Effects of bamboo stands on seed rain and seed limitation in a rainforest

Bamboos often negatively affect tree recruitment, survival, and growth, leading to arrested tree regeneration in forested habitats. Studies so far have focused on the effects of bamboos on the performance of seedlings and saplings, but the influence of bamboos on forest dynamics may start very early in the forest regeneration process by altering seed rain patterns. We tested the prediction that the density and composition of the seed rain are altered and seed limitation is higher in stands of Guadua tagoara (B or bamboo stands), a large-sized woody bamboo native from the Brazilian Atlantic Forest, compared to forest patches without bamboos (NB or non-bamboo stands). Forty 1 m² seed traps were set in B and NB stands, and the seed rain was monitored monthly for 1 year. The seed rain was not greatly altered by the presence of bamboos: rarefied seed species richness was higher for B stands, patterns of dominance and density of seeds were similar between stands, and differences in overall composition were slight. Seed limitation, however, was greater at B stands, likely as a resulted of reduced tree density. Despite such reduced density, the presence of trees growing amidst and over the bamboos seems to play a key role in keeping the seeds falling in B stands because they serve as food sources for frugivores or simply as perches for them. The loss of such trees may lead to enhanced seed limitation, contributing ultimately to the self-perpetuating bamboo disturbance cycle.     

Parent tree effects on reestablishment of Acacia koa in abandoned pasture and the influence of initial density on stand development

Increasingly private landholders in Hawaii are considering native forest restoration for their lands, and some public agencies have already started such work. Initial efforts have focused on reestablishing Acacia koa to recover alien-grass-dominated sites. This study was done in Hakalau Forest National Wildlife Refuge, Island of Hawaii, to determine the efficacy of disk plowing to stimulate natural regeneration of koa from buried seeds. Sites with four different koa parent tree configurations were treated–single live overhead koa canopy, multiple live canopies, downed snags, and no parent koa tree. Tree growth and survival were assessed periodically over 21 years. Average initial stand densities ranged from 100 to 1,500 trees ha^?1 of scarified land, although some open areas had as few as 20 trees ha^?1. The distributions of seedlings with increasing distance from plot center were variable within and between parent tree configurations. Initial seedling density was significantly greater for the multiple-live-parent than for the no-parent configuration. Densities for the single-live and dead configurations differed from the no-parent configuration only when densities were based on the entire scarified area of each plot. Stand densities declined 10–67 % during the next 20 years. Survival was a negative, non-linear function of initial stand density. Initial stand density exerted strong control over stem diameter and crown size at age 21-years, but had little effect on the proportion of trees with single-stems. The relationships between stand basal area and density at 21 years conformed to the existing koa stocking guidelines. While moderate to high densities of natural regeneration can be expected from scarifying around live and dead koa trees, single trees or low density stands are likely in open areas.     

Regeneration of Rocky Mountain bristlecone pine (Pinus aristata) and limber pine (Pinus flexilis) three decades after stand-replacing fires

Rocky Mountain bristlecone pine (Pinus aristata) and limber pine (Pinus flexilis) are important high-elevation pines of the southern Rockies that are forecast to decline due to the recent spread of white pine blister rust (Cronartium ribicola) into this region. Proactive management strategies to promote the evolution of rust resistance and maintain ecosystem function require an improved understanding of the role of disturbance on the population dynamics of both species and environmental conditions that favor seedling establishment. We examined patterns of bristlecone and limber pine regeneration across the perimeters of three, 29-year-old, high-severity burns in northern, central, and southern Colorado: Ouzel, Badger Mountain, and Maes Creek, respectively. Both species exhibited a very protracted regeneration response to these fires. Bristlecone pine regeneration was concentrated near burn edges and beneath surviving seed sources. This spatial pattern is consistent with limitations incurred by wind-dispersal, also borne out by the low occurrence of seedling clusters. Relative to unburned stands, the absolute abundance of bristlecone pine generally increased only on plots retaining some surviving trees. Limber pine regeneration pattern varied between sites: high in the burn interior at Ouzel, concentrated at burn edges at Badger, and mostly in unburned stands at Maes. Clark’s Nutcracker dispersal of limber pine in each study area was indicated by high seedling distance from possible seed sources and high frequencies of clustered stems. Except at Ouzel, the absolute abundance of limber pine decreased in burns. Across sites, establishment by both species was boosted by nearby nurse objects (rocks, fallen logs, and standing tree trunks), a relationship that extended out at least as far as the closest three such objects, usually found within 50 cm. Fire decreased the frequency of Pedicularis but increased Castilleja and Ribes species (alternate hosts of white pine blister rust), though only one species, R. cereum, was positively associated with either pine species. We conclude that regeneration of bristlecone and limber pine may benefit from natural disturbance or proactive management creating appropriately sized openings and microtopographic structure (e.g., abundant fallen logs); however, beneficial responses may require many decades to be achieved.     

Are silvopastoral systems compatible with forest regeneration? An integrative approach in southern Patagonia

We used an integrated approach to analyze the influence of silvopastoral management on the biotic and abiotic factors influencing on the natural recruitment of native forests in Tierra del Fuego (Argentina). The probabilities of transition from flowers to seeds to seedlings were estimated in forests with silvopastoral management (i.e., stands that had been both grazed and thinned), secondary growth stands, and unmanaged old-growth areas. Pre-dispersal losses were caused by microclimate and insect predation acting on flowers and immature fruits. Post-dispersal losses resulted from the impact of reduced litterfall and microclimate. But the most critical stage of the overall cycle was seedling establishment. Silvopastoral practices and stand age modified the main drivers of regeneration. While flowering was unaffected by management, fruiting and seed production were more successful in unmanaged forests. Seedling establishment and survival were favored by canopy cover reduction in silvopastoral stands. The increase of solar radiation and soil moisture in managed forests positively influenced the seedling establishment and survival, while in second-growth forests it was limited by suitable micro-site availability. Thinning practices aimed at increasing the understory heterogeneity in mature forests and restoring canopy complexity of second-growth stands could be suitable for sustainable management of these temperate forests.     

Regeneration dynamics in remnant Tsuga canadensis stands in the northern Lake States: Potential direct and indirect effects of herbivory

We examined the effects of white-tailed deer (Odocoileus virginianus) herbivory and microsite limitation on Tsuga canadensis regeneration in 39 randomly selected remnant T. canadensis stands in Michigan's Upper Peninsula. Deer of the region migrate to and congregate in T. canadensis stands in winter resulting in strong seasonal habitat use patterns. In each study stand, we quantified vegetation, microsite availability, and deer use (via pellet counts). While some stands contained high densities of T. canadensis regeneration (stems < 4.0 cm dbh), we found complete T. canadensis regeneration failures in 6 out of 39 stands. Additionally, 17 and 22 stands respectively, had complete failures in the small and large sapling categories. General linear models suggested that deer use was the primary limiting factor in the small sapling size class, even at relatively low levels of deer use. T. canadensis seedling density was positively associated with the availability of high-decay coarse woody debris and negatively associated with basal area of Acer saccharum in the overstory. This latter association may be due, at least in part, to negative effects of broadleaf litter on T. canadensis establishment and a general trend toward increasing Acer abundance in the regeneration layer. Our results suggest that differential tolerance to browsing (Tsuga vs. Acer) in conjunction with reduced germination substrate availability may set up a scenario where successful T. canadensis establishments is more limited by legacy and indirect than direct effects given contemporary levels of deer use.     

Flying vs. climbing: Factors controlling arboreal seed removal in oak-beech forests

Nuts are heavy and nutritious seeds that need animals to be successfully dispersed. Most studies address nut removal by a single animal species once seeds fall onto the ground. However, nuts are also accessible before the seed drop and usually to a wide guild of seed foragers. This study examines the factors controlling arboreal seed removal in oak-beech forests within the whole guild of nut foragers. We found that seed-dispersing rodents (Apodemus sylvaticus) were the main acorn removers in the oaks (up to 3.75 m height), with a rapid seed encounter and a high removal rate. However, rodents did not climb the beech trees, probably due to their smoother bark in comparison to oak bark and/or the lower nutritional value of beechnuts with regard to acorns. Jays (Garrulus glandarius) were more abundant in oak stands (both dense and scattered) and clearly preferred acorns to beechnuts whereas nuthatches (Sitta europaea) were more abundant in beech stands and preferred beechnuts to acorns. Non-storing birds such as great tits (Parus major) also removed acorns and beechnuts, especially in the stands where oaks are dominant. Jays and rodents preferred sound seeds over insect-infested seeds but such a preference was not found for nuthatches. This study highlights that pure beech stands showed a reduced guild of arboreal nut foragers in comparison to oak stands. This different guild could probably affect the spatial patterns of seed dispersal, with a proportionally higher number of long dispersal events for acorns (mostly jay-dispersed) than for beechnuts (mostly nuthatch-dispersed). Long-distance dispersal of beechnuts (by jays) is determined by the presence of other preferred species (oaks) and their frequency of non-mast years. Seed location in different habitats strongly determines the contribution of different arboreal removers (including climbing rodents) and their removal speed, leading to a differential seed fate that will eventually affect tree regeneration. As nuthatches are sedentary birds, it is important to maintain old and dead trees where they can breed (crevices), forage (arthropods) and store seeds in order to favor beechnut dispersal and gene flow. By maintaining or favoring oak trees within beech stands we will ensure a wider guild of arboreal nut dispersers.     

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.     

Regeneration and structure of mixed conifer forests under single-tree harvest management in the western Bhutan Himalayas

We examined the regeneration and structure of mixed conifer forests under single-tree harvest management in western Bhutan. Sixteen 900 m² (30 m × 30 m) plots were sampled at four Forest Management Units (FMUs; Chamgang, Gidakom, Paro-Zonglela, and Haa-East) representing the forest type, including half the plots in single-tree harvest stands and half in unlogged stands. In addition, we solicited information on traditional forest management practices from informants using survey questionnaires and collected tree species data from felling records from respective local forest offices. Rural timber demand is concentrated on the removal of straight and well-formed bluepine trees for beams, planks, and scaffolding. Single-tree harvest, however, has not significantly altered stand structures from unlogged stands. Similarly, tree regeneration is not different when comparing single-tree harvest and unlogged stands, except at Chamgang FMU, where seedling densities were generally higher in harvested stands than in unlogged stands. These results indicate that single-tree harvest is not detrimental to regeneration and utilization of mixed conifer forests in western Bhutan.     

Early seedling establishment of two tropical montane cloud forest tree species: The role of native and exotic grasses

Tropical montane cloud forest has been undergoing a drastic reduction because of its widespread conversion to pastures. Once these forests have been cleared exotic grasses are deliberately introduced for forage production. Exotic grass species commonly form monodominant stands and produce more biomass than native grass species, resulting in the inhibition of secondary succession and tree regeneration. The purpose of this study was to assess the effect of native vs. exotic grass species on the early establishment of two native tree seedlings (Mexican alder, Alnus acuminata and Jalapa oak, Quercus xalapensis) on an abandoned farm in central Veracruz, Mexico. Seedling survival and growth were monitored (over 46 weeks) in relation to grass cover and height, and available photosynthetic active radiation (PAR). More seedlings survived in the presence of the native grass Panicum glutinosum than those growing with the exotic grass Cynodon plectostachyus (92% vs. 48%). The causes of seedling mortality varied between species; Q. xalapensis was affected by herbivory by voles but mainly in the exotic grass-dominated stands, whereas A. acuminata seedlings died due to competition with the exotic grass. A. acuminata seedlings increased more in height in the exotic grass-dominated stands (102 ± 7.8 cm) compared to native grass-dominated stands (51 ± 4.7 cm). Grass layer height, cover and available PAR were correlated (Pearson; p < 0.05). In the exotic grass dominated plots, grass layer height was correlated with the relative height growth rates of Q. xalapensis (Pearson; p < 0.05). These results indicate that the exotic grass may be affecting tree regeneration directly (grass competition) and indirectly (higher herbivory). Passive restoration may occur once P. glutinosum dominated pastures are abandoned. However, when C. plectostachyus dominates, introduction of early and mid successional tree seedlings protected against vole damage is needed.     

Forest management conditioning ground ant community structure and composition in temperate conifer forests in the Pyrenees Mountains

The search for indicators to monitor management impact on biodiversity is a crucial question because management practices promote changes in community structure and composition of different animal groups. This study explores the effect of widely conducted management practices (forest logging and livestock) in Pinus uncinata forests in the Pyrenees range (NE Spain) on the structure and composition of ground ant communities compared to those of old-growth stands. Forest structure clearly differed in stands with different forest managements. These stands managed for different uses also showed marked differences in structure and composition of ground ant communities. There was a great dominance of a single species, Formica lugubris, which accounted for 99% of ants collected in pitfall traps. Rarefaction curves indicated that species richness was highest in old-growth stands and lowest in even-aged ones, with woodland pasture stands showing an intermediate value. Classification methods allowed us to identify two groups of species: six species related to old-growth plots and three species (including F. lugubris) associated to managed stands. Habitat structure played an important role in determining the structure of ant communities: forests with high tree density but low basal area were the most favourable forest type for F. lugubris, while the abundance of the remaining ant species was negatively affected by the abundance of F. lugubris and by tree cover.     

Effects of ground preparation and microenvironment on germination and natural regeneration of Juniperus procera and Afrocarpus gracilior in Ethiopia

The seedling establishment of Juniperus procera Hochst. ex Endl. and Afrocarpus gracilior (Pilger) C. N. Page was assessed in the Afromontane forests of Ethiopia. Percent light transmission, litter depth and percentage cover of vegetation were assessed for seedling microsites in five sites with different levels and history of disturbance. The response of natural and artificial regeneration to burning, mechanical scarification (removal of all logging waste and ground vegetation) and cultivation following clear felling and timber extraction was assessed 19 months after treatment.There was no evidence that regeneration was correlated with light intensity. Despite the presence of a viable seed bank in the undisturbed forest floor, removal of the overstorey vegetation by clear felling did not encourage natural regeneration of J. procera. This suggests that light may not be the main factor limiting regeneration of J. procera.Natural regeneration of J. procera can withstand exposure and is compatible with management by ‘clear cutting with seeding from adjacent stands’ together with ground treatment, particularly controlled burning which exposes the minearl soil and releases nutrients. In contrast, both clear felling and surface disturbance will discourage the natural (or artificial) regeneration of A. gracilior suggesting that J. procera is a pioneer species which is more exposure-tolerant, whilst A. gracilior is more shade-tolerant and exposure-intolerant.     

Stand and landscape-level factors related to bird assemblages in exotic pine plantations: Implications for forest management

Plantations cover a substantial amount of Earth's terrestrial surface and this area is expected to increase dramatically in the coming decades. Pinus plantations make up approximately 32% of the global plantation estate. They are primarily managed for wood production, but have some capacity to support native fauna. This capacity likely varies with plantation management. We examined changes in the richness and frequency of occurrence of bird species at 32 plots within a Pinus radiata plantation (a management unit comprising multiple Pinus stands) in south-eastern Australia. Plots were stratified by distance to native forest, stand age class and thinning regime. We also assessed the landscape context of each plot to determine relationships between bird assemblages and stand and landscape-level factors. Bird species richness was significantly higher at plots ≥300 m from native forest and in mature (∼20 years since planting) and old (∼27 years since planting) thinned pine stands. We were able to separate the often confounding effects of stand age and thinning regime by including old stands that had never been thinned. These stands had significantly fewer species than thinned stands suggesting thinning regime, not age is a key factor to improving the capacity of pine plantations to support native species (although an age × thinning interaction may influence this result). At the landscape level, species richness increased in pine stands when they were closer to native riparian vegetation. There were no significant differences in species composition across plots. Our study indicates the importance of stand thinning and retention of native riparian vegetation in improving the value of pine plantations for the conservation of native fauna.     

Wildfire promotes broadleaves and species mixture in boreal forest

Postfire tree species compositions are predicted to be the same prior to fire according to the direct regeneration hypothesis (DRH). We studied 94 upland boreal forest stands between 5 and 18 years after fire in Ontario, Canada. Postfire species-specific regeneration density was positively related to prefire stand basal area for Pinus banksiana, Populus spp., Betula papyrifera and Picea mariana, but not for Picea glauca and Abies balsamea. In addition, seedling density of Populus spp., B. papyrifera, P. mariana, P. glauca and A. balsamea were positively affected by build up index and, except Populus spp., their density increased with age of burn. To facilitate testing the DRH, we introduced a term called compositional difference (CD) that is the difference in a species relative percentage between the postfire and prefire stand. The testable null hypothesis is CD = 0 for a given species. CD was not different from 0 for P. banksiana, was 19.8% for Populus spp., 10.4% for B. papyrifera, −17.9% for P. mariana, −14.6% for P. glauca, and −14.9% for A. balsamea, indicating fire increases broadleaves at the expenses of mid- and late-successional coniferous species. Compositional increases of Populus spp. and B. papyrifera in postfire stands occurred mostly where these species were a minor component prior to fire. In conclusion, the DRH was supported by the specific positive relationships between postfire regeneration densities and prefire basal area for P. banksiana, Populus spp., B. papyrifera and P. mariana. However, if the DRH is used for predicting postfire composition, P. banksiana is the only species that had the same composition between postfire and prefire stands. Nevertheless, CD for P. banksiana was negatively related to its prefire composition. Similarly, CD for other species was negatively related to their prefire compositions with varying effects of build up index and age of burn. Our results suggest, if fire occurrences increase with global change, the boreal landscape will be more dominated by hardwoods and mixtures of conifers and hardwoods.     

Can native vegetation recover after slash pine cultivation in the Brazilian Savanna?

There is a widespread view that forest plantations with exotic species are green deserts, unable to sustain biodiversity. Few studies have demonstrated, however, that planted stands of exotic trees have a greater negative effect on the plant diversity of savanna vegetation. We compared the native woody flora under four stands of slash pine of about 45 years old with four stands where the previously existing native Cerrado vegetation was preserved and protected from disturbances for the same period, has changed into dense vegetation - the “cerradão”, at Assis municipality, São Paulo State, Brazil. Aiming at understanding the potential ecological filters driving these communities, we assessed air and soil humidity, light availability and classified the native species on the basis of shade tolerance, dispersal syndrome and biomes in which they occur (Atlantic Forest or Cerrado). We recorded an average of 70 (±13) species under pine stands and 54 (±16) species in cerradão. Of the total of 136 species recorded, 78 occurred in both habitats, eight were exclusive to the “cerradão” (shade tolerant and also occurring in forest ecosystems) and 18 were recorded only under pine stands (82% heliophytic, exclusive to the Cerrado biome). Among the functional attributes and abiotic variables analyzed, only light availability explained the floristic differences found. Since richness was higher under pine, we refuted the hypothesis that exotic species constrain the establishment of the native species richness in the understory. On the other hand, the dark environment under the closed-canopy of the “cerradão” acts as a filter inhibiting the establishment of typical Cerrado species. Since pine stands, if managed in long cycle, maintain a reasonable pool of Cerrado endemic species in the understory pine plantations may be a good starting point for savanna restoration.     

Characterizing structural conditions in mature managed red pine: Spatial dependency of metrics and adequacy of plot size

Restoration of the range of forest types and stages that once composed the landscape mosaic of the Upper Great Lakes region of North America will involve manipulating managed red pine stands to recreate now rare structural conditions. Because many of the attributes used to characterize structural condition depend upon spatial arrangement, sampling schemes to assess condition must match sampling extent to attribute variability. To evaluate the metrics and scales appropriate for characterizing structural complexity in managed red pine, we applied metrics that incorporated one-, two-, and three-dimensional structural attributes to eight 1.0 ha mature stem-mapped stands. Most metrics were also calculated within simulated moving windows of 0.05–1.0 ha in sampling extent (“plot size”) within each stand. Two standards were used to evaluate the adequacy of plot sizes for these metrics: (1) estimates were precise, varying less than 10% among moving windows for a given scale, and (2) estimates were accurate to within 10% of the 1.0 ha value at both the 5th and 95th percentiles of the moving window distributions. Necessary sample sizes to achieve precise and accurate estimates were also calculated for each scale.     

Long-term effects of single prescribed fires on hardwood regeneration in oak shelterwood stands

One of the arguments against using prescribed fire to regenerate oak (Quercus spp.) forests is that the improvement in species composition of the hardwood regeneration pool is temporary and multiple burns are necessary to achieve and maintain oak dominance. To explore this concern, I re-inventoried a prescribed fire study conducted in the mid-1990s to determine the longevity of the effects of a single prescribed fire on hardwood regeneration. The initial study was conducted in three oak shelterwood stands in central Virginia, USA. In 1994, each stand was divided into four treatments (spring, summer, and winter burns and a control) and the hardwood regeneration was inventoried before the fires. During the burns, fire intensity was measured and categorized in each regeneration sampling plot. Second-year postfire data showed marked differences in species mortality rates, depending on season-of-burn and fire intensity: oak and hickory (Carya spp.) regeneration dominated areas burned by medium- to high-intensity fire during the spring and summer while yellow-poplar (Liriodendron tulipifera) and red maple (Acer rubrum) seedlings dominated unburned areas and all areas treated with low-intensity fire regardless of season-of-burn. The treatments were re-inventoried in 2006 and 2007 to determine whether these fire effects were still present. The new data show that the species distributions by season-of-burn and fire intensity found in 1996 still existed 11 years after the treatments. The fact that fire effects in oak shelterwood stands can last at least a decade has important management implications for resource professionals interested in sustaining oak forests in the eastern United States.     

Soil seed banks in four 22-year-old plantations in South China: Implications for restoration

To better understand the potentials of the soil seed banks in facilitating succession towards a more natural forest of native tree species, we quantified the size and composition of the soil seed banks in established plantations in South China. The seed banks were from four typical 22-year-old plantations, i.e., legume, mixed-conifer, mixed-native, and Eucalyptus overstory species. Species diversity in the seed banks was low, and the vegetation species differed from those found in the seed bank in each plantation. A total of 1211 seedlings belonging to eight species emerged in a seedling germination assay, among which Cyrtococcum patens was most abundant. All species detected were shrubs and herbs, and no viable indigenous tree seeds were found in soil samples. Size and species composition of the seed banks might be related to the overstory species compositions of the established plantations. The seed bank density in soils was highest in the mixed-conifer plantation followed by Eucalyptus, mixed-native, and legume plantations. Species richness among the seed banks of plantations was ranked as follows: Eucalyptus > mixed-conifer > mixed-native = legume. The results indicated that the soil seed banks of the current plantations are ineffective in regenerating the former communities after human disturbances. Particularly, the absence of indigenous tree species seeds in the seed banks would limit regeneration and probably contribute to arrested succession at the pioneer community stage. It would appear from these data that the soil seed banks under the current plantations should not be considered as a useful tool leading the succession to more natural stages. Introduction of target indigenous species by artificial seeding or seedling planting should be considered to accelerate forest regeneration.     

Pinus chiapensis, a keystone species: Genetics,ecology, and conservation

We present an overview of recent studies carried out on Pinus chiapensis (Mart.) Andresen (Pinus strobus var. chiapensis Mart.) and provide management and conservation recommendations. Because of its wood quality, and being commonly used by 12 ethnic groups, this pine is an outstanding forest resource at mid-altitude humid mountains of southern Mexico and Guatemala. P. chiapensis appears to be a distinctive species, closely related with North American white pines, and a potential valuable resource for establishing breeding programs with such species. P. chiapensis is the most abundant tree species in early successional stands of the tropical montane cloud forest playing a key role in ecosystem regeneration particularly in areas managed under slash-and-burn practices. However, many natural stands of this pine are severely reduced. Molecular studies based on isozymes and DNA markers reveal low genetic diversity, the lowest compared with its closest relatives (P. ayacahuite, P. monticola and P. strobus). Heterozygosity and seed viability increase significantly with population size, and inbreeding depression appears to significantly decrease seed viability, suggesting the involvement of genetic factors on population decline. Low population size is associated with both lack of perturbation in well-preserved habitats and high deforestation rates in severely disturbed habitats. Conservation and management practices require preserving and restoring connections between suitable habitats to enhance gene flow between populations, and on careful programs that monitor and control slash-and-burn practices. Restoration practices should use seeds from as many tree sources as possible to reduce inbreeding risks. Spline climate models predict significant increases in temperature, decreases in precipitation and consequently an increase of aridity along the range of P. chiapensis. Thus, assisted migration would be needed to match present genotypes to forecasted climate changes.