Explore the vast range of titles available.

1. According to the insurance hypothesis, more diverse plant communities are more likely to be resistant to drought. Whilst many experiments have been carried out to determine the effects of plant diversity on plant community insurance, the results are still contradictory. 2. Here, we conducted a drought experiment where we tested whether the presence of subordinate species increases plant community insurance. In Swiss Jura grassland, we combined a removal experiment of subordinate species with a summer drought event using rainout shelters. 3. Plant community composition was determined after the drought and based on biomass measurements; we estimated resistance, recovery and resilience of the plant community for each combination of treatments. Moreover, to assess drought impacts on water-use efficiency (WUE), we analysed carbon isotope ratios (δ¹³C values) in plant leaves of two dominants and two subordinates collected at the end of the drought period. 4. We showed that subordinate species are more resistant to drought and increased community resistance by enhancing their above-ground biomass production during the imposed drought. These patterns were associated with decreased competitiveness of dominant species whose biomass decreased during drought. Significant increase in δ¹³C values in plant tissue under drought indicated a better WUE for the measured species. Interestingly, the WUE was significantly higher in plots where subordinates were removed. Recovery and resilience were not affected by the summer drought, but the absence of subordinates reduced overall above-ground biomass in both watered and drought plots. 5. Synthesis. We demonstrated that, independent of plant diversity, the presence of drought-resistant subordinate species increases plant community insurance against drought and, hence, is important for the functioning of grassland ecosystems.

The ongoing expansion of shrub cover in response to climate change represents a unique opportunity to explore the link between soil microbial communities and vegetation changes. This link is particularly important in peatlands where shrub expansion is expected to feed back negatively on the carbon sink capacity of these ecosystems. Microbial community structure and function were measured seasonally in four peatlands located along an altitude gradient representing a natural gradient of climate and associated vascular plant abundance. We show that increased soil temperature and reduced water content are associated with greater vascular plant biomass, in particular that of ericoids, and that this, in turn, is correlated with greater microbial biomass. More specifically, microbial community structure is characterized by an increasing dominance of fungi over bacteria with improved soil oxygenation. We also found that the carbon and nitrogen stoichiometry of microbial biomass differs in relation to soil microbial community structure and that this is ultimately associated with a different investment in extracellular enzymatic activity. Our findings highlight the fact that the determination of the structural identity of microbial communities can help to explain the biogeochemical dynamics of organic matter and provide a better understanding of ecosystem response to environmental changes.

Aims Previous cover crop studies mainly focused on the links between plant uptake and soil fertility, and there is a clear knowledge gap regarding the role of microbes in these processes. Our aim was then to better understand the effects of plant mixtures (versus monoculture) and the specific effects of each plant species on nitrogen (N) and phosphorus (P) partitioning between plant, soil, and more particularly microbial pools. Methods Monocultures and mixtures composed of black oat, field pea and Indian mustard were grown during two months in a greenhouse. The concentrations of carbon (C), N and P were measured in both plant and microbial biomass at final harvest, together with soil available N and P. Results Overall, our findings highlight stronger selection effect (i.e. , presence of key species) rather than complementarity effects (i.e. , species mixture) to affect the measured parameters. The presence of pea increased the biomass production of oat and mustard, as well as the nutrient concentration of oat, whereas pea P concentration decreased in presence of oat and mustard N and P concentrations were negatively impacted respectively by the presence of oat and pea. We also observed a strong competition between plants and microbes for both soil N and P. Conclusions The oat-pea and the oat-pea-mustard mixtures represented the best compromise between biomass production, nutrient storage and biomass C:N ratio, thus insuring a good organic matter decomposition and nutrient provision for the following main crop.

This Special Feature on sustainable land-use practices in European mountain regions presents results from the inter- and transdisciplinary research project MOUNTLAND. The goal was to investigate the sensitivity of the provision of ecosystem services to both climatic and land-use changes and to suggest alternative policies and governance structures for mitigating the impact of such changes and enhancing sustainable management practices in mountain regions. The individual articles provide: (1) new scientific findings regarding the impacts of climate and land-use changes on ecosystem processes in three sensitive mountain regions of Switzerland; (2) an assessment of the feedback effects arising from changing socioeconomic and political conditions, land use, and adaptation to climate change, using modeling techniques and transdisciplinary stakeholder interactions; and (3) suggestions for alternative policy solutions to ensure sustainable land use in mountain regions. In our synthesis of the project, we provide insights from the ecological, socioeconomic, and political sciences in the context of human-environment interactions in mountain regions. The innovation of this Special Feature lies in the fact that all articles present truly inter- or transdisciplinary research, ranging from natural sciences to economics and political sciences, based on an overarching set of unifying research questions.

ABSTRACT Alteration of flooding regimes due to global change may have cascading effects on plant community composition and associated ecosystem services. Here, we experimentally investigated the effects of six flooding regimes with contrasting combinations of flooding duration (5.5, 6 and 6.5 months) and submergence rate (from 3.3 to 17.5 cm/day) on the growth and reproductive traits of Carex cinerascens, a dominant plant species of the Poyang Lake wetland in southern China. The time span of this study included a summer flooding event and the following growing seasons (autumn of first year and spring of following year) before the return of the next flooding event. The six flooding treatments affected plant traits during the flooding and the following growing seasons, but the different submergence rates under the same flooding duration did generally not show significant influence on plant traits. The 6.5‐month flooding treatments had many fewer old (0.4 on average) and new stems (1 on average) than the 5.5‐month treatments (8.3 and 29 stems, respectively) at the end of the flooding. The treatments with 5.5 months of flooding had 23% more stems than the other treatments and 26% more community biomass than the 6‐month flooding treatments during the autumn growing season. The effects of summer flooding persisted in spring of the following year, but with an opposite trend of C. cinerascens growth traits response to flooding treatments compared to autumn. In addition, the 6‐month flooding treatments induced a higher number of inflorescences (39) than the 5.5‐month (22) and 6.5‐month floods (3). Altogether, our findings highlighted the important legacy effects of summer flooding with some trade‐offs between growth recovery (autumn) and resilience (following spring) and between resource allocation to biomass production in autumn and resource allocation to sexual reproduction in the following spring, that were both mediated by flooding duration. We experimentally investigated the effects of six flooding regimes with contrasting combinations of flooding duration and submergence rate on the growth and reproductive traits of Carex cinerascens, a dominant plant species of the Poyang Lake wetland in southern China. The effects observed on the growth and reproductive traits of Carex cinerascens were only dependent on flooding duration but not submergence rate. The effects of summer flooding persisted in spring of the following year, but with an opposite trend of C. cinerascens growth traits response to flooding treatments compared to autumn.

In peatland ecosystems, plant communities mediate a globally significant carbon store. The effects of global environmental change on plant assemblages are expected to be a factor in determining how ecosystem functions such as carbon uptake will respond. Using vegetation data from 56 Sphagnum -dominated peat bogs across Europe, we show that in these ecosystems plant species aggregate into two major clusters that are each defined by shared response to environmental conditions. Across environmental gradients, we find significant taxonomic turnover in both clusters. However, functional identity and functional redundancy of the community as a whole remain unchanged. This strongly suggests that in peat bogs, species turnover across environmental gradients is restricted to functionally similar species. Our results demonstrate that plant taxonomic and functional turnover are decoupled, which may allow these peat bogs to maintain ecosystem functioning when subject to future environmental change. Peatland plant communities are expected to be affected by environmental change, though how assemblages respond is not fully understood. Here, Robroek et al. show that peatland species occur in two distinct clusters, and functional identity and redundancy was maintained under taxonomic turnover.

Mixotrophic protists are increasingly recognized for their significant contribution to carbon (C) cycling. As phototrophs they contribute to photosynthetic C fixation, whilst as predators of decomposers, they indirectly influence organic matter decomposition. Despite these direct and indirect effects on the C cycle, little is known about the responses of peatland mixotrophs to climate change and the potential consequences for the peatland C cycle. With a combination of field and microcosm experiments, we show that mixotrophs in the Sphagnum bryosphere play an important role in modulating peatland C cycle responses to experimental warming. We found that five years of consecutive summer warming with peaks of +2 to +8°C led to a 50% reduction in the biomass of the dominant mixotrophs, the mixotrophic testate amoebae (MTA). The biomass of other microbial groups (including decomposers) did not change, suggesting MTA to be particularly sensitive to temperature. In a microcosm experiment under controlled conditions, we then manipulated the abundance of MTA and showed that the reported 50% reduction of MTA biomass in the field was linked to a significant reduction of net C uptake (-13%) of the entire Sphagnum bryosphere. Our findings suggest that reduced abundance of MTA with climate warming could lead to reduced peatland C fixation.

ABSTRACT Increases in droughts may disrupt the life‐supporting services of grasslands, including the forage provision for herbivores. However, less is known about drought impacts on forage quality (i.e., dynamics of the cell characteristics of leaves and stems of herbs). Leaf economic traits reflect drought effects on plant communities, but whether they can predict forage quality patterns under drought remains unclear. We assessed the effects of early‐ and late‐season extreme droughts on (i) forage quality parameters [readily digestible, internal cellular constituents: protein, minerals, water‐soluble carbohydrate (WSC); and non‐readily digestible, cell wall components: neutral detergent fibre (NDF) and acid detergent fibre (ADF)]; (ii) community‐weighted leaf traits [specific leaf area (cwmSLA) and leaf dry matter content (cwmLDMC)]; and (iii) leaf traits–quality parameters relationships across three grasslands over two growing seasons. Both early and late droughts decreased ash and ADF and increased WSC across sites, while early drought slightly reduced protein and NDF. Both droughts decreased cwmSLA and increased cwmLDMC across sites. Community‐weighted leaf traits and forage quality parameters were unrelated under early ambient conditions, but their relationships under early‐season drought imply that lower cwmSLA and higher cwmLDMC communities had higher forage quality (higher protein and less lignified fibre contents) than higher cwmSLA and lower cwmLDMC communities. Under late‐season ambient or drought conditions, most relationships indicate that lower cwmSLA and cwmLDMC communities had higher forage quality (higher protein and ash, and more digestible fibre contents) than higher cwmSLA and cwmLDMC communities. Overall, forage quality was higher under late‐season ambient conditions compared to the early season, and both drought types had limited negative effects on forage quality in the studied grasslands. Moreover, leaf traits can predict forage quality patterns and plants' adaptation under certain circumstances, including regular intra‐seasonal dry periods and extreme drought conditions. We assessed the effects of early‐ and late‐season extreme droughts on (i) forage quality parameters [readily digestible, internal cellular constituents: protein, minerals, water‐soluble carbohydrate (WSC); and non‐readily digestible, cell wall components: neutral detergent fibre (NDF) and acid detergent fibre (ADF)]; (ii) community‐weighted leaf traits [specific leaf area (cwmSLA) and leaf dry matter content (cwmLDMC)]; and (iii) leaf traits–quality parameters relationships across three temperate permanent grasslands over two growing seasons. We found that forage quality was higher under late‐season ambient conditions compared to the early season, and both drought types had limited negative effects on forage quality. Moreover, leaf traits can predict forage quality patterns and plants' adaptation under certain circumstances, including regular intra‐seasonal dry periods and extreme drought conditions.

Climate warming is releasing carbon from soils around the world, constituting a positive climate feedback. Warming is also causing species to expand their ranges into new ecosystems. Yet, in most ecosystems, whether range expanding species will amplify or buffer expected soil carbon loss is unknown. Here, we used two whole-community transplant experiments and a follow-up glasshouse experiment to determine whether the establishment of herbaceous lowland plants in alpine ecosystems influences soil carbon content under warming. We found that warming (transplantation to low elevation) led to a negligible decrease in alpine soil carbon content, but its effects became significant and 52% ± 31% (mean ± 95% confidence intervals) larger after lowland plants were introduced at low density into the ecosystem. We present evidence that decreases in soil carbon content likely occurred via lowland plants increasing rates of root exudation, soil microbial respiration, and CO 2 release under warming. Our findings suggest that warming-induced range expansions of herbaceous plants have the potential to alter climate feedbacks from this system, and that plant range expansions among herbaceous communities may be an overlooked mediator of warming effects on carbon dynamics. In a terrestrial ecosystem, the carbon cycle primarily represents the balance between plants consuming carbon dioxide from the atmosphere and soil microbes releasing carbon stored in the soil into the atmosphere (mostly as carbon dioxide). Given that carbon dioxide traps heat in the atmosphere, the balance of carbon inputs and outputs from an ecosystem can have important consequences for climate change. Rising temperatures caused by climate warming have led plants from lowland ecosystems to migrate uphill and start growing in alpine ecosystems, where temperatures are lower and most carbon is stored in the soil. Soil microbes use carbon stored in the soil and exuded from plants to grow, and they release this carbon – in the form of carbon dioxide – into the atmosphere through respiration. Walker et al. wanted to know how the arrival of lowland plants in alpine ecosystems under climate warming would affect carbon stores in the soil. To answer this question, Walker et al. simulated warmer temperatures by moving turfs (plants and soil) from alpine ecosystems to a warmer downhill site and planting lowland plants into the turfs. They compared the concentration of soil carbon in these turfs to that of soil in alpine turfs that had not been moved downhill and had no lowland plants. Their results showed that the warmed turfs containing lowland plants had a lower concentration of soil carbon. This suggests that climate warming will lead to more soil carbon being released into the atmosphere if lowland plants also migrate into alpine ecosystems. Walker et al. also wanted to know the mechanism through which lowland plants were decreasing soil carbon concentration under warming. They find that lowland plants probably release more small molecules into the soil than alpine plants. Soil microbes use the carbon and nutrients in these molecules to break down more complex molecules in the soil, thereby releasing nutrients and carbon that can then be used in respiration. This finding suggests that soil microbes breakdown and respire native soil carbon faster in the presence of lowland plants, releasing more carbon dioxide into the atmosphere and reducing carbon stores in the soil. Walker et al.’s results reveal a new mechanism through which uphill migration of lowland plants could increase the effects of climate change, in a feedback loop. Further research as to whether this mechanism occurs in different regions and ecosystems could help to quantify the magnitude of this feedback and allow scientists to make more accurate predictions about climate change.

Groundwater level is crucial for wetland plant growth and reproduction, but the extent of its effect on plant growth can vary along with changed precipitation and temperature at different seasons. In this context, we investigated the effect of two groundwater levels (10 cm vs. 20 cm depth) on growth and reproductive parameters of Carex cinerascens, a dominant plant species in the Poyang Lake wetland, during three seasons (spring, summer, and autumn) and during two consecutive years (2015 and 2016). Carex cinerascens showed low stem number, height, and individual and population biomass in summer compared to spring and autumn. 10 cm groundwater level was overall more suitable for plant growth resulting in higher stem height and biomass. However, the interactive effect between groundwater level and season clearly demonstrated that the effect of groundwater level on plant growth occurred mainly in autumn. After the withering of the plant population in summer, we observed that C. cinerascens growth recovered in autumn to similar values observed in spring only with 10 cm groundwater level. Consequently, we could deduce that lowering groundwater level in the studied Poyang Lake wetland will negatively impact C. cinerascens regeneration and growth particularly during the second growth cycle occurring in autumn. Additionally, our results showed that, independently of the season and groundwater level, population biomass of C. cinerascens was lower during drier year. Altogether, our findings suggest that water limitation due to both reduction in precipitation and decreased groundwater level during the year can strongly impact plant communities. We investigated the effect of groundwater level on growth and reproductive parameters of Carex cinerascens, a dominant plant species in the Poyang Lake wetland, during two consecutive years. We clearly demonstrated that the effects of groundwater level on plant growth occur mainly in autumn.