Accelerated organic matter decomposition in thermokarst lakes upon carbon and phosphorus inputs
AbstractMineralization of dissolved organic matter (DOM) in thermokarst lakes plays a non-negligible role in the permafrost carbon (C) cycle, but remains poorly understood due to its complex interactions with external C and nutrient inputs (i.e., aquatic priming and nutrient effects). Based on large-scale lake sampling and laboratory incubations, in combination with 13C-stable-isotope labeling, optical spectroscopy, and high-throughput sequencing, we examined large-scale patterns and dominant drivers of priming and nutrient effects of DOM biodegradation across 30 thermokarst lakes along a 1100-km transect on the Tibetan Plateau. We observed that labile C and phosphorus (P) rather than nitrogen (N) inputs stimulated DOM biodegradation, with the priming and P effects being 172% and 451% over unamended control, respectively. We also detected significant interactive effects of labile C and nutrient supply on DOM biodegradation, with the combined labile C and nutrient additions inducing stronger microbial mineralization than C or nutrient treatment alone, illustrating that microbial activity in alpine thermokarst lakes is co-limited by both C and nutrients. We further found that the aquatic priming was mainly driven by DOM quality, with the priming intensity increasing with DOM recalcitrance, reflecting the limitation of external C as energy sources for microbial activity. Greater priming intensity was also associated with higher community-level ribosomal RNA gene operon (rrn) copy number and bacterial diversity as well as increased background soluble reactive P concentration. In contrast, the P effect decreased with DOM recalcitrance as well as with background soluble reactive P and ammonium concentrations, revealing the declining importance of P availability in mediating DOM biodegradation with enhanced C limitation but reduced nutrient limitation. Overall, the stimulation of external C and P inputs on DOM biodegradation in thermokarst lakes would amplify C-climate feedback in this alpine permafrost region.
Авторы
Li Ziliang1,2,3
,
Xu Weijie1,2,3
,
Kang Luyao1,2,3
,
Kuzyakov Yakov4,5,6
,
Chen Leiyi1,2
,
He Mei1,2
,
Liu Futing7
,
Zhang Dianye1,2
,
Zhou Wei1,2,3
,
Liu Xuning1,2
,
Yang Yuanhe1,2,3
1 State Key Laboratory of Vegetation and Environmental Change Institute of Botany, Chinese Academy of Sciences Beijing China
2 China National Botanical Garden Beijing China
3 University of Chinese Academy of Sciences Beijing China
4 Department of Soil Science of Temperate Ecosystems University of Göttingen Göttingen Germany
5 Department of Agricultural Soil Science University of Göttingen Göttingen Germany
6 Peoples Friendship University of Russia (RUDN University) Moscow Russia
7 Key Laboratory of Forest Ecology and Environment of National Forestry and Grassland Administration Ecology and Nature Conservation Institute, Chinese Academy of Forestry Beijing China