Here, we conducted a meta-analysis of experimental drought manipulation studies using rainout shelters in five sites of natural grassland ecosystems of Europe. The single studies assess the effects of extreme drought on the intraspecific variation of the specific leaf area (SLA), a proxy of plant growth. We evaluate and compare the effect size of the SLA response for the functional groups of forbs and grasses in temperate and sub-Mediterranean systems. We hypothesized that the functional groups of grasses and forbs from temperate grassland systems have different strategies in short-term drought response, measured as adjustment of SLA, with SLA-reduction in grasses and SLA-maintenance in forbs. Second, we hypothesized that grasses and forbs from sub-Mediterranean systems do not differ in their drought response as both groups maintain their SLA. We found a significant decrease of SLA in grasses of the temperate systems in response to drought while SLA of forbs showed no significant response. Lower SLA is associated with enhanced water-use efficiency under water stress and thus can be seen as a strategy of phenotypic adjustment. By contrast, in the sub-Mediterranean systems, grasses significantly increased their SLA in the drought treatment. This result points towards a better growth performance of these grasses, which is most likely related to their strategy to allocate resources to belowground parts. The observed SLA reduction of forbs is most likely a direct drought response given that competitive effect of grasses is unlikely due to the scanty vegetation cover. We point out that phenotypic adjustment is an important driver of short-term functional plant response to climatic extremes such as drought. Differential reactions of functional groups have to be interpreted against the background of the group's evolutionary configuration that can differ between climatic zones. © 2017 John Wiley & Sons Lt

No abstract

Although specific leaf area (SLA) has been proposed to reflect plant responses to climatic changes, the link between SLA and temperature has never been systematically evaluated. Using in situ measured SLA values for 223 species occurring in 29 calcareous grasslands along a temperature gradient in the Bavarian Alps, we explored the SLA-temperature relationship at population (intraspecific), species (interspecific) and community level and investigated the relative impact of other environmental factors on SLA variation along the temperature gradient at the community level. Only 14 % of the studied species showed significant changes in their SLA values along the temperature gradient, despite high intraspecific variability of the SLA values. At the species level, we revealed a very weak positive SLA-temperature relationship (r 2 = 0.04, p \ 0.001). A very strong positive correlation between SLA and temperature was detected at the community level (r 2 = 0.70, p \ 0.001). In addition to temperature, disturbance also had a significant influence on trait variation at the community level. We conclude that the variation in SLA along the temperature gradient comes primarily from changes in the relative abundances of species, whereas the trait variation at the population and the species levels was affected by other environmental factors. We therefore recommend the use of community-weighted mean values in studies employing SLA-temperature relationships because they reveal more regular patterns than the underlying distribution of within-and among-site SLA values.

Summary Reproductive stages of life cycle are important for the explanation of distribution patterns of plant species at different scales, due to their extreme vulnerability to environmental conditions. Despite reported evidences that seed germination is related to habitat macroclimatic characteristics such as mean annual temperature (MAT) and precipitation, the role of this trait in controlling plant species distribution is not systematically and quantitatively evaluated yet. Using the data on seed germination along a temperature gradient for 49 species originating from contrasting climatic conditions, we test here whether initial temperature of seed germination (Tmin) is a direct correlate for predicting species distribution ranges along the temperature gradient. Our study reveals that Tmin is strongly negatively correlated with habitat temperature; among the studied species, Tmin clearly increased with decreasing MAT (r2 = 0·57, P < 0·001). Considering phylogenetic biases, co‐evolution of seed traits as well as precipitation along with microclimatic factors did not affect the strength of this relationship. The results suggest that the Tmin–MAT relation can provide insights particularly into species distribution patterns, vegetation dynamics and community assembly rules along altitudinal and latitudinal gradients. We argue that including the Tmin in species distribution models may help to improve the accuracy and specificity of predictions of vegetation shifts under global change scenarios.

Summary Assumptions about the germination ecology of alpine plants are presently based on individual species and local studies. A current challenge is to synthesise, at the global level, the alpine seed ecological spectrum. We performed a meta‐analysis of primary data from laboratory experiments conducted across four continents (excluding the tropics) and 661 species, to estimate the influence of six environmental cues on germination proportion, mean germination time and germination synchrony; accounting for seed morphology (mass, embryo : seed ratio) and phylogeny. Most alpine plants show physiological seed dormancy, a strong need for cold stratification, warm‐cued germination and positive germination responses to light and alternating temperatures. Species restricted to the alpine belt have a higher preference for warm temperatures and a stronger response to cold stratification than species whose distribution extends also below the treeline. Seed mass, embryo size and phylogeny have strong constraining effects on germination responses to the environment. Globally, overwintering and warm temperatures are key drivers of germination in alpine habitats. The interplay between germination physiology and seed morphological traits further reflects pressures to avoid frost or drought stress. Our results indicate the convergence, at the global level, of the seed germination patterns of alpine species.

Background and Aims Hydroperiod drives plant community composition in wetlands, resulting in distinct zonation patterns. Here, we explored the role of seed germination traits in shaping wetland community assembly along a hydroperiod gradient. Specifically, we tested the hypothesis that seeds of reed, mudflat, swamp, shallow- and deep-water communities only germinate under a specific set of environmental factors characterized by the community-specific optimal conditions for seedling survival and growth. Methods In a three-factorial experiment, we tested the seed germination response of 50 species typical for temperate wetlands of Europe to temperature fluctuations (constant vs. fluctuating temperature), illumination (light vs. darkness) and oxygen availability (aerobic vs. hypoxia). Phylogenetic principal component analysis, cluster analysis and phylogenetic linear regressions were used to confirm the community-specific seed germination niches. Key Results Our study revealed the presence of five distinct, community-specific seed germination niches that reflect adaptations made by the study communities to decreasing light intensity, temperature fluctuations and oxygen availability along the hydroperiod gradient. Light as a germination trigger was found to be important in mudflats, swamps and shallow water, whereas the seeds of reed and deep-water species were able to germinate in darkness. A fluctuating temperature is only required for seed germination in mudflat species. Germination of species in the communities at the higher end of the hydroperiod gradient (reed and mudflat) demonstrated a strict requirement for oxygen, whereas swamp, shallow- and deep-water species also germinated under hypoxia. Conclusions Our study supports the recent argument that the inclusion of seed germination traits in community ecology adds significant insights to community response to the abiotic and biotic environment. Furthermore, the close relationship between seed germination adaptations and community assembly could help reach a better understanding of the existing patterns of wetland plant distribution at local scales and wetland vegetation dynamics, as well as facilitate nature conservation measures and aquatic habitat restoration.

No abstract

Question A better understanding of species distribution and establishment requires in‐depth information on their seed ecology. We hypothesised that seed traits of mudflat species may indicate a strong environmental adaptation in their highly specialised habitat. Furthermore, we asked the question, do seeds of mudflat species have a specific trait value to contribute high adaptability to small‐scale variation in their unpredictable habitat? Location Central Europe. Methods Seeds of 30 typical mudflat species were used to measure 15 traits that govern seed dispersal (buoyancy and production), persistence (seed desiccation, mass and persistence in soil), and germination and establishment (germination response to different light, temperature and oxygen conditions). Cluster analysis and phylogenetic principal components analysis (pPCA) were conducted to define potential mudflat species functional groups as per their ecological optima. Results Seed production and seed mass displayed extremely high variation while seed buoyancy, desiccation and persistence in soil showed almost no variation. All study species produced buoyant, desiccation‐tolerant and long‐term persistent seeds. Germination and establishment traits also displayed similarity in their responses to different germination treatments as the majority (73%) of species has a moderate seed germination niche width. They germinated well under light/aerobic conditions irrespective to temperature fluctuations. The cluster analysis and pPCA separated species into three potential plant functional groups as ‘true’, ‘flood‐resistant’ and ‘facultative’, mudflat species. Conclusion Moderate variation in the seed traits of mudflat plants suggests they employ different ecological strategies that seem highly predictive to the peculiarity of their specific micro‐habitats, which are largely controlled by the hydroperiod gradient. It implies that seed trait information, which further needs to be tested for their adaptability, can advance our understanding of how community composition at the micro‐habitat level depends on trait values of participating species.