Biological nitrogen fixation (BNF) is a fundamental part of nitrogen cycling in tropical forests, yet little is known about the contribution made by free-living nitrogen fixers inhabiting the often-extensive forest canopy. We used the acetylene reduction assay, calibrated with 15N2, to measure free-living BNF on forest canopy leaves, vascular epiphytes, bryophytes and canopy soil, as well as on the forest floor in leaf litter and soil. We used a combination of calculated and published component densities to upscale free-living BNF rates to the forest level. We found that bryophytes and leaves situated in the canopy in particular displayed high mass-based rates of free-living BNF. Additionally, we calculated that nearly 2 kg of nitrogen enters the forest ecosystem through free-living BNF every year, 40% of which was fixed by the various canopy components. Our results reveal that in the studied tropical lowland forest a large part of the nitrogen input through free-living BNF stems from the canopy, but also that the total nitrogen inputs by free-living BNF are lower than previously thought and comparable to the inputs of reactive nitrogen by atmospheric deposition.

• Klíčová slova
• (15)N(2), Bryophytes, Canopy soil, Epiphytes, Leaves, Litter, Terrestrial LIDAR,
• MeSH
• dusík MeSH
• ekosystém MeSH
• fixace dusíku * MeSH
• lesy MeSH
• půda * MeSH
• stromy MeSH
• tropické klima MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• dusík MeSH
• půda * MeSH

Semivolatile persistent organic pollutants (POP) are bioaccumulative and toxic contaminants. Their global distribution depends on source distribution, atmospheric transport, degradation, and the exchange with ocean and land surfaces. Forests are crucial terrestrial reservoirs due to the commonly envisaged high capacity of their surface soils to store and immobilize airborne contaminants bound to soil organic matter. Our results show that POPs can be unexpectedly mobile in the soil of a tropical rainforest due to fast litter turnover (leading to rapid POP transfer to the subsoil) and leaching rates exceeding degradation rates especially for more hydrophobic congeners. Co-transport in association with leaching fine particulate and dissolved organic matter appears as a relevant driver of this PCB export. A markedly different distribution pattern is displayed in this soil in comparison to soils of colder environments with lower overall storage capacity. These findings show that biogeochemistry of organic matter degradation and weathering can influence POP soil fate. Because tropical forests represent 60% of the global terrestrial productivity, the highlighted dynamics might have an implication for the general distribution of these contaminants.

• MeSH
• deštný prales MeSH
• látky znečišťující půdu analýza   MeSH
• organické látky analýza   MeSH
• půda chemie   MeSH
• tropické klima MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• látky znečišťující půdu MeSH
• organické látky MeSH
• půda MeSH

Trees are known to emit methane (CH4 ) and nitrous oxide (N2 O), with tropical wetland trees being considerable CH4 sources. Little is known about CH4 and especially N2 O exchange of trees growing in tropical rain forests under nonflooded conditions. We determined CH4 and N2 O exchange of stems of six dominant tree species, cryptogamic stem covers, soils and volcanic surfaces at the start of the rainy season in a 400-yr-old tropical lowland rain forest situated on a basaltic lava flow (Réunion Island). We aimed to understand the unknown role in greenhouse gas fluxes of these atypical tropical rain forests on basaltic lava flows. The stems studied were net sinks for atmospheric CH4 and N2 O, as were cryptogams, which seemed to be co-responsible for the stem uptake. In contrast with more commonly studied rain forests, the soil and previously unexplored volcanic surfaces consumed CH4 . Their N2 O fluxes were negligible. Greenhouse gas uptake potential by trees and cryptogams constitutes a novel and unique finding, thus showing that plants can serve not only as emitters, but also as consumers of CH4 and N2 O. The volcanic tropical lowland rain forest appears to be an important CH4 sink, as well as a possible N2 O sink.

• Klíčová slova
• basaltic lava flows, cryptogams, methane flux, nitrous oxide flux, soil, tree stem, tropical lowland rain forest, uptake,
• MeSH
• deštný prales MeSH
• lesy MeSH
• methan MeSH
• oxid dusný * MeSH
• oxid uhličitý MeSH
• půda MeSH
• stromy * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Réunion MeSH
• Názvy látek
• methan MeSH
• oxid dusný * MeSH
• oxid uhličitý MeSH
• půda MeSH

The impacts of degradation and deforestation on tropical forests are poorly understood, particularly at landscape scales. We present an extensive ecosystem analysis of the impacts of logging and conversion of tropical forest to oil palm from a large-scale study in Borneo, synthesizing responses from 82 variables categorized into four ecological levels spanning a broad suite of ecosystem properties: (i) structure and environment, (ii) species traits, (iii) biodiversity, and (iv) ecosystem functions. Responses were highly heterogeneous and often complex and nonlinear. Variables that were directly impacted by the physical process of timber extraction, such as soil structure, were sensitive to even moderate amounts of logging, whereas measures of biodiversity and ecosystem functioning were generally resilient to logging but more affected by conversion to oil palm plantation.

• MeSH
• Arecaceae MeSH
• biodiverzita * MeSH
• deštný prales * MeSH
• lesnictví * MeSH
• půda chemie   MeSH
• stromy MeSH
• tropické klima * MeSH
• zachování přírodních zdrojů * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Borneo MeSH
• Názvy látek
• půda MeSH

Logging, pervasive across the lowland tropics, affects millions of hectares of forest, yet its influence on nutrient cycling remains poorly understood. One hypothesis is that logging influences phosphorus (P) cycling, because this scarce nutrient is removed in extracted timber and eroded soil, leading to shifts in ecosystem functioning and community composition. However, testing this is challenging because P varies within landscapes as a function of geology, topography and climate. Superimposed upon these trends are compositional changes in logged forests, with species with more acquisitive traits, characterized by higher foliar P concentrations, more dominant. It is difficult to resolve these patterns using traditional field approaches alone. Here, we use airborne light detection and ranging-guided hyperspectral imagery to map foliar nutrient (i.e. P, nitrogen [N]) concentrations, calibrated using field measured traits, over 400 km2 of northeastern Borneo, including a landscape-level disturbance gradient spanning old-growth to repeatedly logged forests. The maps reveal that canopy foliar P and N concentrations decrease with elevation. These relationships were not identified using traditional field measurements of leaf and soil nutrients. After controlling for topography, canopy foliar nutrient concentrations were lower in logged forest than in old-growth areas, reflecting decreased nutrient availability. However, foliar nutrient concentrations and specific leaf area were greatest in relatively short patches in logged areas, reflecting a shift in composition to pioneer species with acquisitive traits. N:P ratio increased in logged forest, suggesting reduced soil P availability through disturbance. Through the first landscape scale assessment of how functional leaf traits change in response to logging, we find that differences from old-growth forest become more pronounced as logged forests increase in stature over time, suggesting exacerbated phosphorus limitation as forests recover.

• Klíčová slova
• imaging spectroscopy, leaf traits, logging, nutrient availability, phosphorus, specific leaf area, topography, tropical forest,
• MeSH
• ekosystém * MeSH
• lesy MeSH
• spektrální analýza MeSH
• stromy * MeSH
• tropické klima MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Borneo MeSH

BACKGROUND: The availability of soil phosphorus (P) often limits the productivities of wet tropical lowland forests. Little is known, however, about the metabolomic profile of different chemical P compounds with potentially different uses and about the cycling of P and their variability across space under different tree species in highly diverse tropical rainforests. RESULTS: We hypothesised that the different strategies of the competing tree species to retranslocate, mineralise, mobilise, and take up P from the soil would promote distinct soil 31P profiles. We tested this hypothesis by performing a metabolomic analysis of the soils in two rainforests in French Guiana using 31P nuclear magnetic resonance (NMR). We analysed 31P NMR chemical shifts in soil solutions of model P compounds, including inorganic phosphates, orthophosphate mono- and diesters, phosphonates, and organic polyphosphates. The identity of the tree species (growing above the soil samples) explained > 53% of the total variance of the 31P NMR metabolomic profiles of the soils, suggesting species-specific ecological niches and/or species-specific interactions with the soil microbiome and soil trophic web structure and functionality determining the use and production of P compounds. Differences at regional and topographic levels also explained some part of the the total variance of the 31P NMR profiles, although less than the influence of the tree species. Multivariate analyses of soil 31P NMR metabolomics data indicated higher soil concentrations of P biomolecules involved in the active use of P (nucleic acids and molecules involved with energy and anabolism) in soils with lower concentrations of total soil P and higher concentrations of P-storing biomolecules in soils with higher concentrations of total P. CONCLUSIONS: The results strongly suggest "niches" of soil P profiles associated with physical gradients, mostly topographic position, and with the specific distribution of species along this gradient, which is associated with species-specific strategies of soil P mineralisation, mobilisation, use, and uptake.

• Klíčová slova
• Diversity, Metabolomics, P metabolomic niche, Phosphorus, Rainforest,
• MeSH
• deštný prales MeSH
• fosfáty MeSH
• fosfor * MeSH
• mikrobiota * MeSH
• půda MeSH
• stromy MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Francouzská Guyana MeSH
• Názvy látek
• fosfáty MeSH
• fosfor * MeSH
• půda MeSH

Tropical rainforest soils harbor a considerable diversity of soil fauna that contributes to emissions of N2O. Despite their ecological dominance, there is limited information available about the contribution of epigeal ant mounds to N2O emissions in these tropical soils. This study aimed to determine whether ant mounds contribute to local soil N emissions in the tropical humid rainforest. N2O emission was determined in vitro from individual live ants, ant-processed mound soils, and surrounding reference soils for two trophically distinct and abundant ant species: the leaf-cutting Atta mexicana and omnivorous Solenopsis geminata. The abundance of total bacteria, nitrifiers (AOA and AOB), and denitrifiers (nirK, nirS, and nosZ) was estimated in these soils using quantitative PCR, and their respective mineral N contents determined. There was negligible N2O emission detected from live ant individuals. However, the mound soils of both species emitted significantly greater (3-fold) amount of N2O than their respective surrounding reference soils. This emission increased significantly up to 6-fold in the presence of acetylene, indicating that, in addition to N2O, dinitrogen (N2) is also produced from these mound soils at an equivalent rate (N2O/N2 = 0.57). Functional gene abundance (nitrifiers and denitrifiers) and mineral N pools (ammonium and nitrate) were significantly greater in mound soils than in their respective reference soils. Furthermore, in the light of the measured parameters and their correlation trends, nitrification and denitrification appeared to represent the major N2O-producing microbial processes in ant mound soils. The ant mounds were estimated to contribute from 0.1 to 3.7% of the total N2O emissions of tropical rainforest soils.

• Klíčová slova
• Ant mounds, Atta mexicana, Microbial denitrification, N-cycle genes, Nitrous oxide emission, Solenopsis geminata, Tropical forest soil,
• MeSH
• Bacteria genetika   metabolismus   MeSH
• bakteriální geny MeSH
• denitrifikace genetika   MeSH
• deštný prales MeSH
• Formicidae metabolismus   mikrobiologie   MeSH
• nitrifikace genetika   MeSH
• oxid dusný analýza   metabolismus   MeSH
• půda chemie   MeSH
• půdní mikrobiologie * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• oxid dusný MeSH
• půda MeSH

Tropical forest canopies are the biosphere's most concentrated atmospheric interface for carbon, water and energy1,2. However, in most Earth System Models, the diverse and heterogeneous tropical forest biome is represented as a largely uniform ecosystem with either a singular or a small number of fixed canopy ecophysiological properties3. This situation arises, in part, from a lack of understanding about how and why the functional properties of tropical forest canopies vary geographically4. Here, by combining field-collected data from more than 1,800 vegetation plots and tree traits with satellite remote-sensing, terrain, climate and soil data, we predict variation across 13 morphological, structural and chemical functional traits of trees, and use this to compute and map the functional diversity of tropical forests. Our findings reveal that the tropical Americas, Africa and Asia tend to occupy different portions of the total functional trait space available across tropical forests. Tropical American forests are predicted to have 40% greater functional richness than tropical African and Asian forests. Meanwhile, African forests have the highest functional divergence-32% and 7% higher than that of tropical American and Asian forests, respectively. An uncertainty analysis highlights priority regions for further data collection, which would refine and improve these maps. Our predictions represent a ground-based and remotely enabled global analysis of how and why the functional traits of tropical forest canopies vary across space.

• MeSH
• biodiverzita MeSH
• lesy * MeSH
• listy rostlin fyziologie   chemie   anatomie a histologie   MeSH
• nejistota MeSH
• půda chemie   MeSH
• stromy * fyziologie   anatomie a histologie   chemie   klasifikace   MeSH
• tropické klima MeSH
• Země (planeta) * MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Afrika MeSH
• Asie MeSH
• Názvy látek
• půda MeSH

Mycorrhizae, a form of plant-fungal symbioses, mediate vegetation impacts on ecosystem functioning. Climatic effects on decomposition and soil quality are suggested to drive mycorrhizal distributions, with arbuscular mycorrhizal plants prevailing in low-latitude/high-soil-quality areas and ectomycorrhizal (EcM) plants in high-latitude/low-soil-quality areas. However, these generalizations, based on coarse-resolution data, obscure finer-scale variations and result in high uncertainties in the predicted distributions of mycorrhizal types and their drivers. Using data from 31 lowland tropical forests, both at a coarse scale (mean-plot-level data) and fine scale (20 × 20 metres from a subset of 16 sites), we demonstrate that the distribution and abundance of EcM-associated trees are independent of soil quality. Resource exchange differences among mycorrhizal partners, stemming from diverse evolutionary origins of mycorrhizal fungi, may decouple soil fertility from the advantage provided by mycorrhizal associations. Additionally, distinct historical biogeographies and diversification patterns have led to differences in forest composition and nutrient-acquisition strategies across three major tropical regions. Notably, Africa and Asia's lowland tropical forests have abundant EcM trees, whereas they are relatively scarce in lowland neotropical forests. A greater understanding of the functional biology of mycorrhizal symbiosis is required, especially in the lowland tropics, to overcome biases from assuming similarity to temperate and boreal regions.

• MeSH
• ekosystém MeSH
• mykorhiza * MeSH
• půda MeSH
• stromy MeSH
• živiny MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• půda MeSH

Tropical forests store 40-50 per cent of terrestrial vegetation carbon1. However, spatial variations in aboveground live tree biomass carbon (AGC) stocks remain poorly understood, in particular in tropical montane forests2. Owing to climatic and soil changes with increasing elevation3, AGC stocks are lower in tropical montane forests compared with lowland forests2. Here we assemble and analyse a dataset of structurally intact old-growth forests (AfriMont) spanning 44 montane sites in 12 African countries. We find that montane sites in the AfriMont plot network have a mean AGC stock of 149.4 megagrams of carbon per hectare (95% confidence interval 137.1-164.2), which is comparable to lowland forests in the African Tropical Rainforest Observation Network4 and about 70 per cent and 32 per cent higher than averages from plot networks in montane2,5,6 and lowland7 forests in the Neotropics, respectively. Notably, our results are two-thirds higher than the Intergovernmental Panel on Climate Change default values for these forests in Africa8. We find that the low stem density and high abundance of large trees of African lowland forests4 is mirrored in the montane forests sampled. This carbon store is endangered: we estimate that 0.8 million hectares of old-growth African montane forest have been lost since 2000. We provide country-specific montane forest AGC stock estimates modelled from our plot network to help to guide forest conservation and reforestation interventions. Our findings highlight the need for conserving these biodiverse9,10 and carbon-rich ecosystems.

• MeSH
• biomasa MeSH
• datové soubory jako téma MeSH
• deštný prales * MeSH
• geografická kartografie MeSH
• klimatické změny MeSH
• postoj * MeSH
• sekvestrace uhlíku * MeSH
• stromy metabolismus   MeSH
• tropické klima * MeSH
• uhlík analýza   MeSH
• zachování přírodních zdrojů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Afrika MeSH
• Názvy látek
• uhlík MeSH