Alpine forest soil in the southeastern Qinghai–Xizang Plateau plays a crucial role in regional and global climate and biogeochemical cycles,yet the elevational distribution of soil nitrogen(N)availability and losing ...Alpine forest soil in the southeastern Qinghai–Xizang Plateau plays a crucial role in regional and global climate and biogeochemical cycles,yet the elevational distribution of soil nitrogen(N)availability and losing risk is unresolved.In this study,we characterized soil N composition and key N transformation processes across different elevations in 3 typical mounts of the Qinghai–Xizang Plateau.In contrast to previous suggestions,soil total N and ammonium are found to accumulate in high elevation zones.This accumulation of N at higher altitudes is due to a consistent soil net N mineralization rate coupled with an extremely low net nitrification rate,which is suppressed by low p H and high soil moisture in high elevation zones.Moreover,the elevated rates of biological N fixation along the elevation further contribute to N accumulation in high elevation regions in which the acid-tolerant Bradyrhizobium,plant-associated Herbaspirillum,and Klebsiella are identified as the key diazotrophic microbial taxa responsible for active N fixation.Collectively,our results suggest that total N and NH_(4)^(+)-N accumulation in higher altitude zone is a ubiquitous phenomenon in the southeast Qinghai–Xizang Plateau,with lower nitrification rates and higher biological nitrogen fixation being key processes enabling this occurrence.展开更多
基金supported by the Second Qinghai-Xizang Plateau Scientific Expedition and Research Program(2019QZKK0306 and 2019QZKK0308)
文摘Alpine forest soil in the southeastern Qinghai–Xizang Plateau plays a crucial role in regional and global climate and biogeochemical cycles,yet the elevational distribution of soil nitrogen(N)availability and losing risk is unresolved.In this study,we characterized soil N composition and key N transformation processes across different elevations in 3 typical mounts of the Qinghai–Xizang Plateau.In contrast to previous suggestions,soil total N and ammonium are found to accumulate in high elevation zones.This accumulation of N at higher altitudes is due to a consistent soil net N mineralization rate coupled with an extremely low net nitrification rate,which is suppressed by low p H and high soil moisture in high elevation zones.Moreover,the elevated rates of biological N fixation along the elevation further contribute to N accumulation in high elevation regions in which the acid-tolerant Bradyrhizobium,plant-associated Herbaspirillum,and Klebsiella are identified as the key diazotrophic microbial taxa responsible for active N fixation.Collectively,our results suggest that total N and NH_(4)^(+)-N accumulation in higher altitude zone is a ubiquitous phenomenon in the southeast Qinghai–Xizang Plateau,with lower nitrification rates and higher biological nitrogen fixation being key processes enabling this occurrence.
