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Understanding how evolutionary constraints shape the elevational distributions of tree lineages provides valuable insight into the future of tropical montane forests under global change. With narrow elevational ranges, high taxonomic turnover, frequent habitat specialization, and exceptional levels of endemism, tropical montane forests and trees are predicted to be highly sensitive to environmental change. Using plot census data from a gradient traversing > 3,000 m in elevation on the Amazonian flank of the Peruvian Andes, we employ phylogenetic approaches to assess the influence of evolutionary heritage on distribution trends of trees at the genus‐level. We find that closely related lineages tend to occur at similar mean elevations, with sister genera pairs occurring a mean 254 m in elevation closer to each other than the mean elevational difference between non‐sister genera pairs. We also demonstrate phylogenetic clustering both above and below 1,750 m a.s.l, corresponding roughly to the cloud‐base ecotone. Belying these general trends, some lineages occur across many different elevations. However, these highly plastic lineages are not phylogenetically clustered. Overall, our findings suggest that tropical montane forests are home to unique tree lineage diversity, constrained by their evolutionary heritage and vulnerable to substantial losses under environmental changes, such as rising temperatures or an upward shift of the cloud‐base. [ABSTRACT FROM AUTHOR]

Background:The slopes of the eastern Andes harbour some of the highest biodiversity on Earth and a high proportion of endemic species. However, there have been only a few and limited descriptions of carbon budgets in tropical montane forest regions. Aims:We present the first comprehensive data on the production, allocation and cycling of carbon for two high elevation (ca. 3000 m) tropical montane cloud forest plots in the Kosñipata Valley, Peruvian Andes. Methods:We measured the main components and seasonal variation of net primary productivity (NPP), autotrophic (Ra) and heterotrophic (Rh) respiration to estimate gross primary productivity (GPP) and carbon use efficiency (CUE) in two 1-ha plots. Results:NPPfor the two plots was estimated to be 7.05 ± 0.39 and 8.04 ± 0.47 Mg C ha−1year−1,GPPto be 22.33 ± 2.23 and 26.82 ± 2.97 Mg C ha−1year−1andCUEwas 0.32 ± 0.04 and 0.30 ± 0.04. Conclusions:We found strong seasonality inNPPand moderate seasonality ofRa, suggesting that forestNPPis driven by changes in photosynthesis and highlighting the importance of variation in solar radiation. Our findings imply that trees invest more in biomass production in the cooler season with lower solar radiation and more in maintenance during the warmer and high solar radiation period. [ABSTRACT FROM PUBLISHER]

Background:Tropical montane cloud forests (TMCF) are unique ecosystems with high biodiversity and large carbon reservoirs. To date there have been limited descriptions of the carbon cycle of TMCF. Aims:We present results on the production, allocation and cycling of carbon for two mid-elevation (1500–1750 m) tropical montane cloud forest plots in San Pedro, Kosñipata Valley, Peru. Methods:We repeatedly recorded the components of net primary productivity (NPP) using biometric measurements, and autotrophic (Ra) and heterotrophic (Rh) respiration, using gas exchange measurements. From these we estimated gross primary productivity (GPP) and carbon use efficiency (CUE) at the plot level. Results:The plot at 1500 m was found very productive, with our results comparable with the most productive lowland Amazonian forests. The plot at 1750 m had significantly lower productivity, possibly because of greater cloud immersion. Both plots had similar patterns ofNPPallocation, a substantial seasonality inNPPcomponents and little seasonality inRa. Conclusions:These two plots lie within the ecotone between lower and upper montane forests, near the level of the cloud base. Climate change is likely to increase elevation of the cloud base, resulting in shifts in forest functioning. Longer-term surveillance of the carbon cycle at these sites would yield valuable insights into the response of TMCFs to a shifting cloud base. [ABSTRACT FROM PUBLISHER]

This paper revisits various hypotheses about oligarchic patterns in Amazonian tree communities put forward by Pitman et al. (2001). Together, these hypotheses predict that most lowland sites in the Amazon are located within large patches of relatively homogeneous edaphic and other environmental conditions, where an oligarchy of common, frequent tree species accounts for a majority of trees. To assess the degree to which these hypotheses have been corroborated or refuted over the last ten years, we reviewed > 200 studies published since 2001. We found overwhelming support for the hypo thesis that large-scale oligarchies of common and frequent species are a common feature of Amazonian tree communities. At least 22 studies have documented oligarchies in Amazonian woody plant communities to date, and no studies have looked for oligarchies as defined by Pitman et al. (2001) and failed to find them. We argue that six publications that offer critiques of the oligarchy hypothesis do not constitute valid tests. The other hypotheses in Pitman et al. (2001)- one regarding the specific oligarchic taxa that dominate forests near the eastern base of the Andes and one that attempts to explain why oligarchic species exist - are less well supported by the literature, in large part because they have not been subjected to many tests. We discuss links between these hypotheses and other well-known patterns and hypotheses in ecology (the abundance-occupancy relationship, the Janzen-Connell hypothesis, the niche-environment hypothesis, and the niche breadth hypothesis), and provide additional detail to facilitate rigorous tests in the future. The paper concludes by presenting remote sensing evidence that large patches of relatively homogeneous environmental conditions account for most of the upland forest landscape across Amazonian Peru. [ABSTRACT FROM AUTHOR]

Climate change causes shifts in species distributions, or 'migrations'. Despite the centrality of species distributions to biodiversity conservation, the demonstrated large migration of tropical plant species in response to climate change in the past, and the expected sensitivity of species distributions to modern climate change, no study has tested for modern species migrations in tropical plants. Here we conduct a first test of the hypothesis that increasing temperatures are causing tropical trees to migrate to cooler areas. Tropical Andes biodiversity hotspot, south-eastern Peru, South America. We use data from repeated (2003/04-2007/08) censuses of 14 1-ha forest inventory plots spanning an elevational gradient from 950 to 3400 m in Manu National Park in south-eastern Peru, to characterize changes in the elevational distributions of 38 Andean tree genera. We also analyse changes in the genus-level composition of the inventory plots through time. We show that most tropical Andean tree genera shifted their mean distributions upslope over the study period and that the mean rate of migration is approximately 2.5-3.5 vertical metres upslope per year. Consistent with upward migrations we also find increasing abundances of tree genera previously distributed at lower elevations in the majority of study plots. These findings are in accord with the a priori hypothesis of upward shifts in species ranges due to elevated temperatures, and are potentially the first documented evidence of present-day climate-driven migrations in a tropical plant community. The observed mean rate of change is less than predicted from the temperature increases for the region, possibly due to the influence of changes in moisture or non-climatic factors such as substrate, species interactions, lags in tree community response and/or dispersal limitations. Whatever the cause(s), continued slower-than-expected migration of tropical Andean trees would indicate a limited ability to respond to increased temperatures, which may lead to increased extinction risks with further climate change. [ABSTRACT FROM AUTHOR]

Predicted climate change in the Andes will require plant species to migrate upslope to avoid extinction. Central to predictions of species responses to climate change is an understanding of species distributions along environmental gradients. Environmental gradients are frequently modelled as abiotic, but biotic interactions can play important roles in setting species distributions, abundances, and life history traits. Biotic interactions also have the potential to influence species responses to climate change, yet they remain mostly unquantified. An important interaction long studied in tropical forests is postdispersal seed predation which has been shown to affect the population dynamics, community structure, and diversity of plant species in time and space. This paper presents a comparative seed predation study of 24 species of tropical trees across a 2.5 km elevation gradient in the Peruvian Andes and quantifies seed predation variation across the elevational gradient. We then use demographic modelling to assess effects of the observed variation in seed predation on population growth rates in response to observed increasing temperatures in the area. We found marked variation among species in total seed predation depending on the major seed predator of the species and consistent changes in seed predation across the gradient. There was a significant increase in seed survival with increasing elevation, a trend that appears to be driven by regulation of seed predators via top-down forces in the lowlands giving way to bottom-up (productivity) regulation at mid- to high elevations, resulting in a ninefold increase in effective fecundity for trees at high elevations. This potential increase in seed crop size strongly affects modelled plant population growth and seed dispersal distances, increasing population migration potential in the face of climate change. These results also indicate that species interactions can have effects on par with climate in species responses to global change. [ABSTRACT FROM AUTHOR]

Andean plant species are predicted to shift their distributions, or 'migrate,' upslope in response to future warming. The impacts of these shifts on species' population sizes and their abilities to persist in the face of climate change will depend on many factors including the distribution of individuals within species' ranges, the ability of species to migrate and remain at equilibrium with climate, and patterns of human land-use. Human land-use may be especially important in the Andes where anthropogenic activities above tree line may create a hard barrier to upward migrations, imperiling high-elevation Andean biodiversity. In order to better understand how climate change may impact the Andean biodiversity hotspot, we predict the distributional responses of hundreds of plant species to changes in temperature incorporating population density distributions, migration rates, and patterns of human land-use. We show that plant species from high Andean forests may increase their population sizes if able to migrate onto the expansive land areas above current tree line. However, if the pace of climate change exceeds species' abilities to migrate, all species will experience large population losses and consequently may face high risk of extinction. Using intermediate migration rates consistent with those observed for the region, most species are still predicted to experience population declines. Under a business-as-usual land-use scenario, we find that all species will experience large population losses regardless of migration rate. The effect of human land-use is most pronounced for high-elevation species that switch from predicted increases in population sizes to predicted decreases. The overriding influence of land-use on the predicted responses of Andean species to climate change can be viewed as encouraging since there is still time to initiate conservation programs that limit disturbances and/or facilitate the upward migration and persistence of Andean plant species. [ABSTRACT FROM AUTHOR]

The author discusses the study conducted by G. P. Asner and his team on the functional traits of forest canopies in Andes and western Amazon. The team examines biochemistry and foliage traits of about 2,420 canopy tree species at 19 sites in highest diversity tropical forests of the Earth. The team found that canopy functional traits varied throughout soil gradients in predictable ways and high phylogenetic diversity of forests in Western Amazon were interlinked with high functional diversity.