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6 résultat(s) recherche sur le mot-clé 'changement de végétation' 
trié(s) par (Pertinence décroissant(e), Titre croissant(e)) Affiner la recherche Générer le flux rss de la rechercheBiodiversity, vegetation gradients and key biogeochemical processes in the heathland landscape / Maaike De Graaf in Biological conservation, vol. 142, n°10 (Année 2009)
Titre : Biodiversity, vegetation gradients and key biogeochemical processes in the heathland landscape Type de document : Livre Auteurs : Maaike De Graaf, Auteur ; Roland Bobbink, Auteur ; Nina Smits, Auteur ; Rudy Van Diggelen, Auteur ; Jan G. M. Roelofs, Auteur Année de publication : 2009 Article en page(s) : pp. 2191-2201 Langues : Anglais Catégories : [habitats/milieux] 31 - Landes et fruticées
[Thèmes] Pédologie (sol)
[Thèmes] Relation sol - végétationMots-clés : restauration conservation communauté végétale paysage relevé de végétation acidification eutrophisation analyse de données changement de végétation Résumé : "The northwest European heathland landscape with its characteristic communities of nutrient-poor and acidic soils has a high nature value, because of its locally high biodiversity and the distinct site conditions. In order to conserve and restore the heathlands, numerous rehabilitation projects have been performed, although with varying success. This is partly due to the fact that the key biogeochemical processes distinguishing the various vegetation types within the heathlands are not known in detail.
Therefore, we performed a statistical survey on the main communities and their soil characteristics. In addition, we analyzed the data for key factors determining biodiversity in the heathland landscape.
Data from previous studies and surveys was used to compile a dataset of 267 vegetation relevés (classified as EUNIS habitat types) with extensive soil measurements (22 parameters). A canonical discriminant analysis revealed that soil acidity explained most of the differences between the habitat types, while soil moisture content and soil fertility were less important. Acidity-related factors as Al3+, Al/Ca-ratio and pH were also strongly correlated to plant diversity in the majority of the habitat types, respectively, the species-rich Nardus grasslands, the Rhynchosporion communities and the species-rich Molinia meadows. In the dry heaths and over the total heathland landscape, plant diversity was negatively correlated with soil
-concentrations. Only in wet heath, nutrient availability, in this case P, was the primary factor in explaining plant diversity.
This study presents ranges for all major soil parameters for the studied well-developed heathland habitat types, thereby providing clear guidelines for conservation and restoration." (source : auteurs)Type de publication : périodique Référence biblio : De Graaf M., Bobbink R., Smits N., Van Diggelen R., Roelofs J.-M., 2009 - Biodiversity, vegetation gradients and key biogeochemical processes in the heathland landscape. Biological conservation, 142 (10) : 2191-2201. ID PMB : 70401 DOI : 10.1016/j.biocon.2009.04.020 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=70401
in Biological conservation > vol. 142, n°10 (Année 2009) . - pp. 2191-2201[article]Exemplaires
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Titre : Dynamic soil processes on heathland due to changes in vegetation to oak and Sitka spruce Type de document : Livre Auteurs : Knud Erik Nielsen, Auteur ; Ulla LLadekarl, Auteur ; Per Nørnberg, Auteur Année de publication : 1999 Article en page(s) : pp. 107-116 Langues : Anglais Catégories : [Thèmes] Pédologie (sol)
[Thèmes] Relation sol - végétationMots-clés : changement de végétation acidification du sol forêt de chênes épicéa de Sitka lysimètre Résumé : "Soil and soil water chemistry under three different vegetation-types on a former heath area were investigated in Jutland, Denmark. An unmanaged heathland left undisturbed since the start of this century is now invaded by the oaks. Together with a small Sitka plantation (age 60 years), soil development due to vegetation changes was investigated. The typical heathland podzol soil had changed within decades under the oak trees towards an acid brown soil. The soil under the Sitka spruce had changed towards a more strongly podzolized soil compared to the former heath soil. Present processes occurring within the soil were investigated by analysis of soil solution chemistry. The leaching of inorganic ions and soluble organic matter had increased manifold under Sitka spruce. Nitrification increased markedly with soil depth probably due to effects of higher pH. The increase of nitrate with soil depth was followed by a similar increase in dissolved aluminium. The equivalence of the dissolved organic carbon varies under oak and heath between 6 and 10 m eqv g−1 TOC and under Sitka the equivalence of the dissolved carbon was between 10 and 15 m eqv g−1. No nitrate and only traces of ammonium were found in soil water from the upper 30 cm of the soil under heath. Soil nitrogen was almost exclusively (more than 90%) connected to the carbon cycle. Under Sitka spruce generally less than 20% of soil water nitrogen was coupled to the carbon cycle, i.e. most of the nitrogen in the soil water leaving the rooting zone under Sitka spruce was nitrate. In the oak forest, nitrate only appeared as traces in the soil water in the winter period and in the summer period in relatively higher amounts. Generally, between 80% and 90% of the nitrogen was coupled to the carbon cycle in the winter and in the summer only 50%." (source : auteurs) Type de publication : périodique Référence biblio : Nielsen K., LLadekarl U., Nørnberg P., 1999 - Dynamic soil processes on heathland due to changes in vegetation to oak and Sitka spruce. Forest Ecology and Management, 114 (1) : 107-116. ID PMB : 70406 DOI : 10.1016/S0378-1127(98)00385-5 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=70406
in Forest Ecology and Management > vol. 114, n°1 (Année 1999) . - pp. 107-116[article]Exemplaires
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Titre : Effects on soils of an oak invasion of a Calluna heath, Denmark, I. Morphology and chemistry Type de document : Livre Auteurs : Knud Erik Nielsen, Auteur ; Kristian Dalsgaard, Auteur ; Per Nørnberg, Auteur Année de publication : 1987 Article en page(s) : pp. 79-95 Langues : Anglais Catégories : [habitats/milieux] 31 - Landes et fruticées
[Espèces (in biblio)] Calluna
[Thèmes] Relation sol - végétationMots-clés : changement de végétation Résumé : "Where oak has been invading Hjerl Hede for the last century, four profiles were described and sampled for analyses in a trench extending into a Calluna stand from a pioneer oak about 70 years old. Three additional profiles were studied, one opposite to the oak, a second in another stand of Calluna and a third in an oak forest. Comparisons were then made of the morphology and chemistry of the profiles to identify early changes associated with the invasion.
Principal differences attributed to the oak invasion were a marked reduction in the surface layer of organic matter and its conversion from mor to moder, a slight increase in pH of the uppermost horizons under the oak, slight changes in colours from black to brown in deeper horizons and the blurring of their boundaries. Amounts of iron extractable by pyrophosphate and tetraborate from the B horizons in the trench were smaller under the oak than under the Calluna." (source : auteurs)Type de publication : périodique Référence biblio : Nielsen K., Dalsgaard K., Nørnberg P., 1987 - Effects on soils of an oak invasion of a Calluna heath, Denmark, I. Morphology and chemistry. Geoderma, 41 : 79-95. ID PMB : 70409 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=70409
in Geoderma > vol. 41, n°1-2 (Année 1987) . - pp. 79-95[article]Exemplaires
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Titre : Effects on soils of an oak invasion of a Calluna heath, Denmark, II. Changes in organic matter and cellulose decomposition Type de document : Livre Auteurs : Knud Erik Nielsen, Auteur ; Kristian Dalsgaard, Auteur ; Per Nørnberg, Auteur Année de publication : 1987 Article en page(s) : pp. 97-106 Langues : Anglais Catégories : [ZG] Danemark
[habitats/milieux] 31 - Landes et fruticées
[Thèmes] Relation sol - végétationMots-clés : changement de végétation Résumé : "The investigation had two parts. In the first, organic matter was extracted from samples of the O through Bh horizons of seven profiles and then split into humic and fulvic acids. Part of the fulvic acid was treated with polyvinyl-pyrrolidone. In the other part, strips of cotton cloth were placed into the soils for two months, removed and tested for tensile strength to measure their decomposition.
The amounts of humic and fulvic acids were both greater under Calluna than under the oaks. Profile distribution was also sharply contrasted under Calluna, being very low in the O horizons and high in the B horizons. Distribution was virtually uniform under the oak. The adsorption of fulvic acids by polyvinyl-pyrrolidone and the decomposition of the cotton strips indicated greater biological activity under the oaks than in the heath. These several differences are attributed to the replacement of one type of vegetation by another." (source : auteurs)Type de publication : périodique Référence biblio : Nielsen K., Dalsgaard K., Nørnberg P., 1987 - Effects on soils of an oak invasion of a Calluna heath, Denmark, II. Changes in organic matter and cellulose decomposition. Geoderma, 41 : 97-106. ID PMB : 70408 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=70408
in Geoderma > vol. 41, n°1-2 (Année 1987) . - pp. 97-106[article]Exemplaires
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Titre : Leaf-nutrient accumulation and turnover at three stages of succession from heathland to forest Type de document : Livre Auteurs : Michael Rode, Auteur Année de publication : 1993 Article en page(s) : pp. 263-268 Langues : Anglais Catégories : [Espèces (in biblio)] Betula
[Espèces (in biblio)] Calluna
[Espèces (in biblio)] Fagus
[Espèces (in biblio)] Pinus
[Espèces (in biblio)] Quercus
[Thèmes] Pédologie (sol)
[Thèmes] Relation sol - végétationMots-clés : apport nutritif nutriment changement de végétation Résumé : "Accumulation of nutrients in leaves of the dominating species of three ecosystems, characterizing the secondary succession from Genisto-Callunetum heathland through Leucobryo-Pinetum birch-pine woodland to mature Querco-Fagetum oak-beech forest, as well as nutrient turnover within these ecosystems was studied. The objective of the study was to establish potential variations in quantity and quality of nutrient supply to the plants with respect to succession dynamics. The results show very low leaf nutrient concentrations of all species investigated, coinciding with low nutrient availability in the soil. However, the nutrient content of leaves and leaf litter of Quercus petraea and Fagus sylvatica, which dominate the late succession stages, and in Betulapéndula are higher than in the photosynthetic organs (leaves and young shoots) of Calluna vulgaris and Pinus sylvestris.
The combination of the higher nutrient content of the leaves and an increasing leaf-litter production during succession results in an increased nutrient turnover via leaf-litter fall. However, due to the high leaf biomass, the storage of nutrients in the leaf biomass is highest within the birch-pine woodland. From this, it may be assumed that the low demand and the low loss of nutrients via leaf-litter fall are favourable for Pinus at the early stages of forest succession on poor sandy soils. In contrast, Quercus and Fagus are provided with better growth conditions at the later stages of succession resulting from the accumulation of plant-available nutrients in the ecosystem by Pinus sylvestris, combined with a higher nutrient turnover as compared with the heathland." (source : auteur)Type de publication : périodique Référence biblio : Rode M., 1993 - Leaf-nutrient accumulation and turnover at three stages of succession from heathland to forest. Journal of Vegetation Science, 4 (2) : 263-268. ID PMB : 70410 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=70410
in Journal of Vegetation Science > vol. 4, n°2 (Année 1993) . - pp. 263-268[article]Exemplaires
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