Varying soil respiration under long-term warming and clipping due to shifting carbon allocation toward below-ground

Abstract

Listen

Translate article

Global warming and land-use change have profound impacts on soil respiration (Rs), with consequent changes in carbon exchange between terrestrial ecosystem and atmosphere and its feedback to climate change. However, it is not clear how soil respiration and its components (heterotrophic respiration, Rh; and autotrophic respiration, Ra) respond to long-term warming and clipping in alpine meadow, and what are the controlling factors for the responses of soil respiration. To answer these questions, we conducted a field experiment of warming and clipping in an alpine meadow on the Qinghai-Tibet Plateau from 2014 to 2019. Infrared heaters were used to simulate climate warming and plots were clipped once a year to mimic hay or biofuel harvest. The results showed that warming decreased Rh by 5.06% but stimulated Ra by 10.08% across years, while clipping enhanced Rs, Rh and Ra by 12.31%, 18.65% and 1.29%, respectively, and marginally interacted with warming in impacting Ra across the years. Furthermore, the warming effect on soil respiration and its components varied largely over years, which was mostly attributable to the changes in the ratio of above-ground to below-ground net primary productivity (ANPP/BNPP, A/B) and soil temperature. Increased allocation of photosynthate toward below-ground caused the gradual increase in Ra and Rs under long-term warming. While soil temperature changes explained the variation of warming effects on Rh across years. The results demonstrated that soil respiration and its components in the alpine meadow are highly sensitive to climate warming and hay harvest but with large interannual variations in their responses. We highlight that plant carbon allocation is an emerging property in determining soil respiration under climate warming.