Legacy Effect Of Warming On The Heterotrophic Respiration Of Alpine Grassland On The Qinghai-Tibet Plateau

The response of soil microbial decomposition of soil organic carbon (C) to temperature variation against an average warming background is of great importance to understand how climate change affects the ecosystem C cycling. In this study, a warming and step-wised stop-warming experiment was conducted to examine whether the response of soil respiration (Rs) and heterotrophic respiration (Rh) persists post-warming and to understand the underlying mechanisms. The treatment plots (10 plots) were warmed (similar to 1.5 degrees C at 10 cm soil depth) in 2017, then warming was stopped in one group (5 plots) in 2018 (WS18) and stopped in another group (the remaining 5 plots) in 2019 (WS19). Plant biomass, soil microbial biomass, and soil microbial community composition were measured from 2017 to 2019.On average, warming increased Rh by 28% in 2017. The Rh in WS18 was stilled increased by 26% in 2018, which was lower than the warming induced increase in Rh in WS19 at the same period. The Rh in WS18 showed no difference with the control and that in WS19 was higher than the control in only June in 2019. Aboveground biomass of WS18 and WS19 increased by 20% and 29%, respectively in 2017, and they were still increased by 12% and 17% in 2019 even the warming stopped one two years and one years, respectively. Belowground biomass, microbial biomass, and diversity indices showed no significant differences among treatments in 2018 or 2019. The fungal community was significantly different among WS18, W19, and the control in both 2018 and 2019. The relative abundance of Ascomycetes, which made the largest contribution to the differences in the fungal community, was negatively correlated with Rh (r = -0.4, n = 30, p < 0.05). Our results indicate a warming legacy effect on the microbial decomposition of soil organic C, resulting from the increase in plant productivity and fungal community change when warming stopped.