Natal dispersal of hazel grouse Bonasa bonasia in relation to habitat in a temperate forest of South Korea

Natal dispersal and habitat selection of hazel grouse Bonasa bonasia juveniles were assessed by radio tracking in a temperate forest of South Korea during June 2003–November 2006. The birds used in the dispersal analysis (n = 43), 88% of birds dispersed. The average dispersal of hazel grouse from the natal area was 2231 ± 494 m (mean ± SD); range 134–6267 m. There were no significant differences in dispersal rate and distance between sexes. Hazel grouse’ habitat use differed from random use of available natal dispersals. In this natal dispersal scale of habitat selection, natural deciduous forest ranked highest, followed by mixed forest, coniferous plantation, deciduous plantation and others (rock and bare lands). We found that in general, the hazel grouse is an active disperser. Knowledge of aspects of habitat use that are relevant to dispersal may provide a better assessment of the fitness effects of dispersal in proximate and ultimate terms.     

Gene flow pattern and mating system in a small population of Quercus semiserrata Roxb. (Fagaceae)

Pollen flow from external sources is important for the conservation of tree species in fragmented forests or small populations, because it can be sufficient to prevent differentiation among them, and appears to be able to prevent the loss of their genetic diversity through genetic drift. In this study, we examined the genetic heterogeneity of pollen pools accepted by each Quercus semiserrata seed parent at the Khun Wang Royal Agriculture Research Center, Thailand, both within and among two mast fruiting years (2005 and 2007), using paternity analysis and analysis of molecular variance (AMOVA). The mating systems of the trees were also examined using the multilocus mating system model (MLTR), after determining the genotypes at eight microsatellite loci of 26 seed-trees and 435 seeds from 8 seed-trees in the 2 mast fruiting years. The average distance of effective pollen flow within the plot was estimated to be 52.4 m, and 95% of effective pollen was dispersed within 200 m, indicating that effective pollen flow is highly localized and that most effective pollen is contributed by near-neighbor trees. The proportion of effective pollen that immigrated from external sources was estimated to be 26.2%. The AMOVA analysis based on the pollen haplotypes showed that the pollen pools, both total and for each reproductive year, significantly genetically differed among the seed parents. Using a mixed mating model, the estimate of biparental inbreeding for the total population (t_m − t_s) was 0.013, indicating that a low proportion of mating occurred among close relatives. The effective number of pollen donors (N_ep) was estimated to be 9.987 using the TwoGener model, or 10.989 using the mixed mating model. The effective number of pollen donors of seeds was higher in the mast fruiting year 2005 than in the other examined year, 2007. Consequently the allelic richness and genetic diversity of seeds produced in 2005 were higher than those produced in 2007. Overall, the results show that high outcrossing rates, high levels of gene flow from other populations and heterogeneity in the pollen received by an individual may enhance the ability of populations to maintain effective population sizes. Therefore, these processes may be sufficient to prevent loss of genetic diversity through genetic drift of Q. semiserrata at this study site.     

Short distance pollen movement in a wind-pollinated tree, Quercus lobata (Fagaceae)

Short distance pollen dispersal shapes the local genetic structure of plant populations and determines the opportunity for genetic drift and local selection. In this paper we focus on short distance dispersal (SDD) of pollen in a low-density stand of a savannah oak, Quercus lobata Née. Specifically, we are interested in the proportional contributions of pollen donors, the pollen dispersal kernel that describes local matings, the extent to which wind influences mating success, and the extent to which pollen sources vary within the large canopy of these trees. Using maximum likelihood paternity analysis, we assigned sires for 474 outcrossed progeny of five seed trees, representing 120 of 160 potential mating pairs within a 250 m radius of each focal tree (ca. 20 ha plots). We first established that the effective number of pollen donors for progeny with sires within the plot was about 10 individuals, with average weighted pollination distances of 114.1 m. We estimated 18.5% pollen immigration into the 20 ha plots. We next established that the SDD portion of the dispersal kernel is best described by the exponential power, inverse power, and Weibull functions, all that capture high local dispersal with steep decay. Two of these models suggest that long distance dispersal is abundant, represented by a fat tail, while the Weibull indicates depauperate long distance dispersal, represented by a thin tail. The addition of a directional component corresponding to the predominant wind axis had no meaningful impact on these models. Finally, we established that different parts of an individual tree canopy of Q. lobata sample from the same homogeneous pollen pool showing no bias towards pollen sources near that part of the canopy. Overall findings suggest low-density Q. lobata populations show steep decay of SDD. Policies and ordinances governing the amount of allowable tree removal of savannah oak populations should recommend the preservation of local clusters of adults, as well as some connectivity among clusters.     

EST-SSRs development and paternity analysis for <Emphasis Type="Italic">Liriodendron</Emphasis> spp

Liriodendron are ideal plants for research on mating system, systemic evolution and population genetics. Here we report the development and application of a set of simple sequence repeat (SSR) markers derived from expressed sequence tags (ESTs) of L. tulipifera. In total, 176 primer pairs were developed and yielded 132 EST-SSR markers that amplified clear SSR bands with genomic DNA of L. tulipifera. Transferability of these EST-SSR markers to related species and genera was further examined. Twelve highly informative loci screened from 132 EST-SSR markers were applied to explore the effective pollen dispersal patterns and male reproductive success of Liriodendron. A provenance trial population of Liriodendron comprised 12 L. chinense (Hemsl.) Sarg provenances and 5 L. tulipifera provenances. The four maternal trees were randomly sampled as tested maternal trees in the population. Paternities of 220 open-pollination progenies from 4 maternal trees above were potentially identified by means of paternity analysis, of which 138 progenies (accounting for 62.7%) were assigned to 49 male parents at the 95% confidence level. The cumulative exclusion probability of 12 EST-SSR loci was 98.5%. The average effective pollen dispersal distance of pollen donors ranged from 15 to 35 m, with the maximum dispersal distance of 77 m. There were obvious male reproductive success differences among individuals, ranging from 0 to 10.9%. The cumulative male reproductive success of individuals within 35 m radius around the known maternal trees reached 51.4%. Diversiform mating patterns, including selfing, intra-species mating and interspecies mating, coexisted in the occasion of open-pollination in Liriodendron.     

Densification, stand-replacement wildfire, and extirpation of mixed conifer forest in Cuyamaca Rancho State Park, southern California

A century of fire suppression culminated in wildfire on 28 October 2003 that stand-replaced nearly an entire 4000 ha “sky island” of mixed conifer forest (MCF) on Cuyamaca Mountain in the Peninsular Range of southern California. We studied the fire affected Cuyamaca Rancho State Park (CRSP), which represents a microcosm of the MCF covering approximately 5.5 × 10⁶ ha (14%) of California, to evaluate how fire suppression unintentionally destabilizes this ecosystem. We document significant changes in forest composition, tree density, and stem diameter class distribution over a 75-year period at CRSP by replicating ground-based measurements sampled in 1932 for the Weislander Vegetation Type Map (VTM) survey. Average conifer density more than doubled, from 271 ± 82 trees ha⁻¹ (standard error) to 716 ± 79 ha⁻¹. Repeat aerial photographs for 1928 and 1995 also show significant increase in canopy cover from 47 ± 2% to 89 ± 1%. Changes comprise mostly ingrowth of shade-tolerant Calocedrus decurrens [Torr.] Floren. in the smallest stem diameter class (10–29.9 cm dbh). The 1932 density of overstory conifer trees (>60 cm dbh) and 1928 canopy cover at CRSP were similar to modern MCF in the Sierra San Pedro Mártir (SSPM), 200 km S in Baja California, Mexico, where fire suppression had not been practiced, verifying that the historical data from the early twentieth century represent a valid “baseline” for evaluating changes in forest structure. Forest successions after modern crown fires in southern California demonstrate that MCF is replaced by oak woodlands and shrubs. Post-fire regeneration in severely burned stands at CRSP includes abundant basal sprouting of Quercus chrysolepis Liebm. and Quercus kelloggii Newb., but only few seedlings of Abies concolor [Gord. and Glend.] Lindl (average 16 ± 14 ha⁻¹), while whole stands of C. decurrens, Pinus lambertiana Dougl., and Pinus ponderosa Laws. were extirpated. Prescribed burning failed to mitigate the crown fire hazard in MCF at CRSP because the low-intensity surface fires were small relative to the overall forest area, and did not thin the dense understory of sapling and pole-size trees. We propose that larger, more intense prescribed understory burns are needed to conserve California's MCF.     

Genetic succession and spatial genetic structure in a natural old growth Cryptomeria japonica forest revealed by nuclear and chloroplast microsatellite markers

Spatial genetic structure and diversity of Cryptomeria japonica trees in old growth forest but selectively logged in approximately 300 years ago were analyzed using seven nuclear microsatellite markers and one chloroplast microsatellite marker. The individuals were sampled from a 4-ha natural forest plot (200 m × 200 m), which are consisted of three size classes including newly regenerated individuals such as regenerated individuals (REG class; stem diameter at breast height (DBH), 5–110 cm), remaining individuals (REM class; DBH ≥ 110 cm), and old stumps. Genetic diversity was similar between the three groups. These results suggest that genes from the old growth forest may have been passed on to the next generation (i.e., the current forest). DNA extraction and analysis from old stumps was partly successful and we could compare the genetic diversity between old stumps and living trees using four microsatellite loci. Patterns of spatial genetic structure detected by analyses of the nuclear and chloroplast markers differed substantially; all nuclear markers showed significant positive autocorrelation (P < 0.05) over short distances, but the chloroplast marker showed no significant autocorrelation over any distance. We concluded that Moran's I spatial autocorrelation pattern for the chloroplast microsatellite may have been influenced by the extensive pollen flow characteristic of this species, because chloroplast DNA of C. japonica is paternally inherited through pollen and is a wind-pollinated species that produces abundant pollen every few years. In contrast, Moran's I spatial autocorrelation pattern for nuclear microsatellites may reflect limited seed dispersal in gaps where the forest has regenerated and low levels of seed shadow overlap due to past logging. The average seed dispersal distance was 86.0 m at the study site and about 34.0% of the seeds were from the outside of the site, which revealed by parentage analysis. The individuals remaining after logging, and the extensive pollen flow from outside our study plot, may play important roles in maintaining the forests on this island. Gaps created by the selective logging activities appear to have been important for the regeneration of this species in the past but in the present time, natural disturbances such as typhoon and landslide are also important for gap creation.     

Rehabilitation silviculture in a high-graded temperate mixedwood stand in Quebec,Canada

Vast areas of hardwood and mixedwood forests of eastern North America have been high-graded in the past and need silvicultural treatments to increase their value and productivity. To rehabilitate a high-graded temperate mixedwood stand, in Quebec, Canada, we used a split–split-split plot design with three replicates to assess different seed-tree and strip cutting systems, in combination with scarification and planting. The experiment consisted of three regeneration cuts in main plots: 10 seed-trees/ha, 40 seed-trees/ha and a 40-m wide strip clearcut (0 seed-tree/ha) with 60 seed-trees/ha in leave strips, thereby resulting in four levels of tree retention, and all included understory brushing. We applied two types of scarification (patch scarification or disk-trenching) to subplots, two regeneration modes (natural regeneration or planting with white spruce [Picea glauca]) to sub-subplots and two mechanical release treatments (softwood or mixedwood production) to planted sub–sub-subplots. Density of seed-trees did not affect the natural regeneration dynamics after 5 years, but disk-trenching was more efficient for the establishment of yellow birch (Betula alleghaniensis) and sugar maple (Acer saccharum). Few seed-trees of desirable white spruce were present and most died standing, confirming the importance of supplemental planting. Height growth of planted seedlings was 15% higher in the 0 and 10 (26–27 cm/year) than in the 40 and 60 (23 cm/year) seed-trees/ha treatments, and release doubled mean height growth (33.1 vs. 16.6 cm/year). Despite intensive site preparation, pre-established beaked hazel (Corylus cornuta) and mountain maple (Acer spicatum) were present at high densities in the regeneration stratum. Controlling this recalcitrant layer might be the greatest challenge for rehabilitating degraded stands of the mixedwood forest, especially since the use of herbicides is prohibited on Quebec’s public lands.

     

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.     

Pollen dispersal in a hinoki (Chamaecyparis obtusa) seed orchard detected using a chloroplast DNA marker

Pollen dispersal was estimated in two test plots in a hinoki (Chamaecyparis obtusa) seed orchard using a chloroplast DNA marker, the spacer region between thetrnD andtrnY genes, and SSCP (single strand conformation polymorphism). In Plot 1, 2,020 seeds from 40 trees within 30 m of the marker tree were analyzed using the PCR-SSCP method. In Plot 2, 1,850 seeds from 37 trees were analyzed in the same manner. The results revealed that the maximum pollen dispersal distance in the two plots exceeded 25 m. Pollen dispersal appeared to be inversely proportional to the distance from the marker tree. The effective pollen dispersal was suggested to be less than about 20 m in a mature hinoki seed orchard. Adjacent trees had an excessive influence when the pollen density was increased by artificial flower stimulation. Therefore, it was suggested that seed production better resembles ideal random mating when carried out as naturally as possible. In conclusion, the SSCP chloroplast DNA marker was a useful tool for amassing basic information on pollen management in seed orchards of coniferous species.     

Polylepis australis’ regeneration niche in relation to seed dispersal,site characteristics and livestock density

Establishment of Polylepis forests endemic to the mountains of South America may be affected by seed dispersal, site characteristics and livestock density. Polylepis australis (“tabaquillo”) grows in the high mountains of central Argentina, where we set up 76 square study plots of 900 m². To determine dispersal distance, we distributed 6 seed traps per plot in and around 20 plots. To determine the best site characteristics and livestock stoking rates, at two river basins differing in historic stocking rates, we analyzed the presence of seedlings in 56 plots and recorded topography, vegetation types and indicators of livestock activity. We also measured microsite characteristics in a sample of 32 comparable pairs of 1 m² quadrats, with and without seedlings. Maximum recorded dispersal distance of P. australis seeds was 6 m, and seedlings were found no more than 10 m from seed trees. The numbers of seedlings and seed trees were 3.5 and 4 times higher, respectively, in the basin with less livestock. At the 900 m² plot scale, a Poisson regression indicated a positive relationship between seedling number and P. australis canopy cover. At the quadrat scale (1 m²), seedlings were found in quadrats with significantly lower evidence of soil erosion than comparison quadrats without seedlings. We conclude that the main limitations to recruitment are short seed dispersal distances, lack of seed trees and extreme soil erosion. Management should therefore aim at preserving seed trees and reducing livestock density to prevent erosion.     

Density-dependent selfing and its effects on seed performance in a tropical canopy tree species, Shorea acuminata (Dipterocarpaceae)

In the conservation and management practices of natural forests, sound reproduction and regeneration form the basis of the maintenance and viability of the tree populations. To obtain and serve biological information for sustainable forest management, we investigated reproductive biology and inbreeding depression in seeds of an important dipterocarp tree species, Shorea acuminata (Dipterocarpaceae), by both field and laboratory experiments. Results of parental analysis of immature and mature seeds showed that selfing rates varied greatly, from 7.6 to 88.4% among eight mother trees, and the mean overall selfing rate was 38.3%. Observed outcrossing events within a 40-ha study plot were predominantly (76.5%) short-distance events with a mating distance (md) ≤ 100 m. Since the selfing rate sharply decreased with increase in the number of flowering conspecifics (i.e., individuals of the same species) within a 100-m radius from the mother trees, the local density of flowering conspecifics appears to be the key factor determining the outcrossing rate in S. acuminata. However, the extremely high selfing rate (88.4%) observed for one tree could not be simply explained by the low local density of flowering conspecifics. Instead, differences in its flowering phenology (its flowering peaked ca. a week earlier than most of the other examined individuals) may have severely limited its receipt of pollen from other conspecifics, and thus promoted selfing. Since there were no significant differences in the proportion of selfed progeny between immature and mature seed stages, there was no evidence of selective abortion of selfed seeds during seed development. However, the seed mass of outcrossed progeny was heavier than that of selfed progeny, and heavier seeds showed higher success rates at germination and seedling establishment. These results suggest that inbreeding depression resulted in reductions in seed mass and may reduce the fitness of selfed seeds in S. acuminata. In addition, the outcrossing rate of S. acuminata was more sensitive to low local conspecific flowering-tree densities than that of a sympatric bee-pollinated dipterocarp species with greater pollination distances. These results suggest that the management of local adult-tree densities is important for avoiding selfing and inbreeding depression in future generations, especially in a species like S. acuminata with predominantly short-distance pollination.     

Factors influencing the dispersion of Arceuthobium oxycedri in Central Spain: evaluation with a new null model for marked point patterns

The dwarf mistletoe, Arceuthobium oxycedri, is found on populations of Juniperus oxycedrus, in central Spain. This species can have negative effects on the physiology of its host, including mortality. Understanding the mechanisms that control its distribution and dispersal is critical to assessing its potential for spread. We assessed dwarf mistletoe distribution within a population of J. oxycedrus, including infected and uninfected host individuals. A new null model of parasitic dispersion was built using two dispersal kernel forms that were simulated with lower and upper envelopes for second‐order functions to summarize a point pattern, such as Ripley's K, nearest‐neighbour distribution and pair correlation functions. Nine dispersal scenarios were constructed with half‐bandwidth kernels (10, 20, 30 m) and initial population of infected trees (P₀ = 05, 10 and 20). These scenarios were compared with the observed pattern and evaluated using the goodness‐of‐fit test. Significant differences at short distance (r < 10 m) were found between the observed pattern and simulated patterns, corresponding to the range of seed dispersal of the dwarf mistletoe. Interactions between infected and uninfected hosts patterns at all scales were identified, suggesting that A. oxycedri uses other mechanisms in addition to ballistic seed shooting as secondary dispersal agents to spread to distances greater than 20 m. Given that the seed characteristics facilitate dispersal by adhesion, we infer that spread between host individuals is amplified by seed transport by birds or small mammals.     

Below-ground root yield and distribution in natural and replanted mangrove forests at Gazi bay, Kenya

Estimation of total biomass in woody ecosystems is important because of its relevance to nutrient turnover and the potential to store carbon. Most work on mangrove biomass, particularly in the Western Indian Ocean Region, has concentrated on the above-ground component; comparatively little is known on below-ground biomass. The current study was conducted at Gazi bay on the southern coast of Kenya. The objective was to determine the below-ground biomass of three species of mangrove, Rhizophora mucronata Lamarck, Avicennia marina (Forsk.) Vierh and Sonneratia alba J. Smith, in natural and replanted stands. The effects of distance from the tree base and of soil depth on root biomass and size distributions were also studied using coring. Live below-ground biomass (mean ± S.E.) ranged from 7.5 ± 0.4 t/ha to 35.8 ± 1.1 t/ha, 48.4 ± 0.7 t/ha to 75.5 ± 2.0 t/ha and 39.1 ± 0.7 t/ha to 43.7 ± 1.7 t/ha for R. mucronata, S. alba and A. marina, respectively, depending on the age of the stand. Including dead roots produced total biomass values of 34.9 ± 1.8–111.5 ± 5.6 t/ha, 78.9 ± 3.3–121.5 ± 7.3 t/ha and 49.4 ± 1.1–84.7 ± 5.4 t/ha for R. mucronata, S. alba and A. marina. These values imply carbon contents of live roots ranging between 3.8 ± 0.2 C t/ha and 17.9 ± 0.6 C t/ha, 24.2 ± 0.4 C t/ha and 37.7 ± 1.0 C t/ha and 19.5 ± 0.4 C t/ha and 21.9 ± 0.9 C t/ha for R. mucronata, S. alba and A. marina stands, respectively, and 17.4 ± 0.9 C t/ha and 55.7 ± 2.8 C t/ha, 39.4 ± 1.7 C t/ha and 60.7 ± 3.6 C t/ha and 24.7 ± 0.6 C t/ha and 42.4 ± 2.9 C t/ha for R. mucronata, S. alba and A. marina stands, respectively if dead roots are included. Stand densities were 4650 ± 177 stems/ha, 3800 ± 212 stems/ha and 3567 ± 398 stems/ha for R. mucronata 6-year old, 12-year-old and natural stands respectively. Mean stem diameter, and basal area were highest in the 12-year-old plantation while below-ground root biomass increased with age. Stand density for S. alba, was highest in the 12-year-old plantation (7900 ± 141 stems/ha) while the 9-year-old stand had trees with the largest diameter (7.7 ± 0.9 cm). Below-ground biomass was highest in the 12-year old (75.5 ± 2.0 t/ha) and lowest in the natural stand (48.4 ± 0.7 t/ha). Stand density for A. marina was highest in the 12-year-old plantation (4300 ± 919 stems/ha) while mean stem diameter (7.9 ± 0.7 cm) and basal area (16.2 ± 2.1 m²/ha) were highest in the natural stand. Below-ground biomass in the 12-year-old (43.7 ± 1.7 t/ha) and natural stands (39.1 ± 0.7 t/ha) was similar. Root densities decreased with soil depth and with distance from the base of trees for all species and stands. Fine roots (diameter <5 mm) constituted between 24% and 45% of the total stand live root biomass. The information generated is important in establishing the total biomass and thus the potential amount of carbon sequestered by mangroves in the study area.     

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.     

Characterisation of Afzelia africana Sm. habitat in the Lama forest reserve of Benin

A study was carried out in the Lama forest reserve of Benin to characterize the habitat of Afzelia africana Sm., an endangered multipurpose tree species (found in African humid, dry forests and woodlands), in order to define a sustainable management strategy for its conservation. An estimation of species density was done on 100 square plots of 1 ha each, while tree height and dbh of all the species were measured on subplots of 50 m × 30 m within the 1 ha plots. The regenerations of A. africana (dbh < 10 cm) were counted in the diagonal quadrats of the principal plots. Presence–absence data of the species was subjected to multidimensional scaling and results showed four vegetation communities including: young fallow, old fallow, typical dense forest and degraded dense forest. Significant differences were noted between the four communities with respect to dendrometric parameters of the species. High values of these parameters were noted for the species in typical dense forest (5.2 stems/ha, 66.7 cm, 17.9 m, 7.9 m²/ha and 38.8% for the tree-density, the mean diameter, the mean height, basal area and basal area contribution of the species, respectively) whereas the lowest values were obtained for the old preforest fallow as far as the mean diameter (59.7 cm), the mean height (15.7 m) and the basal area contribution (27.7%) of the species were concerned. In general, the basal area of A. africana in the over vegetation types was less than 3 m²/ha. No A. africana tree was found in the young preforest fallow while more than 80% of A. africana trees were found in the typical dense forest community. Stem diameter and height structures of the species in all the four communities showed a left dissymmetric Gaussian shape and were well adjusted to Weibull distribution.     

Crown plasticity and neighborhood interactions of European beech (Fagus sylvatica L.) in an old-growth forest

Competition for canopy space is a process of major importance in forest dynamics. Although virgin and old-growth European beech (Fagus sylvatica L.) forests in Europe have been studied for many years, there are to date no studies of individual-tree crown plasticity and the way this is influenced by local neighborhood interactions in these forests. In this study, we analyzed crown plasticity and local neighborhood interactions of individual trees in the upper canopy of the old-growth beech forests of Serrahn, northeast Germany. In a 2.8-ha sample plot, we measured crown radii of all upper canopy trees and analyzed the direction and extent of crown asymmetry. Size, relative position, and distance of neighboring trees were used to construct vectors of neighborhood asymmetry within different distances from target trees. The crowns of beech trees showed strong morphological plasticity. Mean absolute and relative displacement of crown centers from the stem base were 1.95 m and 0.37, respectively. Circular–circular rank correlation coefficients between the direction of crown displacement and the direction of neighborhood pressure showed that trees strongly positioned their crowns away from local neighbors. Highest correlation coefficients were obtained when basal area and relative position of neighboring trees within a radial distance of 12 m were considered. Clark and Evans index and Ripley’s K-function showed that crowns were more regularly distributed than stems. Projected canopy cover was about 10% higher than canopy cover with simulated circular crowns. We conclude that the crowns of older beech trees have a high ability to plastically respond to changes in the local canopy conditions, enabling very effective exploitation of canopy space.     

Do restoration fellings in protected forests increase the risk of bark beetle damages in adjacent forests? A case study from Fennoscandian boreal forest

Gap fellings are used to promote multi-cohort structures and to restore other natural forest structures and processes in protected areas that have been altered by anthropogenic activities. Gaps and felled trees may also provide breeding material for species that in high numbers can cause significant tree mortality, growth reduction and consequent economic losses in surrounding production forests. In this study, the effect of restoration gap fellings on feeding intensity of Tomicus spp. (pine shoot beetles) was evaluated by counting fallen pine shoots at different distances from gaps in a protected area in eastern Finland. Gap fellings had a clear effect on the feeding intensity of the beetles. The average density of fallen shoots m⁻² was 17 within a 10-m distance from gaps but decreased rapidly to around 4 at the distance of 50 m and beyond. The distance decay in shoot feeding is described well by the negative exponential models. Our results suggest that gap fellings have only a localized effect on shoot feeding by Tomicus in the forests surrounding the restoration gaps. In practical restoration, a buffer zone of 100–200 m around the gap fellings, as implemented here, is enough to minimize economically significant growth reduction in surrounding production forests. As shown in this study, restoration of natural forest structures and dynamics to protect biodiversity is not necessarily in conflict with forest hygiene objectives in production forests.     

Influence of coarse wood and pine saplings on nitrogen mineralization and microbial communities in young post-fire Pinus contorta

Nitrogen (N) limits productivity in many coniferous forests of the western US, but the influence of post-fire structure on N cycling rates in early successional stands is not well understood. We asked if the heterogeneity created by downed wood and regenerating pine saplings affected N mineralization and microbial community composition in 15-yr old lodgepole pine (Pinus contorta var. latifolia) stands established after the 1988 fires in Yellowstone National Park (Wyoming, USA). In three 0.25-ha plots, we measured annual in situ net N mineralization in mineral soil using resin cores (n = 100 per plot) under pine saplings, downed wood (legacy logs that survived the fire, and fire-killed trees that had fallen and were contacting or elevated above the ground), and in bare mineral soil. Annual in situ net N mineralization and net nitrification rates were both greater in bare mineral soil (8.4 ± 0.6 and 3.6 ± 0.3 mg N kg_soil⁻¹ yr⁻¹, respectively) than under pine saplings, contact logs, or elevated logs (ca. 3.9 ± 0.5 and 0.8 ± 0.1 mg N kg_soil⁻¹ yr⁻¹, respectively). Net nitrification was positively related to net N mineralization under all treatments except for elevated logs. In laboratory incubations using ¹⁵N pool dilution, NH₄⁺ consumption exceeded gross production by a factor of two in all treatments, but consumption and gross production were similar among treatments. Contrary to our initial hypothesis, microbial community composition also did not vary among treatments. Thus, two- to three-fold differences in in situ net N mineralization rates occurred despite the similarity in microbial communities and laboratory measures of gross production and consumption of NH₄⁺ among treatments. These results suggest the importance of microclimate on in situ annual soil N transformations, and differences among sites suggest that broader scale landscape conditions may also be important.     

Sustainability of extraction and production of copaiba (Copaifera multijuga Hayne) oleoresin in Manaus, AM, Brazil

We evaluate the ecological sustainability of extracting the oleoresin of Copaifera multijuga Hayne and some factors influential in its production. We monitored oleoresin production after initial extraction in 43 mother trees in the Adolpho Ducke Forest Reserve, near Manaus, Brazil (2°57′43″ S, 59°55′38″ W). We evaluated production relative to tree diameter (DBH), collection interval, soil clay content, competition intensity, and termite infestation. 57% of productive trees had DBH ≥ 41 cm and were responsible for 95% of total production. Although these trees had the highest initial production, after one year only 28% of initial oleoresin production was recuperated, much slower than in trees with DBH < 41 cm. Production was positively correlated with DBH and dominance within mother tree. Oleoresin production varied slightly with season. Trees that never produced oleoresin did not have termite infestations.