Advances in the study of shrubland facilitation on herbs in arid and semi-arid regions

doi:10.17521/cjpe.2021.0382

Abstract

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

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[J]. Chin J Plant Ecol, 2022, 46(11): 1321-1333.

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References 136

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