Effects of selective logging on the mating system and pollen dispersal of Hymenaea courbaril L. (Leguminosae) in the Eastern Brazilian Amazon as revealed by microsatellite analysis

Using nine microsatellite loci, we studied the effects of selective logging on genetic diversity, mating system and pollen dispersal in a population of the tree species Hymenaea courbaril, located in a 546 ha plot in the Tapajós National Forest, Pará State, Brazil. We analyzed 250 offspring (nursery reared seedlings) collected after a logging episode from 14 open-pollinated seed trees. These were compared to 367 seedlings from 20 open-pollinated seed trees previously collected from the pre-logging primary forest. The genetic diversity was significantly lower in the post-logging seed cohort. In contrast to the pre-logging population, significant levels of selfing were detected in the post-logging population (t_m = 0.962, P < 0.05). However, correlated matings were reduced and the effective number of pollen donors almost doubled after harvesting (3.8 against 7.2). Logging also reduced pollen immigration into the plot (from 55% to 38%) and we found no significant correlation between the size of the pollen donors and the number of seeds fathered. Inside the plot, pollen dispersal distance was shorter before logging than after (827 and 952 m, respectively) and the reproductive pollination neighbor area (A_ep) was larger (average of 178 ha). The individual and average variance effective population size within families (ranged from 1.80 to 3.21, average of 2.47) was lower than expected in panmictic populations (N_e = 4). The results indicate that while logging greatly reduced the levels of genetic diversity after logging, it also increased genetic recombination within the population and constrained crossing among related individuals. The results show that low-density tropical tree species such as H. courbaril, when harvested in moderate levels may be resilient to a reduction in the reproductive population and may maintain similar levels of outcrossing and pollen dispersal after logging.     

Roles of seed and pollen dispersal in natural regeneration of Castanopsis fargesii (Fagaceae): Implications for forest management

Natural regeneration is an important process to reverse the loss of forests. Understanding the process of natural regeneration is crucial for achieving sustainable forest management. In this study, we examined the effects of seed and pollen dispersal in naturally regenerated populations of Castanopsis fargesii. Genetic variation in six populations along two successional series (three successional stages in each series: early, pre-climax, and climax) was assayed using RAPD (random amplified polymorphic DNA) markers. High genetic variability was observed as measured with Shannon's information index. A majority of genetic variation was distributed within populations (Φ_st = 0.1271) and significant isolation by distance existed among populations. A contrasting pattern of genetic variation along these two series was observed, representing different scenarios of natural regeneration processes. The ratio of the number of migrants between the mature populations to the number of migrants from the mature to immature populations was estimated as 1.146 ± 0.099 to 1.981 ± 0.164, implying that comparable seed and pollen dispersal might exist at a fine spatial scale (∼2 km²). The results suggest the critical role of seed dispersal in shaping genetic composition and diversity in the second-growth forests. Barriers to seed dispersal from a variety of genetic sources could result in low genetic diversity in naturally regenerated populations. Management that facilitates the connectivity of newly regenerated stands with mature forests could be effective for natural regeneration given the predominant role of short-distance dispersal of seeds in this species.     

Effect of patch size and isolation on mating patterns and seed production in an urban population of Chinese pine (Pinus tabulaeformis Carr.)

Fragmentation is a critical issue for tree populations because the creation of small patches can reduce local population size and increase isolation, both of which can promote inbreeding and its negative consequences, as well as loss of genetic diversity. To test the hypothesis that patch size and isolation influence mating patterns or seed production in forest trees, we utilize the spatial array of trees of an urban population of Chinese Pine (Pinus tabulaeformis Carr.) planted in patches around Beijing. Our design includes 28 urban patches, with patch size ranging from 1 to 2000 adult trees and isolation (edge distance index) ranging from 37.5 m to 245.8 m. We examined the average number of seeds per cone and percentage of viable seed per cone for each patch as measures of seed production. By utilizing seven paternally inherited chloroplast microsatellite loci, we estimated the mating pattern parameters for each patch, including the level of selfing, the amount of immigrant pollen and the effective number of pollen sources (N_ep). Using a general linear model selection procedure based on AIC value, we found patch size was the best predictor of the selfing and immigration rate; smaller patches had a higher selfing and immigration rate. Small patches with one adult had relatively high N_ep which indicates connectivity among urban patches. However, due to the reduced amount of immigrant pollen and limited diversity of local pollen, intermediate sized patches (with 5–10 adults) had the lowest N_ep among the study patches. For patches with more than 10 adults, N_ep was increased with patch size. The percentage of viable seeds per cone significantly decreased with patch size, indicating a possible negative consequence of inbreeding. The effect of patch size on mating patterns and seed production suggests that the patches of trees experience less connectivity than trees within continuous forest. These findings indicate that forest management practices should emphasize the maintenance of an optimal patch size because, despite the fact that tree species show the potential for long distance pollen movement, the number of local trees strongly influences the mating patterns.     

The effects of burning and dead-wood creation on the diversity of pioneer wood-inhabiting fungi in managed boreal spruce forests

The loss of natural forest habitats due to forestry is the main reason for the decline in boreal forest biodiversity of the Nordic countries of Europe. Ecological rehabilitation may provide means to recover and sustain biodiversity. We analyzed the effects of controlled burning and dead-wood creation (DWC) on the diversity of pioneer wood-inhabiting fungi in managed Norway spruce (Picea abies) forests in southern Finland. Altogether 18 stands were first subjected to a partial cutting with ordinary logging residues in form of cut stumps and treetops left on site. The subsequent rehabilitation treatments consisted of a controlled burning applied in half of the stands and three levels of dead-wood creation (5, 30 and 60 m³ ha⁻¹). The DWC involved creation of logs; felling of whole trees to mimic downed logs formed by natural disturbance processes. Each treatment was replicated three times. Inside each stand, substrates were sampled in two different biotopes; one on mineral soil and one on mineral soil with a thin peat layer. We surveyed the fungal flora on the logs (n = 364) and the ordinary residue stumps (n = 1767) and tops (n = 845) five years after the treatments.When comparing different stands, controlled burning had a significant effect on species composition; certain species were significantly more frequent on substrates in burned stands than in unburned stands, indicating that these species were favored by controlled burning. By contrast, we found no significant effects of DWC levels or biotope on species composition or richness. When comparing different substrates, 99% of the logs hosted at least one species and the occurrence probability of certain species was significantly higher on logs than on ordinary residue stumps and tops. Yet, volume-based rarefaction analyses showed that residues were more species dense than the logs, indicating that ordinary logging residues constitute important resources for many pioneer species.We conclude that controlled burning combined with DWC have strong effects on biodiversity; it modifies the composition of the pioneer wood-inhabiting fungal species found in managed forests and may thereby also influence the further succession and diversity of the secondary fungal flora.     

Contemporary pollen flow and mating patterns of a subtropical canopy tree Eurycorymbus cavaleriei in a fragmented agricultural landscape

China's subtropical forests have experienced severe deforestation and most native forests have been fragmented into an archipelago-like landscape. The genetic effect of habitat fragmentation depends largely on the level of gene flow within and among population fragments. In the present study, Eurycorymbus cavaleriei, a canopy tree found throughout subtropical China, was selected as a representative insect-pollinated plant species to assess genetic consequence of forest fragmentation. Contemporary pollen dispersal and mating patterns were estimated in two physically isolated stands of E. cavaleriei within fragmented forests using six highly polymorphic microsatellite loci. We found high genetic diversity (H_E = 0.670–0.754) in both adults and offspring in the fragmented agricultural landscape, suggesting that habitat fragmentation did not necessarily erode genetic diversity of E. cavaleriei. Although substantial pollen travelled less than 100 m, paternity analysis revealed that a large amount of long-distance pollination events occurred, with the average pollen dispersal distance being 1107 m and 325 m for the two stands, respectively. Extensive pollen immigration (39.3–42.6%) indicated that there was effective genetic connectivity among E. cavaleriei stands in the fragmented forests. twogener analysis revealed that the exponential power model was the best-fitting dispersal curve with a fat-tailed (b < 1) dispersal feature. The results from a multilocus mating system analysis suggested that a small amount of biparental inbreeding and some correlated mating events occurred in the fragmented forests, which were similar to our parallel findings in the continuous forests of E. cavaleriei. Estimates of pollen pool structure (Φ_FT = 0.128–0.174) indicated large genetic differences between pollen clouds accepted by maternal trees. The number of effective pollen donors (N_ep) in E. cavaleriei, estimated using both mltr (N_ep = 4.2–5.3) and twogener (N_ep = 2.9–3.9) models, was equivalent to the number of effective pollen donors detected in continuous forests of E. cavaleriei. The pollen dispersal and mating patterns detected here indicated that habitat fragmentation did not have a negative impact on pollen movement in E. cavaleriei, possibly due to its generalist pollination system and the resilient foraging behavior of its pollinators in response to changes in landscape structure. The long distances of pollen-mediated gene flow between patches highlight the conservation value of remnant forest fragments in maintaining genetic connectivity at the landscape scale in subtropical China.     

Origins and diversity of the Portuguese Landrace of Eucalyptus globulus

The Portuguese Landrace of Eucalyptus globulus is of unknown origin, with the earliest plantings of this tree species dating back to the early 19th century. In Portugal it is currently a major seed source for plantations and is also used in breeding programs. Eucalyptus globulus is native to south-eastern Australia. The substantial genetic differentiation of chloroplast and nuclear DNA markers between different native geographic races of this species allowed us to uncover the Australian origins of the Portuguese Landrace and to study its genetic diversity. To achieve this, we sequenced a highly polymorphic region of chloroplast DNA from 47 Portuguese Landrace individuals, and genotyped 34 of these using seven nuclear microsatellites. We compared these individuals to those in a database comprising chloroplast DNA sequence profiles from 292 native trees and seven nuclear microsatellites from 372 native trees. The majority of the Portuguese Landrace samples had closest affinities, in both marker systems, to native trees from south-eastern Tasmania, but some had affinities to trees from south-eastern Victoria. The discrepancies in the affinities indicated by chloroplast versus nuclear DNA markers could be explained by inter-race hybridisation after introduction. The genetic diversity in the Portuguese Landrace was less than that found in native E. globulus at the species level, but was similar to the average diversity found in native races of the species. This study demonstrates the power of using independent marker systems to identify the origins and diversity of domesticated populations, by comparison with variation in native stands.     

Distribution of carabid beetles among 40-year-old regenerating plantations and 100-year-old naturally regenerated forests in Southwestern China

Effects of reforestation by native tree species on species assemblages of carabid beetles were studied between 40-year-old regenerating plantations and 100-year naturally regenerated forests in Southwestern China. Two old naturally regenerated forest types (ca.100 years old) were chosen: hemlock-spruce forests (Tsuga chinensis and Picea brachytyla) and birch forests (Betula albo-sinensis). Three young regenerating forest types (ca. 40 years old), including spruce plantations (P. brachytyla), larch plantations (Larix kaempferi and Larix mastersian), and natural broad-leaved forests, were established after the logging of the old naturally regenerated forests. Using pitfall traps, we compared the distribution of carabid beetles in the five forest types. Three replicated plots for each forest type were chosen, and each plot was investigated with four trap sites twice each month during the growing season (May to October) in 2004. Our results showed that species richness and abundance were significantly higher in the young regenerating forests than in the old naturally regenerated forests. Analysis of complementarity in carabid species lists across the forest ages and types showed that the old naturally regenerated birch forests had the lowest similarity with the young regenerating larch plantations, and the highest similarity was shown between the two young regenerating plantations. Although PCoA ordination grouped the carabid assemblages according to forest type and forest age, the overall similarity among all forest types was high. Moreover, quantitative character species analysis did not detect significant species associated with forest types and ages. Based on the specificity and fidelity, most carabid species were abundant in all habitats, and only a few species were restricted in one or two forest types. Multiple linear regression between the species richness, abundance and Shannon diversity of carabids and of five environmental variables showed that the cover of canopy and herbaceous layer, and the depth of leaf litter had significant effects in determining richness, abundance and diversity of carabid beetles. Thus, the young regenerating forests at the mature stage could provide an appropriate habitat for most forest species of carabids survived in adjacent old naturally regenerated forests and might replace the role in part of the old-growth forests in sustaining the diversity of carabid assemblages. But some species are still restricted in old naturally regenerated forests, so in order to protect the diversity of carabid assemblages, it is necessary to sustain the intact old naturally regenerated forests when reforesting with some native tree species following natural succession.     

Contributions of root and stump sprouts to natural regeneration of a logged tropical dry forest in Bolivia

A major impediment to the sustainable management of tropical dry forests in Bolivia is the scarcity of natural regeneration of commercial timber tree species. Where regeneration is present, true seedlings of many species are outnumbered by vegetative sprouts from roots, broken stems, and the stumps of felled trees. This study evaluates the importance of resprouts promoted by logging operations for the regeneration of commercially important canopy tree species. The objectives of the study were: (1) to characterize stump and root sprouting behaviors of canopy tree species harvested for timber; (2) to quantify the effect of logging on relative abundances and growth rates of stump sprouts, root sprouts, and true seedlings; (3) to relate the species-specific probabilities of stump sprouting to stump diameter and stump height; and (4) to explore how sprouting varies with the ecological requirements of canopy tree species. The study was carried out 1–5 years after logging of a privately owned land in a Bolivian tropical dry forest. Twenty-seven of the 31 species monitored resprouted at least occasionally, among which Centrolobium microchaete (Leguminosae-Fabaceae) and Zeyheria tuberculosa (Bignoniaceae) were the most frequent stump sprouters, and Acosmium cardenasii (Leguminosae-Fabaceae) and C. microchaete were the most frequent root sprouters. In all species the number of sprouts declined with increasing stump diameter and stump height. The probability of stump resprouting differed among species but did not vary consistently with stump diameter, except in Z. tuberculosa in which it declined. Approximately 45% of juveniles <2 m tall of canopy tree species originated from root or stem sprouts. Light-demanding species tended to regenerate more from seeds and root sprouts than from stumps. Seedling densities were higher in microsites opened by logging, while root and stem sprouts were equally common across microsites. Given their abundance and the fact that root and stem sprouts at least initially grew faster than true seedlings, we conclude that vegetative regeneration in this tropical dry forest is an important mode of post-logging regeneration especially for species that regenerate poorly from seed. Resprout management should be considered as a potentially effective strategy for the procurement of regeneration following logging, especially for species that do not readily recruit from seed.     

Stocks and decay dynamics of above- and belowground coarse woody debris in managed Sitka spruce forests in Ireland

Coarse woody debris (CWD) has become recognised as an important component of the carbon (C) pool in forest ecosystems. In Ireland, managed Sitka spruce (Picea sitchensis (Bong) Carr.) forests account for 52.3% of the total forest estate. To determine the stock and decay dynamics of above and belowground CWD, field surveys using fixed area sample plots, were conducted in six even-aged Sitka spruce stands, representing the young, intermediate and mature stages of a typical commercial rotation. The volume, mass, density loss and C:N ratio of all CWD types (logs, stumps, and coarse roots) were determined using a five-decay class (DC) system. The decay rates and half life of CWD was also determined. To estimate CWD coarse root mass; roots associated with stumps classified in different decay classes were excavated. The coarse roots were categorised into small (2-10 mm), medium (10-50 mm) and large (>50 mm) diameter classes.CWD C-mass ranged from 6.98 to 18.62 Mg ha⁻¹ and was highest in an intermediate forest (D35), while the aboveground volume varied from 6.31 to 42.27 m³ ha⁻¹. Coarse roots accounted for 21% to 85% of the total CWD C-pool in the surveyed stands. The total CWD C-mass was poorly correlated with the number of thinning events (R² = 0.29), when data from D35 was excluded. The density loss was significant in logs (45%), stumps (58%), and small- (38%), medium- (50%) and large roots (38%) as decay progress from DC 0 to 4. There was a 46%, 41%, 51%, 72% and 57% decline in C:N ratio of logs, stumps, small-, medium- and large roots, respectively, as decay progressed from DC 0 to 4. The density decay rates were 0.059, 0.048 and 0.036 kg m⁻³ year⁻¹ for logs, stumps and coarse roots, respectively. The size classification of roots did not significantly affect their decay rate. The half life (50% decomposition) of CWD was estimated has 12-, 14- and 19 years for logs, stumps and roots of Sitka spruce. Regression curves showed a strong correlation between the density and C:N ratio (R² = 0.69, 0.74 and 0.93 for logs, stumps and coarse roots, respectively). The long term storage of C and its slow rate of decomposition make CWD a vital structural and functional component of the CWD C-pool and a major controller of forest ecosystem C-retention.     

Allozyme and microsatellite data reveal small clone size and high genetic diversity in aspen in the southern Cascade Mountains

The most widely distributed tree in North America, quaking aspen (Populus tremuloides, Michx.), reproduces sexually via seed and clonally via suckers. The size of aspen clones varies geographically, generally smaller in the east and large in the arid Intermountain West. In order to describe clone size and genetic structure of aspen in the southern Cascade Mountains, 864 stems from six sites were assayed at 15 isozyme and 6 microsatellite loci. Although isozymes reveal significantly lower levels of allelic richness (P < 0.001) and expected heterozygosity (P < 0.01), differences in genet diversity (isozyme G/N = 0.45, microsatellite G/N = 0.47) and allele frequency variation (isozyme F_ST = 0.02, microsatellite F_ST = 0.03) were nonsignificant. While a majority of stands were monoclonal, such stands were small, and the number of clones per stand was positively correlated with stand size (P < 0.0001). High genetic diversity, low genetic differentiation, and a rapid decay of spatial genetic structure consistent with long distance gene flow during seedling recruitment indicate that sexual reproduction is a significant factor contributing to the genetic structure of these populations. These findings further resolve the geographic variation in clonal structure observed in aspen across North America, providing novel information for land management and conservation efforts.     

Stand structure of hemiboreal old-growth forests: Characteristic features,variation among site types,and a comparison with FSC-certified mature stands in Estonia

To improve the silvicultural targets for ecologically sustainable forestry, we quantified functionally important structural features for the first time in a representative set of old-growth forests in hemiboreal Europe. Altogether, 23 old-growth stands of four site-type groups were compared with mature commercial stands nearby in the Estonian state forests that hold the Forest Stewardship Council (FSC) certificate of sustainable forestry. These two treatments did not differ significantly in terms of tree-species diversity, volumes of woody debris of <20 cm diameter (including fine woody debris) and its decay-stage composition. However, mature stands had many more early-successional trees and lacked late-successional deciduous species; they also had a higher overall density and volume of live trees, due to abundant individuals of 10–39 cm diameter at breast height. Old-growth stands had at least twice as many live trees ≥40 cm, standing dead trees ≥30 cm and lying wood ≥20 cm in diameter, any freshly fallen debris, and regeneration. For lying wood ≥20 cm in diameter, the treatment effect depended on site type: both treatments of Vaccinium-type dry boreal forests were remarkably deadwood-poor (indicating historical management of the old-growth stands), while mature eutrophic stands of Aegopodium-type were most impoverished relative to old-growth levels. We conclude that many functional characteristics of old growth were present in the FSC-certified, mostly naturally regenerated, commercial stands. The main problem is the lack of very large trees, particularly of late-successional deciduous species, which should be addressed by their well-planned retention in cut areas and reconsideration of salvage logging strategies. A dense regeneration in old-growth stands also indicated the potential of selection cuttings. The study highlighted the need for region- and site-type specific numerical targets for sustainable forest management, which in the hemiboreal region should address the characteristic occurrence of late-successional deciduous trees on fertile soils and higher natural deadwood volumes than in typical boreal forests. For certification, the issues of structural impoverishment revealed both the inadequacy of some silvicultural practices and some indicators set by the national FSC-standard in Estonia.     

The influence of reproductive traits on liana abundance 10 years after conventional and reduced-impacts logging in the eastern Brazilian Amazon

Balancing timber production and conservation in tropical forests requires an understanding of the impacts of silvicultural manipulations on specific groups of organisms. Lianas are characteristic of many tropical forests, where they contribute to species diversity, ecosystem functioning, and biomass. However, lianas can also impede timber production by increasing logging damage and slowing tree growth. Cutting lianas prior to logging can mitigate the negative effects, but may adversely affect a forest's value for conservation. To evaluate the effects of forest management activities on lianas, this study assessed the impacts of logging, both with and without pre-logging liana cutting, on the relative abundance and population structure of five species of lianas that differed in primary reproductive strategies.Inventories of the five study species were conducted 10 years following logging in 4.4 ha plots in three adjacent treatment areas: (1) an old-growth forest reserve, (2) a selectively-logged forest that used conventional practices for the region, and (3) a forest that was logged using reduced-impact logging (RIL) techniques including complete liana cutting prior to logging. Liana species responses to logging varied according to their primary modes of reproduction. Croton ascendens, a pioneer species with a persistent seed bank, had a higher abundance in the two logging treatments relative to the old-growth forest, while Serjania caracasana, an early successional species lacking a persistent seed bank, showed abundant regeneration following conventional logging but negligible regeneration following RIL. In contrast, Acacia multipinnata, also an early successional species, showed abundant regeneration following RIL owing to the sprouting of persistent prostrate stems present on the forest floor prior to logging. In both logged areas, Bauhinia guianensis recruited abundant climbing stems from self-supporting seedlings that were present prior to logging, but it showed greatly reduced seedling density following RIL. By sprouting profusely from both fallen stems and stumps, Memora schomburgkii recruited abundant small-diameter climbing stems in both of the logging treatments. The results of this study demonstrate that there are interspecific differences in liana responses to different types of logging and that knowing species’ primary modes of reproduction is a valuable first step toward predicting those responses.     

Coppice forests and genetic diversity: A case study in Quercus pyrenaica Willd. from Central Spain

The amount of standing genetic diversity found in oak coppice forests has been subjected to intense debate amongst forest ecologists and managers. In this study, the level of vegetative propagation and the genetic diversity found in a coppice forest of rebollo oak (Quercus pyrenaica) was examined. The current range of rebollo oak in the Iberian Peninsula reveals its adaptation to sub-Mediterranean mountain ecosystems. High sprouting capability, mainly by root suckers, has favoured traditional exploitation of rebollo oak in coppice forests. Using nine microsatellite loci, we have detected 14 clone assemblies compounded by 2–4 stems (7.9 ± 1.3 ramets per genet, considering stand density) and covering an average surface of 11.4 m² per genet. The levels of genetic diversity and the amount of unique genotypes were high (D = 0.9972, G/N = 0.86) and similar to the clonality levels found in a nearby open oak woodland. Despite numerous clear-cutting rotations, known at least since 1750, and the heavy root sprouting observed after a thinning event, low clonal propagation (∼27%) was detected. This fact pointed towards the long-term persistence of several small clonal assemblies in this coppice. Our findings suggest that intense thinning practices are unadvisable in the conversion of Q. pyrenaica coppice into high forest due to the significant losses of genetic diversity when removing unique genotypes.     

Comparison of direct and indirect genetic methods for estimating seed and pollen dispersal in Fagus sylvatica and Fagus crenata

The comparison between estimates of historical gene flow, using variance in allelic frequencies, and estimates of contemporary gene flow, using parentage assignment, is expected to provide insights into ecological and evolutionary processes at work within and among populations. Genetic variation at microsatellite loci was used to quantify genetic structure in two wind pollinated, gravity and animal-dispersed tree species (Fagus sylvatica L. and Fagus crenata Blum.) and to derive historical estimates of gene flow. The gene dispersal distances estimated assuming effective population density to be 1/4 of the observed density were ∼77 m in European beech and ∼40 m in Japanese beech. Parentage analyses and a neighbourhood model approach were used to estimate contemporary patterns of seed and pollen dispersal. Our results suggest restricted seed dispersal abilities in both European beech (δ_s = 10.5 m) and Japanese beech (δ_s = 12.4 m), with an exponential shaped seed dispersal kernel. A non-negligible rate of seed immigration (m_s = 27%) was detected in European beech sites but not in Japanese beech site. Pollen dispersal within studied sites also appeared limited (δ_p = 41.63 m in European beech and δ_p = 79.4 m in Japanese beech), despite high rate of pollen immigration (m_p = 68% in European beech and m_p = 40% m in Japanese beech). Interestingly, contemporary and historical estimates of gene flow were within the same order of magnitude (a few tens of meters).     

Centuries-old logging legacy on spatial and temporal patterns in understory herb communities

Understory herb communities in the Southern Appalachians are among the highest biodiversity plant communities in North America. In the mid-1990s, a debate began over whether understory herb communities recover to their pre-disturbance states following logging. Studies showing reduced herb-layer diversity in previously logged forests were criticized for not accounting for intersite environmental heterogeneity. More recent studies have addressed environmental heterogeneity, but have neglected long-term recovery by using “mature forests” as young as 80 years old as the benchmark for diversity comparison, even though old growth stands have disturbance return intervals exceeding 500 years. Here we address concerns clouding previous studies of high-diversity Appalachian herb communities and investigate their long-term recovery by comparing paired sites of old growth forest and forest logged 100–150 years ago. We found that species richness and individual abundance is greater in old growth forests than mature forests and that species composition differed significantly between the two. Turnover in species among old growth and mature forests accounted for 11% of the total species richness and was significantly greater than expected. Species turnover at intermediate (5–50 m) and landscape-scales (>10 km) contributed the most towards total species richness. Herb communities in rich cove forests have successional trajectories that exceed 150 years, with important community changes still occurring long after the forest returns to what has been previously termed a “mature” state. To conserve the diverse herb layer, we conclude that mature forest stands are too young to serve as baselines for recovery, landscape-scale preservation of multiple forest stands is needed to maximize species richness, and maintaining 100–150-year logging rotations will likely lead to loss of biodiversity.     

Fragmentation and spatial genetic structure in Tabebuia ochracea (Bignoniaceae) a seasonally dry Neotropical tree

In this study we investigate the effect of fragmentation and disturbance on the spatial genetic structure, heterozygosity and inbreeding in Tabebuia ochracea (Bignoniaceae) in a seasonally Neotropical dry forest in the medium São Francisco River basin, Centre-East Brazil, based on the polymorphism at seven microsatellite loci. Four populations with different histories of disturbance and fragmentation were sampled: two continuous population (CP1 and CP2), with no history of recent disturbance and two fragmented and isolated population (FP1 and FP2), with recent history of disturbance due to logging for pasture establishment. Fragmented and continuous populations did not differ in any estimated parameter. However, all populations showed low levels of polymorphism and genetic diversity and high levels of inbreeding. Also, no spatial genetic structure was detected for populations using SPAGeDI software and no differentiation between these four populations was detected by Bayesian analyses performed with STRUCTURE software (K = 1). Differentiation measure by Wright's θ (0.032) and Hedrick G_ST (0.032) were significant but low. Our results strongly suggest that continuous populations are seed sources for the fragmented populations and that fragmentation and disturbance have been affecting these populations of T. ochracea in the Centre-East Brazil, leading to low levels of polymorphism and genetic diversity, and high inbreeding. Therefore, conservation efforts should increase in this region, with a reduction of agriculture expansion and the remove of cultivated areas and cattle from the Mata Seca and Lagoa do Cajueiro State Parks.     

Intra and inter-annual variation in seed rain in a secondary dry tropical forest excluded from chronic disturbance

Domestic livestock grazing and firewood extraction are chronic and pervasive disturbances in dry secondary forest that reduce diversity and modify composition. Exclosure of such disturbances may allow the reestablishment of original diversity. To investigate potential vegetation recovery following 30 years of perturbation, seed rain was evaluated monthly during 3 years in 96 0.78 m² seed traps located in eight exclosures established in 2006 in a species-poor secondary dry forest in central Mexico. Twelve additional seed traps were located outside the exclosures in 2010 for comparison purposes. Baseline diversity of seed sources (trees, ?5 cm DBH) was recorded to compare standing tree composition with seed rain. Also, baseline diversity of potential primary (birds) and secondary (ants) dispersal vectors were registered to infer current plant-animal interactions. Total seed rain over 3 years within the exclosures comprised 180,375 seeds from 61 woody species, an average of 1.12 seeds/m²/month. Half of these species (31) and 95% of the seeds falling within the exclosures belonged to trees typical of perturbed sites. Sixty percent of all recorded seeds belonged to an early-successional, bird-dispersed shrub (Hamelia patens Jacq., Rubiaceae). Seed rain at one non-excluded plot was dominated by the wind-dispersed early-successional tree Heliocarpus sp. (Tiliaceae). Richness and seed density increased significantly in the second year of exclusion; however, by the third year, richness remained constant while seed density decreased. Seed rain was richer and more abundant during the dry season and was dominated by wind-dispersed species. Phenology, successional status and the dispersal modes of woody species explained most variance in richness and seed density of seed rain in early-successional dry forest. Seeds of early-successional species were dispersed in equal measure by abiotic and biotic vectors, whereas biotic vectors dispersed a higher density of late-successional seeds. The amount and timing of fall of abiotically dispersed seeds of the three most abundant species in the standing tree community may prolong their current domination of the landscape. However, even when richness in the seed rain within exclosures remained constant through time, composition was gradually shifting towards animal-dispersed species which may start a positive feedback producing an increase in animal visitation and a further increase of richness.     

Medicinal plants in old-growth, degraded and re-growth forests of NW Pakistan

Many old-growth forest stands in northwest Pakistan have been structurally transformed as a consequence of logging and livestock grazing, some of which are thereafter left to secondary succession. These forests represent an important resource for local inhabitants who gather and sell medicinal plants as part of their livelihood. With this in mind, the main objectives of our study were: (1) to assess differences in the structure of the tree layer and the abundance of medicinal plants among differently transformed forests, (2) to evaluate the recovery potential of medicinal plants under re-growth forests, and (3) to assess relationships between tree stand structural characteristics and the occurrence of medicinal plants.The first step of the study involved creating an approximate map covering an area of 90 km² for five forest-use types (old-growth forest, forest degraded by logging, derived woodland, agroforest and re-growth forest). Fifteen plots per forest-use type were randomly allocated at altitudes ranging from 2200 m to 2400 m asl, within which the abundance of 10 locally important medicinal herb species was assessed.The study stands differed greatly in tree basal area, which was highest in old-growth forest (48 m² ha⁻¹), lowest in agroforest areas (6 m² ha⁻¹) and intermediate in re-growth forest (20 m² ha⁻¹). All ten medicinal plant species were encountered in old-growth and in re-growth forests, but only five of these species also occurred on agroforest plots. The mean coverage of study medicinal plants was highest in old-growth forest (7%), low in forest degraded by logging, derived woodland and agroforest (0.3-2%), and intermediate in re-growth forest (4%). The Jaccard abundance based similarity index indicates a considerable similarity (0.6) between re-growth and old growth forest for both trees and medicinal plants. The overall abundance of medicinal plants increased with increasing tree basal area and canopy cover. The abundance of some particular species decreased; however, the most sought-after medicinal species Bergenia ciliata, Valeriana jatamansi and Viola cancescens increased with tree basal area within specific forest-use type and also across forest-use types. In conclusion, our data suggest that anthropogenic forest degradation leads to a reduction in the abundance of economically viable medicinal plants for the study region. It is further indicated that this can be reversed if degraded forests are allowed to regenerate.     

Modelling the long-term impacts of selective logging on genetic diversity and demographic structure of four tropical tree species in the Amazon forest

In the last three decades, Amazon tropical forests have experienced high rates of deforestation, both by clearing for agriculture and by logging. In this study, we use computer simulations to examine the potential effects of forest logging on genetic diversity and demographic recovery (basal area development) of four neotropical tree species over a time frame reflecting multiple logging events. The study species, Bagassa guianensis Aubl., Hymenaea courbaril L., Manilkara huberi (Ducke) Chevalier, and Symphonia globulifera L.f., are all taxa which are commonly exploited for timber in the Brazilian Amazon. The simulations were parameterized using empirical data from field studies in the Tapajós National Forest, Pará State, Brazil, including genotypes at microsatellite loci, demography, ecology and growth for each species. Eight scenarios, combining two different cutting cycles and two minimum cutting diameters, were examined for each of the four species. The scenarios represent the actual forest practices used in Brazil and French Guiana (cutting diameter 45 and 60 cm, and cutting cycle of 30 and 65 years, respectively). Logging scenarios were applied for six cutting cycles, and final genetic and demographic data were compared to baseline data from corresponding control scenarios. At the end of the simulated period the basal area was strongly reduced under all conditions in B. guianensis, H. courbaril, and M. huberi. In only two scenarios was a species able to recover its basal area following logging (S. globulifera with both 45- and 60-cm cutting diameters under a 65-year cutting cycle). In the logging scenarios, all species showed a loss of alleles and genotypes and an increased genetic distance (calculated between each population at the start and the end of the simulations). These effects were higher under the most intensive logging cycles (30 years, 45 cm). However, effective number of alleles, expected and observed heterozygosities, and the fixation index were little affected by the logging simulations. Over all, we conclude that, even under very optimistic conditions for growth and recruitment, current logging practices are not sustainable in terms of basal area. Our simulations show that different species respond differently to logging, both demographically and genetically. No single set of logging parameters can be applied to the forest as a whole. Rather, forest management practices must be species-specific, taking into account not only growth parameters but also ecological and reproductive variables, in order to move toward long-term forest sustainability.     

Genetic variation of Fraxinus angustifolia natural populations in Greece based on nuclear and chloroplast microsatellite markers

Assessment of genetic variation within and among populations is an essential parameter for the effective conservation of forest genetic resources. In this work, the genetic diversity within and among natural populations of the forest tree species Fraxinus angustifolia Vahl in Greece was studied using selected nuclear and chloroplast microsatellite DNA loci. Eight natural populations of F. angustifolia were identified in different locations of the mainland of Greece, and a total of 230 individuals were studied. High polymorphism was observed within populations, while the genetic differentiation among populations was moderate. Intra-population diversity was correlated with geographical coordinates, but no isolation by distance was observed. Of the three haplotypes identified, only one was dominant. Putative ancestral haplotypes were found at small spatial scales suggesting that population expansions could have originated in the region. This study located in sympatry haplotypes that in other parts of Europe are in allopatry, reinforcing the notion of population expansions from the south of Balkans including Greece. Suggestions for conservation and management of F. angustifolia are also reported.