Responses of soil active carbon and nitrogen to short-term warming in alpine treeline of west Sichuan, China

Abstract

Alpine treeline ecosystem is more sensitive to global warming under low temperature limitation with the aggravation of greenhouse effect, which may directly affect plant growth and soil carbon and nitrogen processes. We expected that climate warming would change soil active carbon and nitrogen content in alpine ecosystems. This experiment was conducted in long-term research station of alpine forest ecosystems, in Lixian County, Sichuan Province. The open top camber (OTC) was used to simulate warming, intact soil core (soil organic layer and mineral soil layer) of OTC and CK were collected in April, July and October 2017. Soil dissolved organic carbon (DOC), soil microbial biomass carbon (MBC), dissolved organic nitrogen (DON) and soil microbial biomass nitrogen (MBN) were measured. The results showed that average temperature increased by 0.88 ℃ for air, 0.48 ℃ for soil organic layer and 0.23 ℃ for mineral soil layer. The simulated warming did not significantly change soil organic matter and water content, but significantly increased pH of mine-ral soil layer, and significantly reduced DOC and DON contents of mineral soil layer in non-growing season. There was significant seasonal variation for the contents of DOC, DON and MBN in the two layers, but not for MBC. The MBC and MBN contents of soil organic layer were significantly higher than that of mineral soil layer. There was a significant positive correlation between active carbon and nitrogen with soil organic matter and water content. There was a significant positive correlation between MBC, MBN and soil pH, whereas MBN was negatively correlated with soil temperature.

Keywords: alpine treeline; climate change; open-top camber; soil activated carbon; soil activated nitrogen.