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Achat D.L.,French National Institute for Agricultural Research | Deleuze C.,ONF | Landmann G.,ECOFOR | Pousse N.,ONF | And 2 more authors.
Forest Ecology and Management | Year: 2015

Increasing attention is being paid to using modern fuelwood as a substitute for fossil energies to reduce CO2 emissions. In this context, forest biomass, particularly harvesting residues (branches), and stumps and associated coarse roots, can be used to supply fuelwood chains. However, collecting harvesting residues can affect soil properties and trees, and these effects are still not fully understood. The main objective of the present study was to compile published data worldwide and to quantify the overall effects of removing harvesting residues on nutrient outputs, chemical and biological soil fertility and tree growth, through a meta-analysis. Our study showed that, compared with conventional stem-only harvest, removing the stem plus the harvesting residues generally increases nutrient outputs thereby leading to reduced amounts of total and available nutrients in soils and soil acidification, particularly when foliage is harvested along with the branches. Losses of available nutrients in soils could also be explained by reduced microbial activity and mineralization fluxes, which in turn, may be affected by changes in organic matter quality and environmental conditions (soil compaction, temperature and moisture). Soil fertility losses were shown to have consequences for the subsequent forest ecosystem: tree growth was reduced by 3-7% in the short or medium term (up to 33years after harvest) in the most intensive harvests (e.g. when branches are exported with foliage). Combining all the results showed that, overall, whole-tree harvesting has negative impacts on soil properties and trees that may have an impact on the functioning of forest ecosystems. Practical measures that could be taken to mitigate the environmental consequences of removing harvesting residues are discussed. © 2015 Elsevier B.V.

PubMed | ECOFOR, French National Institute for Agricultural Research and Agro ParisTech
Type: | Journal: Scientific reports | Year: 2015

Forests play a key role in the carbon cycle as they store huge quantities of organic carbon, most of which is stored in soils, with a smaller part being held in vegetation. While the carbon storage capacity of forests is influenced by forestry, the long-term impacts of forest managers decisions on soil organic carbon (SOC) remain unclear. Using a meta-analysis approach, we showed that conventional biomass harvests preserved the SOC of forests, unlike intensive harvests where logging residues were harvested to produce fuelwood. Conventional harvests caused a decrease in carbon storage in the forest floor, but when the whole soil profile was taken into account, we found that this loss in the forest floor was compensated by an accumulation of SOC in deeper soil layers. Conversely, we found that intensive harvests led to SOC losses in all layers of forest soils. We assessed the potential impact of intensive harvests on the carbon budget, focusing on managed European forests. Estimated carbon losses from forest soils suggested that intensive biomass harvests could constitute an important source of carbon transfer from forests to the atmosphere (142-497 Tg-C), partly neutralizing the role of a carbon sink played by forest soils.

Peyron J.-L.,ECOFOR | Herve J.-C.,Ign Institute National Of Linformation Geographique Et Forestiere
Revue Forestiere Francaise | Year: 2012

The rate of removals is the main factor to which reference is made to assess logging intensity of forest resources. However, other factors, commented on in this article, are also involved. In particular, an imbalance between the various stages of maturity may be grounds for more intensive logging (an aged forest on one in the process of being rejuvenated) or less intensive logging (young forest or one whose asset value is on the increase) as compared to net biological production. An adequate assessment of logging intensity is therefore based not only on the average national rate of removals but also on a breakdown of that rate between geographic areas or categories of species, the density and mortality rate of trees, and on the rate of removals for improvement and their rate for regeneration purposes. © AgroParisTech, 2013.

The five technical workshops organised at Regefor 2009, together with the plenary discussion organised during this event, are summarised here and commented upon. The diversity of the opinions and analyses is very apparent from this overview: increased production in combination with better protection; the need for research and the focus of the latter; evaluation of forestry resources; silvicultural practices; soils; research and development; social sciences.

Since 1995, in the framework of the Pan-European process of Ministerial Conferences on the Protection of Forests in Europe, every five years France establishes sustainable management indicators for forests in metropolitan France. The four successive publications now available provide information, according to the six criteria for sustainable forest management formulated in Helsinki in 1993, on developments over time in the state of French forests and the activities they generate. They also give rise to questions about the extent to which this follow-up meet the needs of forests in the area of public policies, including the fight against the greenhouse effect and adaptation to climate change. In addition, they suggest improvements for the short, medium and long term aimed at enhancing the switch from a statistical description to a strategic vision, as well as harmonisation and coherence of information, and extending the legal, political, institutional and geographic scope of sustainable forest management indicators. © AgroParisTech, 2013.

Glukharev N.,Ecofor
ZKG International | Year: 2014

The V-separator has been widely adopted for processing of comminuted material, mainly for closed circuit systems with roller press. It is a really static and energy-saving apparatus that has high reliability in operation. It also carries out the function of disaggregation of material cakes after compacting by the roll. The cakes fall down by the slanted step grate of the separator. They are then divided into parts and scavenged by transversal airflow. A positive electrostatic charge of comminuted material is actively discharged by an active neutralizer and conducted in grounding whilst the material falls through the slanted metal step grate. The cakes of pressed materials have many cracks inside between particles of different sizes. Some of the cracks in the small-sized particles cannot be opened inside a separator due to adhesion. These particles adhere to the large ones and decrease the efficiency of the separator. The adhesion force has components of electrostatic and intermolecular interaction.

This article focuses on possible developments in silvicultural practices in connection with the projected increased use of timber for energy purposes and higher demand for workable and industrial timber. In the first section, it offers a characterisation of the various types of silvicultural practices. It then discusses possible developments in various silvicultural treatments (forests not under management, occasional treatments, periodic treatments, coppice with standards, coppice, short rotation coppice and very short rotation coppice) under various assumptions: continued present trend, increased logging in the near future under the multifunctional intensification scenario and industrial Intensification scenario.

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