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Question: How does the diversity of successional forests evolve with stand age, and to what extent do permanent plots validate the previously studied successional patterns of tree diversity and composition observed through chronosequences? To evaluate the role of successional forests as reservoirs for many species, it is essential to examine how biodiversity recovers with the age of the stand. We studied patterns of taxonomic and functional diversity, as well as species composition during forest succession, by combining chronosequences and permanent plot monitoring. Location: Subtropical montane forests in NW Argentina. Methods: We used data from two chronosequences of plots monitored for 30 years in lower and upper montane forests dominated by native trees (LMF‐Native and UMF‐Native), and one chronosequence of plots dominated by the exotic tree Ligustrum lucidum, monitored for 10 years in low montane forests (LMF‐Invaded). We analyzed changes in taxonomic (species richness, Shannon diversity, Simpson diversity) and functional diversity, as well as composition with forest age. Results: Taxonomic and functional diversity increased between 30 and 70 years of succession in LMF‐Native and UMF‐Native. Successional LMF‐Native forests reached the diversity of mature forests earlier than UMF‐Native. In LMF‐Invaded, taxonomic and functional diversity decreased in the same period because of the increasing dominance of the exotic species Ligustrum lucidum. In non‐invaded chronosequences (LMF‐Native and UMF‐Native) we observed a convergence towards the composition of mature forests; however, each successional forest kept its identity for 30 years. Conclusions: Diversity and composition followed different successional trajectories depending on the type of forest. We found that successional patterns, such as changes in taxonomic and functional diversity, predicted with the chronosequence approach, were confirmed with data from plot monitoring. The effects of pre‐abandonment conditions persist in the diversity and composition of successional forests monitored between 10 and 30 years. [ABSTRACT FROM AUTHOR]

Aims: High-Andean vegas are key functional wetlands in the Puna ecoregion. Plant communities in combination with ecogeographic characteristics determine their functional processes. In this study, we identified groups of vegas based on their plant composition and characterized these groups with spatial and spectral variables representing their ecogeographic context. Location: Argentine Puna and High-Andean ecoregions. Methods: We recorded the species composition and cover of plants in 50 vegas distributed along a ecogeographic gradient. We calculated six spatial and 14 spectral variables for each vega. We performed a correspondence analysis (CA) to explore species data and used the site's scores in a k-means analysis to identify groups of vegas. Then, we characterized each group of vegas with spatial and spectral variables with the v.test using the ‘catdes’ function in the FactoMineR package. Results: The CA showed five groups of vegas segregated by the plant species composition. Each group was related to different spatial and spectral variables showing an ecogeographic gradient. Vegas with Poaceas were located at higher altitude and lower latitude and longitude (Group 1, Festuca nardifolia and Deschampsia hackelii). Vegas dominated by cushion species had higher humidity (Group 2, Oxychloe andina), and higher and more stable productivity (Group 3, Eleocharis pseudoalbibracteata), while vegas with halophytic species were associated with a larger area, higher salinity, and lower humidity (Group 4, Amphiscirpus nevadensis), and lower productivity (Group 5, Lycium humile and Salicornia pulvinata). Conclusions: Our results are the first floristic classification and remote-sensing characterization of high-Andean vegas at a regional scale. This information shows the variation of these ecosystems and suggests that remote sensing, complemented with field information, could help to identify types of vegas at regional scales. This information is relevant for land planning and sustainable management of these key ecosystems in the context of threats of global change. [ABSTRACT FROM AUTHOR]

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Aim: Ecological niches shape species commonness and rarity, yet, the relative importance of different niche mechanisms within and across ecosystems remains unresolved. We tested the influence of niche breadth (range of environmental conditions where species occur) and niche position (marginality of a species' environmental distribution relative to the mean environmental conditions of a region) on tree‐species abundance and occupancy across three biogeographic regions. Location: Argentinian Andes; Bolivian Amazon; Missouri Ozarks. Time period: 2002–2010. Major taxa studied: Trees. Methods: We calculated abiotic‐niche breadths and abiotic‐niche positions using 16 climate, soil and topographic variables. For each region, we used model selection to test the relative influence of niche breadth and niche position on local abundance and occupancy in regional‐scale networks of 0.1‐ha forest plots. To account for species–environment associations caused by other mechanisms (e.g., dispersal), we used null models that randomized associations between species occurrences and environmental variables. Results: We found strong support for the niche‐position hypothesis. In all regions, species with higher local abundance and occupancy occurred in non‐marginal environments. Observed relationships between occupancy and niche position also differed from random species–environment associations in all regions. Surprisingly, we found little support for the niche‐breadth hypothesis. Observed relationships between both local abundance and niche breadth, and occupancy and niche breadth, did not differ from random species–environment associations. Main conclusion: Niche position was more important than niche breadth in shaping species commonness and rarity across temperate, sub‐tropical and tropical forests. In all forests, tree species with widespread geographic distributions were associated with environmental conditions commonly found throughout the region, suggesting that niche position has similar effects on species occupancy across contrasting biogeographic regions. Our findings imply that conservation efforts aimed at protecting populations of common and rare tree species should prioritize conservation of both common and rare habitats. [ABSTRACT FROM AUTHOR]

Within the tropics, a marked gradient in rainfall between dry and wet forests correlates with a well documented turnover of plant species. While water availability along these gradients is an important determinant of species distributions, other abiotic and biotic factors correlate with rainfall and may also contribute to limit species distribution. One of these is soil fertility, which is often lower in the wetter forests. To test its possible role in species distribution along a rainfall gradient, we performed a screen-house experiment where we measured the growth performance of seedlings of 23 species with contrasting distributions across the Isthmus of Panama. We grew seedlings in soils collected from the drier Pacific side and the wetter Atlantic side. Differences in soil fertility across the Isthmus were large enough to significantly influence the growth performance of the seedlings. However, we found no evidence of home-soil advantage among species with contrasting distributions. Dry-distribution species grew on average slower than wet-distribution species suggesting a cost to drought adaptations. The response to soil differences correlated with the growth rate of the species, such that fast-growing species responded more to changes in soil quality. We hypothesize that inherently slow growth rates of some dry-distribution tropical species may be a more important factor limiting their colonization of wetter sites along the rainfall gradient. [ABSTRACT FROM AUTHOR]