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Bottinelli N.,French National Institute for Agricultural Research | Hallaire V.,French National Institute for Agricultural Research | Hallaire V.,Agrocampus Ouest | Goutal N.,Office National des Forets ONF | And 2 more authors.

Processes and rate of macroporosity changes following heavy traffic in forest ecosystems are seldom studied. The aim of this study was to determine the ability of forest soils to regenerate their macroporosity naturally. The study was performed on 2 silty temperate-forest soils classified as sensitive to compaction located in north-eastern France. Macroporosity was measured in control and trafficked plots at 3 depths (0-7, 15-30 and 30-45cm) over 2-3years. Soil macroporosity characteristics (shape, size and orientation) were assessed on polished sections through 2D-image analysis and micromorphic observations. Immediately after heavy traffic, macroporosity decreased by 96 to 49% from 0 to 45cm in depth. Natural regeneration of macroporosity occurred in the upper 7cm of soil, while the soil below remained compacted. Small and medium macropores (0.05-0.8mm2) dominated by rounded and irregular pores regenerated completely. Large macropores (>0.8mm2) originally dominated by vughs, mammilated vughs and channels rarely regenerated and were gradually replaced by horizontally oriented planar pores. Our results suggest that initial stages of natural macroporosity recovery are likely due to plant-root penetration and physical processes (shrink-swell, freeze-thaw), whereas recovery due to fauna activities appears later.© 2013 Elsevier B.V. Source

Bontemps J.-D.,French National Institute for Agricultural Research | Herve J.-C.,Directorate General of Armaments | Leban J.-M.,French National Institute for Agricultural Research | Dhote J.-F.,Office National des Forets ONF
Trees - Structure and Function

Environmental drivers of forest productivity increases have been much debated. Evidence for the suggested role of increasing nitrogen supply is lacking over long-term time scales. Tracking the footprint of environmental factors by using long-term growth records may thus prove decisive. We analysed growth chronologies of common beech in two areas of contrasting nutritional status in France. Dominant height growth was used as a proxy for productivity. Growth was compared between old and young paired stands sampled at the same sites to factor out effects of ageing and site. Growth chronologies were estimated with a statistical modelling procedure. The environmental causality of growth changes was addressed by combining (1) a comparison of growth changes between regions, (2) a regional comparison of growth chronologies with chronologies of environmental factors and (3) growth-environment relationships established from climate/soil data. Historical growth increases followed very similar courses in the two areas. Remarkably, the magnitude of change was 50% lower in the area that had reduced nutritional status and nitrogen deposition. Historical variations in environmental factors and growth were congruent with the roles of nitrogen availability and deposition, and of atmospheric CO2 increase. Low-frequency variations in climate and growth were not coincident. However, our analysis demonstrated the role of climatic anomalies in short-term growth variations. Growth-environment relationships further indicated a nitrogen constraint. These observations corroborate the enhancing role of increased nitrogen availability on forest biomass accumulation previously reported in ecosystem experiments and process-based modelling explorations. © 2010 Springer-Verlag. Source

Goutal N.,Office National des Forets ONF | Goutal N.,French National Institute for Agricultural Research | Boivin P.,University of Geneva | Ranger J.,French National Institute for Agricultural Research
Soil Science Society of America Journal

Soil compaction is a major contributor to forest soil degradation. To make a decision on soil remediation, both the soil compactness after heavy traffic of forest machinery and the natural soil recovery rate must be estimated. We estimated the impact of heavy traffic on soil specific volume (V) and its recovery rate on two forest sites by yearly collecting steel cylinders close to field capacity, as currently recommended, at different depths (D) during 3 to 4 yr. Though collected at water contents (w) as homogeneous as possible, the comparison of sample volumes led to inconsistent results. Using w as covariate was necessary to quantify the initial compaction and the V recovery with time and D. Moreover, compared to the soil V and w determined with shrinkage analysis, some field values were very large, suggesting an artifact due to hammering the cylinder at large w. The surface layer (0-10 cm) of the less compacted site showed no residual compactness 3 yr after heavy traffic and the 10- to 20-cm layer compactness decreased significantly with time. The compactness of the second site decreased significantly only in the 0- to 10-cm layer, and the recovery was still ongoing after the third year of monitoring. This site had less swelling clays and larger clay content. The recovery of the soil volume was attributed to shrink-swell processes. Longer monitoring is required to validate these trends, and further research should evaluate the need for more accurate monitoring based on shrinkage analysis and the use of soil organic carbon (SOC) and clay content as covariates. © Soil Science Society of America. Source

Procopio L.C.,National Institute of Amazonian Research | Gayot M.,Office National des Forets ONF | Sist P.,CIRAD - Agricultural Research for Development | Ferraz I.D.K.,National Institute of Amazonian Research
Acta Botanica Brasilica

Understanding the range of a species is essential to understanding its ecology and conservation. In this study we collected data on the composition, abundance, diametric structure, and geographic distribution of "tauari" species (Lecythidaceae), which are among the most exploited timber trees of the Amazonian forest. We used herbarium data to define the areas of distribution and inventories of 401.25 ha from six areas of Amazonia to list species for estimating abundance and diametric structure. Of the 14 species that occur in the biome, nine were sampled in the inventories. Couratari guianensis had the largest continuous area of distribution, but always at low densities. Couratari stellata had the second largest distribution, but it was discontinuous and usually at high densities. Cariniana micrantha and Couratari multiflora had wide distributions and variable densities, whereas most of the other species showed regional or restricted ranges and densities below one individual per hectare. The classification of species according to rarity type diverged from that described for Couratari guianensis and C. multiflora. These results point out the lack of data for timber species in the most deforested regions of Amazonia, the need for local and regional abundance investigation for better understanding of distribution patterns, and to provide support for reviewing the categories and criteria of threats of Couratari species on the IUCN Red List. Source

Bontemps J.-D.,French National Institute for Agricultural Research | Herve J.-C.,Directorate General of Armaments | Dhote J.-F.,Office National des Forets ONF
Forest Ecology and Management

While forest productivity is usually inferred from height growth indices, retrospective analyses of tree rings have been intensively used to assess long-term trends in forest productivity. However, radial growth is sensitive to the degree of competition between trees and influenced by management practices or local disturbances. Whether radial growth is accurate for diagnosing and quantifying productivity changes remains a debated question. In a previous study (Bontemps et al., 2009), we assessed historical variations in dominant height growth of even-aged stands of common beech in north-eastern France as a proxy for their productivity changes. The analysis was based on a sampling design including 14 pairs of young/old (75/150 yr) neighbour stands growing under the same site conditions. Dominant height was reconstructed from stem analyses and was compared between generations using a statistical modelling procedure. In this analysis, we tested whether radial and height growth of dominant trees may provide compatible indications on long-term trends. We therefore measured and analysed the radial growth of dominant trees at breast height for the same sampled trees. The effects of site, developmental stage, and calendar date were separated by applying a similar modelling approach. Consideration of the developmental stage effect led to the formulation of an original growth equation. Analysis of radial growth revealed: (i) a long-term positive increase; (ii) a magnitude of +50% over the last century; and (iii) growth declines in the 1940s and 1990s. These features were remarkably similar to those reported on dominant height, and indicated that radial growth of dominant trees delivered a sound picture of productivity changes. The radial growth chronology also differed by showing a more acute acceleration phase in the early century, and a recent but significant difference between stand generations. © 2010 Elsevier B.V. All rights reserved. Source

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