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2. Laetia procera (Poepp.) Eichler can be included in polycyclic management programs for timber production, replacing species intensively harvested in the Amazon forest.

Author

Ferreira, Ana Paula Souza, Pereira de Carvalho, João Olegário, Costa dos Santos, Cassio Rafael, Silva da Silva, Washington Duarte, da Cunha Castro, Tatiana, Filho, Afonso Figueiredo, and Ruschel, Ademir Roberto

Subjects
SUSTAINABILITY, LOGGING, FOREST conservation, NUMBERS of species, POPULATION dynamics
Abstract

Many tree species in tropical natural forests are unknown or little studied, especially regarding their ecological, silvicultural, and wood use characteristics. Studies on the dynamics of these species are necessary to assist in planning their uses, with minimal impact on the ecosystem, aiming for economic, ecological, and social benefits. The present study aimed to evaluate the population dynamics and potential for sustainable timber production of the species Laetia procera (Poepp.) Eichler over a period of 31 years in a dense managed terra firme forest in the Eastern Amazon. Abundance, dominance, frequency, importance value index, diameter distribution of trees, recruitment, mortality, and annual periodic increment in diameter were evaluated. The structure of the L. procera population benefited from the increased solar radiation in the forest, due to logging and thinning, favoring its growth and establishment in the area until the end of monitoring. Its dynamics over the 31 years of evaluation, based on the evaluated parameters, can guarantee its conservation in managed forests and suggest its inclusion in management programs, aimed at sustainable timber production. • Replacing part of the species in each cut leads to continuous timber production. • Laetia procera can increase the number of tree species managed in Amazonian forests. • Dynamics of Laetia procera guarantees its conservation in logged Amazonian forests. • Laetia procera needs large gaps in natural forests to adapt and grow faster. [ABSTRACT FROM AUTHOR]

Published
2024
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3. Century-long tree population dynamics in a deciduous forest stand in central Sweden.

Author

Hytteborn, Håkan, Svensson, Brita M., Kempe, Kerstin, Press, Andreas, Rydin, Håkan, and Nakashizuka, Tohru

Subjects
*DECIDUOUS forests, *TREE populations, *CLIMATE change, *HAZEL, *DUTCH elm disease, *PLANT species diversity, *PLANT mortality, *PLANTS
Abstract

Question We quantify tree dynamics over a century of free development in a small broad-leaved forest dominated by Fraxinus excelsior and Ulmus glabra. What are the internal and external factors driving the changes, and how predictable are they? What were the time scale and effects of the spread of Dutch elm disease ( DED)? Location Vårdsätra, eastern central Sweden. Methods The survival, growth and recruitment of all trees (≥12 cm girth) were monitored in 1912, 1967, 1988 and 2013 (more often for a part of the forest). Woody species in the field and shrub layers were surveyed in permanent plots in 1976 and 2012. We used transition matrix models to project changes in population sizes and species composition within the century and for 2050. Results The results indicate that the forest was in a successional development during the first period. The species composition had stabilized by 1967, except for an expansion of Acer platanoides and the drastic effect of DED that struck the forest around 2000. It took only a decade to kill virtually all large elms in the forest, leading to strong decrease in stem density and basal area. The evidence for effects of DED is still weak, but there has been an increase in saplings, notably of Fraxinus, Prunus padus, Ulmus, and of shoots of Corylus avellana. Several species that are abundant in the vicinity and as seeds fail to establish ( Picea abies, Betula spp., Quercus robur, Populus tremula). Projections for 2050 based on the third period (1988-2013) are probably unrealistic since Fraxinus may also disappear because of the recent arrival of ash dieback. Conclusions Slow dynamics in forests that could follow from climate change will locally probably be overruled by unforeseen catastrophes, such as invasions of forest pathogens. These initiate changes with long lag phases that are difficult to quantify. Still, a dense deciduous forest can resist invasion of colonist species and of regionally dominant conifers; the reason being unfavourable conditions for establishment rather than dispersal limitation. [ABSTRACT FROM AUTHOR]

Published
2017
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4. Drivers of plant invasion vary globally: evidence from pine invasions within six ecoregions.

Author

Taylor, Kimberley T., Maxwell, Bruce D., Pauchard, Aníbal, Nuñez, Martin A., Peltzer, Duane A., Terwei, André, and Rew, Lisa J.

Subjects
*PLANT invasions, *ECOLOGICAL regions, *ECOSYSTEMS, *PLANT populations, *CLIMATE change, *BIOGEOGRAPHY
Abstract

Aim To determine biotic and abiotic controls on pine invasion globally within six ecoregions that include both introduced and native ranges. Locations Río Negro province, Argentina; Aysén and Araucanía regions, Chile; South Island (two ecoregions), New Zealand; Greater Yellowstone ecosystem, USA. Methods We quantified tree abundance and size across invasion fronts of the widespread invasive tree species Pinus contorta at each of the nine sites, encompassing both the native and introduced range. We also determined the relative importance of propagule pressure, abiotic characteristics and biotic factors for invasion success. Finally, key plant population metrics such as individual tree growth rates and reproductive effort were compared between native and introduced ranges. Results Pinus contorta density decreased with increasing distance from source population in all cases, but the importance and shape of this relationship differed among sites due, primarily to biotic factors. For example, areas dominated by native southern beech forest (Fuscospora cliffortioides or Nothofagus spp.) were not invaded, and this biotic resistance was not overcome by high propagule pressure. In contrast, shrublands were more highly invaded than grasslands, contradicting previous generalizations about pine invasions. Pinus contorta growth was faster, age to maturity was earlier and reproductive effort was higher in the introduced ranges compared with the native range, suggesting a demographic shift towards more rapid population growth in introduced regions. Climatic differences between the ranges may explain, at least in part, the observed pattern. Main conclusions We demonstrate that although biological invasions are driven by propagule pressure across different ecoregions, these processes interact strongly with biotic factors. Intriguingly, our results suggest that propagule pressure may become less important than biotic interactions as invasions proceed. Multi-region studies including both the native and introduced ranges provide unparalleled opportunities for understanding how these interactions change among regions as invasions proceed. [ABSTRACT FROM AUTHOR]

Published
2016
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6. Patrones espaciales de tamaño y mortalidad del roble (Quercus robur L.) en un bosque del litoral de Cantabria

Author

Rozas, Vicente and Fernández Prieto, José A.

Subjects
Spatial patterns, Autocorrelación espacial, Tree population dynamics, Mortalidad, Ripley's K, Mortality, Competencia intraespecífica, Intraspecific competition, Patrones espaciales, Quercus robur L, Dinámicas de poblaciones, Spatial autocorrelation, K de Ripley
Abstract

La descripción e interpretación de los patrones espaciales de los árboles permite extraer conclusiones sobre los factores que condicionan tanto el establecimiento de las cohortes como su variación temporal. En el presente trabajo se analizan las distribuciones espaciales de tamaño y mortalidad del roble (Quercus robur L.) en dos parcelas de bosque. Obtenemos evidencias significativas de agregación para las clases de tamaño pequeñas y de distribución aleatoria en la clase de tamaño mayor. La disponibilidad de espacios abiertos parece ser el principal factor que condiciona la regeneración, estructura y mortalidad en las poblaciones de roble. Una de las poblaciones estudiadas se habría originado sin limitación de espacios abiertos, presentando poca organización espacial y un patrón aleatorio de la mortalidad, lo cual es indicativo de una escasa incidencia de la competencia intraespecífica. En otra población, que corresponde a una parcela de bosque maduro con escasos espacios abiertos, la regeneración del roble está asociada a «fase de claro», formándose grupos compuestos por árboles de tamaños similares y en distintas fases de madurez. En este caso, la mortalidad de roble tiene lugar predominantemente dentro de los grupos formados por árboles de poca talla y está, al menos en parte, causada por competencia intraespecífica. Quantitative spatial analysis provide inferences on tree population dynamics. Spatial patterns of pedunculate oak (Quercus robur L.) in two forest plots were analysed in this work. Significative evidences of clumping for trees of smaller sizes and a random pattern for larger-sized ones were given. This results would be related to self-thinning occurrence. Open space availability seems to be the main factor that drive the structure evolution and the regeneration and mortality processes within oak populations. In one of the studied stands, poor spatial arrangement and random mortality are linked to oak populations developed in open space, and there are evidences of scarce intraspecific competition. In the other studied stand, established in old-growth forest, oak regeneration occurs in canopy gaps and, as a result, even-sized groups of trees in different ripeness stage arise. In the old-growth plot, oak mortality mainly occurs within small-sized groups of trees as a consequence of intraspecific competition.

Published
2021

7. Biotic interactions and population dynamics : Empirical and theoretical approaches of pre-dispersal seed predation by insects

Author

Doublet, Violette, Unité de Recherches Forestières Méditerranéennes (URFM), Institut National de la Recherche Agronomique (INRA), Université Montpellier, and François Lefèvre

Subjects
Allee effect, Interactions arbres-Insectes, [SDV.SA]Life Sciences [q-bio]/Agricultural sciences, Prédation pré-Dispersion, Effet Allee, Tree population dynamics, Masting, Tree-Insect interactions, Impacts démogénétiques, Demogenetic impacts, Dynamique des peuplements forestiers, Pre-Dispersal seed predation
Abstract

Biotic interactions are among key processes in population dynamics and critical issues for the renewal and persistence of species within ecosystems. In particular, herbivory by pre-dispersal seed insect predators is a major ecological process in forest dynamics due to its impact on tree reproductive success and on natural regeneration. However, its consequence on tree population dynamics and evolution remain poorly documented. This thesis contributed to fill this gap as an integrative combination of empirical and theoretical approaches. The empirical approach aimed to characterize the drivers of the spatio-temporal dynamics of seed predation rates in natural forest. We used a system of tree-insect interactions involving seed predators (Megastigmus spp., Hymenoptera: Torymidae) and their obligate host, the Atlas Cedar (Cedrus atlantica, Pinaceae), located in south-eastern France. At the host population scale, our results revealed that the transient pattern of the spatial distribution of insects was primarily explained by spatiotemporal variations in seed density. Thus, Cedar masting appeared to be a major driving force of the insects’ spatial and temporal dynamics. We have also highlighted the existence of an inter-individual variation in the sensitivity of trees to seed predation. A preliminary analysis has suggested that such variation is partly under genetic control and we propose further analyses to be carried out in such perspective. The theoretical approach aimed to analyse the joint effects of masting and the spatial distribution of pre-dispersal seed predation by insects on demographic processes and genetic diversity in an expanding tree population. The analytical modelling of these interactions revealed on the one hand that pre-dispersal seed predation induce Allee effects that may affect the spatial structure of genetic diversity in the expanding tree population, and on the other hand, that masting was likely to buffer such demogenetic impact of seed predation. This work has shed new light on the possible implications of pre-dispersal predation by insects in the dynamics and evolution of forests.; Les interactions biotiques figurent parmi les processus clés de la dynamique des populations et constituent un enjeu fort pour le renouvellement et la persistance des espèces au sein des écosystèmes. En particulier, l’herbivorie par les insectes prédateurs des graines avant dispersion est un processus écologique majeur de la dynamique forestière par son impact sur le succès reproducteur des arbres et leur régénération naturelle. Cependant, les conséquences de cette herbivorie sur la dynamique et l’évolution des populations d’arbres demeurent des fronts de science, qui ont été abordés dans cette thèse de façon intégrative en combinant des approches empirique et théorique. L’approche empirique a visé la caractérisation des déterminants de la dynamique spatio-temporelle du taux de prédation des graines en forêt naturelle. Le système modèle d’interactions arbres-insectes analysé implique des Hyménoptères séminiphages (Megastigmus spp., Torymidae) et leur hôte obligatoire, le Cèdre de l’Atlas (Cedrus atlantica, Pinaceae), localisé dans le sud-est de la France. À l’échelle de la population d’hôtes, les résultats ont révélé le caractère transitoire de la distribution spatiale des insectes qui est fortement déterminée par les variations spatio-temporelles de la densité des graines. En outre, la dynamique de fructification de type ‘masting’ du Cèdre est un moteur majeur de la dynamique spatio-temporelle des insectes. De plus, on a pu montrer l’existence d’une variation inter-individuelle de la sensibilité des arbres à la prédation des graines. Une analyse préliminaire a suggéré que cette variation est en partie d’origine génétique, et les travaux complémentaires à mener en ce sens ont pu être précisés. L’approche théorique a permis d’analyser les effets conjoints du masting et de la distribution spatiale des prédateurs des graines sur les processus démographiques et la diversité génétique dans une population d’arbres en expansion naturelle. La modélisation analytique de ces interactions a révélé d’une part que la prédation des graines avant dispersion génère des effets Allee influençant la mise en place de la diversité génétique de la population d’arbres au cours d’une expansion, et que le masting est susceptible de tempérer cet impact de la prédation des graines. Ces travaux ont apporté un éclairage nouveau sur les implications possibles des insectes prédateurs des graines avant dispersion dans la dynamique et l’évolution des peuplements forestiers.

Published
2020

8. Small-scale disturbance and stand structure dynamics in an old-growth Picea abies forest over 54 yr in central Sweden.

Author

Hytteborn, Håkan, Verwijst, Theo, and Collins, Beverly

Subjects
*TAIGA ecology, *FOREST dynamics, *VEGETATION dynamics, *POPULATION biology, *FOREST regeneration, *ECOLOGICAL succession, *TREE populations
Abstract

Questions Can assumptions of the existence of spatially distinct patches (delineated structurally homogeneous parts of the forest, being either areas consisting of canopy trees or areas without canopy trees but in an early or later regenerative phase) and of directional development over time of the vegetation in such patches, as implied by current theory of storm gap dynamics, be verified by remapping previous study sites? Location Natural, unmanaged boreo-nemoral spruce-dominated forest in eastern central Sweden. Methods By re-mapping three plots, ca, 50 yr after the first inventory, we studied the structure and dynamics of gaps (patches without canopy tree cover) and major tree populations. The old and new maps allowed us to compare two independent assessments of the forest dynamics: one based on tree population changes and one on changes in gap area over time. Results The current population structure could partly be described through the earlier-encountered structures of the different tree populations and consecutive processes of recruitment and mortality. However, the re-mapping exercise showed that spatially delineated patches did not develop directionally over time, nor was their development spatially discrete. Conclusions Patch dynamics proceeds in such a way that the fate of a single patch may depend on the development of neighbouring patches. As gaps may partly close or merge into larger gaps, and as gap disappearance rate is a function of actual gap size, performance of an initially delimited patch is largely determined by developments in neighbouring patches and cannot be predicted from its momentary patch characteristics. Consequently, we propose an 'open matrix model' to describe the changes in a boreo-nemoral spruce forest, rather than a 'storm gap dynamics' model. [ABSTRACT FROM AUTHOR]

Published
2014
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9. Interplay between field observations and numerical modeling to understand temporal pulsing of tree root throw processes, Canadian Rockies, Canada.

Author

Martin, Y.E., Johnson, E.A., and Chaikina, O.

Subjects
*GEOMORPHOLOGICAL research, *FIELD theory (Physics), *SCIENTIFIC observation, *PLANT roots, *MOUNTAIN plants
Abstract

Abstract: During the cycle of forest disturbance, regeneration, and maturity, tree mortality leading to topple is a regular occurrence. When tree topple occurs relatively soon after mortality and if the tree has attained some threshold diameter at breast height (dbh) at the time of death, then notable amounts of soil may be upheaved along with the root wad. This upheaval may result in sediment transfers and soil production. A combination of field evidence and numerical modeling is used herein to gain insights regarding the temporal dynamics of tree topple, associated root throw processes, and pit-mound microtopography. Results from our model of tree population dynamics demonstrate temporal patterns in root throw processes in subalpine forests of the Canadian Rockies, a region in which forests are affected largely by wildfire disturbance. As the forest regenerates after disturbance, the new cohort of trees has to reach a critical dbh before significant root plate upheaval can occur; in the subalpine forests of the Canadian Rockies, this may take up to ~102 years. Once trees begin to reach this critical dbh for root plate upheaval, a period of sporadic root throw arises that is caused by mortality of trees during competition. In due course, another wildfire will occur on the landscape and a period of much increased root throw activity then takes place for the next several decades; tree sizes and, therefore, the amount of sediment disturbance will be greater the longer the time period since the previous fire. Results of previous root throw studies covering a number of regional settings are used to guide an exercise in diffusion modeling with the aim of defining a range of reasonable diffusion coefficients for pit-mound degradation; the most appropriate values to fit the field data ranged from 0.01m2 y−1 to 0.1m2 y−1. A similar exercise is then undertaken that is guided by our field observations in subalpine forests of the Canadian Rockies. For these forests, the most appropriate range of diffusion coefficients is in the range 0.001m2 y−1 to 0.01m2 y−1. Finally, the model of tree population dynamics is combined with the model of pit-mound degradation to demonstrate the integration of these combined processes on the appearance of pit-mound microtopography and soil bioturbation in subalpine forests of the Canadian Rockies. We conclude that the appearance of notable pit-mound microtopography is limited to very specific time periods and is not visible for much of the time. Most of the hillslope plot is affected by root throw during the 1000-year model run time. [Copyright &y& Elsevier]

Published
2013
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10. The trade-off between flood- and shade-tolerance: A mortality episode in Carpinus caroliniana in a floodplain forest, Texas.

Author

Mann, Lisa E., Harcombe, Paul A., Elsik, I. Sandra, and Hall, Rosine B. W.

Subjects
*FLOODPLAIN forests, *FORESTS & forestry, *CARPINUS, *TREES, *FLOODS, *MORTALITY, *EXPERIMENTAL design, *SEASONS
Abstract

Question: Is a rapid decline in abundance of a dominant species in a bottomland hardwood forest evidence for a trade-off between flood- and shade-tolerance? Location: Bottomland hardwood forest in east Texas, USA. Methods: We used 23 years of data on marked individuals to examine abundance, mortality, recruitment and growth of trees before and after a long growing season flood. Results: A decline of 47% in abundance and 49% in basal area of Carpinus caroliniana (Betulaceae) occurred between 1989 and 1994 in a bottomland hardwood forest following a long summer flood. Other major species showed little change in abundance or basal area. The Carpinus decline was greater at low elevations suggesting the importance of flooding. Carpinus is rated among the least flood-tolerant species in the system. It differs from other species of similar flood tolerance in adult stature (midstory) and shade tolerance (tolerant). Conclusions: The trade-off between flood tolerance and shade tolerance can influence dynamics of floodplain forests. [ABSTRACT FROM AUTHOR]

Published
2008
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11. Tree species population dynamics in a secondary forest at Ile-Ife, Nigeria after a ground fire.

Author

Muoghalu, Joseph Ikeckukwu

Subjects
*PLANT species, *TREES, *PLANT populations, *FORESTS & forestry, *RAIN forests, *FOREST fires
Abstract

Tree species population dynamics were studied in a 0.25-ha secondary rain forest plot which was accidentally burnt in 1983 by a severe ground fire. The effect of the fire on tree species in the plot was assessed after 14 months in 1984 and 14 years in 1997 to establish the changes in tree species composition and structural characteristics of the plot after the fire. The present study investigated the changes in species composition, mortality, recruitment rates and some structural characteristics of the plot 18 years after the fire. The results from this study were compared with previous studies in the plot. Tree species richness of the plot (37 per 0.25 ha in 1983), which increased to 40 and 71 species 1 and 14 years respectively after the fire dropped to 63 species 18 years after. Fifteen species, which were not originally present before the fire, are established and abundant now. Ten woody species, each of which were originally present and which established 1 year after the fire have died. Stem density increased from 3192 trees ha−1 1 year to 10,064 trees ha−1 18 years after the fire. Basal area increased while species diversity, which increased to 3.41 14 years after, decreased to 3.07 18 years after. The annual mortality rate was 2.1% 14 years after and annual recruitment rates were 74.5% year−1 and 35.7% year−1 1 and 18 years after the fire, respectively. These observations give insight to secondary forest succession after fire. Résumé On a étudié la dynamique des populations d'arbres dans une parcelle de 0,25 ha de forêt pluviale secondaire qui a été brûlée accidentellement en 1983. L'effet du feu sur les espèces d'arbres contenues dans la parcelle a étéévalué après 14 mois, en 1984, et après 14 ans, en 1997, pour déterminer les changements de la composition des espèces d'arbres, et les caractéristiques structurelles de la parcelle après le feu. La présente étude analyse les changements de la composition des espèces, la mortalité, le taux de régénération et quelques caractéristiques structurelles de la parcelle 18 ans après l'incendie. Les résultats sont comparés à ceux des études précédentes au même endroit. La richesse en espèces de la parcelle (37 pour 0,25 ha en 1983) qui était passée à 40 un an après le feu et à 71 après 14 ans, s'est réduite à 63 espèces après 18 ans. Quinze espèces qui n’étaient pas présentes avant l'incendie sont maintenant bien établies et abondantes. Dix espèces ligneuses qui étaient présentes originellement et qui étaient installées un an après le feu ont disparu. La densité des pousses a augmenté de 3.192 arbres/ha, un an après le feu, à 10.064 arbres/ha après 18 ans. La surface terrière a augmenté tandis que la diversité des espèces, qui avait aussi augmenté jusqu’à 3,41, a diminuéà 3,07 18 ans plus tard. Le taux de mortalité annuel était de 2,1%, 14 ans après le feu, et le taux de régénération était de 74,5% et de 35,7% respectivement un an et 18 ans après l'incendie. Ces observations donnent un aperçu de l’évolution d'une forêt secondaire après un feu. [ABSTRACT FROM AUTHOR]

Published
2007
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12. Interactions biotiques et dynamiques des populations

Author

Doublet, Violette and Lucas, Nelly

Subjects
pre-dispersal seed predation, Allee effect, tree-insect interactions, [SDV] Life Sciences [q-bio], [SDE.BE] Environmental Sciences/Biodiversity and Ecology, tree population dynamics, prédation pré-dispersion, impacts démogénétiques, dynamique des peuplements forestiers, demogenetic impacts, masting, interactions arbres-insectes, effet Allee
Abstract

Biotic interactions are among key processes in population dynamics and critical issues for the renewal and persistence of species within ecosystems. In particular, herbivory by pre-dispersal seed insect predators is a major ecological process in forest dynamics due to its impact on tree reproductive success and on natural regeneration. However, its consequence on tree population dynamics and evolution remain poorly documented. This thesis contributed to fill this gap as an integrative combination of empirical and theoretical approaches. The empirical approach aimed to characterize the drivers of the spatio-temporal dynamics of seed predation rates in natural forest. We used a system of tree-insect interactions involving seed predators (Megastigmus spp., Hymenoptera: Torymidae) and their obligate host, the Atlas Cedar (Cedrus atlantica, Pinaceae), located in south-eastern France. At the host population scale, our results revealed that the transient pattern of the spatial distribution of insects was primarily explained by spatiotemporal variations in seed density. Thus, Cedar masting appeared to be a major driving force of the insects’ spatial and temporal dynamics. We have also highlighted the existence of an inter-individual variation in the sensitivity of trees to seed predation. A preliminary analysis has suggested that such variation is partly under genetic control and we propose further analyses to be carried out in such perspective. The theoretical approach aimed to analyse the joint effects of masting and the spatial distribution of pre-dispersal seed predation by insects on demographic processes and genetic diversity in an expanding tree population. The analytical modelling of these interactions revealed on the one hand that pre-dispersal seed predation induce Allee effects that may affect the spatial structure of genetic diversity in the expanding tree population, and on the other hand, that masting was likely to buffer such demogenetic impact of seed predation. This work has shed new light on the possible implications of pre-dispersal predation by insects in the dynamics and evolution of forests., Les interactions biotiques figurent parmi les processus clés de la dynamique des populations et constituent un enjeu fort pour le renouvellement et la persistance des espèces au sein des écosystèmes. En particulier, l’herbivorie par les insectes prédateurs des graines avant dispersion est un processus écologique majeur de la dynamique forestière par son impact sur le succès reproducteur des arbres et leur régénération naturelle. Cependant, les conséquences de cette herbivorie sur la dynamique et l’évolution des populations d’arbres demeurent des fronts de science, qui ont été abordés dans cette thèse de façon intégrative en combinant des approches empirique et théorique. L’approche empirique a visé la caractérisation des déterminants de la dynamique spatio-temporelle du taux de prédation des graines en forêt naturelle. Le système modèle d’interactions arbres-insectes analysé implique des Hyménoptères séminiphages (Megastigmus spp., Torymidae) et leur hôte obligatoire, le Cèdre de l’Atlas (Cedrus atlantica, Pinaceae), localisé dans le sud-est de la France. À l’échelle de la population d’hôtes, les résultats ont révélé le caractère transitoire de la distribution spatiale des insectes qui est fortement déterminée par les variations spatio-temporelles de la densité des graines. En outre, la dynamique de fructification de type ‘masting’ du Cèdre est un moteur majeur de la dynamique spatio-temporelle des insectes. De plus, on a pu montrer l’existence d’une variation inter-individuelle de la sensibilité des arbres à la prédation des graines. Une analyse préliminaire a suggéré que cette variation est en partie d’origine génétique, et les travaux complémentaires à mener en ce sens ont pu être précisés. L’approche théorique a permis d’analyser les effets conjoints du masting et de la distribution spatiale des prédateurs des graines sur les processus démographiques et la diversité génétique dans une population d’arbres en expansion naturelle. La modélisation analytique de ces interactions a révélé d’une part que la prédation des graines avant dispersion génère des effets Allee influençant la mise en place de la diversité génétique de la population d’arbres au cours d’une expansion, et que le masting est susceptible de tempérer cet impact de la prédation des graines. Ces travaux ont apporté un éclairage nouveau sur les implications possibles des insectes prédateurs des graines avant dispersion dans la dynamique et l’évolution des peuplements forestiers.

Published
2020

13. Patchy Fires Promote Regeneration of Longleaf Pine (Pinus palustris Mill.) in Pine Savannas

Author

Charles E. Faires, Kevin M. Robertson, and William J. Platt

Subjects
0106 biological sciences, Canopy, tree population dynamics, animal structures, regeneration niche, media_common.quotation_subject, regeneration bottlenecks, 010603 evolutionary biology, 01 natural sciences, complex mixtures, Competition (biology), Grassland, fire effects, Regeneration (ecology), media_common, Tree canopy, geography, geography.geographical_feature_category, fungi, food and beverages, Forestry, lcsh:QK900-989, prescribed fire regime, Litter, Spatial ecology, lcsh:Plant ecology, Environmental science, Mulch, 010606 plant biology & botany
Abstract

Research Highlights: Spatial patterns of fire spread and severity influence survival of juvenile pines in longleaf pine savannas. Small areas that do not burn during frequent fires facilitate formation of patches of even-aged longleaf pine juveniles. These regeneration patches are especially associated with inner portions of openings (gaps) and where canopy trees have died in recent decades. Patterns of prescribed fire can thus have an important influence on stand dynamics of the dominant tree in pine savannas. Background and Objectives: Savannas are characterized by bottlenecks to tree regeneration. In pine savannas, longleaf pine is noted for recruitment in discrete clusters located within gaps away from canopy trees. Various mechanisms promoting this pattern have been hypothesized: light limitations, soil moisture, soil nutrients, pine needle mulching, competition with canopy tree roots, and fire severity associated with pine needle litter. We tested the hypothesis that regeneration patches are associated with areas that remain unburned during some prescribed fires, as mediated by gaps in the canopy, especially inner portions of gaps, and areas re-opened by death of canopy trees. Materials and Methods: We mapped areas that were unburned during prescribed fires applied at 1&ndash, 2 year intervals from 2005&ndash, 2018 in an old-growth pine savanna in Georgia, USA. We compared the maps to locations of longleaf pine juveniles (&lt, 1.5 m height) measured in 2018 and canopy cover and canopy tree deaths using a long-term (40 year) tree census. Results: Logistic regression analysis showed juveniles to be associated with unburned areas, gaps, inner gaps, and areas where canopy trees died. Conclusions: Patterns of fire spread and severity limit survival of longleaf pine juveniles to patches away from canopy trees, especially where canopy trees have died in recent decades. These processes contribute to a buffering mechanism that maintains the savanna structure and prevents transition to closed canopy forest or open grassland communities.

Published
2019

14. The social-ecological drivers across land-use intersects driving marula tree population dynamics in north-eastern South Africa.

Author

Blair, Amy M., Thompson, Dave I., Twine, Wayne C., and Grab, Stefan

Subjects
POPULATION dynamics, NON-timber forest products, TREE felling, FOREST density, WILDLIFE conservation, HUMAN settlements
Abstract

• Exploring resource sustainability in social-ecological systems (SES) • Combined social and ecological methodologies for tree population dynamics. • Human inhabited savanna woodlands of Southern Africa. • Resource utilisation of common property resources (CPRs) in savannas. • Tree stewardship in communal rangelands. A range of social and economic factors impact tree species, such as Sclerocarya birrea subsp. caffra (marula), which provide livelihood sustenance for local communities in the savanna woodlands of southern Africa. As an ecologically important savanna species, valued both culturally and economically, it is imperative to understand if resource use is sustainable. Population stability can be understood by comparing tree density and size-class distribution (SCD) profiles across land-use types (homestead yards, fields and rangelands) in non-conservation savanna social-ecological systems. Marula tree population data were gathered in rangeland transects and randomly selected fields and yards from four human settlements in the Bushbuckridge municipality of north-eastern South Africa. Total density was lowest in fields (mean ± SE = 7.4 ± 0.7 trees/ha) and highest in homestead yards (mean ± SE = 25.7 ± 4.1 trees/ha). Social data revealed that elevated seedling and sapling population densities in yards is linked to discarded kernels from marula beer making. Total densities increased in yards over a 15-year period but declined in rangelands, with female densities remaining almost constant across land-use types over this period. This is an important finding as it is a strong indication of socially-mediated population structure changes, confirming that combined cultural and economic value can lead to examples of species conservation. In this case, the prioritization of female trees as the distinguished fruit producers. SCD revealed weak recruitment in fields and rangelands. Diminished regeneration, combined with overharvesting for fuelwood in rangelands and felling trees in yards, is likely to negatively impact population stability in the long-term. Understanding resource conservation and degradation in the context of important non-timber forest products (NTFPs) is a key knowledge challenge, with this study serving as an updated inventory benchmark for marula populations in the area. Important lessons learned here can be applied to other social-ecological contexts where a key natural resource is responsible for sustaining livelihoods. [ABSTRACT FROM AUTHOR]

Published
2021
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16. Dinâmica da comunidade e populações arbóreas da borda e interior de um remanescente florestal na Serra da Mantiqueira, Minas Gerais, em um intervalo de cinco anos (1999-2004)

Author

Gislene de Carvalho Castro, Evandro Luiz Mendonça Machado, Vivette Appolinário, Jaqueline M. Alves, Ary Teixeira de Oliveira Filho, Rubens Manoel dos Santos, Pedro Higuchi, Ana Carolina da Silva, Warley Augusto Caldas Carvalho, Bruno S. Corrêa, and Luís F. Borges

Subjects
forest dynamics, forest fragmentation, tree population dynamics, Fragmentation (computing), tropical semideciduous forest, Forestry, Biology, dinâmica de comunidades arbóreas, fragmentação florestal, Basal area, tree community dynamics, dinâmica florestal, dinâmica de populações arbóreas, floresta tropical semidecídua
Abstract

A dinâmica da comunidade arbórea e de 26 populações componentes foi investigada em um fragmento de floresta estacional semidecídua em Piedade do Rio Grande, Minas Gerais, com base em inventários conduzidos em 1999 e 2004 em 30 parcelas de 400 m², 12 das quais foram locadas na borda do fragmento e 18 em seu interior. O objetivo foi verificar se a comunidade e populações arbóreas (a) estavam estáveis no período, e (b) mostraram uma dinâmica mais acelerada na borda do fragmento que em seu interior. Foram obtidas taxas de mortalidade e recrutamento de árvores e taxas de ganho e perda de área basal para a amostra total, seus dois setores, classes de diâmetro e populações. A hipótese da estabilidade foi rejeitada porque, tanto na borda como no interior, as taxas de mortalidade superaram as de recrutamento, as taxas de ganho superaram as de perda de área basal e as distribuições de tamanho mudaram devido ao declínio na densidade de árvores menores. Tais mudanças gerais se relacionaram, possivelmente, (a) a efeitos de longa duração da fragmentação ainda em curso, (b) a uma fase particular de um ciclo florestal rítmico e/ou (c) à suposta aceleração global das taxas de rotatividade florestal devido ao aumento do CO2 atmosférico. Os dois setores de fato diferiram nas taxas de rotatividade mais elevadas na borda que no interior da floresta, provavelmente devido à maior abundância de luz na borda, mas também porque populações de espécies pioneiras e exigentes de luz, de rápido crescimento, são mais abundantes na borda. The dynamics of the tree community and 26 component populations was investigated in a fragment of tropical semideciduous forest in Piedade do Rio Grande, SE Brazil, based on surveys done in 1999 and 2004 in 30 400 m² plots, 12 of which were located on the edge of the fragment and 18 in its interior. The purpose was to assess whether the tree community and populations (a) were stable in the period, and (b) showed a more accelerated dynamics on the fragment edge than in its interior. Rates of mortality and recruitment of trees and gain and loss of basal area were obtained for the whole sample, its two sectors, diameter classes and tree populations. The stability hypotheses was rejected because, in both the edge and interior, mortality rates surpassed recruitment rates, gain rates of basal area surpassed loss rates, and size distributions changed, with declining density of smaller trees. These overall changes were possibly related to (a) ongoing long-lasting fragmentation effects, (b) a particular phase of a rhythmic forest cycle and, or (c) the alleged recent global acceleration of forest turnover due to increased CO2 in the atmosphere. The two sectors did differ in their turnover rates higher on the edge than in the forest interior, probably because of more abundant light at the edge, but also because tree populations of fast-growing pioneer and light-demanding species are more abundant at the edge.

Published
2007
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17. Patchy Fires Promote Regeneration of Longleaf Pine (Pinus palustris Mill.) in Pine Savannas.

Author

Robertson, Kevin M., Platt, William J., and Faires, Charles E.

Subjects
PATCH dynamics, FOREST fires, LONGLEAF pine, FOREST regeneration, SAVANNAS
Abstract

Research Highlights: Spatial patterns of fire spread and severity influence survival of juvenile pines in longleaf pine savannas. Small areas that do not burn during frequent fires facilitate formation of patches of even-aged longleaf pine juveniles. These regeneration patches are especially associated with inner portions of openings (gaps) and where canopy trees have died in recent decades. Patterns of prescribed fire can thus have an important influence on stand dynamics of the dominant tree in pine savannas. Background and Objectives: Savannas are characterized by bottlenecks to tree regeneration. In pine savannas, longleaf pine is noted for recruitment in discrete clusters located within gaps away from canopy trees. Various mechanisms promoting this pattern have been hypothesized: light limitations, soil moisture, soil nutrients, pine needle mulching, competition with canopy tree roots, and fire severity associated with pine needle litter. We tested the hypothesis that regeneration patches are associated with areas that remain unburned during some prescribed fires, as mediated by gaps in the canopy, especially inner portions of gaps, and areas re-opened by death of canopy trees. Materials and Methods: We mapped areas that were unburned during prescribed fires applied at 1–2 year intervals from 2005–2018 in an old-growth pine savanna in Georgia, USA. We compared the maps to locations of longleaf pine juveniles (<1.5 m height) measured in 2018 and canopy cover and canopy tree deaths using a long-term (40 year) tree census. Results: Logistic regression analysis showed juveniles to be associated with unburned areas, gaps, inner gaps, and areas where canopy trees died. Conclusions: Patterns of fire spread and severity limit survival of longleaf pine juveniles to patches away from canopy trees, especially where canopy trees have died in recent decades. These processes contribute to a buffering mechanism that maintains the savanna structure and prevents transition to closed canopy forest or open grassland communities. [ABSTRACT FROM AUTHOR]

Published
2019
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18. Comparing short and long-distance dispersal: Modelling and field case studies

Author

Diana E. Marco, Sergio A. Cannas, Marcelo A. Montemurro, Marco D.E., Montemurro M.A., and Cannas S.A.

Subjects
education.field_of_study, tree population dynamics, ecological invasion, Ecology, Population, Biology, Spatial distribution, Field (geography), Life history theory, Spatial heterogeneity, Density dependence, Habitat, fractal, Biological dispersal, education, Ecology, Evolution, Behavior and Systematics
Abstract

Dispersal is a factor of great importance in determining a species spatial distribution. Short distance dispersal (SDD) and long distance dispersal (LDD) strategies yield very different spatial distributions. In this paper we compare spatial spread patterns from SDD and LDD simulations, contrast them with patterns from field data, and assess the significance of biological and population traits. Simulated SDD spread using an exponential function generates a single circular patch with a well-defined invasion front showing a travelling-wave structure. The invasive spread is relatively slow as it is restricted to reproductive individuals occupying the outer zone of the circular patch. As a consequence of this dispersal dynamics, spread is slower than spread generated by LDD. In contrast, the early and fast invasion of the entire habitat mediated by power law LDD not only involves a significantly greater invasion velocity, but also an entirely different habitat occupation. As newly dispersed individuals soon reach very distant portions of the habitat as well as the vicinity of the original dispersal focus, new growing patches are generated while the main patch increases its own growth absorbing the closest patches. As a consequence of both dispersal and lower density dependence, growth of the occupied area is much faster than with SDD. SDD and LDD also differ regarding pattern generation. With SDD, fractal patterns appear only in the border of the invasion front in SDD when competitive interaction with residents is included. In contrast, LDD patterns show fractality both in the spatial arrangements of patches as well as in patch borders. Moreover, values of border fractal dimension inform on the dispersal process in relation with habitat heterogeneity. The distribution of patch size is also scale-free, showing two power laws characteristic of small and large patch sizes directly arising from the dispersal and reproductive dynamics. Ecological factors like habitat heterogeneity are relevant for dispersal, although its importance is greater for SDD, lowering the invasion velocity. Among the life history traits considered, adult mortality, the juvenile bank and mean dispersal distance are the most relevant for SDD. For LDD, habitat heterogeneity and changes in life history traits are not so relevant, causing minor changes in the values of the scale-free parameters. Our work on short and long distance dispersal shows novel theoretical differences between SDD and LDD in invasive systems (mechanisms of pattern formation, fractal and scaling properties, relevance of different life history traits and habitat variables) that correspond closely with field examples and were not analyzed, at least in this degree of detail, by the previously existing models. © 2011 The Authors. Ecography © 2011 Ecography.

Published
2011

20. Spatial patterns of tree size and mortality of pedunculate oak ( Quercus robur L.) in a forest of the Cantabria lowlands

Author

Rozas Ortiz, Vicente Fernando and Fernández Prieto, José Antonio

Subjects
Autocorrelación espacial, Quercus robur L, education, Ripley's K, Competencia intraespecífica, Patrones espaciales, Dinámicas de poblaciones, K de Ripley, Spatial patterns, Tree population dynamics, Mortalidad, Mortality, Intraspecific competition, Spatial autocorrelation
Abstract

[EN] Quantitative spatial analysis provide inferences on tree population dynamics. Spatial patterns of pedunculate oak (Quercus robur L. ) in two forest plots were analysed in this work. Significative evidences of clumping for trees of smaller sizes and a random pattern for larger-sized ones were given. This results would be related to self-thinning occurrence. Open space availability seems to be the main factor that drive the structure evolution and the regeneration and mortality processes within oak populations. In one of the studied stands, poor spatial arrangement and random mortality are linked to oak populations developed in open space, and there are evidences of scarce intraspecific competition. In the other studied stand, established in old-growth forest, oak regeneration occurs in canopy gaps and, as a result, even-sized groups of trees in different ripeness stage arise. In the old-growth plot, oak mortality mainly occurs within small-sized groups of trees as a consequence of intraspecific competition., [ES] La descripción e interpretación de los patrones espaciales de los árboles permite extraer conclusiones sobre los factores que condicionan tanto el establecimiento de las cohortes como su variación temporal. En el presente trabajo se analizan las distribuciones espaciales de tamaño y mortalidad del roble (Quercus robur L. ) en dos parcelas de bosque. Obtenemos evidencias significativas de agregación para las clases de tamaño pequeñas y de distribución aleatoria en la clase de tamaño mayor. La disponibilidad de espacios abiertos parece ser el principal factor que condiciona la regeneración, estructura y mortalidad en las poblaciones de roble. Una de las poblaciones estudiadas se habría originado sin limitación de espacios abiertos, presentando poca organización espacial y un patrón aleatorio de la mortalidad, lo cual es indicativo de una escasa incidencia de la competencia intraespecífica. En otra población, que corresponde a una parcela de bosque maduro con escasos espacios abiertos, la regeneración del roble está asociada a «fase de claro», formándose grupos compuestos por árboles de tamaños similares y en distintas fases de madurez. En este caso, la mortalidad de roble tiene lugar predominantemente dentro de los grupos formados por árboles de poca talla y está, al menos en parte, causada por competencia intraespecífica.

Published
1998

21. Patrones espaciales de tamaño y mortalidad del roble (Quercus robur L.) en un bosque del litoral de Cantabria

Author

Rozas Ortiz, Vicente Fernando and Fernández Prieto, José Antonio

Subjects
Spatial patterns, Autocorrelación espacial, Tree population dynamics, Quercus robur L, Mortalidad, Ripley's K, Mortality, Competencia intraespecífica, Intraspecific competition, Patrones espaciales, Dinámicas de poblaciones, Spatial autocorrelation, K de Ripley
Abstract

[EN] Quantitative spatial analysis provide inferences on tree population dynamics. Spatial patterns of pedunculate oak (Quercus robur L. ) in two forest plots were analysed in this work. Significative evidences of clumping for trees of smaller sizes and a random pattern for larger-sized ones were given. This results would be related to self-thinning occurrence. Open space availability seems to be the main factor that drive the structure evolution and the regeneration and mortality processes within oak populations. In one of the studied stands, poor spatial arrangement and random mortality are linked to oak populations developed in open space, and there are evidences of scarce intraspecific competition. In the other studied stand, established in old-growth forest, oak regeneration occurs in canopy gaps and, as a result, even-sized groups of trees in different ripeness stage arise. In the old-growth plot, oak mortality mainly occurs within small-sized groups of trees as a consequence of intraspecific competition. [ES] La descripción e interpretación de los patrones espaciales de los árboles permite extraer conclusiones sobre los factores que condicionan tanto el establecimiento de las cohortes como su variación temporal. En el presente trabajo se analizan las distribuciones espaciales de tamaño y mortalidad del roble (Quercus robur L. ) en dos parcelas de bosque. Obtenemos evidencias significativas de agregación para las clases de tamaño pequeñas y de distribución aleatoria en la clase de tamaño mayor. La disponibilidad de espacios abiertos parece ser el principal factor que condiciona la regeneración, estructura y mortalidad en las poblaciones de roble. Una de las poblaciones estudiadas se habría originado sin limitación de espacios abiertos, presentando poca organización espacial y un patrón aleatorio de la mortalidad, lo cual es indicativo de una escasa incidencia de la competencia intraespecífica. En otra población, que corresponde a una parcela de bosque maduro con escasos espacios abiertos, la regeneración del roble está asociada a «fase de claro», formándose grupos compuestos por árboles de tamaños similares y en distintas fases de madurez. En este caso, la mortalidad de roble tiene lugar predominantemente dentro de los grupos formados por árboles de poca talla y está, al menos en parte, causada por competencia intraespecífica.

Published
1998

22. Patrones espaciales de tamaño y mortalidad del roble (Quercus robur L.) en un bosque del litoral de Cantabria

Author

Rozas, Vicente, Fernández Prieto, José A., Rozas, Vicente, and Fernández Prieto, José A.

Abstract

La descripción e interpretación de los patrones espaciales de los árboles permite extraer conclusiones sobre los factores que condicionan tanto el establecimiento de las cohortes como su variación temporal. En el presente trabajo se analizan las distribuciones espaciales de tamaño y mortalidad del roble (Quercus robur L.) en dos parcelas de bosque. Obtenemos evidencias significativas de agregación para las clases de tamaño pequeñas y de distribución aleatoria en la clase de tamaño mayor. La disponibilidad de espacios abiertos parece ser el principal factor que condiciona la regeneración, estructura y mortalidad en las poblaciones de roble. Una de las poblaciones estudiadas se habría originado sin limitación de espacios abiertos, presentando poca organización espacial y un patrón aleatorio de la mortalidad, lo cual es indicativo de una escasa incidencia de la competencia intraespecífica. En otra población, que corresponde a una parcela de bosque maduro con escasos espacios abiertos, la regeneración del roble está asociada a «fase de claro», formándose grupos compuestos por árboles de tamaños similares y en distintas fases de madurez. En este caso, la mortalidad de roble tiene lugar predominantemente dentro de los grupos formados por árboles de poca talla y está, al menos en parte, causada por competencia intraespecífica., Quantitative spatial analysis provide inferences on tree population dynamics. Spatial patterns of pedunculate oak (Quercus robur L.) in two forest plots were analysed in this work. Significative evidences of clumping for trees of smaller sizes and a random pattern for larger-sized ones were given. This results would be related to self-thinning occurrence. Open space availability seems to be the main factor that drive the structure evolution and the regeneration and mortality processes within oak populations. In one of the studied stands, poor spatial arrangement and random mortality are linked to oak populations developed in open space, and there are evidences of scarce intraspecific competition. In the other studied stand, established in old-growth forest, oak regeneration occurs in canopy gaps and, as a result, even-sized groups of trees in different ripeness stage arise. In the old-growth plot, oak mortality mainly occurs within small-sized groups of trees as a consequence of intraspecific competition.

Published
1998

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