Remnant Trees Research Articles

Regional landscape-scale comparison of species composition and recruitment in remnant tree patches 3 years after the 2011 Great East Japan Earthquake and tsunami

Understanding species composition and other characteristics of remnant trees that survive large-scale low-frequency disturbances such as tsunamis is an important step in monitoring and managing the process of recovery. This research was implemented in a study area along the shores of Sendai Bay, a region that was heavily damaged by the tsunami following the Great East Japan Earthquake of 2011. Field surveys of all the remnant patches of trees in the study area were conducted in 2014, three years after the disturbance. A total of 202 remnant patches were identified, and all the tree species, including both canopy trees and newly established seedlings, were recorded for each patch. The identified trees totaled 88 species, which were classified into three indicator-species types by a hierarchical cluster analysis. Comparisons based on species composition and similarity showed that species composition and other characteristics of the remnant patches were influenced by vegetation histories and other factors that only become visible at the regional landscape scale. The number of tree and seedling species per unit area was highest in patches that originated from pine plantations. Seven of the 25 seedling species identified were not present in any of the canopy layers in the study area, indicating that they dispersed from outside this area. These results show that, despite the immense scale of the tsunami, many diverse patches of trees managed to survive the disturbance. These patches function as hubs for species dispersion and accelerate recovery of species diversity in the disturbed area.

Effectiveness of regulatory policy in curbing deforestation in a biodiversity hotspot

Recent rates of deforestation on private lands in Australia rival deforestation hotspots around the world, despite conservation policies in place to avert deforestation. This study uses causal impact estimation techniques to determine if a controversial conservation policy—the Vegetation Management Act (VMA)—has successfully reduced deforestation of remnant trees in the Brigalow Belt South, a 21.6 Mha biodiversity hotspot in Queensland. We use covariate matching to determine the regulatory effect of the policy on deforestation rates over time, compared to two counterfactual scenarios representing upper and lower estimates of policy impact. The VMA significantly reduced the rate of remnant deforestation in the highest impact scenario, saving 17, 729 ± 1733 ha during 2000–2016. In the lowest scenario, ‘panic clearing’ before and after enactment of the VMA minimized the amount of remnant forests saved and may have marginally increased deforestation relative to the counterfactual (−404 ± 617 ha). At peak effectiveness, the VMA successfully counteracted the amount of remnant deforestation during 2010–2012, but this only represents 4.78% of the 371, 252 ha of remnant forests cleared in the bioregion since enactment in 1999. Thus, while deforestation rates in the region have substantially reduced since the policy was enacted, our results of positive yet limited direct regulatory impact suggests the policy’s effectiveness is strongly confounded by other deforestation drivers, like changing socio-economic or climate conditions, as well as new social signals provoked by the policy. The mechanisms through which the policy influences deforestation behavior must be further investigated to ensure real, desirable change is achieved.

Drivers of biomass recovery in a secondary forested landscape of West Africa

The rapidly growing human population in West Africa has generated increasing demand for agricultural land and forest products. Consequently 90% of the original rainforest cover has now disappeared and the remainder is heavily fragmented and highly degraded. Although many studies have focused on carbon stocks and fluxes in intact African forests, little information exists on biomass recovery rates in secondary forests. We studied a chronosequence of 96 secondary and old-growth forest fragments (0.2 ha each) where 32.103 trees with Diameter at Breast Height >2.5 cm have been censused. We modelled the biomass recovery trajectories in a time-explicit Bayesian framework and tested the effect on recovery rates of a large set of covariates related to the physical environment, plot history, and forest connectivity. Recovery rate trajectory is highly non-linear: recovery rates accelerated from 1 to 37 years, when biomass recovery reached 4.23 Mg·ha−1·yr−1, and decelerated afterwards. We predict that, on average, 10%, 25% and 50% of the old-growth forest biomass is respectively recovered 17, 30, and 51 years after abandonment. Recovery rates are strongly shaped by both the number of remnant trees (residuals of the former old-growth forest) and the previous crop cultivated before abandonment. The latter induced large differences in the time needed to recover 50% of an old-growth forest biomass: from 38 years for former Yam fields up to 86 years for former rice fields. Our results emphasize (i) the very slow recovery rates of West African forests, as compared to Neotropical forests (ii) the long-lasting impacts of past human activities and management choices on ecosystem biomass recovery in West African degraded forests.

Calicioid diversity in humid inland British Columbia may increase into the 5th century after stand initiation

AbstractMaintenance of biodiversity in managed forested landscapes requires detailed knowledge of the ecological requirements of specialist organisms linked to key microhabitats. Here we examine the relationship of 37 lichenized and unlichenized epiphytic calicioid species to stand age and substratum type in seven pairs of mid-seral (70–165 y) and old (220–470 y) forest stands in humid east-central British Columbia. Based on our inventory of eight host tree species, total calicioid diversity and mean species richness are highest in old stands, with 12 species not detected and nine additional species much less frequent in mid-seral stands.Thuja plicatasupports by far the highest level of total calicioid diversity, with 31 of 37 species; mostly associated with very old trees. Owing primarily to the late recruitment of lignicolous calicioids, stand-level calicioid richness continues to increase into the 5th century after stand initiation. Our study thus has two major findings pertinent to the maintenance of forest biodiversity in managed forests: first, stand-level calicioid richness increases slightly for at least three centuries past the acquisition of old-growth status; second, remnant trees and snags carried forward into mid-seral, regenerating stands enhance overall calicioid species richness. These results suggest that very old old-growth (= ‘antique’) forests might play an important role in the long-term maintenance of calicioid species richness, further suggesting that the standard practice of lumping all forests above a set age into a single old-growth category is not ecologically tenable for all taxonomic groups.

Landscape change alters reproductive phenology and sex expression in Attalea palms (Arecaceae) of southwestern Amazonia

As deforestation and land-use/land-cover change advance in tropical forest regions, an understanding of how plants adjust phenology and reproductive dynamics to altered landscapes can provide insights into plasticity, productivity, and population persistence. We compared the reproductive phenology, sex expression, and flower and fruit production of two monoecious Amazonian palms, Attalea phalerata and Attalea speciosa, in old-growth forest and as remnant trees growing in actively grazed pastures. Using 2 years of phenology data collected from natural populations near Vila Extrema, Rondonia, and eastern Acre, Brazil, we compared flowering and fruiting in the two habitats and tested for effects of palm height, crown size, and light availability on inflorescence and sex expression. Forest conversion to pasture stimulated greater overall flowering and fruiting in individual Attalea palms. As a population, remnant pasture palms continuously bore flowers and fruits year-round, while forest palms flowered seasonally in isolated peaks with consecutive months of inactivity. Crown size and greater light exposure affected flowering and fruiting dynamics in A. phalerata and A. speciosa, respectively, and increased light availability shifted A. speciosa sex expression towards greater female investment, primarily through regulation of sex determination and bud abortion. Removal of tropical forest does not always lead to the downfall of remnant tree populations, and under favorable conditions, such as abandonment of cropland and pasture, higher levels of reproduction can facilitate recovery of future generations. Tree species with flexible sex expression may be particularly resilient in the face of land-use and land-cover change.

Avian community characteristics and demographics reveal how conservation value of regenerating tropical dry forest changes with forest age.

Expansion of secondary forests following the abandonment of agriculture may have important implications for bird conservation, but few studies have examined the dynamics of this process. We studied bird use of a chronosequence of differently-aged abandoned pastures regenerating to dry forest to better understand how the value of these habitats to birds changes over time. In a five year study on Hispaniola, we recorded 7,315 net captures of 60 species of landbirds in sites that began the study at two, five, 10, and 20 years post-abandonment, and in mature native dry forest. Twenty-five species made up 97% of all net captures. Highest capture rates were in the two youngest sites. These early-successional habitats had many over-wintering Neotropical migrants; among residents, granivores and frugivores predominated. In contrast, both the twenty-year-old and mature forest sites had few migrants, more resident insectivores and omnivorous species, and a greater proportion of endemics. Age and sex ratios, body condition and site persistence suggest early successional sites were sub-optimal for most over-wintering migrants, but habitat improved with age for three migratory species; results for permanent residents varied among species. Remnant trees and understory shrubs in the agroecological matrix likely contributed to avian diversity in regenerating dry forest sites, and proximity to mature forest also likely affected the diversity and abundance of birds in regenerating habitat. Our study shows that regenerating forests do not fully compensate for loss of mature dry forest habitat, even after 24 years of regeneration; natural restoration of complex microhabitats in dry forest sites converted to agriculture may take decades or longer. The highest value of regenerating forests may be as habitat for some over-wintering Neotropical migrants, and in creating a buffer zone that enhances biodiversity conservation by re-integrating these lands into the protected tracts of mature forest needed by the islands more unique and endemic bird species.

Thermal quality influences habitat use of two anole species

Regeneration of secondary forests on previously deforested or degraded land is one of the most dominant forms of land-use change in the tropics. However, the response of animal communities to forest regeneration is poorly understood. To evaluate support for thermal quality as a mechanism driving reptile species distributions during secondary forest succession, we measured operative temperatures and occupancy in three successional forest stages (pasture, secondary forest, and old growth forest) for two anole species common in the landscape (Norops humilis and Norops limifrons). We then measured thermal preference in laboratory experiments and used operative temperature and temperature preference measurements to determine how thermal quality of habitat changes over the course of secondary forest succession, and if occupancy varies as a function of thermal quality. We found that thermal quality was lowest in pasture habitat because of a large frequency of temperatures above the thermal preference range. However, in low thermal quality pasture sites, riparian habitats and remnant trees provided a thermal refuge for both lizard species. Our results support thermal quality as a mechanism for reptile species distributions in altered landscapes and highlight the importance of the maintenance of riparian corridors.

Land use legacy effects on woody vegetation in agricultural landscapes of south‐western Ethiopia

AbstractAimPast land use legacy effects—extinction debts and immigration credits—might be particularly pronounced in regions characterized by complex and dynamic landscape change. The aim of this study was to evaluate how current woody plant species distribution, composition and richness related to historical and present land uses.LocationA smallholder farming landscape in south‐western Ethiopia.MethodsWe surveyed woody plants in 72 randomly selected 1‐ha sites in farmland and grouped them into forest specialist, generalist and pioneer species. First, we investigated woody plant composition and distribution using non‐metric multidimensional scaling. Second, we modelled species richness in response to historical and current distance from the forest edge. Third, we examined diameter class distributions of trees in recently converted vs. permanent farmland.ResultsHistorical distance was a primary driver of woody plant composition and distribution. Generalist and pioneer species richness increased with historical distance. Forest specialists, however, did not respond to historical distance. Only few old individuals of forest specialist species remained in both recently converted and permanent farmlands.Main conclusionsOur findings suggest that any possible extinction debt for forest specialist species in farmland at the landscape scale was rapidly paid off, possibly because farmers cleared large remnant trees. In contrast, we found substantial evidence of immigration credits in farmland for generalist and pioneer species. This suggests that long‐established farmland may have unrecognized conservation values, although apparently not for forest specialist species. We suggest that conservation policies in south‐western Ethiopia should recognize not only forests, but also the complementary value of the agricultural mosaic—similar to the case of European cultural landscapes. A possible future priority could be to better reintegrate forest species in the farmland mosaic.

Birds as suppliers of pest control in cider apple orchards: Avian biodiversity drivers and insectivory effect

Making farming compatible with biodiversity conservation requires identifying the biodiversity drivers that operate in agricultural landscapes, while also addressing the role of biodiversity in ecosystem services. Such integrative information is, however, rare for specific biodiversity groups and services. Here, we focus on insectivorous birds in cider apple orchards in northern Spain, ascertaining the relationships between landscape- and orchard-scale features and bird biodiversity. We conducted field observations and experiments to estimate the potential of birds for controlling arthropod abundance and pest outbreaks in apple trees. Twenty-nine tree-dwelling, insectivorous bird species were observed during one year, inside and around cider apple orchards, with six abundant species representing a predictable core across sites and seasons. Bird abundance and richness increased with the availability of semi-natural woody habitats (hedgerows, remnant trees, and forest patches) both in the immediate neighborhood of the orchard and in the landscape within a 1-km radius of the orchard. Orchards with higher cover of apple tree canopy also harbored a greater abundance and richness of birds. Apple tree branches that were cage-excluded from birds and manually infested with aphids suffered increased shoot damage and aphid outbreak, compared to those that were aphid-infested but open to birds. Bird exclusion led to increased abundances of pest insects other than aphids, and also of other arthropods considered as natural enemies or mutualists of pests. Arthropod abundance was lower in those orchards showing higher abundances of insectivorous birds during spring and summer. Multi-scaled farming management, involving both within-field practices and regional land use schemes, should be considered in order to promote win–win scenarios in cider apple orchards, whereby species-rich assemblages of insectivorous birds provide effective pest control service.

Resource tracking and its conservation implications for an obligate frugivore (Procnias tricarunculatus, the three‐wattled bellbird)

AbstractIn Monteverde, Costa Rica, the vulnerable Three‐wattled Bellbird (Procnias tricarunculatus) feeds primarily upon the fruit of Lauraceae species during its reproductive and post‐reproductive seasons. To understand and advance appropriate conservation measures, this study identified the bellbird's foraging challenges in its search for a temporally and spatially fluctuating resource. Although there are at least 96 species of Lauraceae found in the five life zones of Monteverde, the distinct distributions of tree species both among and within life zones require the bellbirds to track seasonal fruiting across the various zones. In this 6‐year study, we monitored the fruiting of tree species and bellbird abundance in 24 study plots within its post‐reproductive life zone, the Premontane Wet forest, to identify preferred bellbird food resources and how the fruiting of these species drives the spatial distribution of the bellbird. Our research revealed phenological patterns of annual, biennial, and triennial fruiting with high levels of fruiting synchrony within several identified key fruit species. Of critical conservation importance is that no single species of Lauraceae produced a consistent food supply for bellbirds each year. Therefore, even within life zones, the bellbird's survival depends on its mobility to search for and obtain fruit, as well as the availability of fruits of multiple tree species. The conservation implications include focused attention on multiple core areas within given life zones, protection of existing forest and remnant trees, and forest restoration with plantings of multiple tree species. We suspect that other tropical frugivorous species face similar conservation challenges.

Human-induced vegetation changes did not affect tree progeny performance in a seasonally dry forest of central Argentina

Regeneration by seed is scarce in seasonally dry mountain forests; in these areas, shrub-grass patches intermingled with remnant trees are widespread due to anthropogenic fires and post-fire livestock grazing. We hypothesized that progeny performance of remnant trees would be reduced due to soil loss, water limitation and damage to tree structures. We assessed the progeny performance of three tree species (70 trees per species) distributed in seven sites in central Argentina; in those sites, forest patches and shrub-grass patches with remnant trees coexist at a relatively close distance. Our main results showed no significant differences between progeny of trees located in forest patches and that of shrub-grass patches regarding seed mass, germination percentage in laboratory, seedling growth in greenhouse and survival and growth of outplanted saplings. Thus, our results do not support a hypothesis of human disturbances causing loss of progeny performance in remnant trees. Trees may be resistant to environmental changes, or there may be compensatory mechanisms, such as reduction of competition from neighbor trees, or increased resource allocation to reproduction at the expense of adult survival. We conclude that remnant trees are valuable resources for forest restoration because the quality of their progeny is still intact.

Remnant Trees in Enrichment Planted Gaps in Quintana Roo, Mexico: Reasons for Retention and Effects on Seedlings

Natural forest management in the tropics is often impeded by scarcity of advanced regeneration of commercial species. To supplement natural regeneration in a forest managed by a community in the Selva Maya of Mexico, nursery-grown Swietenia macrophylla seedlings were planted in multiple-tree felling gaps, known as bosquetes. Remnant trees are often left standing in gaps for cultural and economic reasons or due to their official protected status. We focus on these purposefully retained trees and their impacts on planted seedlings. Sampled bosquetes were 400–1800 m2, of which remnant trees covered a mean of 29%. Seedling height growth rates over the first 18 months after out-planting more than doubled with increased canopy openness from 0.09 m year−1 under medium cover to 0.22 m year−1 in full sun. Liana infestations and shoot tip damage were most frequent on seedlings in the open, but, contrary to our expectations, height growth rates were 0.14 m year−1 faster for liana-infested seedlings than non-infested and did not differ between damaged and undamaged seedlings. Apparently the more rapid height growth of well-illuminated seedlings more than compensated for the effects of lianas or shoot tip damage. Despite the abundance of remnant trees and their negative effects on seedling growth, enrichment planting in bosquetes has potential for community-based natural forest management in the tropics in supplementing natural regeneration of commercial species. One obvious recommendation is to leave fewer remnant trees, especially those of commercial species that are non-merchantable due to stem defects and trees retained for no apparent reason, which together constituted half of the remnant crown cover in the sampled bosquetes. Finally, given the rapid growth of lianas and understory palms in large canopy gaps, at least the most vigorous of the planted seedlings should be tended for at least two years.

Effects of urbanization intensity on forest structural-taxonomic attributes, landscape patterns and their associations in Changchun, Northeast China: Implications for urban green infrastructure planning

Understanding the associations between urbanization intensity and urban forest structural-taxonomic attributes is a central theme of urban ecology, biodiversity conservation and forest management for maximizing ecological services to design proper urban green infrastructure. By selecting a typical provincial capital city of Changchun as an example, the effects of urbanization intensity (low, medium and heavy urbanization as measured by impervious surface area, ISA) on landscape patterns and structural-taxonomic attributes of urban forests were investigated in this study. The results showed that the urban forest Patch Density (PD), Landscape Shape Index (LSI), Interspersion & Juxtaposition Index (IJI), Tree Density (TD), Canopy Density (CD), Species Richness (SR) and Species Diversity (H’ index) exhibited strictly monotonic increases with urbanization intensity, increasing by 162%, 60%, 44%, 37%, 50%, 85%, and 84% from low to heavy urbanization areas, respectively. In contrast, the forest Mean Euclidian Nearest Neighbor Distance (ENN-MN) and Health Condition grade (HC) monotonically decreased by 12% and 37%, respectively. Furthermore, regression analysis suggested that structural-taxonomic attributes were closely associated with forest-related landscape patterns, but urbanization intensity dramatically influenced these associations. Our findings highlight that the planning of urban green infrastructure, in particular, urban afforestation and associated management, should be different at different urbanization intensities. In low urbanization areas, low Total area (TA, forest area) requires construction of larger forest patches and the protection of large remnant trees, and TD and above ground biomass (AGB) could be increased by enhancing the Mean Fractal Dimension (FRAC-MN) and PD, respectively. In medium urbanization areas, the same increases in TD and AGB could be more effectively achieved by decreasing the IJI and Area-Weighted Mean Contiguity (CONTIG-MN). Moreover, in heavy urbanization areas, more attention should be paid to increasing forest patch aggregation and contiguity, and both tree diversity and evenness could be increased by enhancing the FRAC-MN index. Because these structural-taxonomic attributes are the basis of various forest ecological services, our findings indicate that regulation of some of these landscape metrics could improve urban forest services in Changchun.

Estudio de hongos micorrizógenos arbusculares bajo árboles remanentes en un pastizal tropical

The remnant trees in casttle have a significant ecological importance because they alter the microhabitat and also affect biological interactions. Ali these factors improve mycorrhizal fungi establishment and forest vegetation species proliferation. The objective of this study was to determine space-temporal variation of the morphospecies of arbuscular mycorrhiza and their spores number under remnant trees. This study was carried out in a casttle, in the northern edge of the Biology Station of "Los Tuxtlas", Veracruz, Mexico. Four isolated trees (Ampelocera hottlei, Poulsenia armata and Ficus sp.) were chosen. Soil samples were collected under each tree cover during dry, rainy and "nortes" seasons. Thirteen arbuscular mycorrh izal species of the Glomaceae, Acaulosporaceae and Gigasporaceae families were observed. The number of spores among climatic seasons was significant different, the highest value was presented in "nortes" season and the lowest occurred in the dry season. There were no significant differences among isolated tree species, this could imply that the remnant tree function as a unit. Differential water availability, a long the year, may explain spores production variation.

Remnant trees and surrounding vegetation determine avian frugivore visitation of restored forest sites in Taiwan

Natural recovery is an important approach used in forest restoration in many parts of the world. The visitation of avian frugivores, a major source of seed rain in restored sites, is mainly controlled by bird assemblages in surrounding areas and their tendency to enter the restored sites. In this study, we examined the effects of remnant trees, surrounding vegetation, and seasons on avian frugivore visitation in 30 restored sampling plots and 15 edge sampling plots in subtropical Taiwan from 2013 to 2014. The results showed that both remnant trees and the surrounding vegetation were important in avian frugivore visitation of restored sites. Avian frugivores had a higher tendency to enter restored sites with diverse remnant trees and during the non-breeding season. An average of approximately 25% of the avian frugivore individuals in edge sampling plots entered the nearby restored sites within 15 min. Among three surrounding vegetation types, native forests had more frugivores than did conifer plantations. However, if the remnant trees had low species diversity, restored sites surrounded by native forests would have low frugivore visitation similar to restored sites surrounded by conifer plantations. We conclude that the species diversity of remnant trees is more important than the complexity of the surrounding vegetation in increasing avian frugivore visitation. Therefore, in order to promote increased seed rain at restored sites, it is important to maintain the species diversity of remnant trees. For restored sites with limited remnant trees or surrounded by conifer plantations, frugivore visitation would be low, and human intervention might be needed.

Exploring land-use legacy effects on taxonomic and functional diversity of woody plants in a rapidly urbanizing landscape

Urban vegetation is influenced by prior land use due to the dynamic nature of urban landscape. However, limited information is available on how strongly the land-use legacy impacts the diversity of urban vegetation, especially in areas of rapid urbanization. This study quantified the land-use legacy effect on taxonomic and functional diversity of woody plants in Haikou, China. We collected data on land use, percentages of woody vegetation cover, and abundance of woody plants from 461 randomly distributed sample plots. The influence of land-use legacy was examined by analyzing the land-use history of sample plots and taxonomic and functional α- and β-diversity of woody plants. The relative importance of the land use and the percentage of woody vegetation cover on the diversity of woody plants were analyzed using the boosted regression tree model. The result showed that the land-use legacy effect caused significant divergence in taxonomic and functional diversity of woody plants and the effect was most obvious in sites where the lands were currently used as residential areas. Remnant trees, shrubs, and possibly shrubs growing from seed banks and roots contributed to this legacy effect. We also found that taxonomic and functional α-diversities of trees in a site were influenced by how frequent the land use of the place was changed and what type of land use that the place ended up with. Based on our findings, we recommend conservation programs in rapidly urbanizing regions give more attention to vegetation in residential areas and particularly species with low utilitarian value.

Gene flow interruption in a recently human-modified landscape: The value of isolated trees for the maintenance of genetic diversity in a Mexican endemic red oak

Gene flow within and among populations is an important factor to maintain genetic cohesiveness and diversity across landscapes. Nowadays, human land use has led to a large forest conversion, creating many fragmented areas where remnant trees play an important role in conserving biodiversity. In this study, we analyzed the effects of a recent anthropogenic forest fragmentation on the genetic diversity and genetic heterogeneity of pollen pools accepted by individuals of the red oak Quercus castanea growing in forest patches and as isolated trees in central Mexico. Pollen movement was also evaluated by the analysis of outcrossing rates using seven nuclear microsatellites. We assumed that adult trees are remnants of the populations that existed previous to the forest fragmentation, while progenies of these trees are the result of recent reproductive events occurring after the fragmentation. We found high genetic diversity in both adult trees and progenies, even though progenies of isolated trees showed a significant reduction in heterozygosity as compared to their mother trees. However, the results of TWOGENER and mating system analyses indicated similar numbers of pollen donors in the progenies of mother trees from fragments and in isolated trees. Overall, our results suggest that gene flow is still extensive among forest fragments and isolated trees, conferring them a great value for the conservation of genetic diversity and connectivity.

ESTUDO E MODELAGEM DO CRESCIMENTO EM DIÂMETRO DE POVOAMENTOS DE <i>Pinus taeda</i> L. SUBMETIDOS A PODAS E DESBASTES NA ARGENTINA

A presente pesquisa foi realizada com o objetivo de estudar e modelar o efeito dos desbastes pré-comerciais e das podas no crescimento diamétrico, em um povoamento de Pinus taeda L. de 15 anos de idade, no Nordeste da Argentina. O estudo localizou-se em solo vermelho argiloso profundo com um delineamento sistemático de faixas para intensidades de desbastes e subfaixas para intensidades de podas. Os tratamentos de desbaste, realizados aos 3 anos de idade, foram: 1666 (sem desbaste); 833; 416 e 208 árvores ha-1. As podas foram realizadas a partir dos 3 anos e com frequência anual por 2, 3 ou 4 anos consecutivos, com remoção de 30, 50 e 70% da copa viva, respectivamente. O modelo geral obtido por regressão linear permitiu estimar o diâmetro da árvore de área basal média (dg) em função da idade com boa precisão (desvio médio absoluto em percentagem igual a 5.71), sendo as variáveis: árvores remanescentes, copa remanescente e número de podas consideradas nos modelos estimadores dos coeficientes da função geral. Aos 15 anos de idade, os diâmetros variaram entre 25.6 e 41.5 cm, para as densidades de 1666 e 208 árvores ha-1, respectivamente, sem poda. O crescimento do dg foi afetado negativamente pelas podas e positivamente pelos desbastes.

Wind contribution to yearly silver fir (Abies alba Mill.) compression wood development in the Romanian Carpathians

Since the 1950s, wind has represented one of the main disturbances to forest ecosystems in Europe, causing an increase in the frequency and amount of trees uprooted or broken by wind. Such phenomenon has also increased the incidence of compression wood in the xylem of remnant trees, thus leading to a general decrease in timber quality. In this study, we aimed to determine how wind regime affects the incidence of compression wood by reconstructing its chronology at both inter- and intra-annual scale using dendroclimatic methods. Six silver fir stands at different elevations were selected in central Romania, and compression wood time series were obtained from both increment cores from standing trees and radial discs from felled trees. Wood-structure variables were statistically analyzed as time series, while fluctuations of wind frequency and speed over the period 1921-present were reconstructed based on meteorological data. The structural response of sampled trees to wind was assessed based on the annual fluctuation in the frequency and intensity of compression wood. Results showed that the incidence of compression wood in the time series was synchronized with the intensity of the wind, rather than its duration. Wind regime in December of the preceding calendar year was significantly correlated with the frequency of compression wood, whereas its intensity was significantly correlated with wind load of previous September. The response of cambium to the wind stimulus increased with distance from the tree collar, peaking in the section at the base of the crown. At a decennial scale, only high-intensity wind stress triggered structural responses in the studied trees. Wind effects on xylogenesis in the analyzed stands increased over the last decades as a consequence of the local forest management. A better understanding of the structural response of forest trees to wind regime may explain how individual and groups of trees compete for stability and can help to improve forest management strategies in windy regions.

Landscape Factors and Restoration Practices Associated with Initial Reforestation Success in Haiti

Mountainous land in Haiti is highly degraded following decades of deforestation and erosion. Although mountainous landscapes represent an important target for forest recovery, there is a lack of empirical information to guide reforestation of sloping tropical lands. Using sapling survival data from 299 replicated reforestation plots planted with 24 dry forest species during 2007–2008 in Haiti, we examined the association of sapling survival with topographical, climatic, and landscape level variables. Our analysis indicates that the total number of surviving saplings was strongly correlated to sites with higher water availability, including sites with greater precipitation in dry months and sites with cooler (N/E) exposures. Sites with more adult remnant trees had higher sapling survival. Sapling survival was also improved by the use of best management practices of building micro-catchments and planting multiple sapling species into reforestation plots. Year effects were also significant and modified the effects of exposure, nurse trees, and soil rockiness. This temporal variation suggests sapling responses to environmental factors are sensitive to variation in rainfall.