Regional and local effects of disturbance and climate on altitudinal treelines in northern Patagonia

Abstract. In this field study we analysed the regional and local scale effects of disturbance and climate on altitudinal treelines dominated by Nothofagus pumilio in northern Patagonia. We compared two regions west and east of the Andes at 40° S, slopes with warm vs cool aspects and undisturbed vs locally disturbed treelines. This spatial framework allowed us to test (1) for differences among treelines affected by different types of local disturbance and (2) the traditional hypothesis that low temperature limits treeline. Contingency tables and ANOVA showed that local disturbance occurred more frequently than expected on slopes with cool aspects, steep slope angles and concave slope configuration. Disturbed treelines were locally lowered with longer ecotones and lower krummholz growth rates and vegetation cover than undisturbed treelines. Three‐way ANOVA showed the significant influences of study area (regional climate) and aspect (local climate) on treeline elevation, krummholz growth rates and density, tree density and vegetation cover, while accounting for local disturbance. Treeline elevations were higher east of the Andes reflecting the more continental climate in Argentina than in Chile, plus regional impacts of volcanic eruptions. Tree density and vegetation cover were greater west of the Andes reflecting greater precipitation in Chile. Within study areas, local climate had different influences on treeline elevations and krummholz growth rates west and east of the Andes. We predict that increased tree growth and upslope advance of treeline in response to global warming is more likely in Chile than in Argentina near 40° S, unless precipitation increases east of the Andes. To test these predictions, we recommend research be stratified to account for the influences of local disturbance, which may confound climatic impacts. In northern Patagonia, suitable control (undisturbed) study sites will most likely be found at upper slope positions with low slope angles, simple microtopography and straight topographic configuration.     

Numerical modelling of large-scale circulation in Lakes Onega and Ladoga

The results of numerical modelling of large-scale circulation in Lakes Onega and Ladoga are presented, with primary emphasis on the temporal variability of currents with time scales of days. Some typical circulation patterns have been inferred from model calculations. They reflect the existence of different dynamic regimes in the lakes, namely, forced and free circulation regimes. The forced circulation regime is the well-known wind-induced double-gyre circulation accompanied by coastal upwelling and downwelling. A case of double-gyre circulation in Lake Onega was investigated in particular detail. The second dynamic regime is a free response (or a relaxation) of the stratified lake to wind cessation, and is connected closely with the evolution of wind-induced upwelling and thermal front propagation. Diagnostic calculations demonstrate that the regime of relaxation supports the restoration of cyclonic circulation in Lake Onega. Barotropic circulation patterns in Lake Ladoga were calculated with the emphasis on prevailing winds from west to south-east. Our calculations show that the bottom relief of Lake Ladoga causes asymmetry in the double-gyre circulation patterns. In particular, approximately equal cyclonic and anticyclonic circulation cells appearing in the case of southerly wind transform to a single dominant cyclonic cell and several small anticyclonic cells in the case of westerly wind. We also found especially strong sensitivity of the sense of rotation of the largest gyre to the east-west components of the wind vector.     

Topographic controls on the regional-scale biodiversity of the south-western USA

Aim Topography is a fundamental geophysical observable that contains valuable information about the geodynamic, tectonic and climatic history of a region. Here, we extend the traditional uses of topographic analysis to evaluate the role played by topography in the distribution of regional‐scale biodiversity in the south‐western USA. An important aspect of our study is its ability to provide a way to quantify characteristics of the topographic fabric and to construct predictive models that can be used to test hypotheses that relate topography and biodiversity. Location South‐western USA region of the North American Cordillera. Methods Our approach begins with a quantitative analysis of the topography and the construction of a predicted biodiversity map based on measurable topographic quantities: organization, roughness, slope aspect, grain orientation and mean elevation. We then make a quantitative comparison between the predicted and observed biodiversity, based on the assumption that land‐cover diversity is a plausible measure of regional‐scale biodiversity. Land‐cover information used for this study was collected as part of the U.S.G.S. global land cover characteristics (GLCC) project and is derived from satellite (AVHRR) imagery. Results To a first order, the predicted regional‐scale biodiversity based on our topographic model shows a good correlation with the observed biodiversity (as estimated from the land‐cover diversity). Our model overestimates the biodiversity in many parts of the Colorado Plateau, Rio Grande Rift, and the low desert regions of the Southern Basin and Range, suggesting that in these provinces a biodiversity estimate based solely on topography is an over‐simplification. However, much of the Madrean Archipelago and Sierra Madre provinces, which are centres of high biodiversity in this region, show excellent agreement between the observed and predicted biodiversity. Main conclusions While we acknowledge that many other factors in addition to topography have an important influence on biodiversity (particularly on a local scale), we conclude that topography plays a primary role in the regional to continental‐scale biodiversity, particularly in regions characterized by insular mountain fabrics.     

An ecological paradox: high species diversity and low position of the upper forest line in the Andean Depression

Systematic investigations of the upper forest line (UFL) primarily concentrate on mid and high latitudes of the Northern Hemisphere, whereas studies of Neotropical UFLs are still fragmentary. This article outlines the extraordinary high tree diversity at the UFL within the Andean Depression and unravels the links between the comparatively low position of the local UFL, high tree‐species diversity, and climate. On the basis of Gentry′s rapid inventory methodology for the tropics, vegetation sampling was conducted at 12 UFL sites, and local climate (temperature, wind, precipitation, and soil moisture) was investigated at six sites. Monotypic forests dominated by Polylepis were only found at the higher located margins of the Andean Depression while the lower situated core areas were characterized by a species‐rich forest, which lacked the elsewhere dominant tree‐species Polylepis. In total, a remarkably high tree‐species number of 255 tree species of 40 different plant families was found. Beta‐diversity was also high with more than two complete species turnovers. A non‐linear relationship between the floristic similarity of the investigated study sites and elevation was detected. Temperatures at the investigated study sites clearly exceeded 5.5°C, the postulated threshold value for the upper tree growth limit in the tropics. Instead, quasi‐permanent trade winds, high precipitation amounts, and high soil water contents affect the local position of the UFL in a negative way. Interestingly, most of the above‐mentioned factors are also contributing to the high species richness. The result is a combination of a clearly marked upper forest line depression combined with an extraordinary forest line complexity, which was an almost unknown paradox.     

Small montane cloud forest fragments are important for conserving tree diversity in the Ecuadorian Andes

Montane tropical cloud forests, with their complex topography, biodiversity, high numbers of endemic species, and rapid rates of clearing, are a top global conservation priority. However, species distributions at local and landscape scales in cloud forests are still poorly understood, in part because few regions have been surveyed. Empirical work has focused on species distributions along elevation gradients, but spatial variation among forests at the same elevation is less commonly investigated. In this study, the first to compare tree communities across multiple Andean cloud forests at similar elevations, we surveyed trees in five ridge‐top forest reserves at the upper end of the ‘mid‐elevation diversity bulge’ (1900–2250 masl) in the Intag Valley, a heavily deforested region in the Ecuadorian Andes. We found that tree communities were distinct in reserves located as close as 10 to 35 km apart, and that spatially closer forests were not more similar to one another. Although larger (1500 to 6880 ha), more intact forests contained significantly more tree species (108–120 species/0.1 ha) than smaller (30 to 780 ha) ones (56–87 species/0.1 ha), each reserve had unique combinations of more common species, and contained high proportions of species not found in the others. Results thus suggest that protecting multiple cloud forest patches within this narrow elevational band is essential to conserve landscape‐level tree diversity, and that even small forest reserves contribute significantly to biodiversity conservation. These findings can be applied to create management plans to conserve and restore cloud forests in the Andes and tropical montane cloud forests elsewhere.     

Into the Andes: multiple independent colonizations drive montane diversity in the Neotropical clearwing butterflies Godyridina

Understanding why species richness peaks along the Andes is a fundamental question in the study of Neotropical biodiversity. Several biogeographic and diversification scenarios have been proposed in the literature, but there is confusion about the processes underlying each scenario, and assessing their relative contribution is not straightforward. Here, we propose to refine these scenarios into a framework which evaluates four evolutionary mechanisms: higher speciation rate in the Andes, lower extinction rates in the Andes, older colonization times and higher colonization rates of the Andes from adjacent areas. We apply this framework to a species‐rich subtribe of Neotropical butterflies whose diversity peaks in the Andes, the Godyridina (Nymphalidae: Ithomiini). We generated a time‐calibrated phylogeny of the Godyridina and fitted time‐dependent diversification models. Using trait‐dependent diversification models and ancestral state reconstruction methods we then compared different biogeographic scenarios. We found strong evidence that the rates of colonization into the Andes were higher than the other way round. Those colonizations and the subsequent local diversification at equal rates in the Andes and in non‐Andean regions mechanically increased the species richness of Andean regions compared to that of non‐Andean regions (‘species‐attractor’ hypothesis). We also found support for increasing speciation rates associated with Andean lineages. Our work highlights the importance of the Andean slopes in repeatedly attracting non‐Andean lineages, most likely as a result of the diversity of habitats and/or host plants. Applying this analytical framework to other clades will bring important insights into the evolutionary mechanisms underlying the most species‐rich biodiversity hotspot on the planet.     

Pollen Dispersal in a Mountain Area

Atmospheric pollen, phenologic and meteorologic data collected during 12 intervals throughout one year in Tauber traps at different elevations allowed conclusions on vertical pollen dispersal in a mountain/valley system in the Niederhorn, Switzerland. Thus, pollen spectra at higher elevations near the timberline cannot be explained by dispersal through upslope winds but through gradient winds, i.e., winds from the general prevailing direction. The gradient wind direction lying perpendicular to the slope in consideration resulted in high elevation pollen spectra representing a regional aspect whereas the lower elevation spectra more or less faithfully recorded the local vegetation. High pollen numbers occur only during the respective local pollen production period. Secondary high pollen numbers related to precipitation maxima amount to about 10%, exceptionally 20% of the total annual pollen of the respective taxon. Thus, the washout of the pollen filtered in the vegetation seems to be of minor importance. Pollen production decreases quantitatively with increasing elevation, even for the same taxon and apparently independent from the actual growth density. This fact, combined with the regionality of the pollen dispersal at high elevation leads to a distortion of the near timberline pollen assemblages in terms of the local vegetation represented. Thus, lowland pollen dispersal mechanism cannot be used to explain pollen dispersal mechanism in mountain/valley systems.     

Topography controlling the wind regime on the karstic coast: late Pleistocene coastal calcareous sands of eastern mid-Adriatic,Croatia

Aeolian dunes controlled by regional climate have been formed in many coastal areas of the Mediterranean Sea during the Quaternary. Generally, they are formed under a landward-blowing wind, and comprise numerous reworked penecontemporaneous shallow-marine carbonate grains. Along the eastern mid-Adriatic Sea, late Pleistocene aeolian and alluvial sands occur as isolated patches in karstic depressions on several islands and the Pelje?ac Peninsula. At most localities, the sands consist of a mixture of mostly carbonate rock fragments and siliciclastic material. A higher proportion of shallow-marine bioclasts was found only at one locality. The terrestrial material was transported to the coastal area by at least two rivers: paleo-Cetina and paleo-Neretva River, and was subsequently reworked and transported by wind, resulting in aeolian deposition. Sandy units of various thicknesses exhibiting sharp erosional bedding planes and cross-bedding are interpreted as representing aeolian dunes and sand sheets controlled by a complex wind regime. The mineralogical composition at almost all localities indicates near-river flood plains as the main sand source. Although the area was affected by strong winds blowing landward and parallel to the coast, they significantly deviated due to the local topography produced by the tectonically deformed and karstified carbonate basement. In this way, the late Pleistocene aeolian deposits on the mid-Adriatic islands differ from deposits from most Quaternary Mediterranean coastal aeolian belts, as they contain very small quantities of penecontemporaneous shallow-marine carbonate grains and were deposited by winds blowing in varying directions instead of prevailing landward-blowing winds.     

Potential impacts of climate change on the environmental services of humid tropical alpine regions

Aim Humid tropical alpine environments are crucial ecosystems that sustain biodiversity, biological processes, carbon storage and surface water provision. They are identified as one of the terrestrial ecosystems most vulnerable to global environmental change. Despite their vulnerability, and the importance for regional biodiversity conservation and socio‐economic development, they are among the least studied and described ecosystems in the world. This paper reviews the state of knowledge about tropical alpine environments, and provides an integrated assessment of the potential threats of global climate change on the major ecosystem processes. Location Humid tropical alpine regions occur between the upper forest line and the perennial snow border in the upper regions of the Andes, the Afroalpine belt and Indonesia and Papua New Guinea. Results and main conclusions Climate change will displace ecosystem boundaries and strongly reduce the total area of tropical alpine regions. Displacement and increased isolation of the remaining patches will induce species extinction and biodiversity loss. Drier and warmer soil conditions will cause a faster organic carbon turnover, decreasing the below‐ground organic carbon storage. Since most of the organic carbon is currently stored in the soils, it is unlikely that an increase in above‐ground biomass will be able to offset soil carbon loss at an ecosystem level. Therefore a net release of carbon to the atmosphere is expected. Changes in precipitation patterns, increased evapotranspiration and alterations of the soil properties will have a major impact on water supply. Many regions are in danger of a significantly reduced or less reliable stream flow. The magnitude and even the trend of most of these effects depend strongly on local climatic, hydrological and ecological conditions. The extreme spatial gradients in these conditions put the sustainability of ecosystem management at risk.     

Disturbances catalyze the adaptation of forest ecosystems to changing climate conditions

The rates of anthropogenic climate change substantially exceed those at which forest ecosystems – dominated by immobile, long‐lived organisms – are able to adapt. The resulting maladaptation of forests has potentially detrimental effects on ecosystem functioning. Furthermore, as many forest‐dwelling species are highly dependent on the prevailing tree species, a delayed response of the latter to a changing climate can contribute to an extinction debt and mask climate‐induced biodiversity loss. However, climate change will likely also intensify forest disturbances. Here, we tested the hypothesis that disturbances foster the reorganization of ecosystems and catalyze the adaptation of forest composition to climate change. Our specific objectives were (i) to quantify the rate of autonomous forest adaptation to climate change, (ii) examine the role of disturbance in the adaptation process, and (iii) investigate spatial differences in climate‐induced species turnover in an unmanaged mountain forest landscape (Kalkalpen National Park, Austria). Simulations with a process‐based forest landscape model were performed for 36 unique combinations of climate and disturbance scenarios over 1000 years. We found that climate change strongly favored European beech and oak species (currently prevailing in mid‐ to low‐elevation areas), with novel species associations emerging on the landscape. Yet, it took between 357 and 706 years before the landscape attained a dynamic equilibrium with the climate system. Disturbances generally catalyzed adaptation and decreased the time needed to attain equilibrium by up to 211 years. However, while increasing disturbance frequency and severity accelerated adaptation, increasing disturbance size had the opposite effect. Spatial analyses suggest that particularly the lowest and highest elevation areas will be hotspots of future species change. We conclude that the growing maladaptation of forests to climate and the long lead times of autonomous adaptation need to be considered more explicitly in the ongoing efforts to safeguard biodiversity and ecosystem services provisioning.     

Impacts of wind disturbance on fragmented tropical forests: A review and synthesis

Abstract Wind disturbance is an important ecological force in the tropics, especially in the cyclonic and hurricane zones from about 7–20° latitude. Damage from intense winds may be especially severe in fragmented forests because of their abrupt artificial margins and denuded surrounding landscapes. We review available information on the effects of windstorms on fragmented forests, synthesizing studies from Australasia, Amazonia and elsewhere in the tropics. Wind damage in fragmented landscapes can be influenced by a range of factors, such as forest‐edge orientation, edge structure, the size of nearby clearings and local topography. We argue that wind disturbances are likely to interact with, and exacerbate, a range of deleterious environmental changes in fragmented forests. Among the most important of these are altered forest structure, shifts in plant species composition, exotic‐plant invasions, reduced carbon storage and elevated vulnerability to fire. The damaging impacts of winds on fragmented forests could potentially increase in the future, particularly if global warming leads to increasingly severe or frequent windstorms.     

Genetic divergence within frog species is greater in topographically more complex regions

Most global hotspots of biodiversity and endemism are in montane regions. One explanation is that montane regions have intrinsically higher speciation rates than lowland regions because complex mountain topography and climate variation facilitate genetic isolation among populations. Here, we ask from an intraspecific perspective whether frog species whose haplotypes are connected by topographically/climatically complex regions display strong genetic isolation (greater scaled genetic distances), compared with species whose haplotypes are connected by less complex regions. We analysed published DNA sequences of several frog species from tropical Central and South America for the mitochondrial cob, cox1 and 16S rRNA genes. Pairwise genetic distances among haplotypes within each species were scaled to the geographic distances between each pair of haplotypes. Topographic complexity was positively correlated with scaled genetic distances, and isolation‐by‐resistance was supported only in species from more topographically complex regions. This suggests that heterogeneous topographies increase landscape resistance, which in turn favours the appearance of isolation‐by‐resistance. Moreover, we found that the potential barriers that restrict gene flow within species are more closely related to factors associated with temperature and topography than to precipitation.     

Environmental drivers of tree community turnover in western Amazonian forests

A more comprehensive understanding of the factors governing tropical tree community turnover at different spatial scales is needed to support land‐management and biodiversity conservation. We used new forest inventory data from 263 permanent plots in the Carnegie Biodiversity‐Biomass Forest Plot Network spanning the eastern Andes to the western Amazonian lowlands of Peru to examine environmental factors driving genus‐level canopy tree compositional variation at regional and landscape scales. Across the full plot network, constrained ordination analysis indicated that all environmental variables together explained 23.8% of the variation in community composition, while soil, topographic, and climatic variables each explained 15.2, 10.9, and 17.0%, respectively. A satellite‐derived metric of cloudiness was the single strongest predictor of community turnover, and constrained ordination revealed a primary gradient of environmentally‐driven community turnover spanning from cloudy, high elevation sites to warm, wet, lowland sites. For three focal landscapes within the region, local environmental variation explained 13.4–30.8% of compositional variation. Community turnover at the landscape scale was strongly driven by topo‐edaphic factors in the two lowland landscapes examined and strongly driven by potential insolation and topography in the montane landscape. At the regional scale, we found that the portion of compositional variation that was uniquely explained by spatial variation was relatively small (2.7%), and was effectively zero within the three focal landscapes. Overall, our results show strong canopy tree compositional turnover in response to environmental gradients at both regional and landscape scales, though the most important environmental drivers differed between scales and among landscapes. Our results also highlight the usefulness of key satellite‐derived environmental covariates that should be considered when conducting biodiversity analyses in tropical forests.     

Diversification of tanagers, a species rich bird group, from lowlands to montane regions of South America

Synopsis The process of diversification since the late Tertiarywas studied by linking together well-resolved phylogenies andspecies distributions for tanagers (Aves, Thraupini). Speciesrichness patterns reveal very high densities of range-restrictedspecies in the Andes, and to a lesser extent in the Atlanticforests of south-eastern Brazil, and moderate densities of widespreadspecies in the tropical lowlands. Contemporary climate explainswell the variation in species richness for the 25% most widespreadspecies; for the remaining 75% of species with more restricteddistributions, variation can only be explained well from topographyand landscape complexity. Phylogenetically old species are mainlyfound along the Andes and along the Rio coast of Brazil. Mostother areas outside the Andes probably had very moderate ratesof later diversification. In contrast, the humid tropical Andesregion was a centre of intensive speciation throughout the evolutionaryhistory of the group, and species richness patterns here seemlargely to be driven by the rate of speciation, with furtherdiversification from the highlands into adjacent lowlands. Thediversification process in montane areas may be related to highpersistence of lineages in specific areas, something that maybe related to how climatic changes are moderated by local topography.     

Microbial Functional Diversity Associated with Plant Litter Decomposition Along a Climatic Gradient

Predicted changes in climate associated with increased greenhouse gas emissions can cause increases in global mean temperature and changes in precipitation regimes. These changes may affect key soil processes, e.g., microbial CO(2) evolution and biomass, mineralization rates, primary productivity, biodiversity, and litter decomposition, which play an important role in carbon and nutrient cycling in terrestrial ecosystems. Our study examined the changes in litter microbial communities and decomposition along a climatic gradient, ranging from arid desert to humid Mediterranean regions in Israel. Wheat straw litter bags were placed in arid, semi-arid, Mediterranean, and humid Mediterranean sites. Samples were collected seasonally over a 2-year period in order to evaluate mass loss, litter moisture, C/N ratio, bacterial colony-forming units (CFUs), microbial CO(2) evolution and biomass, microbial functional diversity, and catabolic profile. Decomposition rate was the highest during the first year of the study at the Mediterranean and arid sites. Community-level physiological profile and microbial biomass were the highest in summer, while bacterial CFUs were the highest in winter. Microbial functional diversity was found to be highest at the humid Mediterranean site, whereas substrate utilization increased at the arid site. Our results support the assumption that climatic factors control litter degradation and regulate microbial activity.     

Biodiversity of Jinggangshan Mountain: The Importance of Topography and Geographical Location in Supporting Higher Biodiversity

Diversity is mainly determined by climate and environment. In addition, topography is a complex factor, and the relationship between topography and biodiversity is still poorly understood. To understand the role of topography, i.e., altitude and slope, in biodiversity, we selected Jinggangshan Mountain (JGM), an area with unique topography, as the study area. We surveyed plant and animal species richness of JGM and compared the biodiversity and the main geographic characteristics of JGM with the adjacent 4 mountains. Gleason’s richness index was calculated to assess the diversity of species. In total, 2958 spermatophyte species, 418 bryophyte species, 355 pteridophyte species and 493 species of vertebrate animals were recorded in this survey. In general, the JGM biodiversity was higher than that of the adjacent mountains. Regarding topographic characteristics, 77% of JGM’s area was in the mid-altitude region and approximately 40% of JGM’s area was in the 10°–20° slope range, which may support more vegetation types in JGM area and make it a biodiversity hotspot. It should be noted that although the impact of topography on biodiversity was substantial, climate is still a more general factor driving the formation and maintenance of higher biodiversity. Topographic conditions can create microclimates, and both climatic and topographic conditions contribute to the formation of high biodiversity in JGM.     

Global change synergies and trade‐offs between renewable energy and biodiversity

Reliance on fossil fuels is causing unprecedented climate change and is accelerating environmental degradation and global biodiversity loss. Together, climate change and biodiversity loss, if not averted urgently, may inflict severe damage on ecosystem processes, functions and services that support the welfare of modern societies. Increasing renewable energy deployment and expanding the current protected area network represent key solutions to these challenges, but conflicts may arise over the use of limited land for energy production as opposed to biodiversity conservation. Here, we compare recently identified core areas for the expansion of the global protected area network with the renewable energy potential available from land‐based solar photovoltaic, wind energy and bioenergy (in the form of Miscanthus × giganteus). We show that these energy sources have very different biodiversity impacts and net energy contributions. The extent of risks and opportunities deriving from renewable energy development is highly dependent on the type of renewable source harvested, the restrictions imposed on energy harvest and the region considered, with Central America appearing at particularly high potential risk from renewable energy expansion. Without restrictions on power generation due to factors such as production and transport costs, we show that bioenergy production is a major potential threat to biodiversity, while the potential impact of wind and solar appears smaller than that of bioenergy. However, these differences become reduced when energy potential is restricted by external factors including local energy demand. Overall, we found that areas of opportunity for developing solar and wind energy with little harm to biodiversity could exist in several regions of the world, with the magnitude of potential impact being particularly dependent on restrictions imposed by local energy demand. The evidence provided here helps guide sustainable development of renewable energy and contributes to the targeting of global efforts in climate mitigation and biodiversity conservation.     

Responses of annual herb plant community characteristics to increased precipitation and reduced wind velocity in semiarid sandy grassland

Changes in precipitation regimes and wind velocity tend to alter structure and composition of the annual herb plant community, with consequent effects on ecological functioning and biodiversity maintenance. We examined the effects of increased precipitation and reduced wind velocity on annual herb plant community characteristics via a manipulative experiment from the middle of April to middle of August, 2016. There was significant increment in species richness with increased precipitation from June to August, and there were interactive effects between increased precipitation and reduced wind velocity especially in June and the end of July. From June to August, increased precipitation, reduced wind velocity as well as their interaction stimulated sandy plant community development. There was considerable elevation in plant coverage with increased precipitation, and also there was an interactive effect of increased precipitation with 20% reduced wind velocity. However, reduced wind velocity caused more significant stimulation (p < .01) in plant height. Moreover, dominant plants, Salsola collina, Bassia dasyphylla, and Setaria viridis, contributed equally to the elevated community coverage with increased precipitation, whereas S. collina occupied a much larger proportion on the augment of community height compared with the other two species under the increased precipitation and reduced wind velocity. Elevated Shannon–Wiener index was detected with increased precipitation in June and July. Furthermore, increased precipitation and reduced wind velocity enhanced aboveground and belowground biomass, respectively. These species traits‐in structuring and composing plant community were suggested to be conducive to deep understanding the plant functioning and dynamics under global changing precipitation regimes and atmospheric wind velocity scenarios.     

Environmental controls on the distribution and diversity of lentic Chironomidae (Insecta: Diptera) across an altitudinal gradient in tropical South America

To predict the response of aquatic ecosystems to future global climate change, data on the ecology and distribution of keystone groups in freshwater ecosystems are needed. In contrast to mid‐ and high‐latitude zones, such data are scarce across tropical South America (Neotropics). We present the distribution and diversity of chironomid species using surface sediments of 59 lakes from the Andes to the Amazon (0.1–17°S and 64–78°W) within the Neotropics. We assess the spatial variation in community assemblages and identify the key variables influencing the distributional patterns. The relationships between environmental variables (pH, conductivity, depth, and sediment organic content), climatic data, and chironomid assemblages were assessed using multivariate statistics (detrended correspondence analysis and canonical correspondence analysis). Climatic parameters (temperature and precipitation) were most significant in describing the variance in chironomid assemblages. Temperature and precipitation are both predicted to change under future climate change scenarios in the tropical Andes. Our findings suggest taxa of Orthocladiinae, which show a preference to cold high‐elevation oligotrophic lakes, will likely see range contraction under future anthropogenic‐induced climate change. Taxa abundant in areas of high precipitation, such as Micropsectra and Phaenopsectra, will likely become restricted to the inner tropical Andes, as the outer tropical Andes become drier. The sensitivity of chironomids to climate parameters makes them important bio‐indicators of regional climate change in the Neotropics. Furthermore, the distribution of chironomid taxa presented here is a vital first step toward providing urgently needed autecological data for interpreting fossil chironomid records of past ecological and climate change from the tropical Andes.     

Fire as a key driver of Earth's biodiversity

Many terrestrial ecosystems are fire prone, such that their composition and structure are largely due to their fire regime. Regions subject to regular fire have exceptionally high levels of species richness and endemism, and fire has been proposed as a major driver of their diversity, within the context of climate, resource availability and environmental heterogeneity. However, current fire‐management practices rarely take into account the ecological and evolutionary roles of fire in maintaining biodiversity. Here, we focus on the mechanisms that enable fire to act as a major ecological and evolutionary force that promotes and maintains biodiversity over numerous spatiotemporal scales. From an ecological perspective, the vegetation, topography and local weather conditions during a fire generate a landscape with spatial and temporal variation in fire‐related patches (pyrodiversity), and these produce the biotic and environmental heterogeneity that drives biodiversity across local and regional scales. There have been few empirical tests of the proposition that ‘pyrodiversity begets biodiversity’ but we show that biodiversity should peak at moderately high levels of pyrodiversity. Overall species richness is greatest immediately after fire and declines monotonically over time, with postfire successional pathways dictated by animal habitat preferences and varying lifespans among resident plants. Theory and data support the ‘intermediate disturbance hypothesis’ when mean patch species diversity is correlated with mean fire intervals. Postfire persistence, recruitment and immigration allow species with different life histories to coexist. From an evolutionary perspective, fire drives population turnover and diversification by promoting a wide range of adaptive responses to particular fire regimes. Among 39 comparisons, the number of species in 26 fire‐prone lineages is much higher than that in their non‐fire‐prone sister lineages. Fire and its byproducts may have direct mutagenic effects, producing novel genotypes that can lead to trait innovation and even speciation. A paradigm shift aimed at restoring biodiversity‐maintaining fire regimes across broad landscapes is required among the fire research and management communities. This will require ecologists and other professionals to spread the burgeoning fire‐science knowledge beyond scientific publications to the broader public, politicians and media.