Warming and grazing enhance litter decomposition and nutrient release independent of litter quality in an alpine meadow

Abstract

Aims Warming and grazing and the changes in litter quality induced by them co-determine litter decomposition and nutrient releases in grazing ecosystems. However, their effects have previously been studied in isolation. Methods We conducted a two factorial experiment with asymmetric warming using infrared heaters and moderate grazing in an alpine meadow. Litter samples were collected from all plots in each treatment, among which some subsamples were placed in their original plots and other samples were translocated to other treatment plots to test the relative effects of each treatment on litter decomposition and nutrient releases. Important Findings We found that warming rather than grazing alone significantly increased total losses of litter mass, total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) per unit area due to increases in both mass loss rates and litter biomass. However, grazing with warming did not affect their total mass losses because increased mass loss was offset by decreased litter biomass compared with the control treatment. Seasonal mean soil temperature better predicted litter decomposition than litter lignin content or C:N ratio. There were interactions between warming and grazing, but there were no interactions between them and litter quality on litter decomposition. The temperature sensitivity of TN loss was higher than that of TP loss per unit area. Our results suggested that increased temperature had a greater effect on litter decomposition and nutrient release than change in litter quality, and that more N release from litter could result in greater P deficiency in the alpine meadow.

Quantifying changes in soil organic carbon density from 1982 to 2020 in Chinese grasslands using a random forest model

“…In the northern region of China, MAT showed an increasing trend, resulting in a net decrease in SOCD in the region ( Table 3 ; Figure 6B ). This is due to the fact that (i) the fine and coarse root mass quantity and quality reduced with increased temperature, and the decline in root mass was an important cause of the loss in soil organic matter ( Rasse et al., 2005 ; Ofiti et al., 2021 ), and (ii) the temperature rise would accelerate the decomposition of soil organic matter and thus reduce SOCD ( Duan et al., 2013 ; Lv et al., 2020 ; Li B et al., 2022 ). However, in the southern, northwestern, and Qinghai–Tibetan regions, the climate warming seemed to increase SOCD ( Table 3 ; Figures 6A, C, D ).…”

“…It is reported that wind speed, sunshine duration, and humidity also affect SOCD ( Lu et al., 2013 ; Lei et al., 2019 ; Huang et al., 2022 ). As an important anthropogenic factor, grazing and its intensity (standard sheep unit ha −1 year −1 ) can disturb the carbon balance in ecosystems by affecting SOCD ( Zhang et al., 2016 ; Zhou G et al., 2017 ; Li B et al., 2022 ). For example, slight and heavy grazing intensity may result in SOC loss, while moderate grazing intensity probably promoted SOC accumulation ( Jiang et al., 2020 ; Zhang M et al., 2018 ; Xie and Wu, 2016 ).…”

Evaluation of Ecosystem Services in Ruoergai National Park, China

“…The study area, located on the Qinghai-Tibet Plateau, experiences temperature-driven effects on the soil organic carbon cycle in meadow grassland and swamp ecosystems. Global warming is leading to permafrost melting, accelerating plant root production and turnover rates [43], the decomposition of fallen leaves [44,45], and changes in microbial community structure [46], resulting in increased CO 2 release. As atmospheric CO 2 concentration rises, plants' photosynthesis and productivity increase, leading to greater input of carbon into soil carbon pools [47].…”