The sylviculture , étymologiquement the culture of the Forest S (of Latin silvæ , wood and forests), has as a role to make evolve/move the forests, by making profitable the natural ecological factors and potentialities, in order to durably optimize the products and the services which the man can expect.
The “ durable sylviculture ” reinforces the idea that management must take care not to overexploit the medium so that it does not lose its potential in the future. Certain management styles give a more constant attention to the environment and the biodiversity, of which Prosilva, with techniques concerned with what the Anglo-Saxons call “ecoforestry”, which can be validated by labels such as for example FSC.
Adjustment of supply andFor economic reasons, sylviculture seeks to adjust its offer of Bois to the request, which is particularly difficult being given the relative slowness of growth of the trees, and because the request can vary in time (Colbert planted for the Marine, but when the Chêne S became ripe, the ships were built in Acier). A Oil crisis makes climb the price of the wood, which can fall 10 years afterwards. The growth of the tropical wood imports made lose of their profitability with certain wood buildings. A storm, fires, the climatic modifications are badly anticipated risks.
In France, after war, one encouraged the culture of the Résineux for construction, but this market did not answer the hopes of the foresters. It is as a question of ensuring of the incomes the owners, knowing as the Chasse can contribute to it for 50% and more.
Academy of speciesOn the ecological level, the natural or little anthropized forest plays a part of conservation Génétique of animal species and vegetable and, beyond, if its extent is sufficient, of the processes of evolution. But in the northern hemisphere and several tropical zones, the forests were very fragmented and became very artificial, losing part of the remarkable biological elements which they had preserved with last managements. Forestry operations (conversions of very artificial settlements) can be necessary to ensure the perenniality of these elements.
In addition, in certain cases, a forest will protect better against from the departures of Avalanche S, crumbling S or landslides if it presents (permanently) a composition, a structure and adapted age groups, which can be maintained by an active management.
On a social plan or sociocultural, certain forms of sylvicultures make it possible to work or maintain the landscapes appreciated, and to create the various conditions of reception and environment that the public seeks. Certain tree growers seek within this framework to limit the effects of the cuts to white, for example by decreasing their size or while preserving to hide them a wooded band which will also be used as biological Corridor and of protective edge for the planted pieces or in regeneration.
ObjectivesSeeming the means of making evolve the forest to long-term objectives, “desirable” sylviculture in a given place depends schematically on three independent factors:
- “stationnelles” conditions: they determine the use and potentialities for growth of the various plant species; they limit the choice of the gasolines which could be used. They can moreover impose forestry precautions, even certain types of sylvicultures; it is the case of the rare and remarkable forest stations, certain moist environments for example; it is still the case of the fragile stations, subjected at the marked risks of erosion, clogging by increase of the “”, degradation water level of a not very stable ground, etc Its conditions depend on the nature of the ground (Argile, Limon, Podzol,…) and of the Climate.
- the state of the forest ecosystem: it is in particular related on the gasolines, the structures, the densities of the involved settlements, can bring strong constraints to the tree grower. It will be never possible, for example, to apply a treatment of gardened Futaie to an old settlement at weak duration of survival or to clear up strongly and quickly a Futaie become too dense;
- laid down objectives: for the means and the long run, they contribute in a decisive way to the forestry choices. Multiple objectives are generally associated: management known as “is integrated” or “multipurpose”. But certain general or transverse objectives are taken into account in all sylvicultures:
- objective of conservation of all the potentialities to the profit of the future generations, which makes say that the management is “durable”; this objective prohibits any irreversible transformation; it imposes the maintenance, as precaution, of all the resources living, animal species and vegetable, ecotypes, Gène S… ; it is now beyond including the conservation of all the elements of the Biodiversité, a very detailed attention being carried to the most remarkable elements;
- objective of maintenance or control of the forest towards the mosaics of most stable ecosystems thanks to well adapted gasolines and structures and with judicious balance between the various stages of evolution; this objective answers an high level of ambition for a “durable management”;
- objective of maintenance of the types of landscapes characteristic and appreciated or attenuation of the landscape modifications.
Forestry modes and treatmentsThe foresters developed techniques to adapt the forests to their waitings and " conduire" trees until the stage which the tree grower considers being their stage of Maturité.
In moderated zone, one can distinguish 6 classes from mode and forestry mode of treatment
- Coupe shaves (or crosses to white),
- regular Futaie,
- irregular Futaie (possibly mixed, and/or gardened),
- leafy grove mixture/coppice,
- simple Taillis,
- resinous grove mixture/coppice.
- the " coppice " consists of rejections and/or suckers, whose perpetuation is obtained by a cut of renovation, which corresponds to a renewal ensured by vegetative way. The goal of the coppices is to produce wood of small circumferences intended for the Firewood. It requires gasolines which reject stocks (Noisetier, maple, Châtaignier…)
the " grove " is resulting from a forest settlement composed of trees coming directly from Semis on the spot. Its goal is to produce trees which will give a maximum of sawlog.
the mode of the " coppice under-grove " is a mixed mode which has the aim of perpetuating settlements comprising of the trees of which some were born from seeds and others obtained by vegetative way. It makes it possible to produce firewood and sawlog.
Systems of sylvicultureThere exist four principal methods of Forestry development or regeneration called systems of sylviculture. This term describes not only the various cuts, but also with the ways of preparing a new bed of Germination after the demolition of the trees, i.e. the means to regenerate the next settlement.
the cut shaves : one shaves the whole of the forest then one lets push natural sowings. It is an economic solution because one can make mechanical demolition and an easy extraction but one obtains a uniform forest with trees having all the same age.
- the cut of gardening : one cuts periodically only the mature trees. It is an ecological method more but more expensive because one extracts that an minor amount of wood each time without possibility of demolition mechanical and one risks collateral damage with each cut.
- the thinning out : only 10% of the trees are preserved like reproducers in all the zone of cut
- the progressive cut of regeneration : one cuts the oldest trees over one period from ten to fifteen years, in order to allow the natural reproduction and to produce settlements of relatively regular age.
Methods of regeneration
; under the mode of the coppice: Regeneration by vegetative way
; under the mode of grove: regeneration by sexuée way
; under the mode of coppice under grove: combination of the two sexués and vegetative modes
Forestry operationsThey include/understand polishings, thinnings out, prunings, plantations, direct drillings, and fire wall (in the dry areas).
PolishingThe cleared up are cuts of trees of frankly foot or old bits (scaffold-pole X) of a Cépée. They aim at supporting the development of the trees which are of an interest, generally economic by elimination of close trees. This technique can get busy only in the dense settlements. But it should be taken care that the investment in time and men allows an appreciable economic gain in quality and quantity of collected volumes. A modern technology but little employed consists in barking the trees to be eliminated, by means of an especially designed apparatus. They die on foot and produce deadwood and humus, by minimizing the labor and the disturbance (not of noise of slicer, not of transport).
Thinning outThe Dépressage consists in removing certain number of young subjects resulting from a natural regeneration in a very dense settlement of which the height of the dominant stems is generally lower than 9 m, to always improve the growth of those remaining. This operation is carried out using a treedozer with back, by bulk-heading or demolition.
Pruning and size of formationThe pruning and cuts it formation consist in cutting to the short-nap cloth of the trunk the branches for improving the form and quality of the barrel and wood, by reducing the size of the " nœuds" whose fibers are not in the same direction that the remainder of the wood, which involves a weakness in the produced parts or a commercial downgrading. The height of pruning varies in general between 2 and 10 meters, and it is practiced in intensive sylvicultures every 10 years on the young trees. Many species, in condition of competition for the light make a natural Autoélagage, which is favoured in the approaches of the type Prosilva, which reduces the maintenance costs and limit the transmission risks of Champignon S and pathogenic Bactérie S by the size or cutting tools.
Plantation by direct drillingThe plantation by direct drilling or transplantation is especially used in the event of close-cropped cut. They consist in sowing seeds of trees selected for their best growth and their resistance to the diseases or planting seedlings resulting from Pépinière. For the young seedlings, one uses sachets in Polyéthylène or a substrate of Tourbe - Vermiculite. They can also be cultivated in open ground then planted naked roots , which requires an attentive care.
To plant makes it possible to choose the gasolines of trees precisely and thus to create plantations which one hopes for perfectly adapted to the natural conditions. But the Genetic Biodiversity and thus the stability of the settlement or its resistance to diseases (in particular rust for the Poplar) can suffer from it. One proceeds while aligning and by regularly spacing the seedlings, often since the years 1980 after a Sous-solage, a Dessouchage, even a treatment Weeding, a Labor and a contribution of Engrais in the case of certain intensive timberings (Peupleraie S, Eucalyptus). Certain countries impose a source certified of the Graine S from which the seedlings result, which contributed to further decreasing heterogeneity genetics of the planted forests, on the risk to decrease their stability and their capacity of ecological Résilience.
Fire wallThe goal of the Pare-feu is to create a discontinuity in the forest settlement in order to stop or slow down the progression of a fire. They must be installed perpendicular to the dominant winds not on the contrary to become corridors of propagation of fire. A fire wall badly conceived risk also to be a factor of erosion, even of fragmentation écopaysagère. Those which are enherbés and maintained by herbivores (sheep in general) seem most effective. They play generally also a part of Cloisonnement and tailboards of hunting (the hunters await there the game, easier to draw, possibly thorough by the dogs and pickups).
New extensive method
Extensive sylviculture applies mainly in the settlements of beech. It is a soft method by targeted interventions which limits the costs by ensuring a regeneration of quality while preserving the biodiversity. The installation is carried out in three major phases: The acquisition installation-the, compression and routing.
The acquisition installation-theThe forest manager checks that the installation of sowings is in place in order to undertake the final cut of the seed-bearer ones. During the first two years it makes sure that sowings are not competed with by the woody and brambly impression. If necessary, it envisages a passage in coarse release with the treedozer to control the vegetation in order to obtain the strongest regeneration of or objective gasolines.
CompressionThe gourmant beech little sun must remain in compression to support its apical growth. Indeed, if it is too much to release, it will tend to develop by its low branches what will influence major defects like the low forks. The compression which can last fifteen years, will make it possible to obtain at a stage gaulis - low pole plantation of the objective stems without low branches which will reduce the cost of a possible pruning. Nevertheless, of work during this phase are necessary to the calibration of the regeneration of the secondary gasolines and accompaniment as the charm, the ash, the maples as well as the invaluable gasolines like the wild cherry tree and the service-tree torminal. The intervention consists in intervening by method of " cassage" on the concurrent stems in order to support the setting in apical light. At the low stage pole plantation, the breaking will be replaced by the annelation of the singular stems in order to always keep the effectiveness of compression. This stage one can consider aquise the regeneration of 200 stems/hectares.
RoutingRouting contrary to the break is targeted on an indicated stem with a future and is not prone to marketing. The intervention consists on stems (stage pole plantation - high pole plantation) of which the height of ball without branch lies between 7 and 8 meters, to cut down all the surrounding subjects in order to release the houppiers for the final growth. The quantity will be from 80 to 100 /hectare stems and will form the young grove.
Conditions of growth of the forest stations
The characterization of the mediums by the Typologie of the forest stations is a precondition to a reasoned forest management, making it possible to avoid the installation of gasolines not adapted to the ground.
L' anticipation of the risk of Dryness or Inondation of long life is also a factor of success, just as good a genetic Diversité and the protection of the Humus, and could become it more still in a total context of climatic modifications.
La herbaceous competition, and the mutilation by the herbivores (stag, roe-deer, except in the event of strong populations) does not pose theoretically a problem for the settlements, except in the first stage in the event of plantations; herbaceous perspiration is maximum at the beginning of spring when water does not miss. It decreases then whereas with the foliation of raised cover. So that water misses less in summer, it can be useful to restore storage capacities of water and infiltration. (Inevitably It is not a question to decrease the drainage of the forest or to arrange basins there; The return of the Beaver and their tanks was shown from this effective point of view in North America).
History of sylvicultureSylviculture is old. It has probable roots in the Préhistoire and in China which developed it, while quickly deforesting most of the territory as of 8000 years before our days. Sylviculture was a sufficiently recognized science so that when the emperor Qin Shi Huang (name meaning “first universal emperor” 221 years before J.C ordered to burn all the undesirable works, it made 3 exceptions for the only books treating of Médecine, Agriculture and Sylviculture.
On all the continents, open secrecies and knowledge were transmitted on the manners of planting, of selecting, or of cutting the trees. Schools of sylvicultures diffused practices and knowledge to make, with more or less happiness and of effectiveness, which one can classify between two extremes, still today often opposite;
- in the natural forest even, or with its edge, with extensive practices being based on the natural Sylvigenèse and regeneration, with a slow selection, and some plantations (ex: Lemon tree S or Cacao-tree planted in forest, plantation of two Sagou S by sagous crossed.)
- in artificial and intensive systems, pressed on plantations in monoculture, seedbeds and an important selection (genes, seeds, seedlings, scaffold-poles, trees in growth, seed-bearers)…
in FranceIn 2006, 75% of the volume of wood marketed in the national forests was sold “on foot” by Adjudication generally, with 6.658.000 m3 of wood collected annually (average results 1995/2004 expressed in volume “wood forts”); In 2007, the French forest (public and private) covers again more than 25% of the national territory, with the profit of a wider sylviculture (Résineux and Peupleraie S in particular). Its distribution and the composition of its species are not related only to the only edaphic conditions and ic Climat. Before the XXème century, the French forest had strongly regressed: the Middle Ages until the beginning of the XXe century, one attended one period of intensive Défrichage aiming at gaining grounds of culture, to collect more Firewood, of boulange and of work. Colbert and the forest Code of 1827 finally blocked the regression of forest cover. In same time, a forest revival was supported by the fossil alternatives which Charbon then the Pétrole and the Natural gas are the even the nuclear power, but also thanks to the massive exploitation (Surexploitation sometimes) of the Tropical forests. These alternatives in addition strongly contributed to the economic development of the rich countries, which encouraged with a centralized urbanization (and thus a releasing Rural migration of the grounds to the plantations or enfrichement and with the spontaneous forestation). Premiums of state and tax reductions also encouraged the tree growers to extend their timbered surfaces, whereas the improvement of the agricultural outputs and the concentration of agriculture on the richest grounds released the poorest or sloping grounds. This increase in forest surface. But whereas the plantations of weak interest in term of biodiversity gained ground, the Bocage, the traditional Agrosylviculture and isolated trees and alignments moved back or disappeared quickly, with their Biodiversité… the Remembrement S and premiums with the pulling up of the hedges and fruit-lofts, etc had very important impacts in Europe, and in particular in France in the years 1960 to 1980.
To leave this time, one retimbered certain territories to give them in value (the Sologne, the Limousin), to fight the erosion (the Cevennes), to fix the Dune S (Landes).
- Glossary of sylviculture
- Dendrologie, Surface terrière
- National office of the forests
- forest Essence
- forest Aménagement
- Forêt models
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