Global ETD Search

11	From forest to farmland: Effects of land use on understorey birds of Afrotropical rainforests / Von Wald zu Ackerland: Effekte der Landnutzung auf Unterholzvögeln von Afrotropische Regenwaelder Bobo Kadiri, Serge 31 October 2007 (has links) No description available. 500 Naturwissenschaften allgemein Mathematics and Computer Science Afrotropische Regenwaelder Kamerun Nahrungsverfügbarkeit Nestprädation Unterholzvögeln. Afrotropical rainforests Cameroon Community and diversity structure Food availability Nest predation Understorey birds. 43.31 Artenschutz {Biologie}
12	The effect of the spatial scale of tree harvesting on woody seedling establishment and tree dynamic at Ongoye Forest Reserve. Louw, Sharon Lilla. January 2010 Subsistence harvesting pressure in most African countries focuses on the small and mostly unreproductive trees found in the understorey stratum and can have potentially insidious ecological effects. Harvest intensities at Ongoye Forest Reserve (OFR) vary significantly across the forest (range = 87 - 567 stumps ha-1), with harvesting focussed exclusively on poles from tree species that grow only in the understorey. Growing evidence indicates that seedling establishment from the pool of species available beneath a closed canopy is greatly influenced by the differential ability of species to take advantage of the short burst of resources in newly-created understorey gaps. Seedling dynamics in these gaps may determine forest tree diversity and dynamics and consequently harvest gaps have the potential to significantly affect natural forest dynamics. This study examined seedling establishment beneath intact understorey and within artificially created understorey gaps of different sizes (single stem gaps, two stem gaps, four stem gaps, eight stem gaps and control ‘gap’, where no stems were removed) that simulated different spatial scales of harvesting intensity of understorey trees. This experiment examined the proposition that successful seedling establishment and natural succession is strongly dependent on the scale of harvesting. Seedling abundance, species richness, irradiance (photosynthetically active radiation and the red to far-red ratio), soil nutrient composition and herbaceous layer cover was measured in each gap size in 2005 before harvesting, and again in 2007. The mean seedling abundance was not significantly different among gap treatments, although there was a trend towards more seedlings in 2005 than 2007. Seedling abundance in all gaps was greater than at control sites beneath the intact understorey. There was a continuous increase in seedling richness in 2007. An average species richness of 4.3 was recorded in the control sites, beneath a shaded understorey. Here, seedling richness increased by 18.24% with the removal of a single understorey tree (Gap 1). Species richness increased with increasing experimental gap size increased so that the greatest mean species richness (6.2 species) was recorded where eight neighbouring trees were removed (Gap 8). Light transmission reaching the seedling stratum was greater in larger gaps and there was a trend towards more seedlings and greater species richness in the higher light environments of such gaps. Soil nutrient levels did not influence seedling abundance and species richness in gaps. The herbaceous layer suppressed seedling establishment. In the largest gaps (115.4m2) created by harvesting, seedling composition was more deterministic than in small gaps where seedling establishment and density was random, accordingly there were more species in larger gaps from a more defined species assemblage. Current harvesting levels of pole-sized understorey trees, where only small gaps are created in the understorey, are unlikely to alter forest dynamics and species composition at OFR. This study demonstrates that harvesting eight adjacent trees crosses the harvest intensity threshold between sustainable natural tree dynamics and a potential successional shift to an alternative state. Clearly, for natural dynamics to be maintained harvesting intensities will have to be regulated. / http://hdl.handle.net/10413/631 / Thesis (M.Env.Dev.)-University of KwaZulu-Natal, Pietermaritzburg, 2010. Trees--Seedlings. Theses--Environmental science.
13	Fotosyntéza, produkce a růst rostlin při časově proměnné ozářenosti / Photosynthesis, production and growth of plants under temporal light hererogeneity KUBÁSEK, Jiří January 2014 (has links) In this Ph.D. thesis I am dealing with the effect of dynamic irradiance on (i) photosynthesis, growth and bundle sheath leakiness (for CO2) of C4 plants and (ii) bryophyte photosynthesis. Part of this thesis is literature review on broader aspects of the dynamic light effects on photosynthetic and growth processes in plants.
14	Aktivita půdních enzymů v horských smrčinách napadených lýkožroutem smrkovým / Activity of soil enzymes in the Norway spruce forests attacked by bark beetle ŠLAJSOVÁ, Petra January 2011 (has links) Activity of enzymes was investigated in the soils of Norway spruce forests in the Bohemian Forest. The aim of the study was the determintation of the impact of temperature and plants dominant in understorey on the activity of extracellular enzymes in the soils in the watershed of Plešné and Čertovo Lake. The measurement of enzymes activities was conducted using the fluorometric method with model substrates.
15	Contribution relative de la végétation du sous-bois dans la consommation en eau des placettes forestières soumises aux changements de climat et de pratiques / Contribution of understorey vegetation to forest water consumption in stand under climate change and new practices Gobin, Rémy 08 December 2014 (has links) Avec l'augmentation des sécheresses dans les forêts tempérées, la gestion sylvicole envisage de réduire la densité des peuplements adultes pour limiter le déficit hydrique. Cependant, la réduction de la canopée arborée augmente le rayonnement dans le sous-bois et permet le développement de la strate herbacée monopoliste. Nos objectifs étaient de caractériser l'évapotranspiration (ETu) de 4 herbacées monopolistes (Molinia caerulea, Calluna vulgaris, Pteridium aquilinum and Rubus sp.) et de quantifier leur impact sur la teneur en eau du sol (SWC) dans des peuplements de Quercus petraea. L’ETu des quatre herbacées cultivées en pot a été quantifiée en conditions semi-contrôlées caractérisées par deux niveaux d’éclairement relatif et 3 niveaux de SWC. In situ, le SWC, le microclimat et l’ETu de P. aquilinum et M. caerulea ont été mesurés sur 20 dispositifs dans les peuplements forestiers de Q. petraea présentant un gradient croissant de LAI. Chaque dispositif était subdivisé en 2 placettes, l’une était désherbée et l'autre enherbée. M. caerulea et C. vulgaris ont une faible régulation de leur ETu alors que P. aquilinum et Rubus sp. ont une stratégie conservatrice face au stress hydrique. SWC diminue plus rapidement quand le LAI de la strate herbacée augmente, ce qui est directement lié à l’ouverture du couvert arboré avec une valeur seuil de LAI de la strate arborée à 2-3, sous laquelle la contribution de la strate herbacée à l’évapotranspiration du peuplement pourrait compenser la diminution de celle de la strate arborée.Ces résultats montrent la nécessité de considérer la végétation du sous-bois dans la gestion sylvicole notamment lorsque la ressource hydrique est limitante. Ainsi, la réduction de la densité de la strate arborée doit être un compromis entre la réduction de la surface foliaire des arbres pour réduire l’ET, et le maintien d’une densité suffisante de la strate arborée pour limiter la croissance et l'ETu de la végétation du sous-bois. / In the context of ongoing increase of drought in temperate forests, forest managers consider the reduction of stand density to limit soil water depletion. The reduction of tree canopy density increases light below canopy and allows the development of monopolistic understorey vegetation. Our objectives were to characterize the evapotranspiration (ETu) of common understorey plants (Molinia caerulea, Calluna vulgaris, Pteridium aquilinum and Rubus sp.) and to quantify their impacts on soil water content (SWC) in mature oak stands (Quercus petraea).A first experiment was set up in a greenhouse where the 4 understorey species were potted and subjected to 2 levels of light transmittance and 3 levels of SWC. Microclimate and ETu were monitored. A second experiment was carried out on 20 plots (10 with M. caerulea and 10 with P. aquilinum) in oak stands with contrasted LAI. On each plot, two circular areas were set up, one weeded and the other untouched. SWC, microclimate and ETu were monitored.M. caerulea and C. vulgaris are more water spenders, whereas P. aquilinum and Rubus sp. are more water savers under water stress. Soil water depletion was faster with increasing understorey vegetation LAI, which was directly linked to tree canopy opening with a threshold of tree LAI of 2-3 below which the understorey contribution could offset the reduction of tree ET. The experimentations showed that the relative contribution of understory vegetation in the ecosystem water balance is significant, and depends on SWC and on the understorey species identity. These results show the necessity to consider understorey vegetation in forest management when water availability is an issue. Lower tree canopy density could increase the understorey ETu and soil water stress for trees. From a management perspective, thinning should be designed as a compromise between the reduction of tree leaf area to reduce ET, and maintaining sufficient tree canopy to restrict the growth and ETu of understorey vegetation. Evapotranspiration Végétation du sous-bois Surface foliaire Microclimat Changement climatique Molinia caerulea Calluna vulgaris Pteridium aquilinum Rubus sp. Quercus petraea Evapotranspiration Understorey vegetation Leaf area index Microclimate Climate change Molinia caerulea Calluna vulgaris Pteridium aquilinum Rubus sp. Quercus petraea 577.3
16	Understorey management for the enhancement of populations of a leafroller (Lepidoptera: Tortricidae) parasitoid (Dolichogenidea tasmanica (Cameron)) in Canterbury, New Zealand apple orchards Irvin, N. A. January 1999 (has links) This study investigated understorey management in Canterbury, New Zealand, apple orchards for the enhancement of populations of Dolichogenidea tasmanica (Cameron) (Braconidae) for leafroller (Lepidoptera: Tortricidae) biological control. The first objective was to determine the influence of understorey plants on the abundance of D. tasmanica and leafroller parasitism, and to investigate the mechanisms behind this influence. The second was to determine the most suitable understorey plants in terms of their ability to enhance parasitoid abundance, leafroller parasitism, parasitoid longevity, parasitoid fecundity and its ability to not benefit leafroller. Results from three consecutive field trials showed that buckwheat (Fagopyrum esculentum Moench), coriander (Coriandrum sativum L.), alyssum (Lobularia maritima (L.) Desv), and, to a lesser extent, broad bean (Vicia faba L.), enhanced parasitoid abundance and leafroller parasitism. The mechanisms behind the effects of understorey plants had previously been unexplored. However, results here showed that it was the flowers or the buckwheat that 'attracted' the parasitoid to the plant and not the shelter, aphids or microclimate that the plant may also provide. Providing flowering plants in the orchard understorey also increased immigration of parasitoids and enhanced parasitoids and enhanced parasitoid longevity and fecundity in the laboratory. In contrast, the understorey plants had no influence on the female:male ratio of D. tasmanica. Although coriander enhanced leafroller parasitism three-fold in field experiments compared with controls, it failed to enhance the longevity of both sexes of D. tasmanica in the laboratory compared with water-only. Broad bean significantly enhanced parasitoid abundance three-fold and significantly increased parasitism from 0% to 75% compared with the controls on one leafroller release date. However, laboratory trials showed that of male D. tasmancia but it did not enhance female longevity. Also, female D. tasmanica foraging on broad bean produced a total of only three parasitoid cocoons, but this result was based on an overall 6.5% survival of larvae to pupae or to parasitoid cocoon. Furthermore, results suggested that extrafloral nectar secretion decreased as the plants matured. Phacelia (Phacelia tanacetifolia Benth.) did not significantly enhance parasitism rate in the field compared with controls, and numbers of D. tasmanica captured by suction sampling were significantly lower in phacelia treatments compared with alyssum, buckwheat and control plots. Also, laboratory experiments showed that survival of D. tasmanica on phacelia flowers was equivalent to that on water-only and significantly lower than on buckwheat. These results suggest that phacelia does not provide nectar to D. tasmanica, only pollen, and therefore is not a suitable understorey plant for D. tasmanica enhancement in orchards. Buckwheat and alyssum showed the most potential as understorey plants for the enhancement of natural enemies. Buckwheat not only increased numbers of D. tasmanica seven-fold, but also increased numbers of beneficial lacewings (Micromus tasmaniae (Walker)) and hover flies (Syrphidae) captured on yellow sticky traps compared with the controls. It significantly increased leafroller parasitism by D. tasmanica from 0% to 86% compared with the controls (on one date only), and in the laboratory enhanced D. tasmanica longevity and increased fecundity compared with water-only. Similarly, alyssum significantly increased parasitism rate compared with controls, and two-fold more D. tasmanica were suction sampled in these plots compared with controls. It also enhanced longevity of both sexes of D. tasmanica compared with water, and showed the most favourable characteristics in terms of being of no benefit to leafrollers. This is because it was not preferred over apple by leafroller larvae and when they were forced to feed on it, it caused high mortality (94.3%) and low pupal weight (15 mg). Furthermore, alyssum did not enhance the number of fertile eggs produced by adult leafrollers compared with water only. However, further research is required to address the overall effect of buckwheat and alyssum on crop production and orchard management, including effects on fruit yield and quality, frost risk, disease incidence, soil quality, weeds and other pests. Also, research into the ability of these plants to survive in the orchard with little maintenance, and into the optimal sowing rates, would be useful. Sampling natural populations of leafroller within each treatment showed that damage from leafrollers and the number of leafroller larvae were respectively 20.3% and 29.3% lower in the flowering treatments compared with the controls. Furthermore, field trials showed up to a six-fold increase in leafroller pupae in controls compared with buckwheat and alyssum. This suggests that increasing leafroller parasitism rate from understorey management in orchards will translate into lower pest populations, although neither larval numbers/damage nor pupal numbers differed significantly between treatments. Trapping D. tasmanica at a gradient of distances showed that this parasitoid travels into rows adjacent to buckwheat plots, indicating that growers may be able to sow flowering plants in every second or third row of the orchard, and still enhance leafroller biocontrol while minimising the adverse effects of a cover crop. Sowing buckwheat and alyssum in orchard understoreys may enhance biological control of apple pests in organic apple production and reduce the number of insect growth regulators applied in IFP programmes. However, the challenge still remains to investigate whether conservation biological control can reduce leafroller populations below economic thresholds. leafroller Tortricidae parasitoid Dolichogenidea tasmanica understorey management apple orchard enhancement Phacelia tanacetifolia Fagopyrum esculentum Coriandrum sativum Lobularia maritima Vicia faba L. conservation biological control
17	Understorey management for the enhancement of populations of a leafroller (Lepidoptera: Tortricidae) parasitoid (Dolichogenidea tasmanica (Cameron)) in Canterbury, New Zealand apple orchards Irvin, N. A. January 1999 (has links) This study investigated understorey management in Canterbury, New Zealand, apple orchards for the enhancement of populations of Dolichogenidea tasmanica (Cameron) (Braconidae) for leafroller (Lepidoptera: Tortricidae) biological control. The first objective was to determine the influence of understorey plants on the abundance of D. tasmanica and leafroller parasitism, and to investigate the mechanisms behind this influence. The second was to determine the most suitable understorey plants in terms of their ability to enhance parasitoid abundance, leafroller parasitism, parasitoid longevity, parasitoid fecundity and its ability to not benefit leafroller. Results from three consecutive field trials showed that buckwheat (Fagopyrum esculentum Moench), coriander (Coriandrum sativum L.), alyssum (Lobularia maritima (L.) Desv), and, to a lesser extent, broad bean (Vicia faba L.), enhanced parasitoid abundance and leafroller parasitism. The mechanisms behind the effects of understorey plants had previously been unexplored. However, results here showed that it was the flowers or the buckwheat that 'attracted' the parasitoid to the plant and not the shelter, aphids or microclimate that the plant may also provide. Providing flowering plants in the orchard understorey also increased immigration of parasitoids and enhanced parasitoids and enhanced parasitoid longevity and fecundity in the laboratory. In contrast, the understorey plants had no influence on the female:male ratio of D. tasmanica. Although coriander enhanced leafroller parasitism three-fold in field experiments compared with controls, it failed to enhance the longevity of both sexes of D. tasmanica in the laboratory compared with water-only. Broad bean significantly enhanced parasitoid abundance three-fold and significantly increased parasitism from 0% to 75% compared with the controls on one leafroller release date. However, laboratory trials showed that of male D. tasmancia but it did not enhance female longevity. Also, female D. tasmanica foraging on broad bean produced a total of only three parasitoid cocoons, but this result was based on an overall 6.5% survival of larvae to pupae or to parasitoid cocoon. Furthermore, results suggested that extrafloral nectar secretion decreased as the plants matured. Phacelia (Phacelia tanacetifolia Benth.) did not significantly enhance parasitism rate in the field compared with controls, and numbers of D. tasmanica captured by suction sampling were significantly lower in phacelia treatments compared with alyssum, buckwheat and control plots. Also, laboratory experiments showed that survival of D. tasmanica on phacelia flowers was equivalent to that on water-only and significantly lower than on buckwheat. These results suggest that phacelia does not provide nectar to D. tasmanica, only pollen, and therefore is not a suitable understorey plant for D. tasmanica enhancement in orchards. Buckwheat and alyssum showed the most potential as understorey plants for the enhancement of natural enemies. Buckwheat not only increased numbers of D. tasmanica seven-fold, but also increased numbers of beneficial lacewings (Micromus tasmaniae (Walker)) and hover flies (Syrphidae) captured on yellow sticky traps compared with the controls. It significantly increased leafroller parasitism by D. tasmanica from 0% to 86% compared with the controls (on one date only), and in the laboratory enhanced D. tasmanica longevity and increased fecundity compared with water-only. Similarly, alyssum significantly increased parasitism rate compared with controls, and two-fold more D. tasmanica were suction sampled in these plots compared with controls. It also enhanced longevity of both sexes of D. tasmanica compared with water, and showed the most favourable characteristics in terms of being of no benefit to leafrollers. This is because it was not preferred over apple by leafroller larvae and when they were forced to feed on it, it caused high mortality (94.3%) and low pupal weight (15 mg). Furthermore, alyssum did not enhance the number of fertile eggs produced by adult leafrollers compared with water only. However, further research is required to address the overall effect of buckwheat and alyssum on crop production and orchard management, including effects on fruit yield and quality, frost risk, disease incidence, soil quality, weeds and other pests. Also, research into the ability of these plants to survive in the orchard with little maintenance, and into the optimal sowing rates, would be useful. Sampling natural populations of leafroller within each treatment showed that damage from leafrollers and the number of leafroller larvae were respectively 20.3% and 29.3% lower in the flowering treatments compared with the controls. Furthermore, field trials showed up to a six-fold increase in leafroller pupae in controls compared with buckwheat and alyssum. This suggests that increasing leafroller parasitism rate from understorey management in orchards will translate into lower pest populations, although neither larval numbers/damage nor pupal numbers differed significantly between treatments. Trapping D. tasmanica at a gradient of distances showed that this parasitoid travels into rows adjacent to buckwheat plots, indicating that growers may be able to sow flowering plants in every second or third row of the orchard, and still enhance leafroller biocontrol while minimising the adverse effects of a cover crop. Sowing buckwheat and alyssum in orchard understoreys may enhance biological control of apple pests in organic apple production and reduce the number of insect growth regulators applied in IFP programmes. However, the challenge still remains to investigate whether conservation biological control can reduce leafroller populations below economic thresholds. leafroller Tortricidae parasitoid Dolichogenidea tasmanica understorey management apple orchard enhancement Phacelia tanacetifolia Fagopyrum esculentum Coriandrum sativum Lobularia maritima Vicia faba L. conservation biological control
18	Funktionelle Vielfalt von Hymenopteren entlang eines Gradienten agroforstlicher Nutzung in Indonesien / Functional diversity of Hymenoptera along a gradient of agroforestry management in Indonesia Höhn, Patrick 15 November 2007 (has links) No description available. 500 Naturwissenschaften YA 000 Agricultural Sciences Agroforestry systems Hymenoptera land-use intensity pest control predator pollination native bees wasps pumpkin functional diversity species richness species loss Indonesia seasonality tropics local diversity regional diversity complementarity resource use ecology conservation biodiversity habitat loss deforestation trap nests multidimensional scaling additive partitioning shade trees cocoa Theobroma cacao canopy understorey stratification ecosystem service landscape Sulawesi Lore Lindu National Park grassland primary forest Cucurbita moschata antagonists parasitism STORMA population dynamics 48.16
19	Kohlenstoffvorrat, Nährstoffvorräte und Wasserdynamik nach forstlichen Eingriffen in Fichtenreinbestände / Carbon Stock, Nutrient Stocks and Water Dynamics Following Silvicultural Treatments in Pure Norway Spruce Stands Klinck, Uwe 08 July 2009 (has links) No description available. 500 Naturwissenschaften Forest Sciences and Forest Ecology Fichte Kleinkahlschlag Zielstärkennutzung Einzelbaumlücke Waldumbau Kohlenstoff Stickstoff Solling Bodenvegetation PhytoCalc Elementvorrat Inventur Schlagabraum CO2-C-Fluss Wasserdynamik Norway Spruce small-scale clear-cutting selective cutting single tree gap forest conversion carbon nitrogen Solling forest understorey vegetation PhytoCalc element stock inventory slash CO2-C flow water dynamic 48.32 Bodenkunde Bodenbewertung 38.00 Geowissenschaften: Allgemeines 38.88 Regionale Hydrologie YO 000 Forstwirtschaft YP 000 Standortfaktoren YPA 000 Forstliche Bodenkunde YPK 000 Hydrologie YQ 000 Forstbotanik YQO 000 Ökologie
20	Methodological investigations on vegetation typology and phytogeography of rain forests of tropical Africa Senterre, Bruno B.M.L. 17 June 2005 (has links) I. An original methodological discussion is proposed on the problem of the typology of tropical rain forest’s plant communities, based on the study of forest types across gradients of continentality and elevation, within Atlantic central Africa. These investigations were based on the statement that the main problems in forest typology are related to the non-zonal or zonal character of the different vegetation types and to non considering the relations and differences between forest strata. II. Field data consisted in phytosociological homogeneous sample plots localized within different recognized phytogeographical entities, in a region of tropical Africa where these entities are known to be well conserved. A total of 37 such plots were inventoried in the region extending from the littoral forests of Ndoté, Equatorial Guinea, which are wet evergreen forests, to the continental forests of the Dja, Cameroon, known as evergreen seasonal forests. The studied region also included the oriental Atlantic forests of Equatorial Guinea, known as moist evergreen forests or caesalp forests. In various parts of this continentality gradient, some plots were localized within climax non-zonal formations, namely the submontane rain forests. The emphasis was put on the vegetation of the Monte Alén National Park. The sampling methodology was willing to be as "complete ", including all strata, "quantitative ", enumerating all individuals, and "representative ", within each stratum, as possible. These multi-layers plots were realised using nested sub-plots, with a sampling size of 100 individuals for every ligneous stratum recognized (dominant trees, dominated trees and shrubs) and a sampling size of 200m² for the herbaceous and suffrutex stratum. Forest types were defined independently for each stratum and the differences were analysed. A method was proposed for the simultaneous analysis of all floristic data, converting and standardizing the values from ligneous strata, on the one hand, and from understorey strata, on the other hand. III. Ten forest types were described using IndVal and discussed in the general context of the guineo-congolian region, from a syntaxonomic view point (agglomerative classification) and from a phytogeographical view point (divisive classification). Homologies between these two approaches are described. The proposed phytogeographical system is based on an "open " conception of hierarchical classifications, combining advantages of agglomerative and divisive classifications. In concrete terms, the non-zonal criteria, for example the submontane variants, are categorised separately and in analogy with the zonal criteria, related to the usual phytochoria. Analysis of ecological relationships for the 10 communities showed that the main variables related to the floristic variability in our mainland rain forests are elevation, rainfall, hygrometry (estimated using bryophytes cover levels) and distance to the ocean. The two extremes on the vertical microclimatic gradient, dominant trees stratum and herbaceous stratum, give similar typologies, however canonical analysis showed that for the herbaceous layer, non-zonal variables (hygrometry and elevation) were gaining more importance when the influence of the two zonal variables was attenuated. In every case, spatial autocorrelation was less important than the environment in explaining floristic variability but its role increased in the spatial arrangement of understorey species, whose dispersal capacity is generally lower than canopy trees. The phytosociological, phytogeographical and ecological description of forest types is accompanied by a physiognomical description using biological types spectrum, as well as architectural models, leaf sizes, etc. With regard to diversity, we have demonstrated that species richness was higher from upper to lower strata because of the accumulation in lower strata of species from various strata. On the other hand, the proper stratum diversity, i.e. the structural set, decreased from dominant trees to shrubs. The proper diversity of the herb layer showed relatively high figures mainly due to the higher individual density in relation to the existence of microstrata. Within the 37 sample plots, 1,050 taxa have been identified to species or morpho-species levels, for a total of 25,750 individuals. These taxa represent 442 genus among 104 families. The richest forest type is found on the foothills of the Niefang range, on the windward side. This forest type is also characterised by a high number of oligotypic genus and by species belonging to functional types indicators of glacial refuges. These functional types are defined on the basis of the dispersal capacity and on kind of stand needed for effective germination. We formulated the hypothesis that this kind of "foothills refuge ", characterised by his zonal nature, could have been one of the rare refuges for species from mainland rain forests, while montane and fluvial refuges would mainly have preserved species from non-zonal forest types: (sub)montane and riverine. Based on indicator species of submontane forests, a potential distribution map of this forest type has been realised at the Atlantic central African scale. More than 400 submontane forest localities have been mapped. These forests begin at 400m of altitude near the ocean, and progressively at higher altitude for increasing distance to the ocean. Many lowland localities also comprised submontane species, which could indicate the existence of ecological transgressions. These transgressions would allow migratory tracks for submontane species between isolated mountain ranges, not only during glacial periods, through heights at the northern and southern borders of the congo basin, but also contemporarily through the lowland riverine forest network, in the centre of this basin. Finally, a special attention has been attributed to littoral forests and to some cases of choroecological transgressions, coupled to the ecological equalization phenomenon. plant diversity foothills refuge glacial refuge environmental stability conservation rarefaction curves individuals-area curves species-area curves compensations écologiques Guinée Equatoriale Monte Alén Monts de Cristal Réserve de Ndoté rainforest transgression Monte Alén Cristal mountains strate forestière sous-bois ensemble structural groupe écologique modèles architecturaux guilde types fonctionnels synusie genres monotypiques genres paucispecifiques diversité végétale courbes aire-espèces courbes individus-espèces courbes de raréfaction courbes aire-constance aire minimale morpho-espèces pléistocène constancy-area curves minimal area structural ensemble understorey ecological group synusia oligotypic genus Réserve de Biosphère du Dja Cameroun Quaternaire glaciation refuge glaciaire refuge de pied de massifs montagneux stabilité environnementale conservation transgression forestière phytosociology plant community phytogeography open classification non-zonal nested plots forest types IndVal morphospecies pleistocene littoral forest rain forest afromontane submontane altitudinal belt glaciation Quaternary Equatorial Guinea ecological equalization continentality continentalité étage d’altitude forêt littorale forêt dense humide afromontagnard submontagnard IndVal types forestiers phytosociologie phytogéographie classification ouverte azonal relevés emboîtés multistrates monotypic genus architectural model guild plant functional type Ndoté Reserve Cameroon Dja Biosphere Reserve forest stratum forest layer understory

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