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Climate change is affecting biodiversity across all taxonomic groups and ecosystems globally. Mountain ecosystems are particularly sensitive to climate warming, as temperature is generally a limiting factor for their vegetation. The Irano-Anatolian global biodiversity hotspot, which includes high elevations with a rich endemic biodiversity, offers good opportunities to study the effects of future climate change on its plant diversity. We used species distribution models to predict changes in species' habitat suitability by the end of the century (2071–2100) under two extreme shared socioeconomic pathways (SSPs), for 713 endemic plant species of the area. We found that a remarkably high number of species are predicted to experience a shift in their climatically suitable habitats from lower to higher elevations, resulting in a decrease in their potential range areas (79 % and 86 % of species, under the SSP 1–2.6 and SSP 5–5.8 scenarios, respectively). As a consequence, we also predicted a decrease in species richness in the low (< 1200 m) and middle (1200–2500 m) elevational belts, while an increase in species richness in high elevational belt (> 2500 m). This study demonstrates that climate change has the potential to cause a massive restructuring of plant community composition in this area, including the risk of extinction for many species. This poses a significant threat to the biodiversity of this region, which calls for urgent action to mitigate as far as possible the adverse effects of climate change in the region. • We modelled the effects of future climate change on alpine endemic plants of SW Asia • Many species are expected to shift up to higher elevations and towards cooler aspects • The majority of species will face a reduction in their suitable range area • Species richness is predicted to decrease at low elevations but to increase at high elevations [ABSTRACT FROM AUTHOR]

Aim: Species–area relationships (SARs) are among the best investigated patterns in ecology, yet the shape of the function that should describe SARs and the biological meaning of the function parameters are disputed. Elevational gradients offer the opportunity of investigating how biodiversity responds to large variations in environmental characteristics within small geographical areas. We asked which function describes SARs at different elevations and explored how variations in environmental characteristics influence SAR shape. Location: Alborz Mountains (Iran). Taxon: Vascular plants. Methods: We used sets of nested plots (0.001 to 100 m2) placed at 100 m intervals from 2,000 to 4,500 m elevation to construct series of nested SARs as species accumulation curves. Then, we used these curves to assess the appropriateness of different SAR functions at different elevations. We investigated how parameters of the power function varied along the elevational gradient in response to variation in environmental parameters (ruggedness, temperature, precipitation, exposed rock, percentages of soil sand and total nitrogen, and productivity, expressed by the normalized difference vegetation index). Results: The most frequently observed best fit model was the power function, which is controlled by two parameters: z (the velocity in species accumulation with sampled area) and c (the species richness per unit area). z was positively influenced by temperature and soil nitrogen, decreasing with elevation. c was positively influenced by temperature and soil nitrogen, and negatively by rock cover, decreasing with elevation. Main conclusions: The decrease in c‐values with elevation is consistent with the altitudinal decrease in species richness and is explained by the increase in bare rock. By contrast, c was positively influenced by temperature and total nitrogen, which are two factors promoting plant growth. Similarly, z‐values decreased with elevation, thus indicating a decrease in beta diversity. [ABSTRACT FROM AUTHOR]

Climate and environmental heterogeneity are currently discussed as the most important drivers of plant diversity along altitudinal gradients. Compared to functional diversity, taxonomic diversity has received much more attention in research on altitudinal gradients, although functional diversity may provide more information on the ecological mechanisms shaping plant diversity. We assessed the importance of climatic and environmental heterogeneity as drivers of functional diversity in relation to altitude in the central Alborz Mountains, Iran. We sampled 132 vegetation plots along two altitudinal transects. Plant traits including life history, growth form, stem‐leaf ratio, spinescence, hairiness, leaf consistency, dispersal type and plant height were recorded. Functional diversity was measured as functional richness, Rao's quadratic entropy, and their standardized effect sizes (SESs). In general, functional diversity decreased with altitude. The decrease in observed functional diversity was related to the decrease in taxonomic richness. SESs of functional diversity showed contrasting trends, depending on transect and index. At both transects, climatic stress best explained the variation in observed and expected functional diversity. Harsh climatic conditions at higher altitudes decreased the number of species and thus the functional trait space. Environmental heterogeneity played only a minor role for shaping functional diversity. We expect this effect to be due to the length of the sampled altitudinal transects. With increasing length, small‐scale drivers become less effective. The two transects favoured different environmental drivers, meaning that transferability of single studies could be difficult. [ABSTRACT FROM AUTHOR]

Tertiary-relict Hyrcanian (Caspian) forest along the shores of the southern Caspian Sea is a center of biodiversity. Still, there is little information on plant diversity patterns in this area. This study evaluated plant diversity, variation in life forms, and geographical distribution of the zonal vegetation types and their relationships with environmental variables, in the educational and experimental forest of Kheyrudkenar, an important protected area in the central Hyrcanian forest of northern Iran. For this purpose, 226 vegetation plots of 400 m2 were laid out along two altitudinal transects from the lowlands (100 m a.s.l.) to the timberline (2000 m a.s.l.). Four vegetation types were identified using modified TWINSPAN, indirect and direct gradient analyses. Species-related (species diversity indices, life form and phytogeographical elements) and environmental variables (climate, topographic and soil variables) were calculated and subjected to one-way ANOVA among the vegetation types. Both constrained (CCA) and unconstrained (DCA) ordination analyses showed an almost identical variation of the floristic composition along their axes and demonstrated that there are two main gradients in the Hyrcanian forest. Elevation together with annual precipitation and mean annual temperature were the most important factors controlling the floristic composition in the area. Topographic features such as slope inclination and heat index were found to be important within an elevation zone/vegetation type. Soil physical and chemical properties were of secondary importance for the separation of the vegetation types. This knowledge will be useful for forest management and conservation practices in the Hyrcanian area with its distinct and unique flora and vegetation. [ABSTRACT FROM AUTHOR]

This vegetation–environmental relation study is the first large-scale survey along 34 cross-shore transects in 650 km-coastal dune remnants of the south Caspian Sea, Iran. The five vegetation zones dedicated here seem to be driven by both zonal (climate, distance to the sea and pH) and azonal (salinity) factors. To assess conservation status, different attributes of Hdune diversity index, endemicity index (EI) and Naturalness (N) were estimated based on endemic, alien and total species contributions per plot. Contrary to Hdune index, EI followed a decreasing pattern across the coast–inland gradient, whereas N shows a unimodal pattern of distribution with the highest value at the mobile dune zone. Two main gradients of salinity and alkalinity shaping floristic composition are more prominent than climate, distance to the sea and the anthropogenic factors particularly when a full range of coastal habitats are considered. Human-related factors only partially explain the variability of the vegetation data and negatively affect naturalness and endemicity indices, even though their impact on community composition is aggravated in the western parts of the Caspian coasts. Both N and EI indices can be suggested as bioindicators for proper conservation strategies to preserve the last fragments of sand dunes of the Caspian Sea. [ABSTRACT FROM AUTHOR]