Résumé
Potassium (K) is essential for a wide range of physiological functions in plants, and a limiting element for wood productivity in numerous forest ecosystems. However, the contribution of each of the K-sensitive physiological processes to the limitation of wood productivity is poorly known. In trees, K deficiency acts both on the source and the sinks of carbon making it difficult to disentangle its effects on wood productivity. Here, we review the literature dealing with the influence of K-limitation on tree physiological processes. Results from extensively studied tropical Eucalyptus plantations are used to illustrate the physiological processes the most impacted by K deficiency. We identify the main processes that limit the availability of K to the trees and influence the circulation of K ions in the ecosystem. Then, we describe the influence of K bioavailability on carbon assimilation, the water economy of trees, and carbon partitioning. We conclude this review by identifying the main priorities towards the process-based modelling of the influence of K on the carbon and water cycles in forest ecosystems. For each process modelling priority, we identify options that could be used in the current conceptual framework of most eco-physiological models.
Auteurs, date et publication :
Auteurs Ivan Cornut , Guerric Le Maire , Jean-Paul Laclau , Joannes Guillemot , Louis Mareschal , Yann Nouvellon , Nicolas Delpierre
Publication : FOREST ECOLOGY AND MANAGEMENT
Date : 2021
Volume : 494
Catégorie(s)
#ANR-Citation #CIRAD #FORET ItatingaRésumé
Tropical rainforests host exceptional biodiversity and provide important ecosystem services, but they are facing anthropogenic and climatic threats. Preserving the genetic diversity of forest tree populations is essential for their capacity to adapt and exhibit resilience to environmental changes and anthropogenic pressures. Here, we collected conservation genetic baseline information for the heavily exploited timber tree Dicorynia guianensis Amshoff (Fabaceae) at the regional and local levels in French Guiana. Based on genotyping at five microsatellite loci in 1566 individuals collected in 23 forest locations, we documented the genetic differentiation of locations from the West of French Guiana and identified distinctive genetic diversity patterns with higher genetic diversity and some bottlenecked sites in the East and inland. The regional population genetic structure is likely the result of past population isolation in distinct Pleistocene refuges and different demographic histories potentially influenced by Holocene drought periods or palaeofires. Assessment of spatial genetic structure (Sp from 0 to 0.028) in five intensively sampled locations yielded estimates of Wright’s neighborhood size of 35 to 313, indicative of restricted dispersal and local metapopulation dynamics, and useful as baseline information to assess the effects of selective logging for conservation management. These results support the current management strategies with low impact extraction of D. guianensis in three zones of the French Guiana permanent forest domain and allow us to make recommendations for further research and management to best preserve its genetic diversity and adaptive potential.
Auteurs, date et publication :
Auteurs Julien Bonnier , Niklas Tysklind , Valérie Troispoux , Ivan Scotti , Stéphanie Barthe , Olivier Brunaux , Stéphane Guitet , Stéphane Traissac , Myriam Heuertz
Publication : Tree Genetics & Genomes
Date : 2025
Volume : 20
Issue : 1
Pages : 2
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
The biodiversity-productivity relationship (BPR) is foundational to our understanding of the global extinction crisis and its impacts on ecosystem functioning. Understanding BPR is critical for the accurate valuation and effective conservation of biodiversity. Using ground-sourced data from 777,126 permanent plots, spanning 44 countries and most terrestrial biomes, we reveal a globally consistent positive concave-down BPR, showing that continued biodiversity loss would result in an accelerating decline in forest productivity worldwide. The value of biodiversity in maintaining commercial forest productivity alone-US$166 billion to 490 billion per year according to our estimation-is more than twice what it would cost to implement effective global conservation. This highlights the need for a worldwide reassessment of biodiversity values, forest management strategies, and conservation priorities.
Auteurs, date et publication :
Auteurs Jingjing Liang , Thomas W Crowther , Nicolas Picard , Susan Wiser , Mo Zhou , Giorgio Alberti , Ernst-Detlef Schulze , A David McGuire , Fabio Bozzato , Hans Pretzsch , Sergio De-Miguel , Alain Paquette , Bruno Hérault , Michael Scherer-Lorenzen , Christopher B Barrett , Henry B Glick , Geerten M Hengeveld , Gert-Jan Nabuurs , Sebastian Pfautsch , Helder Viana
Publication : Science
Date : 2016
Volume : 354
Issue : 6309
Pages : 196
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Frédéric Mortier , Vivien Rossi , Gilles Guillot , Sylvie Gourlet-Fleury , Nicolas Picard , Olivier Gimene Z
Publication : Methods in Ecology and Evolution
Date : 2013
Volume : 4
Issue : 4
Pages : 316–326
Catégorie(s)
#CIRAD #FORET ParacouRésumé
The spatial distribution of biomass is key to optimize forest inventory designs to estimate forest aboveground biomass. Point process theory sets an appropriate mathematical framework to model the spatial distribution of trees, then to derive analytical expressions for the relationship between the variance of biomass in plots and the characteristics (size and shape) of plots, possibly accounting also for plot autocorrelation in biomass. Models derived from point process theory provided a better fit to data from twenty spatially homogeneous sites in tropical rain forests than the commonly used Taylor power model for biomass variance. The model CV = $ømega$+κ/|A| with CV the coefficient of variation of biomass, |A| the plot area, and $ømega$ and κ parameters to estimate, provided in particular a better fit than the power model when the range of autocorrelation in biomass was greater than the plot width. The twenty tropical forest sites greatly differed in the observed relationship between biomass variance and plot size, reflecting differences in the spatial pattern of biomass according to the fitted point process. Accordingly, optimized forest inventory designs also greatly differed between forest sites, with positive biomass autocorrelation favouring cluster sampling design with a distance between subplots in the order of the range of the biomass autocorrelation. In a spatially heterogeneous context consisting of different homogeneous forest strata, large-scale heterogeneity prevailed upon local biomass autocorrelation in determining the optimized plot size and shape. If uncontrolled through stratification, large-scale heterogeneity resulted in much smaller (approximately 0.1–0.2 ha) optimized plot sizes than the homogeneous case (approximately 1–2 ha).
Auteurs, date et publication :
Auteurs Nicolas Picard , Javier G.P. Gamarra , Luca Birigazzi , Anne Branthomme
Publication : Forest Ecology and Management
Date : 2018
Volume : 430
Pages : 10–20
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Planting nitrogen (N) fixing species can provide substantial levels of N for tree growth, but it can also result in large nutrient losses through deep drainage, threatening soil fertility. Nutrient losses through deep leaching have been little studied in tropical forest plantations and comprehensive studies are needed before planting these species on a large scale. We assessed nutrient fluxes in soil solutions collected in monocultures and mixed plantations of Acacia mangium and Eucalyptus grandis in Sao Paulo state (Brazil) on Ferralsols fertilized with potassium, phosphorus and lime. Soil solution sampling began after replanting the trees in an experiment that had already been conducted for six years in a first rotation. We collected soil solutions beneath the forest floor and at depths of 30, 100 and 300 cm, and determined nutrient concentrations monthly for 3.5 years. Drainage fluxes were calculated at the depth of the lysimeters by modeling the water fluxes with Hydrus 1D. The N concentrations in topsoil solutions were generally higher in Acacia than in Eucalyptus monocultures, confirming that the introduction of Acacia increases soil N availability. However, these differences were no more observed at 100 cm depth and total N leaching at 300 cm depth was low in all the treatments, with an average of 4.8 kg N ha- 1 yr -1, probably due to the rapid root system development and high nutrient requirements of these fast-growing trees. Leaching fluxes of K+, Cl-, Ca2+ and Mg2+ peaked in the upper soil layers after fertilizer appli-cations, but the fluxes drastically decreased in deep soil layers. The low fluxes of dissolved nutrients in deep gravitational solutions in our study suggest that the risks of nutrient leaching losses are low in fast-growing plantations established on deep Ferralsols. Our results show that planting N-fixing trees can enhance the N availability for plants without producing large leaching losses, which confirms the interest of mixed plantations with N-fixing trees.
Auteurs, date et publication :
Auteurs Greta Formaglio , Alex Vladimir Krusche , Louis Mareschal , Jean-Pierre Bouillet , Jose Leonardo de Moraes Gonsalves , Yann Nouvellon , Juan Sinforiano Delgado-Rojas , Alexandra Montebelo , Jacques Ranger , Jean -Paul Laclau
Publication : FOREST ECOLOGY AND MANAGEMENT
Date : 2023
Volume : 537
Catégorie(s)
#ANR-Citation #CIRAD #FORET ItatingaRésumé
Embolism spreading in xylem is an important component of plant drought resistance. Since embolism resistance has been shown to be mechanistically linked to pit membrane characters in stem xylem, we speculate that similar mechanisms account for leaf xylem. We conducted transmission electron microscopy to investigate pit membrane characters in leaf xylem across 18 Neotropical tree species. We also conducted gold perfusion and polar lipid detection experiments on three species covering the full range of leaf embolism resistance. We then related these observations to previously published data on embolism resistance of leaf xylem. We also incorporated previously published data on stem embolism resistance and stem xylem pit membranes to investigate the link between vulnerability segmentation (i.e. difference in embolism resistance) and leaf–stem anatomical variation. Maximum pit membrane thickness (Tpm,max) and the pit membrane thickness-to-diameter ratio (Tpm,max/Dpm) were predictive of leaf embolism resistance, especially when vestured pits were taken into account. Variation in Tpm,max/Dpm was the only trait predictive of vulnerability segmentation between leaves and stems. Gold particles of 5- and 10-nm infiltrated pit membranes in three species, while the entry of 50-nm particles was blocked. Moreover, polar lipids were associated with inner conduit walls and pits. Our results suggest that mechanisms related to embolism spreading are determined by Tpm, pore constrictions (i.e. the narrowest bottlenecks along pore pathways), and lipid surfactants, which are largely similar between leaf and stem xylem and between temperate and tropical trees. However, our mechanistic understanding of embolism propagation and the functional relevance of Tpm,max/Dpm remains elusive.
Auteurs, date et publication :
Auteurs Sèbastien Levionnois , Lucian Kaack , Patrick Heuret , Nina Abel , Camille Ziegler , Sabrina Coste , Clèment Stahl , Steven Jansen
Publication : Plant Physiology
Date : 2022
Volume : 190
Issue : 1
Pages : 371–386
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Both the Canadian Land Surface Scheme (CLASS) and the Soil, Vegetation, and Snow (SVS) land surface models employ a potentially problematic discretization of Richards equation for unsaturated vertical flow in the soil column. It is shown here that this discretization will always overestimate the vertical moisture gradient compared to a better-constructed first-order scheme, which under some circumstances could lead to erroneous moisture drawdown. The problem stems from an interpolation calculation on the irregularly spaced grids traditionally used by these models. While vanishing on uniform grids, this numerical error progressively worsens with increasing layer thickness differences. In this brief technical note a systematic method for developing first and higher order schemes on irregular, staggered grids is presented. To demonstrate the potential impact of the new first–order scheme, multi-year simulations of five FLUXNET sites are presented and discussed. A dramatic improvement in first layer soil moisture is found for two of the sites, which contributes to potentially significant differences in evapotranspiration. Higher order schemes are also possible but must be constructed carefully, in concert with a judicious choice of soil layer spacing in order to minimize discretization error. Given the extensive use of CLASS and SVS in Canadian environmental prediction systems, and the freedom with which users can specify soil layer thicknesses, it is recommended that modellers consider this issue carefully in their applications.
Auteurs, date et publication :
Auteurs Murray D. MacKay , Gesa Meyer , Joe R Melton
Publication : Atmosphere - Ocean
Date : 2025
Volume : 61
Issue : 1
Pages : 1–11
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Amazonia’s floodplain system is the largest and most biodiverse on Earth. Although forests are crucial to the ecological integrity of floodplains, our understanding of their species composition and how this may differ from surrounding forest types is still far too limited, particularly as changing inundation regimes begin to reshape floodplain tree communities and the critical ecosystem functions they underpin. Here we address this gap by taking a spatially explicit look at Amazonia-wide patterns of tree-species turnover and ecological specialization of the region’s floodplain forests. We show that the majority of Amazonian tree species can inhabit floodplains, and about a sixth of Amazonian tree diversity is ecologically specialized on floodplains. The degree of specialization in floodplain communities is driven by regional flood patterns, with the most compositionally differentiated floodplain forests located centrally within the fluvial network and contingent on the most extraordinary flood magnitudes regionally. Our results provide a spatially explicit view of ecological specialization of floodplain forest communities and expose the need for whole-basin hydrological integrity to protect the Amazon’s tree diversity and its function.
Auteurs, date et publication :
Auteurs John Ethan Householder , Florian Wittmann , Jochen Schöngart , Maria Teresa Fernandez Piedade , Wolfgang J. Junk , Edgardo Manuel Latrubesse , Adriano Costa Quaresma , Layon O. Demarchi , Guilherme de S. Lobo , Daniel P. P. de Aguiar , Rafael L. Assis , Aline Lopes , Pia Parolin , Iêda Leão do Amaral , Luiz de Souza Coelho , Francisca Dionízia de Almeida Matos , Diógenes de Andrade Lima Filho , Rafael P. Salomão , Carolina V. Castilho , Juan Ernesto Guevara-Andino
Publication : Nature Ecology & Evolution
Date : 2024
Volume : 8
Issue : 5
Pages : 901-911
Catégorie(s)
#CIRAD #FORET ParacouRésumé
While a recent study showed that significant amounts of the nitrogen (N) requirements of young Eucalyptus trees can be provided by nitrogen-fixing trees (NFTs) in mixed-species plantations through short-term belowground N transfer, the consequences of soil fertility on this facilitation process remain unknown. We assessed the effect of fertilization on the percentage of N derived from transfer (%NDFT) from Acacia mangium trees to Eucalyptus trees in mixed-species plantations. A complete randomized block design with two treatments (fertilized vs unfertilized) and three blocks was set up in mixed-species plantations of A. mangium and Eucalyptus in Brazil, with 50% of each species at 2.5 m x 2.5 m spacing. Collection of litterfall and forest floor made it possible to estimate the annual N release from forest floor decomposition between 46 and 58 months after planting, close to harvest age. N-15-NO3- was injected into the stem of one dominant Acacia tree in each plot, 58 months after planting. The x (N-15) values of Acacia and Eucalyptus fine roots sampled within 1.8 m of the labelled A. mangium tree were determined at 7, 14, 30 and 60 days after labelling. The x(N-15) values in wood, bark, branch and leaf samples were also determined for the 6 labelled Acacia trees and their two closest Eucalyptus neighbours, just before and 60 days after labelling. The amount of N released from forest floor decomposition was 31% higher in fertilized (F+) than in unfertilized (F-) plots. Sixty days after labelling, the aboveground compartments of Eucalyptus trees were significantly N-15 enriched in both treatments. The x(N-15) values of Acacia fine mots were higher than background values from 7 days after labelling onwards in F+ and 30 days after labelling in F-. The x(N-15) values of Eucalyptus fine roots were higher than background values in both treatments, from 30 days after labelling onwards. Mean %NDFT values were 18.0% in F+ and 33.9% in F- over the first 60 days after labelling, and 22.8% in F+ and 67.7% in F- from 30 to 60 days after labelling. Fertilization decreased short-term transfer belowground of N from Acacia trees to Eucalyptus trees. Our study suggests that belowground facilitation processes providing N from NFTs to Eucalyptus trees in mixed-species plantations are more pronounced in low-fertility soils than in nutrient-supplied stands.
Auteurs, date et publication :
Auteurs I. R. Oliveira , B. Bordron , J. P. Laclau , R. R. Paula , A., V Ferraz , J. L. M. Goncalves , G. le Maire , J. P. Bouillet
Publication : FOREST ECOLOGY AND MANAGEMENT
Date : 2021
Volume : 491