Journal of Plant Ecology ›› 2023, Vol. 16 ›› Issue (2): 0-rtac062.DOI: 10.1093/jpe/rtac062

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  • 收稿日期:2021-08-29 修回日期:2021-11-03 接受日期:2022-04-27 出版日期:2023-04-01 发布日期:2022-05-11

The joint effects of resource stress and grazing on plant-plant interactions in alpine meadows on the eastern Qinghai-Tibetan Plateau

Li Mo1,2, Hao Yang1,*, Peng Luo1,*, Cheng-Xiang Mou3, Jun Wang4   

  1. 1Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China;
    2Sichuan Key Laboratory of Conservation Biology for Endangered Wildlife, Chengdu Research Base of Giant Panda Breeding, Chengdu 610081, China;
    3College of Chemistry and Life Sciences, Sichuan Provincial Key Laboratory for Development and Utilization of Characteristic Horticultural Biological Resources, Chengdu Normal University, Chengdu 611130, China;
    4College of Environmental Science and Engineering, China West Normal University, Nanchong 637002, China

摘要: 胁迫梯度假说认为,植物之间的正相互作用频率随着胁迫程度的增加而增加。然而,在高寒草甸生态系统中,放牧干扰和资源胁迫对植物相互作用的联合效应仍不清楚。本研究通过对青藏高原东缘沙化高寒草甸两种优势种[沙生薹草(Carex praeclara;不可食)和藏茴香(Carum carvi;可食)]的空间关联的研究,探讨了放牧和未放牧条件下,3种沙化水平(轻度、中度、重度)上植物相互作用的变化,以检验胁迫梯度假说在青藏高原东缘沙化高寒草甸的普遍性。研究结果表明,在无放牧干扰下,随着沙化程度的增加,沙生薹草和藏茴香的种内相互作用由正转化为负,而种间相互作用由负转化为正。然而,当放牧干扰存在时,各沙化水平下藏茴香的种内相互作用均为中性;在中等胁迫条件下,种间相互作用也由负转化为正,但在严重胁迫梯度下,种间正相互作用崩溃,这与胁迫梯度假说的预测不一致。本研究结果进一步证明,在高寒生态系统中,放牧强烈影响着种内和种间相互作用的平衡。

关键词: 高寒草甸, 沙化梯度, 放牧, 种内和种间相互作用, 青藏高原, 胁迫梯度假说

Abstract: The stress gradient hypothesis (SGH) proposes that the frequency of positive interactions among plants is increased with stress. However, in alpine meadow ecosystems, the joint effects of herbivore grazing and resource stress on plant-plant interactions remain poorly understood. By investigating the spatial associations of two dominant, widely distributed species—Carex praeclara (unpalatable) and Carum carvi (palatable)—we explored changes in plant-plant interactions at three desertification levels (light, moderate and severe) under grazed and ungrazed conditions to test the generality of the SGH in the desertified alpine meadows on the eastern Qinghai-Tibetan Plateau. Without grazing disturbance, intraspecific interactions of C. praeclara and C. carvi changed from positive to negative, while their interspecific interactions shifted from negative to positive along the desertification gradient from light to severe level. However, intraspecific interactions of C. carvi under grazing remained neutral at all desertification levels, while the net interspecific interactions between these species changed from competitive to facilitative under moderate stress. But, the positive interactions collapsed under severe stress, which is inconsistent with the SGH prediction. Our results reinforced the evidence that livestock grazing strongly influences the balance of intra- and interspecific interactions along the stress gradients in the alpine ecosystems.

Key words: alpine meadow, desertification gradients, grazing, intra- and interspecific interactions, Qinghai-Tibetan Plateau, stress gradient hypothesis