Reclamation Enhances the Ratio of Soil to Ecosystem Respiration under Warming in an Alpine Meadow

The construction of cultivated grasslands can increase grass production but also pose a threat to soil carbon storage, and it still remains unclear how construction of cultivated grasslands affects the components of ecosystem respiration (ER) toward a warming climate. Therefore, we conducted a 5-year (2012 to 2016) manipulative warming experiment in an alpine meadow and a cultivated grassland on the Qinghai–Xizang Plateau to explore the separate and interactive effects of warming and reclamation on soil respiration (SR), crop respiration (CR), ER, and the ratio of SR to ER (SR/ER). The plant height, coverage, aboveground production, SR, ER, CR, and SR/ER were measured. We found that warming increased the 5-year mean SR by 61.1% and 63.4% in the alpine meadow and the cultivated grassland, respectively. The 5-year mean SR/ER was increased by warming for the alpine meadow (38.7%) and the cultivated grassland (38.0%). Under warming, reclamation increased the 5-year mean SR/ER by 15.0%. Reclamation increased the sensitivity of SR and CR to warming, resulting in the increase in SR/ER under warming in the cultivated grassland. Overall, our results indicated that reclamation can increase the contribution of SR to the ecosystem carbon emission under warming and is detrimental to the storage of soil carbon in the alpine meadow especially toward a warming climate. Therefore, despite the increase in production by the construction of cultivated grasslands, the increase in carbon emission under warming by reclamation should attract attention.