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The Dehesa ecosystem provides important social and economic values across the Iberian Peninsula. Assessing the temporal dynamics of this system under climate change is important for the maintenance and conservation of these highly valuable ecosystems. Here, we present the baseline data of an observational plot network in the Dehesa that will form the foundation for monitoring long-term dynamics and for experimental manipulations testing the mechanisms driving resilience within the Dehesa. The initial surveys indicate that the forest structure is typical for the Dehesa, which suggests it is an exemplary site for examining temporal dynamics of this ecosystem. We present these initial data to encourage collaborations from international scientists via either direct experimental projects or meta-analyses. [ABSTRACT FROM AUTHOR]

With climate change and an increasing global human population, the concept of agroforestry is gaining economic and environmental interest. The practice of growing trees and crops on the same land is mainly applied in (sub)tropical climate and rarer in temperate areas where farmers fear decreased understorey crop yields due to competition with trees. However, whether competition is stronger below- (soil moisture, nutrients) or aboveground (light) in a temperate silvoarable agroforestry system (AFS) is not clear. The effects of different treatments of light, water and nutrient availability on crop production in two temperate AFS in Central Switzerland were investigated, where summer barley (Hordeum vulgare L.) was grown as understorey crop under 90%, 40% and 0% shade nets, with and without irrigation and/or fertilisation in a fully factorial design. Yield was reduced by 26% under heavy shade; yield reductions under moderate shade were not significant. Fertilisation and irrigation increased crop yield by 13% and 6–9%, respectively, independent from shade. Individual seed mass was significantly increased by fertilisation from an average of 0.041 g (± 0.008 SD) in unfertilised treatments to an average of 0.048 g (± 0.010) in fertilised treatments. Fertilisation had the biggest impact on total seed number (p < 0.001) with on average 36 (± 26) seeds per individual in unfertilised plots and 61 (± 33) in fertilised plots. This study demonstrates that moderate shade (as can be expected in modern AFS) was not a major limiting factor for barley yield in these two AFS in Switzerland, indicating that AFS with appropriate management combined with suitable selection of understorey crops are an option for agricultural production in temperate regions without significant yield losses. [ABSTRACT FROM AUTHOR]

Determining which drivers lead to a specific species assemblage is a central issue in community ecology. Although many processes are involved, plant-plant interactions are among the most important. The phylogenetic limiting similarity hypothesis states that closely related species tend to compete stronger than distantly related species, although evidence is inconclusive. We used ecological and phylogenetic data on alpine plant communities along an environmental severity gradient to assess the importance of phylogenetic relatedness in affecting the interaction between cushion plants and the whole community, and how these interactions may affect community assemblage and diversity. We first measured species richness and individual biomass of species growing within and outside the nurse cushion species, Arenaria tetraquetra. We then assembled the phylogenetic tree of species present in both communities and calculated the phylogenetic distance between the cushion species and its beneficiary species, as well as the phylogenetic community structure. We also estimated changes in species richness at the local level due to the presence of cushions. The effects of cushions on closely related species changed from negative to positive as environmental conditions became more severe, while the interaction with distantly related species did not change along the environmental gradient. Overall, we found an environmental context-dependence in patterns of phylogenetic similarity, as the interaction outcome between nurses and their close and distantly-related species showed an opposite pattern with environmental severity. [ABSTRACT FROM AUTHOR]

Interactions among species determine local-scale diversity, but local interactions are thought to have minor effects at larger scales. However, quantitative comparisons of the importance of biotic interactions relative to other drivers are rarely made at larger scales. Using a data set spanning 78 sites and five continents, we assessed the relative importance of biotic interactions and climate in determining plant diversity in alpine ecosystems dominated by nurse-plant cushion species. Climate variables related with water balance showed the highest correlation with richness at the global scale. Strikingly, although the effect of cushion species on diversity was lower than that of climate, its contribution was still substantial. In particular, cushion species enhanced species richness more in systems with inherently impoverished local diversity. Nurse species appear to act as a 'safety net' sustaining diversity under harsh conditions, demonstrating that climate and species interactions should be integrated when predicting future biodiversity effects of climate change. [ABSTRACT FROM AUTHOR]

Background:In those alpine regions where growing season precipitation is decreasing due to climate change, the capacity of soils to retain water may become an important factor for the persistence of plant species. However, the importance of soil water storage capacity (WSC) for plant species diversity has not been studied so far. Aims:We aim to evaluate the relevance of WSC for species diversity of alpine plant communities in relation to temperature and length of growing season. Methods:Species diversity was determined in 150 plots from a broad range of alpine vegetation types in the calcareous western part of the central Swiss Alps. WSC of soil cores sampled in every plot was determined, as well as rooting zone temperature and snowmelt date. Linear mixed models were used to assess the relationship between environmental data and species diversity. Results:Species diversity was most strongly and positively related to WSC, followed by mean daily minimum temperature (Tmin) of the growing season. Species diversity was significantly related to date of snowmelt only in sites with high WSC and/or Tmin. Conclusions:WSC represents an integrative measure for habitat quality and accounts for differences in species diversity within the study region. In order to understand and predict responses of plant species to climate change in high mountain regions, it may be crucial to also take changes in plant water supply into account. [ABSTRACT FROM PUBLISHER]

Background: Neighbour-removal experiments (NRE) and spatial pattern analyses (SPA) are commonly used methods to investigate plant–plant interactions. Although they address the same issue, they measure different aspects of plant interactions: experiments indicate contemporary processes, whilst observations of spatial patterns integrate the results of interactions that have prevailed in the past. Aim: The aim of this study was to propose a new conceptual approach that takes into account the chronological order between processes and the arising patterns i.e., the time lag between neighbour effects quantified with NRE and SPA, to detect shifts in the balance of plant interactions due to current environmental change. Methods: This conceptual approach was applied to alpine snowbeds. Data from NRE were used to calculate the importance index of current neighbour interactions. Spatial patterns were quantified using variance ratio statistics and were assumed to reflect historic interactions. Results: The results of the two approaches showed a consistent difference in the prevailing type of plant interactions and suggested a shift towards competition in recent times. Conclusions: The simultaneous application of NRE and SPA allows the detection of a recent shift in the balance of plant interactions and provides a deeper and more accurate insight into the temporal dynamics of plant communities that could not be gained using one method alone. [ABSTRACT FROM PUBLISHER]

Over the last 20 years, several studies comparing recent survey data with historical data from the early 20th century documented an increase in species numbers on high mountain summits of the European Alps. This increase has more or less explicitly been attributed to an upward migration of plant species due to anthropogenic climate warming. However, a reconsideration of the historical and recent data has revealed that more than 90% of the recent species occurrences on mountain summits concern species that were already present at the same or even at higher altitudes within the study region at the time of the historical surveys. This finding suggests that suitable habitats already occurred on these summits under the mesoclimatic conditions prevailing at the beginning of the 20th century and that these habitats were, at least in part, occupied by these plant species. Consequently, the observed increase in species number during the last century does not require the additional temperature increase due to anthropogenic climate change. We therefore consider the phenomenon of increasing species number on high mountain summits to be primarily the result of a natural dispersal process that was triggered by the temperature increase at the end of the Little Ice Age and that is still in progress mostly due to the dispersal limitation of the species involved. Since both the natural dispersal process and a potential upward migration due to anthropogenic climate warming would take place at the same time, we suggest seeding and transplanting experiments in order to assess their respective roles in the increase in species number on mountain summits. [ABSTRACT FROM AUTHOR]

Better understanding of the mechanistic basis of plant plasticity will enhance efforts to breed crops resilient to predicted climate change. However, complexity in plasticity's conceptualisation and measurement may hinder fruitful crossover of concepts between disciplines that would enable such advances. We argue active adaptive plasticity is particularly important in shaping the fitness of wild plants, representing the first line of a plant's defence to environmental change. Here, we define how this concept may be applied to crop breeding, suggest appropriate approaches to measure it in crops, and propose a refocussing on active adaptive plasticity to enhance crop resilience. We also discuss how the same concept may have wider utility, such as in ex situ plant conservation and reintroductions. Increasing environmental uncertainty is focussing research interest on plant plasticity. But despite calls for plasticity concepts to be adopted in crop breeding, this does not appear to have happened. Plasticity is a broad and multifaceted concept, making it potentially difficult to identify those aspects of previous research most relevant to the crop breeding context. Given the challenges posed by climate change and the different evolutionary contexts in natural and crop systems, we identify active adaptive plasticity as a key issue for further investigation by crop breeders. We outline and illustrate the experimental and statistical analytical approaches necessary to begin to assess active adaptive plasticity, and we highlight benefits that might arise in other fields from a fuller understanding of the role and regulation of this aspect of plasticity. [ABSTRACT FROM AUTHOR]

Cushion plants' significant role for alpine biodiversity has been demonstrated in particular through their positive effects on plant diversity. However, their effects on higher trophic levels (e.g. insects) remain largely unclear. In this study, by field sampling in the Hengduan Mountains (HDM) in southwestern China, we evaluated the effects of an alpine gynodioecious cushion species, Arenaria polytrichoides (Carophyllaceae), on insect richness, abundance and population dynamics at two different elevations (4427 m vs. 4732 m) separately at two time periods (day vs. night) and in two growing seasons (early vs. late). The results showed that the total insect diversity decreases from low to high elevation sites. Some insect species were exclusively detected within A. polytrichoides cushions, leading to an increase in local insect richness from 7% to 35%. The positive effects of cushions on insect diversity could be attributed to unique biotic properties provided by cushions. Firstly, the effects were determined by the sexual dimorphism of the cushion with hermaphroditic cushions supporting higher insect diversity than female cushions. This could be because hermaphroditic cushions provide more resources, such as nectar and pollen grains, for insects than female cushions. Secondly, the cushions' associated beneficiary plants can also provide extra resources for attracting more insects, but this effect was mediated by the micro-environmental conditions. Finally, the magnitude of cushions' positive effects on insect dynamics were stronger under higher than under lower environmental stress. This study confirmed that facilitation by A. polytrichoides cushions in HDM plays an important role in constructing the alpine insect community and further regulating its dynamics. Moreover, the positive effects of cushions on insect dynamics increase with increasing environmental stress. Therefore, the distribution range of insects would quite possibly be expanded into higher elevation under future climate changes, which will induce new challenges for the local alpine ecosystems. Unlabelled Image • Insect diversity decreases with increasing elevation in the Hengduan Mountains. • The cushion plant Arenaria hosts exclusive insects, thereby increasing local insect diversity. • The positive effects of Arenaria were attributed to biotic properties provided by the cushion. • Cushions' positive effects on insects were determined by environmental severity. [ABSTRACT FROM AUTHOR]

• Nurse plants in alpine systems may enhance species survival under climate change. • We simulated climate change effects on an alpine cushion species. • We also assessed consequences of new climate on its facilitation effect. • Warming enhanced cushion performance but did not alter its facilitation effect. • Global change may alter carbon fixation and respiration, threatening plant survival. Climate change is more pronounced in high-elevation habitats than elsewhere, potentially causing disruptions in plant community structure and dynamics through changes in plant interactions. We tested the effect of warming and rainfall manipulations on growth and gas exchange of a cushion plant species, Arenaria tetraquetra , in the Sierra Nevada Mountains in SE Spain and assessed its consequences for plant interactions. Arenaria tetraquetra is a facilitator that often hosts a variety of beneficiary species within its canopy. Warming and drought could alter cushion growth patterns and canopy compaction, which in turn affect facilitation. We increased temperature using acrylic open-top chambers (OTC) and increased or decreased water availability with rainfall collectors. Our rainfall treatments did not have significant effects on cushion growth or facilitation. Three years of warming enhanced cushion photosynthesis and respiration, leading to larger cushions with thinner leaves, but did not change other cushion traits nor alter its facilitation effects. Some traits, however, readily responded to inter-annual climate variability. Global warming will change cushion plant physiology, as higher temperatures at times increase plant respiration above the level of carbon fixation. However, we did not find changes in interaction between benefactor and beneficiary species, perhaps due to the short-term nature of our experiment. Recorded physiological and morphological changes might be, however, signs of more pronounced, long-term consequences of warming on plant survival and community composition. [ABSTRACT FROM AUTHOR]