Li Ziliang, Xu Weijie, Kang Luyao, Kuzyakov Yakov, Chen Leiyi, He Mei, Liu Futing, Zhang Dianye, Zhou Wei, Liu Xuning, Yang Yuanhe
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
China National Botanical Garden, Beijing, China.
Glob Chang Biol. 2023 Nov;29(22):6367-6382. doi: 10.1111/gcb.16938. Epub 2023 Sep 11.
Mineralization 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 C-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.
热喀斯特湖溶解有机物质（DOM）的矿化作用在多年冻土碳（C）循环中发挥着不可忽视的作用，但由于其与外部碳和养分输入（即水生激发效应和养分效应）的复杂相互作用，人们对其了解甚少。基于大规模湖泊采样和实验室培养，结合碳稳定同位素标记、光谱学和高通量测序，我们沿着青藏高原1100公里的样带，研究了30个热喀斯特湖DOM生物降解的激发效应和养分效应的大规模模式及主要驱动因素。我们观察到，不稳定碳和磷（P）而非氮（N）的输入刺激了DOM生物降解，激发效应和磷效应分别比未添加处理高出172%和451%。我们还检测到不稳定碳和养分供应对DOM生物降解有显著的交互作用，不稳定碳和养分联合添加比单独的碳或养分处理诱导更强的微生物矿化，这表明高山热喀斯特湖中的微生物活动同时受到碳和养分的限制。我们进一步发现，水生激发效应主要由DOM质量驱动，激发强度随DOM难降解性增加而增加，这反映了外部碳作为微生物活动能源的限制。更大的激发强度还与更高的群落水平核糖体RNA基因操纵子（rrn）拷贝数、细菌多样性以及背景可溶性活性磷浓度增加有关。相反，磷效应随DOM难降解性以及背景可溶性活性磷和铵浓度降低而降低，这表明随着碳限制增强但养分限制降低，磷有效性在介导DOM生物降解中的重要性下降。总体而言，外部碳和磷输入对热喀斯特湖DOM生物降解的刺激将放大该高山多年冻土区的碳-气候反馈。
