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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. 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

9. 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

10. 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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11. 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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