Contrasting impacts of grassland restoration methods on soil greenhouse gases emissions under warming conditions in Northern Tibet

Abstract

In the context of climate warming, grassland restoration on Qinghai-Tibet Plateau (QTP) may have a significant impact on greenhouse gases (GHGs) emissions. However, the response of GHGs emissions, global warming potential (GWP) and temperature sensitivity coefficient (Q₁₀) from different restored grasslands on QTP to warming remains unclear. We adopted three restoration methods: natural-restoration (NR), no-till-replanting (S), and till-replanting (TS), using natural-degradation grassland (ND) as a control and an open top chamber (OTC) as a simulated warming (Ws) device to clarify the response mechanism of GHGs emissions to warming, and then we evaluated the GWP and Q₁₀ of restored grasslands on the QTP. Under Wns conditions, S resulted in the lowest GHGs emissions (by 66.22 %) and the lowest GWP related to ND. Under Ws conditions, TS suppressed the emissions of CO₂ (by 23.43 %) and CH₄ (by 46.34 %), maintaining the lowest N₂O increment and significantly reducing GWP compared to Wns (by 23.73 %). Under the Wns and Ws conditions, the contribution rate of CO₂ to GWP exceeded 93 % in all treatments, and Ws led to a decrease in the Q₁₀ of GHGs. Structural equation model analysis showed that Ws and grassland restoration directly affected ROC, DOC, MBC and above-ground biomass (AGB), which in turn affected GWP. In summary, S effectively reduced GWP under Wns conditions, and GWP of TS was effectively alleviated under Ws conditions. Labile organic carbon and AGB are the preferred triggering factor for GWP under the conditions of Ws and grassland restoration. Our study offers a theoretical foundation and technical framework for advancing our comprehension of degraded grassland restoration and its implications for greenhouse gas dynamics on the QTP under climate warming scenarios.