cropland ecosystems and the entire China.