J Plant Ecol ›› 2025, Vol. 18 ›› Issue (2): rtaf031.DOI: 10.1093/jpe/rtaf031

• Research Articles •    

Plant diversity modulates hierarchical responses of carbon cycle processes to warming and grazing in an alpine meadow

Wangwang Lü1, Jianping Sun1, Bowen Li1, Yang Zhou1, Caiyun Luo2, Zhenhua Zhang2, Jingya Lü1,3, Lanying Chen4, Yonghui Wang5, Jin-Sheng He6, Tsechoe Dorji1, Jinzhi Ding1 and Shiping Wang1,4,*   

  1. 1State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment (TPESRE), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
    2Northwestern Institute of Plateau Biology, Chinese Academy of Sciences, Xining 810008, China
    3University of the Chinese Academy of Sciences, Beijing 100049, China
    4Tibet University, Lasa 850000, China
    5Ministry of Education Key Laboratory of Ecology and Resource Use of the Mongolian Plateau, School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
    6Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China

    *Corresponding author: E-mail: wangsp@itpcas.ac.cn
  • Received:2024-09-14 Accepted:2025-03-04 Online:2025-04-10 Published:2025-04-01
  • Supported by:
    This work was supported by projects from the Chinese Academy of Sciences (CAS) Project for Young Scientists in Basic Research (YSBR-037), the Postdoctoral Fellowship Program of CPSF (GZB20240779), projects of the Naqu Science and Technology Bureau (NQKJ-2023-03) and the Ali Science and Technology Bureau (QYTZZX-AL2022-05) of Xizang Autonomous Region.

植物多样性调控高寒草甸不同层级碳循环过程对增温和放牧的响应

Abstract: Isolated individual processes of ecosystem carbon (C) cycles have largely shaped our understanding of C cycle processes under environmental change. Yet, in reality, C cycle processes are inter-related and hierarchical. How these processes respond to warming and grazing has rarely been investigated in a single manipulative experiment. Moreover, biodiversity loss is a major driver of ecosystem change under environmental change, but whether these responses are mechanistically linked to biodiversity remains unclear. Here, we performed a 5-year field manipulative warming with seasonal grazing experiment in an alpine meadow on the Qinghai-Tibetan Plateau. Our results showed that both warming and moderate grazing decreased net ecosystem productivity (NEP) by 42.1% and 38.3%, and their interaction decreased it by 56.2% during the summer grazing period. However, they had no significant effects on NEP during the winter grazing period. Overall, annual gross primary productivity (GPP) and ecosystem respiration (Re) were mainly determined by aboveground rather than belowground processes, and Re variation, which was mainly controlled by aboveground respiration explained 50% of the variation in annual NEP under warming and grazing. Moreover, lower species richness induced by warming and grazing caused smaller NEP with smaller net primary productivity and higher aboveground respiration. The responses of aboveground C cycle processes were greater than that of belowground C cycle processes, suggesting asymmetric above- and belowground responses to warming and grazing. Therefore, our findings suggested that there were higher GPP and Re with lower C sequestration (‘two high with one low patterns’) under warming and moderate grazing. Plant diversity modulated the responses of soil C sequestration to warming and grazing. It is essential to understand the underlying mechanisms of the effects of biodiversity on hierarchical C cycle processes under combined warming and grazing in the future.

Key words: hierarchical responses of carbon cycles, plant diversity, warming, summer and winter grazing, alpine meadow, Qinghai-Tibetan Plateau

摘要:
理解生态系统碳循环不同过程对环境变化的响应对于认识碳-气候反馈关系十分重要。然而,以往研究多聚焦于单一碳循环过程的响应,对于不同层级碳循环过程如何响应增温和放牧仍不清楚。尤其是,环境变化引起的生物多样性丧失是生态系统变化的关键驱动因子,但增温和放牧双重叠加背景下碳循环过程与生物多样性的关联仍缺乏研究。针对上述不足,本研究在青藏高原高寒草甸开展了为期5年的增温和季节性放牧控制试验。研究结果显示,在夏季放牧期间,增温和中度放牧处理下净生态系统生产力(NEP)分别降低了42.1%和38.3%,二者的交互作用使其降低了56.2%;然而,在冬季放牧期间,各处理对NEP均无显著影响。不同处理下总初级生产力和生态系统呼吸的差异主要由地上而非地下过程驱动,其中生态系统呼吸的变化(主要受地上呼吸影响)解释了增温和放牧处理下NEP变异的50%。此外,增温和放牧导致的植物丰富度下降抑制了植被净初级生产力且增加地上呼吸,最终导致NEP的降低。此外,研究发现地上碳循环过程的响应比地下过程更加敏感,表明地上-地下碳循环过程对增温和放牧呈现不对称性响应模式。上述结果表明,增温和中度放牧同时提高了高寒草甸总初级生产力和生态系统呼吸,但是降低土壤固碳潜力(即“两高一低”模式)。同时,植物多样性在土壤碳封存对增温和放牧的响应中起到重要调控作用。因此,将来的研究需要关注增温和放牧耦合作用下植物多样性对不同层级碳循环过程的潜在影响机制。

关键词: 碳循环层级响应, 植物多样性, 增温, 夏季和冬季放牧, 高寒草甸, 青藏高原