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ABSTRACT Aim This paper presents a probabilistic method for the characterization of pollen taxa using attributes, and for the reconstitution of past biomes. The probabilities are calculated on the basis of European floristic and pollen databases sufficiently large and exhaustive to provide robust estimates. Location The analysis is based on data from approximately 1000 sites throughout Europe. Method We use all the pollen data from the European Pollen Database (EPD), which contains about 50 000 pollen assemblages distributed across Europe and covering the period from the Last Glacial Maximum to the present. Using existing floras, each pollen taxon has been characterized by allocating one or more modes of several attributes, chosen according to the biogeography and phenology of the taxon. With this information, conditional probabilities are defined, representing the chance of a given attribute mode occurring in a given pollen spectrum, when the taxa assemblage is known. The concept of co-occurrence is used to provide a greater amount of information to compensate for difficulties in the identification of pollen grains, allowing a better interpretation when there is little diversity in the pollen assemblage. Results The method has been validated using a dataset of modern samples against existing methods of biome classification and remote sensing data. An application is proposed in which the new method is used to produce biomes for pollen data 6000 years ago. This confirms previous results showing an extension of the deciduous forest to the north, east and south, explained by milder winters in western and northern Europe, and cooler and wetter climate in the Mediterranean region. Conclusion The results show the new method to be efficient, reliable and flexible and to be an improvement over the previous method of biomization. They will be used to test simulations of earth system models running on periods with climate significantly different from the present day,... [ABSTRACT FROM AUTHOR]

Aim The continuous increase in anthropogenic nitrogen (N) may have a substantial impact on soil carbon (C) fluxes; thus, understanding the dynamics of soil C fluxes under N enrichment is important. Our main goal was to resolve the conflicting results presented to date and to expand our knowledge about the response of soil respiration (Rs) to N enrichment, which may be affected by the physicochemical properties of soil and environmental factors. Methods We assembled a large dataset for meta-analysis, including 563 datasets on annual and seasonal Rs with N enrichment from 154 published papers at 163 sites, covering seven types of biomes world-wide. Results (1) N enrichment was not significantly related to global Rs but we found a negative relationship in forests and a positive one in other biomes. (2) Rs showed a negative correlation with the N levels in forests and croplands and a positive correlation with the N levels in deserts; heterotrophic respiration exhibited negative correlations with N levels globally, and its response was correlated with the incubation environment. (3) The response of Rs to N enrichment was also correlated with mean annual temperature and soil properties, with 15 °C being the threshold for switching between increasing and decreasing Rs. (4) The estimated total C flux for global terrestrial lands was 97.01 Pg C year-1, and 1 kg of N enrichment at ha-1 year-1 induced an average efflux of 1.33 kg C ha-1 year-1. Main conclusions The response of Rs to future N enrichment should be predicted separately for each biome. The association between changes in Rs and temperature and soil properties under N enrichment makes soil C flux a more complex challenge in the context of future increases in temperature and N deposition. [ABSTRACT FROM AUTHOR]

Aim: Palaeoclimate legacies have been reported to influence microbial communities and carbon (C) stocks even after thousands of years. However, the direct and indirect influences of climate legacies on microbial C processes remain poorly understood and thus limit our capacity to predict how climate legacies regulate C cycling. Here, we conducted microbial, soil and vegetation surveys along a continental latitudinal transect of 4200 km covering a wide range of forest biomes. With these data, we evaluated the potential capacity of climate legacies to predict direct and indirect variations in microbial metabolic quotient (MMQ) across and within three main forest biomes: tropical, subtropical and temperate forests. Location: North–south transect (4200 km), China. Time period: 2019. Major taxa studied: Soil microbes. Methods: We used molecular ecology technology to determine microbial biomass and diversity, in addition to a soil incubation experiment to measure MMQ. Results: Palaeoclimate explained a unique portion of the variation in the continental distribution of MMQ, which showed a hump‐shaped pattern with latitude. Locations with increased isothermality (an index of temperature) over the last 20,000 years also showed the highest MMQ in the present day. Moreover, we found multiple indirect effects of climate legacies on MMQ caused either by changes in key soil properties, such as soil organic carbon and ammonium (NH4+), in lower latitudinal regions or by plant traits in higher latitudinal regions. Furthermore, MMQ was positively related to bacterial richness but negatively to fungal richness across forest biomes. Main conclusions: Climate legacies associated with continuous changes in temperature over the last 20,000 years influenced MMQ across forest biomes. Our findings demonstrate that including climate legacies in climate carbon models is essential for better prediction of the microbe‐driven ecosystem processes under global environmental change. [ABSTRACT FROM AUTHOR]

Motivation: The subdivision of the Earth's terrestrial surface into different biomes, ecozones, bio‐climatic realms or other large ecological land units is an essential reference for global biogeographical and ecological studies. Various classification schemes exist. These differ significantly in terms of the considered criteria for classification and the underlying methodology of class assignments. Evident divergences between global biome concepts are elusive, weakening hereon based analyses and assumptions. Compilation and standardization are essential for obtaining a framework that enables the comparison of different products. To address this need, we created a catalogue of standardized categorial biome maps comprising 31 different global products based on various methodological approaches. These products were processed individually to facilitate their use in large‐scale biogeographical and ecological analyses. Main types of variables contained: We provide a unified RasterStack containing 31 terrestrial biome and land‐cover classifications in different layers. Additional ancillary and processing information is allocated. Spatial location and grain: Global, 10 km × 10 km grain size in equal‐area Mollweide projection. Major taxa and level of measurement: Biomes, ecozones, bio‐climatic zones, and ecological land units. Software format: GeoTiff. [ABSTRACT FROM AUTHOR]

Aim: Agriculture is one of the greatest pressures on biodiversity. Regional studies have shown that the presence of natural habitat and landscape heterogeneity are beneficial for biodiversity in agriculture, but it remains unclear whether their importance varies geographically. Here, we use local biodiversity data to determine which local and landscape variables are most associated with biodiversity patterns and whether their association varies between tropical and non‐tropical regions. Location: Global terrestrial area in forest biomes. Major taxa studied: More than 21,000 species of vertebrates, invertebrates, plants and other taxa. Methods: We used generalized linear mixed‐effects models to analyse the relationships between either community total abundance or species richness (derived from the PREDICTS database) and a number of site‐level (predominant land use and land‐use intensity) and landscape‐level variables (distance to forest, the percentage of natural habitat in the surrounding landscape, landscape homogeneity, the number of land‐cover types in the landscape, and total fertilizer application). We compared the associations of these variables with biodiversity in tropical and non‐tropical regions. Results: In most cases, changes in biodiversity associated with landscape‐level variables were greater than those associated with local land use and land‐use intensity. Increased natural habitat availability was associated with the most consistent increases in biodiversity. Landscape homogeneity was also important but showed different directions of biodiversity change between regions. Associations with fertilizer application or the number of land‐cover types were generally weaker, although still of greater magnitude than for the local land‐use measures. Main conclusions: Our results highlight similarities and differences in the association of local‐ and landscape‐scale variables with local biodiversity in tropical and non‐tropical regions. Landscape natural habitat availability had a consistent positive association with biodiversity, highlighting the key role of landscape management in the maintenance of biodiversity in croplands. Landscape‐scale variables were almost always associated with greater changes in biodiversity than the local‐scale measures. [ABSTRACT FROM AUTHOR]

Aim: The aim was to create global maps of foliar nitrogen‐to‐phosphorus (N:P) ratios across ecosystems, based on modelled climate, soil, and N and P deposition data, to identify global drivers of woody vegetation N:P ratios and to explore the role of genetic legacy (phylogenetics) in foliar N:P ratios of woody plants. Location: Woody cover globally. Time period: Present; data collected from 1990 to 2016. Major taxa studied: Woody plants. Methods: We compiled a database of 20,851 foliar N:P records and assigned them into boreal, temperate coniferous, temperate broadleaved and tropical groups. We applied neural networks to predict N:P global distribution maps, generalized linear models to assess environmental drivers and generalized linear mixed models to disentangle the effect of genetic legacy. Results and main conclusions: Foliar N:P ratios are negatively associated with latitude, with higher N:P ratios occurring in tropical forests and lower N:P ratios in boreal forests. Globally, N:P ratios indicate greater levels of P limitation than N limitation. The influence of environmental factors varied among the four forest biomes, probably owing to contrasting combined environmental conditions; this finding would have been obscured had we conducted a single "forest biome" analysis. Genetic legacy explained significant variation in woody plant foliar N:P ratios, and we suggest its inclusion in future studies to improve N:P ratio predictions. [ABSTRACT FROM AUTHOR]

Motivation: Leaf traits represent an important component of plant functional strategies, and those related to carbon fixation and nutrient acquisition form the leaf economics spectrum. However, observations of functional leaf traits are underrepresented in tropical regions in comparison with those in temperate areas. Brazil, a country with continental scale and vast biodiversity is a timely example, where many biomes are impacted by human activities and climate change. However, leaf traits relevant to understand vegetation responses to these impacts remain poorly quantified for many species found in the country. We compiled an extensive data set of four functional leaf traits for native woody species occurring in the Brazilian territory. In addition to trait observations, sampling dates and geo‐references were compiled and climatic parameters and soil properties of each sampling site were extracted from several databases. Main types of variables contained: The LT‐Brazil data set contains 3,479, 1,216, 775 and 775 clean observations of leaf mass per area, leaf nitrogen (N) concentration per unit mass, leaf phosphorus (P) concentration per unit mass, and leaf N : P ratio, respectively, from native woody species, encompassing information of biome, vegetation, taxonomic data, geographical coordinates, climatic parameters, as well as soil properties. Spatial location and grain: We compiled trait observations from 223 sites under native vegetation distributed in all main biomes (i.e., Amazônia, Caatinga, Cerrado, Mata Atlântica, Pampa and Pantanal) across the Brazilian territory. Time period and grain: The data represent information published and/or sampled during the last 25 years. Major taxa and level of measurement: Our compilation was focused on trait data observed for native woody species, excluding monocots, palm trees, herbs, and hemiparasitic plants. Thus, 108, 478 and 1,321 botanical families, genera and species were included, covering c. 9% of the woody angiosperm flora of Brazil. Software format: Data are provided as comma‐separated value (.csv) files. [ABSTRACT FROM AUTHOR]

Aims: Soil dissolved organic carbon (DOC) is a primary form of labile carbon in terrestrial ecosystems, and therefore plays a vital role in soil carbon cycling. This study aims to quantify the budgets of soil DOC at biome and global levels and to examine the variations in soil DOC and their environmental controls. Location: Global. Time period: 1981–2019. Methods: We compiled a global dataset and analysed the concentration and distribution of DOC across 10 biomes. Results: Large variations in DOC are found among biomes across space and the soil DOC concentration declines exponentially along soil depths. Tundra has the highest soil DOC concentration in 0–30 cm soils [453.75 (95% confidence interval: 324.95–633.5) mg/kg], whereas tropical and temperate forests have relatively lower DOC concentrations, ranging from 30.20 (24.78–36.80) to 54.54 (49.77–59.77) mg/kg. DOC generally accounts for < 1% of total organic carbon in soils, and DOC in 0–30 cm contributes more than half of the total DOC in the 0–100 cm soil profile. Furthermore, variations in DOC are primarily controlled by soil texture, moisture, and total organic carbon. Main conclusions: A global synthesis is combined with an empirical model to extrapolate the DOC concentration along soil profiles across the globe, and global budgets of DOC are estimated as 7.20 Pg C in the top 0–30 cm and 12.97 Pg C in the 0–100 cm soil profile, respectively, with a considerable variation among biomes. The strong soil texture control but weak total organic carbon (TOC) control on DOC variations suggest that the investigation of physical protection of soil organic carbon might need to expand to consider the labile C in soils. The global maps of DOC concentration serve as a benchmark for validating land surface models in estimating carbon storage in soils. [ABSTRACT FROM AUTHOR]

Aim: The aim was to test whether species distribution models (SDMs) can reproduce major macroecological patterns in a species‐rich, tropical region and provide recommendations for using SDMs in areas with sparse biotic inventory data. Location: North‐east Brazil, including Minas Gerais. Time period: Present. Major taxa studied: Flowering plants. Methods: Species composition estimates derived from stacked SDMs (s‐SDMs) were compared with data from 1,506 inventories of 933 woody plant species from north‐east Brazil. Both datasets were used in hierarchical clustering analyses to delimit floristic units that correspond to biomes. The ability of s‐SDMs to predict the identity, functional composition and floristic composition of biomes was compared across geographical and environmental space. Results: The s‐SDMs and inventory data both resolved four major biomes that largely corresponded in terms of their distribution, floristics and function. The s‐SDMs proved excellent at identifying broad‐scale biomes and their function, but misassigned many individual sites in complex savanna–forest mosaics. Main conclusions: Our results show that s‐SDMs have a unique role to play in describing macroecological patterns in areas lacking inventory data and for poorly known taxa. s‐SDMs accurately predict floristic and functional macroecological patterns but struggle in areas where non‐climatic factors, such as fire or soil, play key roles in governing distributions. [ABSTRACT FROM AUTHOR]

Aim: Biomes worldwide are shifting with global change. Biomes whose extents are limited by temperature or precipitation, such as the tundra and savanna, may be particularly strongly affected by climate change. While woody plant encroachment is prevalent across both biomes, its relationship to temperature and precipitation change remains unknown. Here, we quantify the degree to which woody encroachment is related to climate change and identify its main associated drivers. Location: Tundra and savanna biomes. Time period: 1992 ± 20.27–2010 ± 5.62 (mean ± SD). 1876–2016 (range). Major taxa studied: Woody plants (shrubs and trees). Methods: We compiled a dataset comprising 1,089 records from 899 sites of woody plant cover over time and attributed drivers of woody cover change across these two biomes. We calculated cover change in each biome and assessed the degree to which cover change corresponds to concurrent temperature and precipitation changes using multiple climate metrics. Finally, we conducted a quantitative literature review of the relative importance of attributed drivers of woody cover change. Results: Woody encroachment was widespread geographically and across climate gradients. Rates of woody cover change (positive or negative) were 1.8 times lower in the tundra than in the savanna (1.8 vs. 3.2%), while rates of woody cover increase (i.e., encroachment) were c. 1.7 times lower in the tundra compared with the savanna (3.7 vs. 6.3% per decade). In the tundra, magnitudes of woody cover change did not correspond to climate, while in the savanna, greater cover change corresponded with increases in precipitation. We found higher rates of woody cover change in wetter versus drier sites with warming in the tundra biome, and higher rates of woody cover change in drier versus wetter sites with increasing precipitation in the savanna. However, faster rates of woody cover change were not associated with more rapid rates of climate change across sites, except for maximum precipitation in the savanna. Main conclusions: Woody encroachment was positively related to warming in the tundra and increased rainfall in the savanna. However, cover change rates were not predicted by rates of climate change, which can be partially explained by climate interactions in both biomes. Additional likely influences include site‐level factors, time‐lags, plant‐specific responses, and land use and other non‐climate drivers. Our findings highlight the complex nature of climate change impacts in biomes limited by seasonality, which should be accounted for to realistically estimate future responses across open biomes under global change scenarios. [ABSTRACT FROM AUTHOR]

Motivation: The Tundra Trait Team (TTT) database includes field‐based measurements of key traits related to plant form and function at multiple sites across the tundra biome. This dataset can be used to address theoretical questions about plant strategy and trade‐offs, trait–environment relationships and environmental filtering, and trait variation across spatial scales, to validate satellite data, and to inform Earth system model parameters. Main types of variable contained: The database contains 91,970 measurements of 18 plant traits. The most frequently measured traits (> 1,000 observations each) include plant height, leaf area, specific leaf area, leaf fresh and dry mass, leaf dry matter content, leaf nitrogen, carbon and phosphorus content, leaf C:N and N:P, seed mass, and stem specific density. Spatial location and grain: Measurements were collected in tundra habitats in both the Northern and Southern Hemispheres, including Arctic sites in Alaska, Canada, Greenland, Fennoscandia and Siberia, alpine sites in the European Alps, Colorado Rockies, Caucasus, Ural Mountains, Pyrenees, Australian Alps, and Central Otago Mountains (New Zealand), and sub‐Antarctic Marion Island. More than 99% of observations are georeferenced. Time period and grain: All data were collected between 1964 and 2018. A small number of sites have repeated trait measurements at two or more time periods. Major taxa and level of measurement: Trait measurements were made on 978 terrestrial vascular plant species growing in tundra habitats. Most observations are on individuals (86%), while the remainder represent plot or site means or maximums per species. Software format: csv file and GitHub repository with data cleaning scripts in R; contribution to TRY plant trait database (www.try-db.org) to be included in the next version release. [ABSTRACT FROM AUTHOR]

Aim: The forest moss layer plays an important role in water retention, nutrient cycling and forest regeneration. We quantified broad‐scale latitudinal patterns and environmental drivers of moss layer cover in extratropical upland forests where such information has been missing. Location: One thousand, nine hundred and seventy‐seven sites outside the tropical belt (i.e., beyond 26° N and S) across longitudes (from 154° W to 140° E) and elevations (from 0 to 3,950 m a.s.l.). Time period: Current (1969–2016). Major taxa studied: Moss layer bryophytes (mosses, liverworts and hornworts). Methods: We compiled three large datasets from: (a) a global literature search, (b) a national forest inventory database in the USA and (c) an extensive survey along the Appalachian Trail (Eastern USA) to contrast the moss layer cover along latitudinal gradients and among regions. We used correlation analysis and simple (meta‐ and linear‐) regression to test whether moss layer cover increased towards the poles across and within forest biomes, and we used multiple (meta‐ and beta‐) regression to test whether and how climate, forest composition and age and topography influence forest moss layer cover at broad spatial scales. Results: Forest moss cover increased towards the North along a clear latitudinal gradient by c. 2% per 1° of latitude, and it decreased with increasing maximum temperature by c. 1%–5% per 1°C. Thus, cool northern regions (e.g., northern Europe) can be considered forest moss layer hotspots. Moss layer cover was driven mainly by canopy composition when all potential drivers were considered. Compared with broad‐scale systematic surveys, the data from specialized literature overestimated moss cover in broadleaf deciduous forests where moss cover was low and variable. Main conclusions: Our findings highlight that systematic surveys complement specialized literature in accurately modelling abundance on broad scales. Given that temperature, rather than precipitation or seasonality, limited the abundance of forest moss layer on broad scales, the moss layer might be a promising tool for monitoring forest ecosystem responses to climate warming. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To define and map the main biomes of lowland tropical South America (LTSA) using data from tree species inventories and to test the ability of climatic and edaphic variables to distinguish amongst them. Location: Lowland Tropical South America (LTSA), including Argentina, Bolivia, Brazil, Ecuador, Paraguay, Peru and Uruguay. Time period: Present. Major taxa studied: Trees. Methods: We compiled a database of 4,103 geo‐referenced tree species inventories distributed across LTSA. We used a priori vegetation classifications and cluster analyses of floristic composition to assign sites to biomes. We mapped these biomes geographically and assessed climatic overlaps amongst them. We implemented classification tree approaches to quantify how well climatic and edaphic data can assign inventories to biomes. Results: Our analyses distinguish savanna and seasonally dry tropical forest (SDTF) as distinct biomes, with the Chaco woodlands potentially representing a third dry biome in LTSA. Amongst the wet forests, we find that the Amazon and Atlantic Forests might represent different biomes, because they are distinct in both climate and species composition. Our results show substantial environmental overlap amongst biomes, with error rates for classifying sites into biomes of 19–21 and 16–18% using only climatic data and with the inclusion of edaphic data, respectively. Main conclusions: Tree species composition can be used to determine biome identity at continental scales. We find high biome heterogeneity at small spatial scales, probably attributable to variation in edaphic conditions and disturbance history. This points to the challenges of using climatic and/or interpolation‐based edaphic data or coarse‐resolution, remotely sensed imagery to map tropical biomes. From this perspective, we suggest that using floristic information in biome delimitation will allow for greater synergy between conservation efforts centred on species diversity and management efforts centred on ecosystem function. [ABSTRACT FROM AUTHOR]

Motivation: The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community-led open-source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene. Main types of variables included: The database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record. Spatial location and grain: BioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km2 (158 cm2) to 100 km2 (1,000,000,000,000 cm2). Time period and grain: BioTIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year. Major taxa and level of measurement: BioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates. [ABSTRACT FROM AUTHOR]

Aim Global biomes are often classified by mean annual temperature and precipitation, but there is significant overlap between biomes, making it difficult to interpret the role of climate in the distribution of biomes globally. Climate predictability (including long-term reliability of both seasonality and inter-annual variability) varies considerably between biomes and regulates biodiversity distribution, adaptation and evolution, but its global pattern has rarely been investigated. The aim of this study was to characterize climatic space quantitatively for major biomes of the world using temperature and precipitation predictability, and to interpret its biological implications under future climate change. Location Global. Time Period 1901-2012. Methods We calculated global gridded temperature and precipitation predictability based on an information theory approach, and compared climatic spaces defined by these measures within and across biomes. Results We show that temperature predictability has a clear latitudinal gradient, whereas precipitation predictability is geographically variable. We further show that temperature and precipitation predictability form distinct climatic spaces for major biomes across the globe, and importantly, temperature and precipitation predictability can robustly distinguish biomes that are overlapping in mean annual climate statistics. Main conclusions Climatic space created by temperature and precipitation predictability supplements the traditional biome-specific climatic spaces created by annual mean temperature and total precipitation. Quantifying measures of climate predictability helps us to understand adaptation strategies adopted by local organisms within and across biomes. Our results show that quantifying climate predictability is a simple and effective way to delineate more robustly biome climate space and its influences on macroecology and evolutionary biology, which in turn could underpin conservation efforts under future climate change, especially when prevailing climates are comparable in terms of magnitude. [ABSTRACT FROM AUTHOR]

Aim While geographical patterns of species richness are reasonably well explored for single well-studied taxa, less is known about aggregate patterns of total richness for major biomes and their environmental correlates. Here we analyse continental-scale aggregate patterns of macrofaunal diversity for sandy beaches, a dominant habitat along the Atlantic and Pacific coasts of South America. Location South American coastlines. Time period Present day (data amassed from studies performed since 1971). Major taxa studied Benthic macrofauna, including crustaceans, polychaetes and molluscs. Methods We compiled richness information for all macrofaunal groups on 263 sandy beaches in South America using standard criteria. We further matched these data with environmental variables including sea surface temperature (SST), chlorophyll a, grain size, beach slope, tide range and various morphometrics. We used generalized linear mixed models to relate environmental factors to observed variation in total macrofaunal richness across all beaches, testing competing hypotheses about environmental correlates and possible drivers of latitudinal diversity. Results Macrofaunal richness decreased from tropical to temperate beaches in the Pacific and followed a parabolic trend in the Atlantic, with the highest biodiversity found at tropical and mid-latitudinal bands. Beach slope, tidal range and chlorophyll a mostly explained latitudinal trends in macrofaunal richness, followed by grain size, SST and ocean basin. Main conclusions This study indicates that richness of macrofaunal species at a given beach is most closely related to characteristics of the physical habitat, such as beach slope, area and grain size. At this scale, planktonic food supply also appeared to be more important than temperature, which is a dominant explanatory variable of global-scale variation in species richness. [ABSTRACT FROM AUTHOR]

Aim The ecological literature posits that positive interactions are preponderant in stressful environments; however, the net balance between positive and negative interactions at the community level is still under debate. This study analysed the effect of trees on grass biomass in natural and cultivated woody systems distributed along a global aridity index (AI) gradient. Location Global. Methods We conducted a meta-analysis including eight natural biomes and tree plantations distributed in five continents. The final database consisted of 93 data pairs across 65 locations spanning a gradient from AI = 0.1 to AI = 2.1, which covered annual precipitation ranging from 70 to 3500 mm. Effect size was calculated as the difference between above-ground grass biomass beneath and outside the tree canopy. We built linear models to evaluate the importance of different biotic and abiotic variables as potential drivers of the effect size. Multimodel inference, based on the Akaike information criterion (AICc) was used to select the best models. Results The whole data set shows a shift from net facilitation to net competition along an increasing AI gradient. AI had the highest relative importance in explaining the sign and magnitude of the effect size. Tree characteristics (deciduous-evergreen and leguminous-non-leguminous) were the other predictive variables consistently included in almost all the 10 best models. Deciduous and leguminous trees enhanced grass biomass growing beneath them. Increasing soil sand content, C4 grasses and tropical and natural systems all increased the biomass of grasses growing beneath trees, but their relative importance was substantially lower than that of the AI and tree characteristics. Main conclusions The results of our global meta-analysis showed that climatic context and the characteristics of benefactor trees both represent the main drivers of the sign and magnitude of tree-grass interactions. These findings may contribute to advancing knowledge of the mechanisms behind the global patterns. [ABSTRACT FROM AUTHOR]

Aim The present study models the response of vegetation to drought between 1982 and 2011 focusing on the growing season, considering: (1) vulnerable versus resistant ecosystems, (2) ecosystem resilience, (3) the delayed response of vegetation to accumulated precipitation deficits and (4) reduction in productivity due to drought. Location Continental Europe. Methods Vegetation condition was analysed by anomalies of the fraction of photosynthetically active radiation absorbed by vegetation (FAPAR) within the growing season. FAPAR was modelled as a function of: (1) monthly deviation from long-term average drought conditions, (2) past monthly deviation from long-term average drought conditions, and (3) past monthly deviation from long-term average FAPAR conditions. Significant regression coefficients were mapped as ecosystem resistance as well as ecosystem resilience to drought. Annual and long-term growing season productivity were assessed over ecosystems vulnerable to drought within diverse biomes and plant functional types and were studied together with the extent, timing, frequency, duration and intensity of drought events. Results Mediterranean ecosystems showed the least resistance to drought but were resilient. Steppic ecosystems showed weak resistance and also weak resilience. Results also indicated weak resistance against drought of the Atlantic and Continental regions with various recovery rates. Productivity decline was observed when the timing, intensity, frequency and extent of drought events targeted the growing season of the vegetation cover. Main conclusions This study presents an improved method for modelling the impact of drought on the productivity of vegetation by considering the timing, intensity, duration and location of drought events within the growing season, and maps and analyses the resistance and resilience of plant functional types and biomes. [ABSTRACT FROM AUTHOR]

Aim Our research attempts to provide an explicit explanation of human-biome interactions during the last glacial period and how these have influenced current human population genetics at the global scale. Publications to date have not addressed this topic. Location World-wide. Methods Using climate, terrain, hydrographic, fossil pollen and plant-macrofossil data we developed a model of the distribution of biomes during climate deteriorations of the last glacial period. Subsequently, we analysed current human genetic diversity, the origins of genetic lineages and Palaeolithic human sites in relation to the inferred biomes. Results Our analyses indicated that: (1) current human Y- DNA diversity, the places of origin of human Y- DNA lineages and the distribution of Palaeolithic human settlements are best explained by distance from savanna and dry woodland during a series of glacial maxima, and (2) during periods of relatively benign climate conditions, humans dispersed through areas of high primary productivity while avoiding dense forest cover. Main conclusions In a metapopulation of Palaeolithic humans, the biome of savanna and dry woodland supported source populations and other biomes acted as sinks. Present-day genetic, phenotypical and linguistic differences are largely related to discontinuity of and impeded migration between human source populations during glacial periods, rather than simply geographical distance, and in the post-glacial period there has not been enough time for displacements and admixture of human populations to completely blur these differences. [ABSTRACT FROM AUTHOR]

Aim Neotropical biomes are highly threatened by land-use changes, but the catchment-wide biogeochemical effects are poorly understood. Here, we aim to compare exports of dissolved nitrogen (N) and phosphorus (P) from natural and human-impacted catchments in the Neotropics. Location Neotropics. Methods We measured streamwater nutrient concentrations and exports in 20 south-eastern Brazilian catchments with different land uses (natural Cerrado/semideciduous forest, pasture, intensive agriculture and urban areas) and conducted a meta-analysis on nutrient exports from Neotropical catchments, both natural and human-impacted. Results Organic forms dominated dissolved nutrient exports in central/southeast Brazil in both natural and human-dominated catchments. Our meta-analysis suggests that there is wide geographic variability in the natural dominance of organic versus inorganic nutrient exports across the Neotropics, and for N a tendency for inorganic and organic forms to vary inversely across sites. We found strong land-use effects, especially in urban areas. In areas naturally dominated by organic N exports, land use did not overturn that dominance, but rather increased the concentration of both inorganic and organic N. In catchments dominated by inorganic N exports or showing equivalent organic and inorganic exports, land use also caused organic exports to be dominant. Land-use effects on P were unclear, probably owing to a paucity of available data, but our results from south-east Brazil suggested that land use also increases dissolved P exports. Main conclusions We show that dominance of inorganic versus organic nutrient exports is highly variable across natural Neotropical catchments, a pattern contrasting with the general tendency for dominance of organic N in natural temperate catchments. Further, we found a general dominance of organic N in most humanimpacted catchments, which is in contrast to strong dominance of inorganic N in most human-impacted temperate catchments. Finally, we find that urbanization exerts the strongest impacts on nutrient exports, thus underscoring wastewater treatment as a critical management priority under future land-use change. [ABSTRACT FROM AUTHOR]

Aim Convergent evolution and environmental filtering are assumed to often result in deterministic patterns of vegetation structure and function in relation to prevailing environmental conditions regardless of differences in evolutionary history among regions. We systematically evaluate the degree to which biomes located in different biogeographic realms converge in environmental space; identifying globally uniform entities and those diverging systematically among realms. Location Global. Methods Two global biome distribution maps constructed using contrasting approaches are used to evaluate convergence in the environmental space occupied by biomes across biogeographic realms. Environmental conditions are summarized using nine climatic and two edaphic variables known to directly influence plant distributions. Biome maps are analysed accounting for differences in the availability of environments among realms. Results The same biome located in two different realms often overlaps no more in environmental space than two altogether different biomes, with the average overlap on the two biome maps calculated using Schoener's D metric only 0.42 and 0.36. This suggests that the coarse structural and phenological characteristics used to define biomes conceal important differences in plant functioning and responses to environmental drivers. Nonetheless, some biomes, in particular savannas and boreal forests, show high overlap among realms. Others, like mediterranean-type ecosystems and treeless biomes, often occur in vastly different regions of environmental space. Within most biomes though overlap varies greatly depending on the specific realms being compared, with historical biogeography and evolutionary history helping to explain this variation. Main conclusions Biomes often occur under different environmental conditions when comparing regions with distinct evolutionary and environmental histories. The biome concept and efforts to model current and future vegetation patterns needs to be adapted to account for the role of history in determining how vegetation responds to environmental drivers and disturbance. [ABSTRACT FROM AUTHOR]

Aim Although the increase in species richness with increasing area is considered one of the few laws in ecology, the role of environmental and taxon-specific features in shaping species-area relationships ( SARs) remains controversial. Using 421 land-plant floras covering continents, continental islands and oceanic islands, we investigate whether variations in SAR parameters can be interpreted in terms of differences among lineages in speciation mode and dispersal capacities ( TAXON), or of geological history and geographical isolation between continents and islands ( GEO). Location Global. Methods Linear mixed-effects models describing variation in SARs, depending on the factors GEO and TAXON and controlling for differences between realms ( REALM) and biomes ( BIOME). Results The best random-effect structure included both random slopes and random intercepts for GEO, TAXON, REALM and BIOME. This accounted for 77% of the total variation in species richness, substantially more than the 27% statistically explained by the model with fixed effects only (i.e. the simple SAR). The slopes of the SARs were higher for oceanic islands than for continental islands and continents, and higher in spermatophytes than in pteridophytes and bryophytes. The intercepts largely exhibited the reverse trend. TAXON was included in best-fit models restricted to oceanic and continental islands, but not continents. Analysing each plant lineage separately, the intercept of GEO was only included in the random structure of spermatophytes. Main conclusions SAR parameters varied considerably depending on geological history and taxon-specific traits. Such differences in SARs among land plants challenge the neutral theory that the accumulation of species richness on islands is controlled exclusively by extrinsic factors. Taxon-specific differences in SARs were, however, confounded by interactions with geological history and geographical isolation. This highlights the importance of applying integrative frameworks that take both environmental context and taxonomic idiosyncrasies into account in SAR analyses. [ABSTRACT FROM AUTHOR]

Aim We determine whether trait-driven diversification yields similar body size distributions for snakes in local, regional and phylogenetic assemblages. Location United States, North America. Methods Using total length and mass, we examine body size frequency distributions ( BSFD) across 79 sites and respective biomes to determine if these areas represent random subsamples from the source pools of taxon body sizes. Using QuaSSE, we determine if the most probable model of trait-driven diversification in the three most common groups of snakes in North America, the ratsnakes, pitvipers and watersnakes, is similar to the predicted regional BSFD. Results BSFD of snakes at the community, biome, regional and clade scales show symmetric distributions of body size. These patterns may simply be generated from random statistical subsampling. Speciation rates are not highest at or near the modal body size and simulations show that linear trait-driven models can still yield highly symmetric distributions of body size. Main conclusions In this study region, processes such as competition due to size do not alter BSFD from one scale to the other. It is likely that rates of speciation are not highest at the mode in snakes and trait-driven diversification is not likely to account for a regional pool of body sizes from which local communities are drawn, although persistence of modal body sizes through time could yield regional BSFD. [ABSTRACT FROM AUTHOR]