Jean-Paul Laclau

Forest plantations cover large areas globally, but their climate benefits remain unclear, hampering projections of the future land carbon (C) sink. Here, we combined an unprecedented 14‐years series of eddy‐covariance CO ₂ fluxes (net ecosystem productivity, NEP) with biometric measurements to explore C balance in a commercial Eucalyptus plantation in Brazil across three rotations. The plantation exhibited a 14‐year average and maximum annual NEP of 9.8 and 20.2 MgC ha ⁻¹ y ⁻¹ , respectively, which ranks among the highest documented forest productivity. The amount of time before the forest recaptures as much C as was emitted after harvest was substantially shorter than previously published values: 20 and 27 months, for first and second harvest, respectively. Time series of leaf area index, but not trunk biomass growth, were strongly related to NEP dynamics (> 75% of explained variance at annual and monthly scales) suggesting possible amenability to remote‐sensing assessment in Eucalyptus plantations. Estimates of C accumulation in litter and below‐ground stocks varied from positive to negative depending on the methodology used, and showed substantial differences across rotations. This indicates that long‐term C accumulation in commercial Eucalyptus plantations is not guaranteed, despite their high productivity.

Soil animal communities include more than 40 higher-order taxa, representing over 23% of all described species. These animals have a wide range of feeding sources and contribute to several important soil functions and ecosystem services. Although many studies have assessed macroinvertebrate communities in Brazil, few of them have been published in journals, and even fewer have made the data openly available for consultation and further use. As part of ongoing efforts to synthesize the global soil macrofauna communities, and to increase the amount of openly accessible data in GBIF and other repositories related to soil biodiversity, the present paper provides links to 29 soil macroinvertebrate datasets covering 42 soil fauna taxa, collected in various land use systems in Brazil. A total of 82,797 georeferenced occurrences of these taxa are presented, based on quantitative estimates performed using a standardize sampling method commonly adopted worldwide to collect soil macrofauna populations, i.e., the TSBF (Tropical Soil Biology and Fertility Programme) protocol. This consists in digging soil monoliths of 25 x 25 cm area, with hansorting of the macroinvertebrates visible to the naked eye from the surface litter and from within the soil at depths of 10 to 40 cm). The land use systems included anthropogenic sites managed with agricultural systems (e.g., pastures, annual and perennial crops, agroforestry), as well as planted forests, and native vegetation located mostly in the Southern Brazilian state of Paraná (96 sites), with a few additional sites in the neighboring states of São Paulo (21 sites) and Santa Catarina (5 sites). Important metadata on soil properties, particularly soil chemical analyses (mainly pH, C, P, Ca, K, Mg, Al contents, Exchangeable acidity, Cation Exchange Capacity, Base Saturation, and infrequently total N) and particle size distribution (mainly % sand, silt and clay, and infrequently soil moisture, bulk density), as well as on human management practices (land use and vegetation cover) are provided, in order to better estimate land use change impacts on biodiversity and ecosystem functioning. Quantitative estimates are provided for 42 soil animal taxa, for two biodiversity hotspots: the Brazilian Atlantic Forest and Cerrado biomes. Data are provided at the individual monolith level, representing sampling events ranging from February 2001 up to September 2016 in 122 sampling sites and over 1800 samples, for a total of 82,797 ocurrences.

We hypothesized that the nitrogen-fixing tree Acacia mangium could improve the growth and nitrogen nutrition of non-fixing tree species such as Eucalyptus. We measured the N-mineralization and respiration rates of soils sampled from plots covered with Acacia, Eucalyptus or native vegetation at two tropical sites (Itatinga in Brazil and Kissoko in the Congo) in the laboratory. We used a bioassay to assess N bioavailability to eucalypt seedlings grown with and without chemical fertilization for at least 6 months. At each site, Eucalyptus seedling growth and N bioavailability followed the same trends as the N-mineralization rates in soil samples. However, despite lower soil N-mineralization rates under Acacia in the Congo than in Brazil, Eucalyptus seedling growth and N bioavailability were much greater in the Congo, indicating that bioassays in pots are more accurate than N-mineralization rates when predicting the growth of eucalypt seedlings. Hence, in the Congo, planting Acacia mangium could be an attractive option to maintain the growth and N bioavailability of the non-fixing species Eucalyptus while decreasing chemical fertilization. Plant bioassays could help determine if the introduction of N₂-fixing trees will improve the growth and mineral nutrition of non-fixing tree species in tropical planted forests.

Atmospheric deposition of dissolved organic carbon (DOC) to terrestrial ecosystems is a small, but rarely studied component of the global carbon (C) cycle. Emissions of volatile organic compounds (VOC) and organic particulates are the sources of atmospheric C and deposition represents a major pathway for the removal of organic C from the atmosphere. Here, we evaluate the spatial and temporal patterns of DOC deposition using 70 data sets at least one year in length ranging from 40° south to 66° north latitude. Globally, the median DOC concentration in bulk deposition was 1.7 mg L⁻¹. The DOC concentrations were significantly higher in tropical (25°) latitudes. DOC deposition was significantly higher in the tropics because of both higher DOC concentrations and precipitation. Using the global median or latitudinal specific DOC concentrations leads to a calculated global deposition of 202 or 295 Tg C yr⁻¹ respectively. Many sites exhibited seasonal variability in DOC concentration. At temperate sites, DOC concentrations were higher during the growing season; at tropical sites, DOC concentrations were higher during the dry season. Thirteen of the thirty‐four long‐term (>10 years) data sets showed significant declines in DOC concentration over time with the others showing no significant change. Based on the magnitude and timing of the various sources of organic C to the atmosphere, biogenic VOCs likely explain the latitudinal pattern and the seasonal pattern at temperate latitudes while decreases in anthropogenic emissions are the most likely explanation for the declines in DOC concentration.

Fertilization is commonly used to increase growth in forest plantations, but it may also affect tree water relations and responses to drought. Here, we measured changes in biomass, transpiration, sapwood‐to‐leaf area ratio (A_s:A_l) and sap flow driving force (ΔΨ) during the 6‐year rotation of tropical plantations of Eucalyptus grandis under controlled conditions for throughfall and potassium (K) fertilization. K fertilization increased final tree height by 8 m. Throughfall exclusion scarcely affected tree functioning because of deep soil water uptake. Tree growth increased in K‐supplied plots and remained stable in K‐depleted plots as tree height increased, while growth per unit leaf area increased in all plots. Stand transpiration and hydraulic conductance standardized per leaf area increased with height in K‐depleted plots, but remained stable or decreased in K‐supplied plots. Greater A_l in K‐supplied plots increased the hydraulic constraints on water use. This involved a direct mechanism through halved A_s:A_l in K‐supplied plots relative to K‐depleted plots, and an indirect mechanism through deteriorated water status in K‐supplied plots, which prevented the increase in ΔΨ with tree height. K fertilization in tropical plantations reduces the hydraulic compensation to growth, which could increase the risk of drought‐induced dieback under climate change.

O objetivo do presente trabalho foi avaliar as correlações entre produtividade e resposta à seca (RS) do eucalipto entre os atributos do solo em dois tipos climáticos distintos no Brasil. Para isto, foram instalados 24 experimentos no Brasil com 4 clones comuns em todos os experimentos para obter fortes contrastes edafoclimáticos, e, desse modo, mensurar a produtividade e a reposta à seca e descrever as suas relações com os atributos de solos. Foram avaliados dois grupos climáticos: Úmido (relação precipitação: evapotranspiração entre 1,0 a 2,5) e Subúmido (relação precipitação: evapotranspiração entre 0,5 a 1,0). Os atributos dos solos avaliados foram: Areia, Silte, Argila, matéria orgânica (M.O.), capacidade de troca catiônica (CTC). Para os sítios localizados na classe climática Úmida, o VCCC correlacionouse negativamente com a M.O. e argila, e positivamente com a Areia. Para a RS, as correlações foram observadas para clima Subúmido para as variáveis CTC e Areia, e para o clima Úmido, não foram observadas correlações entre os atributos de solos com a RS.

Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.