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Ecology of ectomycorrhizal-basidiomycete communities on a local vegetation gradient / Patrick Nantel (1992) 

Public Citation est un tiré à part de 73 (1) - 1992 (Ecology)   Titre : Ecology of ectomycorrhizal-basidiomycete communities on a local vegetation gradient Type de document : Tiré à part de revue Auteurs : Patrick Nantel (1963-) ; P. Neumann Année de publication : 1992 Importance : 99-117 Langues : Anglais (eng) Catégories : [CBNPMP-Thématique] Mycologie [CBNPMP-Thématique] Variations, races, biotypes, spécialisation parasitaire, génétique Résumé : To understand the factors that structure ectomycorrhizal—basidiomycete communities at a local scale, we measured the strength of the relations among the fungal communities, the tree communities, and the environment of a series of forest ecosystems in southern Quebec. We collected fruit bodies belonging to ectomycorrhizal—basidiomycete families and genera, sampled the woody vegetation, and described soils and landforms at 11 permanent sampling stations. We first calculated similarity matrices among stations, one for each descriptor (fungal species abundance, woody species abundance, and abiotic variables). We then explored the dependence among these matrices using Mantel and partial Mantel tests, path analysis, and comparisons of ordinations and classifications. Similarity among ectomycorrhizal fungus communities was strongly and significantly correlated with tree community similarity, even when controlling for the effect of environmental similarity. When the tests were made with a similarity matrix based on those tree species that are known to be hosts of ectomycorrhizal fungi, abiotic similarity explained a significant portion of the residual variation in the similarity among fungus communities. To explore this complex relationship further, we analyzed species associations. The preference of fungus associations for different sets of abiotic conditions showed that some factors affecting fungal species distribution were different from those affecting the distribution of their tree hosts. Direct and indirect gradient analyses showed that humus characteristics seemed to be important niche dimensions of ectomycorrhizal fungi. The continuum concept was useful to interpret the complex relations among symbiotic species. Trees were the main component of the realized niche of ectomycorrhizal Basidiomycetes, but the fungal symbionts of a particular tree species followed that tree species for only a part of the abiotic gradients over which the host tree was found. This type of distribution predicts that beta diversity of fungi would be generally higher than beta diversity of ectomycorrhizae—forming trees. It also means that the ratio of fungus species richness to woody species richness would be high for most community gradients. Our results and those of previous mycosynecological studies agree with these predictions. The results have implications for the conservation of biodiversity: site selection for conservation based on vegetation classification or mapping, or on distribution of tree species, may miss important fungal species. Lien pérenne : DOI : 10.2307/1938724 Permalink : https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=130217 Nantel, Patrick (1963-), Neumann, P. 1992 Ecology of ectomycorrhizal-basidiomycete communities on a local vegetation gradient. Ecology, 73(1) : 99-117.

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Population viability analysis of American ginseng and wild leek harvested in stochastic environments / Patrick Nantel (1996)

Public Citation est un tiré à part de 10 (2) - 1996 (Conservation Biology) Titre : Population viability analysis of American ginseng and wild leek harvested in stochastic environments Type de document : Tiré à part de revue Auteurs : Patrick Nantel (1963-) ; Daniel Gagnon ; Andree Nault (1961-) Année de publication : 1996 Importance : 2:608-621 Langues : Anglais (eng) Catégories : [CBNPMP-Thématique] Démographie stochastique (aléatoire) [CBNPMP-Thématique] Densité-seuil population [CBNPMP-Thématique] Extinction, régression Mots-clés : Panax quinquefolium  Allium tricoccum Résumé : Many populations of threatened American ginseng (Panax quinquefolium) and vulnerable wild leek (Allium tricoccum) have declined and gone extinct because of overharvesting in Canada. We assessed the impact of harvesting on populations of these species in stochastically varying environments and estimated their extinction thresholds and minimum viable populations. With both species we used four transition matrices taken from the literature in stochastic population projections under various harvesting regimes. For American gingseng the mean population growth rate (λ) declined with increasing harvesting rate (h) according to the number of years between harvests (tr), as −0.54 htr−0.90. When plants with more than two leaves are harvested every 5 years, a harvest rate of approximately 30% was sufficient to bring the λ below the equilibrium value of 1.0. Extinction thresholds, the minimum number of plants needed to rebuild a population, varied from 30 to 90 plants, and the minimum viable population size was estimated at 170 plants. Only a dozen populations known in Canada exceed 170 plants, so most populations could not support any harvesting without serious threats to their long-term persistence. For wild leek, two harvesting strategies were identified from confiscated, illegal harvests from Gatineau Park (Québec): (1) “choosy” harvesters collect fewer but larger bulbs, and (2) “busy” harvesters collect numerous but smaller bulbs. These data allowed simulations of more-realistic harvesting strategies. The rate of the decline λ along the harvest gradient was faster for wild leek than for ginseng and varied with harvesting strategies. At harvesting rates between 1 and 8% the probability that λ falls below the equilibrium value was less than 5%. The extinction threshold of wild leek was estimated at 140–480 plants and the minimum viable population at 300—1030 plants, according to the threshold chosen. Remnant wild leek populations in Québec rarely contain more than a few hundred plants, indicating the serious threat commercial harvesting represents for this species. For both species we found that the whims of a stochastically varying environment significantly reduce sustainable harvest levels. Lien pérenne : DOI : 10.1046/j.1523-1739.1996.10020608.x Permalink : https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=130216 Nantel, Patrick (1963-), Gagnon, Daniel, Nault, Andree (1961-) 1996 Population viability analysis of American ginseng and wild leek harvested in stochastic environments. Conservation Biology, 10(2) : 2:608-621.

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
8077	Nantel P.	Tiré à part	Centre de documentation	Tirés à part	Consultable