88 (3) - 2000 Catalogue en ligne

88 (3) - 2000 (Journal of ecology)

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Titre :	88 (3) - 2000
Type de document :	Imprimé
Année de publication :	2000
Langues :	Français (fre)
Permalink :	https://biblio.cbnpmp.fr/index.php?lvl=bulletin_display&id=28372

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Reduced fecundity and offspring performance in small populations of declining grassland Primula veris and Gentiana lutea / Marc Kéry (2000)

est un tiré à part de 88 (3) - 2000 (Journal of ecology)

Titre :	Reduced fecundity and offspring performance in small populations of declining grassland Primula veris and Gentiana lutea
Type de document :	Tiré à part de revue
Auteurs :	Marc Kéry ; Diethart Matthies ; Hans-Heinrich Spillmann
Année de publication :	2000
Importance :	17-30
Langues :	Français (fre)
Catégories :	[CBNPMP-Thématique] Démographie [CBNPMP-Thématique] Germination : généralités [CBNPMP-Thématique] Stratégie de production de semences (fécondité)
Mots-clés :	Gentiana lutea L. Primula veris L.
Résumé :	1 We studied reproduction and offspring performance in relation to population size in the declining self-incompatible perennials Primula veris and Gentiana lutea. In both species, reproduction was strongly reduced in small populations, where plants produced fewer seeds per fruit and per plant. Total seed mass per plant was higher in large populations, but individual seeds were smaller, indicating a trade-off between seed number and size. Reproduction was depressed most strongly in populations consisting of less than c. 200 (P. veris) and c. 500 plants (G. lutea), respectively. 2 The inclusion of plant size (an integrated measure of habitat quality) in the statistical models did not change the relationships between fecundity and population size. Pollen limitation or inbreeding depression in small populations are therefore more likely explanations for these patterns than is habitat quality. 3 Germination rate and survival of seedlings in a common environment was not related to population size in either species, although P. veris developed into larger rosettes when seeds were derived from large populations. This suggests that inbreeding depression occurs in small populations of P. veris. 4 In a factorial fertilizer-by-competition experiment with P. veris, offspring from larger populations grew significantly larger and responded more strongly to fertilizer. For this declining species genetic deterioration as a result of habitat fragmentation may therefore aggravate the effects of environmental changes such as habitat eutrophication. 5 Our results suggest that small populations may face an increased short-term risk of extinction because of reduced reproduction, and an increased long-term risk because they are less able to respond to environmental changes.
Lien pérenne :	DOI : 10.1046/j.1365-2745.2000.00422.x
Permalink :	https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=130653

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Code-barres	Cote	Support	Localisation	Section	Disponibilité
10761	K	Tiré à part	Centre de documentation	Tirés à part	Consultable

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Positive and negative interactions at different life stages of a colonizing species (Quercus humilis) / Olivier Rousset (2000)

est un tiré à part de 88 (3) - 2000 (Journal of ecology)

Titre :	Positive and negative interactions at different life stages of a colonizing species (Quercus humilis)
Type de document :	Tiré à part de revue
Auteurs :	Olivier Rousset (1965-) ; Jacques Lepart (1947-)
Année de publication :	2000
Importance :	401-412
Langues :	Français (fre)
Catégories :	[CBNPMP-Thématique] Climax, succession plantes, dynamique végétation [CBNPMP-Thématique] Interactions interspécifiques
Mots-clés :	Quercus humilis Miller Buxus sempervirens L. Juniperus communis L.
Note de contenu :	1 The downy oak Quercus humilis has recently recolonized the Causse du Larzac plateau in southern France. We studied the influence of the shrubs Buxus sempervirens and Juniperus communis on Q. humilis establishment, and of Buxus on the growth of established Q. humilis individuals. 2 Percentage germination of experimentally planted Q. humilis was higher under shrubs than in nearby open areas and higher on the north than the south side of the canopy. Germination where part of the canopy has been removed was similar to that away from the shrubs, suggesting that the facilitation mechanism is related to changes in microclimate rather than to a soil effect. 3 When exposed to sheep for 1 month, 100% of 326 unprotected oak seedlings were grazed, causing 44% mortality. The presence of Buxus and Juniperus improved seedling survival by protecting them against sheep grazing and summer drought. Predation by rodents was however greater under shrub cover. 4 The highest leaf dry mass of oak seedlings was recorded under Juniperus where light conditions seem more favourable for growth than under Buxus (direct effect) or in grassland (indirect effect). The growth of naturally established individuals of Q. humilis (in terms of total leaf mass per annual branch and width of rings) was lower under Buxus than in grassland but the values became similar once the canopy was overtopped. 5 The balance between positive and negative interactions varied in relation to the life stage of Q. humilis and the two shrub species. Regeneration of Q. humilis in open grassland was prevented by grazing. The protection offered by shrubs continues to offset the negative interference on growth, particularly under Buxus, so that plants could survive to overtop the shrub canopy and reach maturity. The succession pathway therefore depends closely on the distribution of shrubs in the grassland.
Lien pérenne :	DOI : 10.1046/j.1365-2745.2000.00457.x
Permalink :	https://biblio.cbnpmp.fr/index.php?lvl=notice_display&id=131883

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