The subalpine shrub Dasiphora fruticosa alters seasonal and elevational effects on soil microbial diversity and ecosystem functions on the Tibetan Plateau

Abstract

High‐altitude ecosystems of the Tibetan Plateau are undergoing significant global changes that may stimulate an intense shrub encroachment. The occurrence of shrubs in alpine meadow is commonly thought to alleviating environmental stresses and supporting high diversity which may have important consequences for ecosystem functions. However, few studies have assessed whether and how the role of shrubs interact with season and elevation. In this study, we explored the effects of the shrub, Dasiphora fruticosa, on microbial (α‐ and β‐) diversity and the consequences for ecosystem functions (multifunctionality and the turnover of functions) at five sites along an elevation gradient and across three seasons on the Tibetan Plateau. According to linear mixed‐effect models and structural equation modelling, D. fruticosa altered season and elevation effects and tended to increase microbial α‐diversity, soil carbon–nitrogen (C:N) ratio, understorey biomass and leaf dry matter content, which overall increased soil multifunctionality. We also found that indicators of soil multifunctionality were always positively related to fungal α‐diversity, whereas negatively related to bacterial α‐diversity. Furthermore, the effects of season, elevation, shrub and their interactions on microbial β‐diversity can be explained by temperature, soil water content, pH and understorey biomass, as shown by distance‐based redundancy analysis. Then, we found that D. fruticosa strongly altered the effects of season and elevation on microbial β‐diversity and the turnover of soil C:N ratio, understorey biomass and litter quality, thus influencing ecosystem function turnover. Our results, thus, provided explicit evidences that Dasiphora fruticosa could alter season and elevation effects on species diversity with important consequences on ecosystem functions, highlighting the crucial role of the shrub in affecting ecosystem functions by creating heterogeneous microbial communities and microenvironments in alpine meadows. Our findings can guide management and improve our knowledge on potential implications of changes in the shrub coverage in alpine meadows.

Divergent responses of above- and belowground ecosystem functioning to shrub encroachment in the Tibetan semi-arid alpine steppes

“…In semi-arid alpine regions of the Tibetan Plateau, climatic warming and increased precipitation are expected to cause widespread shrub encroachment into alpine grassland ecosystems (Lu et al, 2022;Wang et al, 2022).Shrubs encroaching will promote plant growth, increase vegetation productivity, and lead to accumulation of soil carbon and nutrients in water-limited alpine grasslands (Pistón et al, 2016;Cui et al, 2023), and, in turn, results in the strengthen of ecosystem functioning (Wang et al, 2023). Consistent with these findings, our study also found that shrub encroachment enhanced ecosystem multifunctionality index of the Tibetan semi-arid alpine steppes (Fig.…”

“…In addition, shrub encroachment could enhance the soil water availability under the shrub canopy by reducing evaporation under the shrub canopy (Iyengar et al, 2017;Liu et al, 2020). It was noted that shrub encroaching induced mitigation of soil water and nutrient deficiencies was the major reason for the abrupt facilitation of ecosystem functioning (Ale et al, 2023;Wang et al, 2023). However, former studies indicated that soil nutrient rather than water availability mainly mediated the encroaching of shrubs caused facilitation impacts on the ecosystem functions of semi-arid alpine grasslands (Cui et al, 2023;Zhao et al, 2023), which is also well reflected by our finding that showed the increased EMF following shrub encroachment (Fig.…”

“…In semi-arid alpine grasslands, increasing evidence suggesting that shrub encroachment can have the potential positive effects on the ecosystem functions, including plant diversity, soil hydrological, and soil fertility (Noumi et al, 2016;Wang et al, 2023). Nevertheless, the degree by which shrub encroachment caused variations in the ecosystem functioning could vary with the traits of encroaching shrubs (e.g., Leguminosae or Non-Leguminosae species).…”

Effect of shrub encroachment on insect herbivory of <i>Polygonum macrophyllum </i>in alpine meadow of Qinghai-Xizang Plateau

“…的现象, 其定义为草地生态系统中原生灌丛生物 量、密度、盖度增加以及草本植物生物量、密度、 盖度减少的现象 (Eldridge et al, 2011;Maestre et al, 2016)。该现象发生的原因包括全球变暖、CO 2 浓度 增加、过度放牧和人类活动等 (Scholes & Archer, 1997;Angassa & Oba, 2007;D'Odorico et al, 2010)。 灌丛化不仅会影响草地生态系统土壤养分、微气候 (温度、湿度等)等非生物因素 (Thompson et al, 2017;Phillips & Wurzburger, 2019;De Frenne et al, 2019), 还会影响植物群落和土壤微生物群落等生物因素 (Pistón et al, 2016;Wang et al, 2019), 从而影响生态 系 统 结 构 和 功 能 (Zhou et al, 2019;Wang et al, 2023)。昆虫植食作用在陆地生态系统中普遍存在, 且扮演着重要角色 (Jankielsohn, 2018;Kristensen et al, 2020), 但目前我们对灌丛化如何影响昆虫植食 作用仍知之甚少。 昆虫植食作用在陆地生态系统中起着重要作 用 (Jankielsohn, 2018;Kristensen et al, 2020)。植食性 昆虫的取食会改变植物代谢、阻碍植物生长繁殖 (Lehndal & Ågren, 2015;Kozlov & Zvereva, 2018), 降低植物群落生物量 (Zhong et al, 2014), 改变植物 群落物种多样性 (Koerner et al, 2018), 并最终影响 生态系统功能 (Zhou et al, 2019)。灌丛化可能会通过 多种途径来影响昆虫植食作用 (Kőrösi et al, 2012;Jaworski & Hilszczański, 2013;Levey et al, 2016;De Frenne et al, 2019): (1)灌丛的冠层下能形成相对稳 定的微气候 (Anthelme et al, 2014), 从而在外界环境 条件较极端(如干旱、高温或低温)时通过缓冲极端 天气的影响为植食性昆虫提供避难所, 增加植食性 昆虫在极端性天气下的存活率(避难所效应, shelter effect) (Reynolds et al, 1999;Jaworski & Hilszczański, 2013;Andrade et al, 2020;Ghazian et al, 2020), 并最 终导致灌丛内的草本植物所遭受的昆虫植食作用 增加。(2)然而与其对应的是, 灌丛在外界环境条件 适宜时不再提供避难所, 反而成为屏障, 阻碍灌丛 外植食性昆虫进入(屏障效应, barrier effect) (Bailey, 1970;Thompson et al, 2017) (Garner & Steinberger, 1989;Ding & Eldridge, 2021) (Herms & Mattson, 1992), 从而更易被植食性昆虫取食(最优...…”

Shrub expansion raises both aboveground and underground multifunctionality on a subtropical plateau grassland: coupling multitrophic community assembly to multifunctionality and functional trade-off

“…Despite the upsurging interest in multifunctionality ( Slade et al, 2017 , Xu et al, 2022 ), multifunctionality changes in response to shrub expansion remain poorly understood ( Chandregowda et al, 2018 ). Although the relationship between biodiversity and multifunctionality has been extensively explored ( Wagg et al, 2014 ; Zhang et al, 2023 ; Wang et al, 2023b ), little is known about the extent to which shrub expansion drives the multifunctionality of aboveground, underground, and entire ecosystems. Although the effects of shrub expansion on aboveground and belowground communities have been studied extensively ( Eldridge et al, 2011 ; Sepp et al, 2021 ; Dengzeng et al, 2022 ; Guo et al, 2022 ; Ding and Eldridge, 2023 ; Wang et al, 2023b ), the relative contributions of aboveground (plant community) and belowground (soil microbial community) diversity to multifunctionality remain largely unresolved ( Berlinches et al, 2022 ; Wang et al, 2023b ), especially for shrub expansion succession.…”