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Anthropogenic nutrient enrichment is driving global biodiversity decline and modifying ecosystem functions. Theory suggests that plant functional types that fix atmospheric nitrogen have a competitive advantage in nitrogen-poor soils, but lose this advantage with increasing nitrogen supply. By contrast, the addition of phosphorus, potassium, and other nutrients may benefit such species in low-nutrient environments by enhancing their nitrogen-fixing capacity. We present a global-scale experiment confirming these predictions for nitrogen-fixing legumes (Fabaceae) across 45 grasslands on six continents. Nitrogen addition reduced legume cover, richness, and biomass, particularly in nitrogen-poor soils, while cover of non–nitrogen-fixing plants increased. The addition of phosphorous, potassium, and other nutrients enhanced legume abundance, but did not mitigate the negative effects of nitrogen addition. Increasing nitrogen supply thus has the potential to decrease the diversity and abundance of grassland legumes worldwide regardless of the availability of other nutrients, with consequences for biodiversity, food webs, ecosystem resilience, and genetic improvement of protein-rich agricultural plant species.

Biotic and abiotic factors interact with dominant plants—the locally most frequent or with the largest coverage—and nondominant plants differently, partially because dominant plants modify the environment where nondominant plants grow. For instance, if dominant plants compete strongly, they will deplete most resources, forcing nondominant plants into a narrower niche space. Conversely, if dominant plants are constrained by the environment, they might not exhaust available resources but instead may ameliorate environmental stressors that usually limit nondominants. Hence, the nature of interactions among nondominant species could be modified by dominant species. Furthermore, these differences could translate into a disparity in the phylogenetic relatedness among dominants compared to the relatedness among nondominants. By estimating phylogenetic dispersion in 78 grasslands across five continents, we found that dominant species were clustered (e.g., co-dominant grasses), suggesting dominant species are likely organized by environmental filtering, and that nondominant species were either randomly assembled or overdispersed. Traits showed similar trends for those sites (<50%) with sufficient trait data. Furthermore, several lineages scattered in the phylogeny had more nondominant species than expected at random, suggesting that traits common in nondominants are phylogenetically conserved and have evolved multiple times. We also explored environmental drivers of the dominant/nondominant disparity. We found different assembly patterns for dominants and nondominants, consistent with asymmetries in assembly mechanisms. Among the different postulated mechanisms, our results suggest two complementary hypotheses seldom explored: (1) Nondominant species include lineages adapted to thrive in the environment generated by dominant species. (2) Even when dominant species reduce resources to nondominant ones, dominant species could have a stronger positive effect on some nondominant

Soil nitrogen mineralisation (Nmin), the conversion of organic into inorganic N, is important for productivity and nutrient cycling. The balance between mineralisation and immobilisation (net Nmin) varies with soil properties and climate. However, because most global-scale assessments of net Nmin are laboratory-based, its regulation under field-conditions and implications for real-world soil functioning remain uncertain. Here, we explore the drivers of realised (field) and potential (laboratory) soil net Nmin across 30 grasslands worldwide. We find that realised Nmin is largely explained by temperature of the wettest quarter, microbial biomass, clay content and bulk density. Potential Nmin only weakly correlates with realised Nmin, but contributes to explain realised net Nmin when combined with soil and climatic variables. We provide novel insights of global realised soil net Nmin and show that potential soil net Nmin data available in the literature could be parameterised with soil and climate data to better predict realised Nmin.

Soil nitrogen mineralisation (Nmin), the conversion of organic into inorganic N, is important for productivity and nutrient cycling. The balance between mineralisation and immobilisation (net Nmin) varies with soil properties and climate. However, because most global-scale assessments of net Nmin are laboratory-based, its regulation under field-conditions and implications for real-world soil functioning remain uncertain. Here, we explore the drivers of realised (field) and potential (laboratory) soil net Nmin across 30 grasslands worldwide. We find that realised Nmin is largely explained by temperature of the wettest quarter, microbial biomass, clay content and bulk density. Potential Nmin only weakly correlates with realised Nmin, but contributes to explain realised net Nmin when combined with soil and climatic variables. We provide novel insights of global realised soil net Nmin and show that potential soil net Nmin data available in the literature could be parameterised with soil and climate data to better predict realised Nmin.

© 2017 IEEE. Knowledge about the biogeographic affinities of the world's tropical forests helps to better understand regional differences in forest structure, diversity, composition, and dynamics. Such understanding will enable anticipation of region-specific responses to global environmental change. Modern phylogenies, in combination with broad coverage of species inventory data, now allow for global biogeographic analyses that take species evolutionary distance into account. Here we present a classification of the world's tropical forests based on their phylogenetic similarity. We identify five principal floristic regions and their floristic relationships: (i) Indo-Pacific, (ii) Subtropical, (iii) African, (iv) American, and (v) Dry forests. Our results do not support the traditional neo- versus paleotropical forest division but instead separate the combined American and African forests from their Indo-Pacific counterparts. We also find indications for the existence of a global dry forest region, with representatives in America, Africa, Madagascar, and India. Additionally, a northern-hemisphere Subtropical forest region was identified with representatives in Asia and America, providing support for a link between Asian and American northernhemisphere forests.

Ecosystem eutrophication often increases domination by non-natives and causes displacement of native taxa. However, variation in environmental conditions may affect the outcome of interactions between native and non-native taxa in environments where nutrient supply is elevated. We examined the interactive effects of eutrophication, climate variability and climate average conditions on the success of native and non-native plant species using experimental nutrient manipulations replicated at 32 grassland sites on four continents. We hypothesized that effects of nutrient addition would be greatest where climate was stable and benign, owing to reduced niche partitioning. We found that the abundance of non-native species increased with nutrient addition independent of climate; however, nutrient addition increased non-native species richness and decreased native species richness, with these effects dampened in warmer or wetter sites. Eutrophication also altered the time scale in which grassland invasion responded to climate, decreasing the importance of long-term climate and increasing that of annual climate. Thus, climatic conditions mediate the responses of native and non-native flora to nutrient enrichment. Our results suggest that the negative effect of nutrient addition on native abundance is decoupled from its effect on richness, and reduces the time scale of the links between climate and compositional change.

129I is a very long-lived radionuclide (T1/2 = 15.7 × 106 years) that is present in the environment both because of natural and anthropogenic sources. In this work 129I concentration and 129I/127I ratio have been determined in seaweed Fucus vesiculosus collected in the Southern Baltic Sea during 1982 and 1986 (post-Chernobyl accident). The resulting data were evaluated in terms of 129I concentrations, 129I/127I and 129I/137Cs ratios. 129I concentrations were found to be in the order of (0.82–5.89) × 109 atoms g−1 in 1982 and (1.33–38.83) × 109 atoms g−1 in 1986. The 129I/127I ratios ranged from (22.7–87.8) × 10−10 for seaweed collected in 1982 and from (26.1–305.5) × 10-10 for seaweed collected in 1986. Also a linear relationship was established for 127I concentrations in seawater and salinity in this area, enabling the estimation of concentration factors for 127I in F. vesiculosus. The high levels of 129I and 129I/127I in the Kattegat and their gradually decreasing trend to the Baltic Sea indicates that the most important contribution to the 129I inventory in the Baltic Sea area comes from Sellafield and La Hague reprocessing plants. With respect to Chernobyl accident, 129I concentrations in samples collected in 1986 were not much higher than those expected in less contaminated samples from 1982. This supports the view that the contribution of the Chernobyl accident to 129I in the Baltic region was not significant.

Objective: We characterize and elaborate the inventory of the herpetofauna of the middle valley of the Ranchería river for subsequent monitoring for conservation. Methodology: Four surveys in eight localities were done in the grounds of Carbones del Cerrejón Ltd during the rainy and dry seasons, the areas included tropical dry forest and subxerophitic formations. The surveys were made following different techniques: visual encounter survey, drift fences with pitfall traps and leaf litter plots. Results: Sixty-two species were identified, which include 18 of amphibians (Anura) and 44 of reptiles (21 snakes, 19 lizards, one crocodilian and two turtles). The highest diversity was found in forested areas and in areas with agricultural activities and cattle production; on the other hand, where the forest has been cleared due to the mining activity, the diversity is lower. Conclusion: This richness represents about 55% of the species reported for the lowlands of the Colombian Caribbean, which gives this area an important value for the conservation of species of tropical dry forest, considering as the most threatened ecosystem in Colombia., Objetivo: Caracterizar y elaborar un inventario de la herpetofauna del valle medio del río Ranchería con fines de conservación y su posterior monitoreo. Metodología: Se realizaron cuatro muestreos en ocho localidades en predios de Carbones del Cerrejón Ltd., los cuales abarcaron las épocas de lluvia y sequía en formaciones de bosque seco tropical en hábitats de bosque de galería y subxerofitia. Los muestreos se realizaron aplicando las metodologías de encuentro visual, barreras de interceptación con trampas de caída y parcelas de hojarasca. Resultados: Se identificaron 62 especies, de las cuales 18 son anfibios (Anura) y 44 reptiles (21 serpientes, 19 lagartos, una babilla y dos tortugas). La mayor concentración de herpetofauna se reportó en áreas con presencia de bosque y actividades de ganadería y agricultura, disminuyendo en las localidades donde la cobertura boscosa se ha perdido por efecto de la minería a cielo abierto. Conclusión: Esta riqueza representa aproximadamente 55% de las especies reportadas para las tierras bajas del Caribe colombiano, lo cual le otorga a esta área un valor importante para la conservación de especies del bosque seco tropical, considerando como el ecosistema más amenazado en Colombia.