Populations Of Tree Species Research Articles

A bridge too far: cold and pathogen constraints to assisted migration of riparian forests

Assisted migration of warm‐adapted genotypes to currently cooler climates may reduce maladaptation from future climate change. Few assisted migration trials have considered limitations of the cooler climates and pathogens currently present at transplant sites. This is especially important to consider in riparian ecosystems that are priority targets for restoration in the western United States as they harbor diverse communities. In an effort to validate assisted migration as an effective strategy for mediating the negative impacts of climate change, we used a provenance trial with replicated genotypes from 19 populations of the foundation riparian tree species, Fremont cottonwood (Populus fremontii), transplanted to a cold site to test for genetic variation in growth, mortality, and resistance to shoot blight fungi (Venturiasp.). Populations from cool sites had up to 4 times faster growth, 3 times higher survival, and 8 times higher resistance toVenturiathan populations from warm sites, providing evidence of local adaptation to both climate and pathogenic fungi. Budburst phenology and shoot blight were correlated with frost damage, subsequent shrub‐form architecture, and mortality. While climate change models predict 6°C increases, plants transferred distances of 6°C at this time would not perform well; an intermediate transfer distance of less than 3°C would avoid maladaptation to the current environment during assisted migration. Thus, multiple and intermediate transfer phases to supplement local genetic variation will likely be necessary for effective assisted migration to accommodate current environments and large changes in climate.

Inbreeding depression at the sapling stage and its genetic consequences in a population of the outcrossing dominant tree species, Castanopsis sieboldii

Highly frequent pollination at short distances combined with spatial genetic structure (SGS) among reproductive individuals, as observed in populations of many forest tree species, may lead to highly frequent pollinations between genetically related individuals located close to each other. This could increase frequencies of biparental inbreeding and strengthen the degree of SGS across generations. However, the degree of SGS observed in forest tree populations is not usually strong, suggesting that such processes are restricted by other factors, which may include inbreeding depression. To test this hypothesis, we examined inbreeding depression in Castanopsis sieboldii saplings in a population known to have significant SGS and high frequencies of short-distance pollination. We determined genotypes at eight microsatellite loci of 125 adult trees and 899 saplings in a 4-ha plot. The neighborhood model approach, assuming an exponential power function, showed highly frequent pollination at short distance among parents of saplings. SGS was significantly stronger among saplings than among adults. The average value of F is (individual inbreeding coefficient based on kinship coefficients between genes within individuals) was also significantly higher among saplings than among adults. Furthermore, average values for saplings were relatively high (0.036–0.052) in 30–50 to 90–110 cm height classes and rapidly decreased to 0.006 for the ≥110-cm class. Analysis of covariance, taking into account the canopy state, showed that inbreeding depression had a significant negative effect on the saplings’ height. Thus, the level of inbreeding in saplings decreased with size classes increasing, probably due to pronounced inbreeding depression resulting in mortality or reduced growth of inbred saplings, and hence, the inbreeding depression may prevent increasing of the level of inbreeding and the degree of SGS in subsequent generations.

A comparative structural and functional study of leaf traits and sap flow in Dracaena cinnabari and Dracaena draco seedlings.

Water relations for two remote populations of Dracaena tree species from the dragon tree group, Dracaena cinnabari Balfour f. and Dracaena draco (L.) L., were studied to test our hypothesis that morphological and anatomical differences in leaf structure may lead to varied functional responses to changing environmental conditions. Sap flow measurements were performed using the heat field deformation method for four Dracaena seedlings grown in one glasshouse and two greenhouses, and leaf traits related to plant-water relationships were characterised. All traits studied confirmed that D. cinnabari leaves are more xeric in their morpho-anatomical structure compared with D. draco leaves. No radial sap flow variability was detected in D. draco plant stems, whereas sap flow was found to be higher in the inner part of D. cinnabari stems. The regular occurrence of reverse sap flow at night in both Dracaena species was consistent with a staining experiment. Vapour pressure deficit (VPD) was found to be the main driver for transpiration for both Dracaena species. However, the relationship between VPD and sap flow appeared to be different for each species, with a clockwise or no hysteresis loop for D. draco and a counter-clockwise hysteresis loop for D. cinnabari. This resulted in a shorter transpiration cycle in D. cinnabari. The observed superior water-saving strategy of D. cinnabari corresponds to its more xeric morpho-anatomical leaf structure compared with D. draco.

Conservation of tropical forest tree species in a native timber plantation landscape

Tropical terrestrial environments are becoming dominated by anthropogenic land-uses, making retention of biodiversity in production landscapes of critical conservation importance. Native timber plantations may represent a land-use capable of balancing production and conservation by potentially supporting understorey plant and tree species otherwise restricted to old-growth forests, with little impact on yield. In this study we investigated the conservation value of native plantation forests in the lowlands of New Britain, Papua New Guinea. We compared the composition of tree species (⩾10cm DBH) of unlogged forest to those of different aged native Eucalyptus deglupta plantations and intervening (historically logged) secondary forests. We found a high capacity for biodiversity conservation within plantations, with 70% of forest tree species persisting in mature plantations (13–15years old). However, compositional analyses revealed lower numbers of large individuals (⩾10cm DBH) in both late-successional and non-vertebrate-dispersed species in the plantations, indicating the difficulty of retaining mature old-growth forest trees in production land-uses. Secondary forest protected by conservation reserves was compositionally indistinct to unlogged forest. Our results demonstrate the potential for tropical native timber plantations to contribute to the retention of biodiversity. However, appropriate management is required to ensure the persistence of source populations of old-growth forest tree species. With careful planning a balance between production and conservation can be achieved in lowland tropical regions.

Genetic and ontogenetic variation in an endangered tree structures dependent arthropod and fungal communities.

Plant genetic and ontogenetic variation can significantly impact dependent fungal and arthropod communities. However, little is known of the relative importance of these extended genetic and ontogenetic effects within a species. Using a common garden trial, we compared the dependent arthropod and fungal community on 222 progeny from two highly differentiated populations of the endangered heteroblastic tree species, Eucalyptus morrisbyi. We assessed arthropod and fungal communities on both juvenile and adult foliage. The community variation was related to previous levels of marsupial browsing, as well as the variation in the physicochemical properties of leaves using near-infrared spectroscopy. We found highly significant differences in community composition, abundance and diversity parameters between eucalypt source populations in the common garden, and these were comparable to differences between the distinctive juvenile and adult foliage. The physicochemical properties assessed accounted for a significant percentage of the community variation but did not explain fully the community differences between populations and foliage types. Similarly, while differences in population susceptibility to a major marsupial herbivore may result in diffuse genetic effects on the dependent community, this still did not account for the large genetic-based differences in dependent communities between populations. Our results emphasize the importance of maintaining the populations of this rare species as separate management units, as not only are the populations highly genetically structured, this variation may alter the trajectory of biotic colonization of conservation plantings.

Ungulate Impact on Natural Regeneration in Spruce-Beech-Fir Stands in Černý důl Nature Reserve in the Orlické Hory Mountains, Case Study from Central Sudetes

The paper presents the results of a study on tree regeneration of forest stands in the Černý důl Nature Reserve, which is situated in the Orlické hory Mountains Protected Landscape area in the Czech Republic. Research was conducted in a spruce-beech stand with an admixture of silver fir, sycamore maple and rowan on two comparative permanent research plots (PRPs) (PRP 1—fenced enclosure and PRP 2—unfenced). Typological, soil, phytosociological and stand characteristics of the two PRPs are similar. The results showed that ungulate browsing is a limiting factor for successful development of natural regeneration of autochthonous tree species. The population of tree species of natural regeneration on the fenced plot (PRP 1) is sufficient in relation to the site and stand conditions. However, natural regeneration on PRP 2 is considerably limited by browsing. Damage is greatest to fir, sycamore maple and rowan; less severe to beech; and the least to spruce.

Forest trees in human modified landscapes: ecological and genetic drivers of recruitment failure in Dysoxylum malabaricum (Meliaceae).

Tropical agro-forest landscapes are global priority areas for biodiversity conservation. Little is known about the ability of these landscapes to sustain large late successional forest trees upon which much forest biodiversity depends. These landscapes are subject to fragmentation and additional habitat degradation which may limit tree recruitment and thus compromise numerous ecosystem services including carbon storage and timber production. Dysoxylum malabaricum is a large canopy tree species in the Meliaceae, a family including many important tropical timber trees. This species is found in highly fragmented forest patches within a complex agro-forest landscape of the Western Ghats biodiversity hot spot, South India. In this paper we combined a molecular assessment of inbreeding with ecological and demographic data to explore the multiple threats to recruitment of this tree species. An evaluation of inbreeding, using eleven microsatellite loci in 297 nursery-reared seedlings collected form low and high density forest patches embedded in an agro-forest matrix, shows that mating between related individuals in low density patches leads to reduced seedling performance. By quantifying habitat degradation and tree recruitment within these forest patches we show that increasing canopy openness and the increased abundance of pioneer tree species lead to a general decline in the suitability of forest patches for the recruitment of D. malabaricum. We conclude that elevated inbreeding due to reduced adult tree density coupled with increased degradation of forest patches, limit the recruitment of this rare late successional tree species. Management strategies which maintain canopy cover and enhance local densities of adult trees in agro-forest mosaics will be required to ensure D. malabaricum persists in these landscapes. Our study highlights the need for a holistic understanding of the incipient processes that threaten populations of many important and rare tropical tree species in human dominated agro-forest landscapes.

First Proposal Of Seed Regions For Frankincense Trees (Boswellia Spp.) On Socotra Island

Abstract The landscape differentiation on seed regions is used in the Czech forestry industry for purposes of seed transfers. The seed regions are created for main commercial tree species and the rules for transfer among these regions are described. The geobiocoenological landscape differentiation and differences among tree species populations were used as main approaches. The same principle is used for Boswellia seed regions differentiation on Socotra island. Eight species of Boswellia genus were determined on the island, all species being endemic. The differentiation is based on Boswellia populations field survey. All populations were described in morphological signs. The vegetation zones and geomorphological differentiation were also taken into account. The result is a map of seed regions for every Boswellia species on Socotra island presented in the article.

Diagnosing the demographic balance of two light-demanding tree species populations in central Africa from their diameter distribution

The diameter distribution of a tree species population in a natural forest reflects its demographic dynamics and the impact of past disturbances. A modal diameter distribution can be the mark of a demographic imbalance or it can be the consequence of a particular growth pattern. By comparing the observed diameter distribution with the one that follows from a reference growth model under the hypothesis of demographic balance, we diagnosed demographic balance. In a forest concession in Gabon before logging, an unbalanced diameter distribution was found for Aucoumea klaineana, a long-lived pioneer species and also a valuable commercial species. The Aucoumea klaineana population consisted of old trees without meaningful recruitment, thus indicating an ageing, declining population. In contrast, in the same concession, a balanced diameter distribution was found for Lophira alata, a pioneer to moderate light-demanding species. The history of this forest concession, once heavily populated and subsequently depleted from human perturbation (shifting cultivation), can be used to interpret these demographic statuses. These results reinforce the view of a forest that is constantly changing and shaped by past human perturbations, with the implication for its conservation that some kind of perturbation should be maintained.

Microsatellite primers identified by 454 sequencing in the floodplain tree species Eucalyptus victrix (Myrtaceae).

• Premise of the study: Microsatellite primers were developed for Eucalyptus victrix (Myrtaceae) to evaluate the population and spatial genetic structure of this widespread northwestern Australian riparian tree species, which may be impacted by hydrological changes associated with mining activity.• Methods and Results: 454 GS-FLX shotgun sequencing was used to obtain 1895 sequences containing putative microsatellite motifs. Ten polymorphic microsatellite loci were identified and screened for variation in individuals from two populations in the Pilbara region. Observed heterozygosities ranged from 0.44 to 0.91 (mean: 0.66) and the number of alleles per locus ranged from five to 25 (average: 11).• Conclusions: These microsatellite loci will be useful in future studies of population and spatial genetic structure in E. victrix, and inform the development of seed sourcing strategies for the species.

Regeneration Failure in a Remnant Stand of Pignut Hickory (Carya glabra) on a Protected Barrier Island in Georgia, USA

Maritime forest communities on barrier islands along the Atlantic and Gulf coasts have been severely fragmented by a continuous history of human land use and natural disturbance. Isolated populations of certain tree species in maritime forest fragments may now be too small to be viable and their inability to regenerate may result in their eventual elimination from barrier islands. Using an 11-year study of a population of pignut hickory (Carya glabra), a common species of remnant maritime forest stands on St. Catherine's Island, Georgia, we present a case study of tree regeneration failure on a barrier island. We found that there has been no recruitment of new hickory individuals into the canopy of this population over the last 65 years. Field evidence of browse and a strong correlation between seedling density distributions and microsite protection from herbivory suggest that this trend in recruitment failure is related to an increased abundance of deer (Odocoileus) and pigs (Sus) on the island. Using a size class population projection model, we estimated that, if such recruitment failure and mortality rates continue, the hickory population will be extirpated from the maritime forest within 200 years. Tree species that are failing to regenerate within maritime forests represent a special challenge that is not currently being addressed in the long-term management of barrier island biodiversity.

Comparative Evaluation Of Tree Species Populations Under Different Land Use Types Within The University Of Port Harcourt Environs

Impact of land use changes and varying levels of habitat disturbance on tree populations was evaluated using the spatial analogue technique of studying ecosystem dynamics. Three sites with low, moderate, and high levels of disturbance were purposively chosen from the Biodiversity Conservation Area (BCA), an Unprotected Secondary Regrowth (USR), and an Arable Farmland (AF) respectively, for the study. Tree density and alpha diversity were evaluated in each site. The level of tree species compositional similarity/variation was also ascertained for each pair of the sites, and the extent of change in populations of individual tree species measured for the unprotected sites – USR and AF. Total tree density was highest in BCA (466 trees/hectare) followed by USR (317 trees/hectare) and AF (73 trees/hectare). Tree diversity was highest and lowest in BCA and AF respectively. Tree species compositional variation was higher between BCA and each of USR & AF (66.7%), than between USR and AF (57.1). Harungana madagascariensis, Berlinia grandiflora, and Eleais guineensis were the most abundant tree species in BCA, USR, and AF, respectively. Although, populations of many tree species were found to be drastically reduced or completely lost in the unprotected sites, improvement was observed in populations of few species with Spondias mombin having the highest improvement index (314.29%) in USR while E. guineensis had the highest improvement index (72.7%) in AF. S. mombin is highly valued in the study area because of its edible fruits and diverse medicinal attributes while palm oil and palm kernel oil from E. guineensis contribute immensely to rural livelihoods. Hence, the rural dwellers tend to favour and encourage their growth. Tropical Agricultural Research and Extension 15(1): 2012: page 1-7 DOI: http://dx.doi.org/10.4038/tare.v15i1.5236

庐山森林景观格局变化的长期动态模拟

Forest succession is a naturally occurring process of reorganization which occurs constantly in forest ecosystems; the term refers to the process of one plant community being replaced by another over time. The process of forest vegetation ecological succession is driven by underlying natural conditions and anthropogenic disturbance. We can infer dynamic changes of landscape patterns and corresponding ecological processes of forest succession using forest landscape dynamic analysis based on vegetation patterns. Research related to vegetational succession provides a foundation for the understanding of dynamic changes of forest landscape patterns. The changes of forest landscape pattern also influence nutrient cycling and energy flows in forest ecosystems while restricting a variety of ecological processes. As a result,the study on forest landscape patterns explains very important dynamic processes of forest succession.The natural laboratory of Mount Lushan provides a unique site for studying ecological succession as it relates to vegetation and restoration ecology. The study of forest succession is the foundation of recovery and restoration activities. This type of research depends on the study of ecological succession of vegetation which can provide a basis for understanding the dynamics of landscape change. Using the spatially explicit landscape simulation model( LANDIS),this paper analyzes forest vegetation on Mount Lushan,by stimulating the dynamics of the vegetation's ecological succession in the next 300 aunder undisturbed natural conditions,and determines the representative landscape pattern indices of each patch. This process includes measures of the proportion of the landscape covered by each type of patch area as well as determining the values for the aggregation,fractal dimension,diversity and evenness indices. This process allows the analysis of the spatial distribution pattern of dominant tree species,which helps reveal the factors regulating vegetation succession and helps predict the future trends in variation of the forest landscape. Finally,the theoretical basis for successfully realizing sustainable development of forest resources is discussed. The results indicate:( 1) Over the next 300 a,the extent of a stable populations of broad-leaved tree species will tend to increase; ecological succession in the entire Mount Lushan forest ecosystem is moving in the direction of the reformation of a complex zonal evergreen broad-leaved forest system.( 2) The aggregation index for broad-leaved tree species exhibits a pattern of slow growth in the next 150 a,and then stabilizes after 150 a. The aggregation index of fir remained steady for the entire 300 a while the degree of aggregation for moso bamboo declined steadily throughout the entire simulation until it stabilized during the end stage of the simulation.( 3) The fractal dimension of all dominant tree species is between 1 and 1. 1,illustrating that the edge of each patch is relatively inerratic and experiences small changes during natural forest vegetation succession.( 4) The diversity index of the research region initially tended to increase and later maintained a slow rate of decline. Also,the evenness index initially declined,then rose and went into a slow decline at the end of the simulation. The results of the simulation indicate that the Mount Lushan ecosystem is trending toward an optimal climax community based on the natural forces of ecological succession occurring in the forest community. During this natural ecological succession,various species predominate before the climate evergreen broad-leaved forest stage becomes dominant. In the next 300 years,the reforestation program implemented in the 1960s will not have an obvious influence on climax forest landscape patterns in Mount Lushan. Our research provides a scientific foundation for current and future forest landscape management practices on Mount Lushan. In the long run,we should continue to implement a strict policy of protecting hillside forest habitat to facilitate ongoing afforestation efforts.

Patterns of Forest Decline and Regeneration Across Scots Pine Populations

To predict future changes in forest ecosystems, it is crucial to understand the complex processes involved in decline of tree species populations and to evaluate the implications for potential vegetation shifts. Here, we study patterns of decline (canopy defoliation and mortality of adults) of four Scots pine populations at the southern edge of its distribution and characterized by different combinations of climate dryness and intensity of past management. General linear and structural equation modeling were used to assess how biotic, abiotic, and management components interacted to explain the spatial variability of Scots pine decline across and within populations. Regeneration patterns of Scots pine and co-occurring oak species were analyzed to assess potential vegetation shifts. Decline trends were related to climatic dryness at the regional scale, but, ultimately, within-population forest structure, local site conditions, and past human legacies could be the main underlying drivers of Scots pine decline. Overall, Scots pine regeneration was negatively related to decline both within and between populations, whereas oak species responded to decline idiosyncratically across populations. Taken together, our results suggest that (1) patterns of decline are the result of processes acting at the plot level that modulate forest responses to local environmental stress and (2) decline of adult Scots pine trees seems not to be compensated by self-recruitment so that the future dynamics of these forest ecosystems are uncertain.

Insights in the chestnut genetic diversity in Canton Ticino (Southern Switzerland)

AbstractCastanea sativa Miller displays a high variability of morphological and ecological traits, vegetative and reproductive habits, nut morphology, wood characteristics, adaptability, and resistance to biotic and abiotic stresses. The present range of distribution of the species has been strongly influenced by human migrations and it is thought that Romans played a crucial role in the spread of the cultivation in Europe, although in some areas there is also evidence of local domestication and spontaneous spread of the tree after the last glacial period. In Switzerland chestnut stands are found mostly in the South (Canton Ticino), a region where the debate about the origin of the local germplasm, whether derived from the survival or spontaneous migration of C. sativa on the territory or due to the introduction of the tree during the Roman colonisation, is still open. This study aims contributing to depict the chestnut genetic situation of the species in Canton Ticino as a contribution to the debate about the native character of the species. The study area is located in Switzerland, on the southern slopes of the Alps, where 3 C. sativa populations were sampled and analysed at 9 SSR loci. Populations showed a high degree of diversity, as it is observed in most natural population of tree species: all nine SSR loci were polymorphic (no fixed alleles were detected), and genetic diversity, measured by expected heterozygosity, was high ranging in the populations between 0.647 and 0.721, on average. Results suggest that three homogeneous gene pools contributed to the formation of the 3 populations sampled. The genetic germplasm structuring of the analysed chestnut stands is very mild as confirmed by the relatively low level of genetic differentiation and divergence observed among sites.

Environmental framework to visualize emergent artificial forest ecosystems

We propose an environmental framework for simulation and visualization of woody plant forests. A complex application software system develops and animates a spontaneous afforestation process within this environment. The system considers several environmental properties and combines computer animation with artificial life. The main goal of the presented software system is to use it in computer animation for synthesis of natural environments and visual analysis of their natural look credibility. The afforestation process is modeled as an ecosystem simulation, where trees struggle for survival based on several growth factors. A detailed description of the procedures for simulating tree growth and the factors that might influence tree growth is provided. All the tree growth simulation procedures and factors are biologically inspired. They have been defined mathematically in the paper by designing a bottom-up agent model which emerges the artificial tree distribution by mediating to the simulation.A flexible and adaptable procedural 3D model is used to visualize trees. Also, growth of individual trees is animated, from development of branch complexity to per-leaf precision, which allows a very realistic perception of the emerging ecosystem. The visualization of trees is sped up so that the models of trees have progressively lower-details proportional to the distance from a certain point of view. Locations and maturity of visualized trees are obtained from the ecosystem simulation results, and the afforestation process is animated over several centuries. The natural look of the artificial tree distribution is confirmed visually and statistically. Visually, it is confirmed from rendered sequences, and statistically, from graphs of tree species populations. Several patterns emerge permanently, such as the number of trees in the ecosystem simulation increasing exponentially and trees growing in communities.

Interaction between tree species populations and windthrow dynamics in natural beech-dominated forest, Czech Republic

Interactions between pit-mound dynamics and tree species populations were studied in a natural mountain (fir)-spruce-beech forest. Pit-mounds are special habitats with unique erosion-sedimentation and microclimatic conditions, which continually influence the trees growing there. Our assumption was that these factors would impact on the competitive potential of the trees and that the interaction between the pit-mound dynamics and the tree layer would not be static, but would change depending on the ages of both the trees and the pit-mounds.Over an area of 74.2ha that was repeatedly studied in 1975, 1997, and 2008 in terms of the tree layer structure (about 23,000 trunks), pit-mound evaluation was performed on a regular network of 354 circular plots with a 23m diameter (1733 pit-mounds in total). Dendrochronological cores were drilled in 1986 samples in order to establish an age structure of the tree layer. Using tree-census, dendrochronological, and mathematical methods, direct or indirect dating of the pit-mounds was performed. The actual occurrence of trees on the pit-mounds was compared with a null model corresponding to random occurrence for various age categories of the trees/pit-mounds.The number of trees decreased smoothly with age in the respective classes. The dominant species was Fagus sylvatica, which like Picea abies and Abies alba reached an age of >450years. A multi-peak pit-mound age structure suggested the occurrence of stronger episodic disturbance events in the past. Mounds covered 8.5% and pits 3.7% of the studied area (121pieces/ha) and the average pit-mound size was 9.92m2. F. sylvatica and other marginally represented trees (A. alba, Sorbus aucuparia, Acer pseudoplatanus, Ulmus glabra) significantly preferred mounds over other microsites (χ2=147.37, p<0.001; resp. χ2=14.73, p=0.005). The preference to mounds by marginally represented tree species decreased with the age of the trees, whereas the affinity of F. sylvatica increased with age. Also, older individuals of P. abies were more frequently found on mounds compared to the null model, although the overall presence of P. abies on mounds was significantly deficient (χ2=11.21, p=0.024). These results suggest that the competitive potential of the trees on mounds decreases with age only in trees of initial succession stages. Mounds older than 101years were most favourable to natural regeneration.

A simulation study on the behavior of allelic richness and inbreeding coefficient over generations in fragmented populations of tree species

Computer simulations were employed in this study aiming to understand the effects of repeated cycles of inbred mating in isolated populations of tree species with different effective sizes and over up to 1000 generations. The results revealed a susceptibility of allelic richness to both, population size and repeated generations under inbred mating and a low but significant increase of the inbreeding coefficient over generations in populations with 50 and 100 plants, but not in populations with 500 and 1000 individuals. The loss of alleles occurred throughout all generations and was largely influenced by the population size. The most outstanding increase in the inbreeding coefficient occurred from the initial generation to the 5th generation, independent of the population size. The comparison of simulated results with data obtained from a field studie corroborated the hy pothesis that isolated populations tend to more drastically suffer with loss of alleles and increase of inbreeding coefficient, wh ile continuous forests, with effective production of fertile seeds and regeneration of seedlings, are inclined to preserve comparatively higher allelic richness and lower inbreeding coefficient over generations. In general, the results obtained highlight the importance of special care in selecting ESUs and preserving isolated populations, towards the conservation of forest genetic resources and adapatedness preservation

Estimation of Population of Ten Selected Forest Tree Species Used by Communities around Kalinzu Forest Reserve, South-Western Uganda

Local communities depend on Kalinzu Forest Reserve (KFR) for plant resources. This resource utilization affects the population of tree species in the forest. This study set out to estimate the population of ten tree species in the forest. Results of this study are hoped to provide a basis for studying future changes in population dynamics of the species. The ten species selected were: Newtonia buchananii, Cynometra alexandrei, Teclea nobilis, Prunus africana, Entandrophragma exelsum, Sapium ellipticum, Diospyros abyssinica, Zanthoxylum gilletii, Rytiginia kigeziensis and Spathodea nilotica. Their selection was based on the results of a study (Aine-Omucunguzi et al., 2010) about utilization of plant resources by the local people around KFR. Species with high demand from the local people were selected. Alternate nested quadrants along five line transects, were used to estimate the population. The plants were categorized into three classes as trees (>5 cm diameter at breast height), saplings (2 cm root collar diameter-5 cm diameter at breast height) and wildings (<2 cm root collar diameter). Population, population density, relative density, frequency, and relative frequency of each species were determined. Generally, the number of wildings, saplings and trees of each species increased away from the forest edge inwards. For all the species, wildings had the highest population density followed by saplings and then trees. Teclea nobilis had the highest number of individual per hectare, followed by Newtonia buchananii, while Rytiginia kigeziensis and Spathodea nilotica had the lowest number of individuals per hectare.

Heterogeneous genetic structure in a natural population of Raulí (Nothofagus nervosa)

Heterozygote deficiencies in natural populations of outbreeding tree species are common and thought to be due mainly to biparental inbreeding. Inbreeding is believed to be caused by family structure within populations, a product of limited seed dispersal and probably limited pollen dispersal. Although both theory and simulation studies predict that structure should be apparent where trees are isolated by distance, most studies of structure in natural populations have detected only a weak spatial genetic structuring. In this contribution, we compare the use of spatial autocorrelation methodology and F statistics with the concept of relatedness to examine the spatial genetic structure in the natural population of a native southern beech and to explore the discrepancy between theory and observations. Autocorrelation detected structure in only a few of the nine enzyme loci tested in an estimated patch size of approximately 10 m. By successively eliminating the largest distances in the Gabriel map, the population was separated into groups or patches of neighbors, which were then tested for relatedness. Three groups of relatives were found interspersed with seven groups of unrelated individuals. The F statistics for these groups also showed weak genetic structure. We suggest that heterogeneity of family structure within natural populations may be one reason why more spatial genetic structure has not been detected