干旱半干旱区灌丛对草本植物的促进作用研究进展

doi:10.17521/cjpe.2021.0382

摘要/Abstract

摘要：

植物间竞争与促进作用是调控物种、群落以及生态系统对环境变化响应的重要机制, 其中促进作用在胁迫生境发挥更重要的作用。该文从灌丛对草本植物的促进作用随水分的变化规律、发生机制以及在植被恢复中的应用3个方面, 总结了最近30年来干旱半干旱区灌丛促进作用的主要研究进展。作为预测植物间相互作用随环境胁迫程度变化的经典模式, 胁迫梯度假说(SGH)认为促进作用随环境胁迫程度的增强而增强。然而, 在以水分为主要限制因子的干旱半干旱生态系统中, SGH存在很大的不确定性, 即灌丛对草本植物的促进作用随水分的减少并不总是线性增强, 这种不确定性不仅与灌丛对土壤水分的复杂影响密切相关, 同时还受到物种特性、植物生活史阶段、研究方法、研究尺度和指标等的影响。干旱半干旱区灌丛通过调节其冠层下土壤水分、养分及微生物群落, 改善冠层内温度和辐射, 抵御取食者等的方式, 直接或间接影响其冠层下植物的存活、生长和繁殖。近年开展的去除实验结果表明, 灌木地下部分对灌丛促进作用的影响强于地上部分。灌丛促进作用被认为是退化生态系统植被恢复的有效手段, 而植被恢复成功与否受到环境胁迫程度、物种特性、植物生活史阶段和土地利用等的综合影响。在气候变化和人类活动的双重影响下, 全球干旱半干旱区面积不断扩大, 灌丛明显扩张。明确灌丛促进作用发生机制, 探索灌丛与草本植物间相互作用随干旱梯度的变化规律, 阐明灌丛对草本植物的影响, 对预测干旱半干旱区物种和生态系统对气候变化的响应具有重要意义。基于目前的研究进展和干旱半干旱区发生的气候和环境变化, 该文对未来灌丛促进作用研究提出以下展望: 1)探索利用生物指标指示环境胁迫程度和植物间相互作用; 2)明确灌木地上和地下部分在促进作用中的相对贡献, 进而阐明灌丛促进作用的发生机制; 3)探索受益物种对护卫植物的反馈作用机制; 4)综合评估护卫植物在植被恢复中的贡献; 5)加强模拟增水实验和长期定位观测研究; 6)加强促进作用与其他研究领域的结合, 如促进作用与生物入侵、灌丛化、生物多样性和生态系统功能的关系, 促进作用对气候变化的响应等。

关键词: 护卫植物, 水分可利用性, 物种丰富度, 胁迫梯度假说, 促进作用, 植被恢复

Abstract:

Competition and facilitation among plants are an important part of the mechanisms regulating the responses of species, communities, and ecosystems to environmental changes. Basically, facilitation plays a more important role than competition in stress environments. The present review summarized the research progress of shrubland facilitation in arid and semi-arid regions in the past 30 years, on the aspects of trends of facilitation along a water availability gradient, mechanisms of shrubland facilitation, and the application of shrubland facilitation in vegetation restoration. As the most important empirical model that predicts the trend of plant-plant interactions along abiotic stress gradient, stress gradient hypothesis (SGH) posits that facilitation increases with increasing abiotic stress. However, SGH has been largely debated in water limiting system. Shrubland facilitation does not always increase linearly with the decreasing water availability, which is not only closely related to the complex impact of shrub on soil water, but also associates with the species identities, plant life history stages, study methods, scales and indicators. Arid shrubs could affect the survival, growth, and reproduction of its understory plants via ameliorating soil moisture and nutrient, mediating soil microbial community compositions, buffering extreme temperature and radiation, and resisting predators. Removal studies have shown that the effects of shrub on belowground play a stronger role than aboveground on shrubland facilitation. Shrubland facilitations are commonly considered a potential effective approach of vegetation restoration in degraded ecosystems. Whereas, the success of vegetation restoration is comprehensively affected by the abiotic stress, species identities, plant life history stages and land use. Under the dual influence of climate change and human activities, the areas of drylands and shrublands are assumed to be expanding. Thus, the studies on mechanisms of shrubland facilitation and trends of shrub-herbs interactions along drought gradient, as well as the effects of shrub on herbs, are critical for predicting the responses of species and grassland to climate change in arid and semi-arid regions. Based on the current research progresses and environmental changes in arid and semi-arid regions, the present review proposes the following issues in the future studies: 1) exploring the biological indicators to the abiotic stress and plant-plant interactions; 2) clarifying the relative contribution of shrub belowground versus aboveground on facilitation, in order to disclose the mechanisms of shrubland facilitation; 3) exploring the feedback effect of beneficiaries on facilitators; 4) assessing the comprehensive role of nurse plants on vegetation restoration; 5) popularizing the study methods of manipulative water experiments and long-term positioning observations on shrubland facilitation; and 6) addressing the study of plant facilitation on related research issues, such as the relationship between facilitation and species invasion, shrub encroachment, biodiversity and ecosystem function, and the response of facilitation to climate change.

Key words: nurse plant, water availability, species richness, stress gradient hypothesis, facilitation, vegetation restoration

崔光帅, 罗天祥, 梁尔源, 张林. 干旱半干旱区灌丛对草本植物的促进作用研究进展. 植物生态学报, 2022, 46(11): 1321-1333. DOI: 10.17521/cjpe.2021.0382

CUI Guang-Shuai, LUO Tian-Xiang, LIANG Er-Yuan, ZHANG Lin. Advances in the study of shrubland facilitation on herbs in arid and semi-arid regions. Chinese Journal of Plant Ecology, 2022, 46(11): 1321-1333. DOI: 10.17521/cjpe.2021.0382

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