Emerging forests on abandoned land: Puerto Rico’s new forests

The species composition of forests change continuously as the earth’s biota evolves and adjusts to environmental change. Humans are accelerating the rate of species turnover by moving species around the planet and dramatically changing environmental conditions. Our focus is on new forests in Puerto Rico that emerge naturally on abandoned lands previously converted to agriculture and degraded. These forest stands have combinations of species that are new to the island’s landscapes. New forests exhibit high species dominance during forest establishment, which includes dominance by alien tree species. These alien tree species establish and maintain forest cover, which may facilitate regeneration of native tree species. Landscape analysis and literature review revealed that these emerging stands are highly fragmented (60% were <1 ha in 1991), function as refugia for native organisms, and at 60–80 years old have similar species richness and structural features as native stands of similar age. However, the island’s new forests exhibit important differences from mature native forests on unconverted forestlands. New forests have fewer endemic species and fewer large trees (≥55 cm dbh) than mature native forests; they have higher soil bulk density and lower soil carbon and litter stocks; and they accumulate aboveground biomass, basal area, and soil carbon more slowly than native forests of similar age. We suggest that new forests will become increasingly prevalent in the biosphere in response to novel environmental conditions introduced to the planet by humans.     

Structure and species composition of novel forests dominated by an introduced species in northcentral Puerto Rico

The African tulip tree, Spathodea campanulata Beauv., is an introduced species forming novel forest types in Puerto Rico. These forests develop naturally after deforestation, agricultural use and land abandonment, and there are many questions as to their ecological characteristics. We sampled structure and species composition of large, small, and juvenile trees (≥10, ≥2.5 to <10, and <2.5 cm diameter at breast height, respectively) in nine secondary forests dominated by S. campanulata on alluvial, karst, and volcanic substrates in northcentral Puerto Rico. No differences were found in S. campanulata forest structure between substrates. Of a total of 79 species found, 17 were introduced. Forests on karst and alluvium had the highest and lowest global species richness, respectively. Species richness increased from large to small to juvenile trees in most sites, but more so on karst. The percentage of introduced species was inversely related to species richness of tree size classes on all substrate types. The dominance of S. campanulata in the large tree size class was highest and lowest in alluvial and volcanic sites, respectively, and decreased from large to small to juvenile trees on all substrate types. Species richness of S. campanulata forests is lower than that of native forests on equivalent substrates. Although land use history affects composition, the juvenile tree species established in S. campanulata forests seems to correspond to the geological substrate were sites are found. This study shows S. campanulata restores forest structure and native tree species on abandoned agriculture and grazing lands in Puerto Rico. Management of these novel forests should consider them as resources were natural processes have the potential of making them more diverse.     

Allometry, biomass, and chemical content of Novel African Tulip Tree (Spathodea campanulata) Forests in Puerto Rico

The African tulip tree, Spathodea campanulata, the most common tree in Puerto Rico, forms novel forest types with mixtures of native and other introduced tree species. Novel forests increase in area in response to human activity and there is no information about their biomass accumulation and nutrient cycling. We established allometric relationships and chemically analyzed plant parts of African tulip trees to determine the concentration and standing stock of chemical elements (C, N, P, K, Ca, Mg, S, Mn, Al, Fe, Na), and ash. Trees ranged in diameter at breast height from 8 to 85 cm and in height from 8.8 to 28 m. The concentrations of N, P, K, and Ca in leaves of the African tulip tree were similar to those of the native pioneer Cecropia schreberiana and higher than those of mature forest tree species in Puerto Rico. The over bark wood volume of African tulip trees in nine forest stands where it was dominant ranged from 163 to 849 m³/ha. Aboveground biomass ranged from 60 to 296 Mg/ha, and N and P stocks ranged from 190 to 988 and 32 to 137 kg/ha, respectively. Novel forests on abandoned agricultural lands can store more biomass and elements than native and plantation forest stands of similar age.     

Diversity and composition of tropical secondary forests recovering from large-scale clearing: results from the 1990 inventory in Puerto Rico

The extensive recovery from agricultural clearing of Puerto Rican forests over the past half-century provides a good opportunity to study tropical forest recovery on a landscape scale. Using ordination and regression techniques, we analyzed forest inventory data from across Puerto Rico’s moist and wet secondary forests to evaluate their species composition and whether the landscape structure of older forest affected tree species composition of recovering forests at this scale. Our results support conclusions from studies conducted in Puerto Rico at smaller scales and temperate forests at larger scales that timing of abandonment and land use history are of overwhelming importance in determining the species composition of recovering forests. Forest recovery is recent enough in Puerto Rico that previous land use is clearly evident in current species composition, and creates new forest communities. As demonstrated in other work, physical factors such as elevation and substrate co-vary with land use history, so that the species composition of the forest landscape results from the interplay between biophysical and socioeconomic forces over time. Our results also indicate that increasing the distance to the largest forest patches occurring in the landscape 12 years previous had a small negative impact on species richness but not species diversity or community composition. We conclude that land use history has as much influence in species composition as biophysical variables and that, at the scale of this study, there is no large influence of forest landscape structure on species diversity or composition.     

Climate shapes the novel plant communities that form after deforestation in Puerto Rico and the U.S. Virgin Islands

Environmental and past land use controls on tree species assemblages on the Commonwealth of Puerto Rico and the U.S. Virgin Islands were characterized to determine whether biophysical factors or land-use history has been more important in determining the species composition of secondary tropical forests after large-scale forest clearing for agriculture, widespread species introduction, and landscape-scale forest fragmentation. Post-deforestation, secondary forest assemblages are comprehensively described, both as broad general assemblages and island-specific variations by calculating species importance values from forest inventory data. Hierarchical clustering and indicator species analysis defined species assemblages, and then correlations between species assemblages and environmental variables were explored with non-metric multidimensional scaling, analysis of variance and χ² testing. These assemblages are arrayed along environmental gradients of decreasing spring moisture stress, decreasing maximum temperatures, and increasing minimum temperatures. Land-use history is not as important to determining variation in species composition across climatic zones, although several species assemblages are associated with certain geology types or land-use histories. Naturalized tree species are prominent in these secondary forests and contribute to the formation of some novel assemblages, but native late and early successional species also colonize former agricultural land, all influenced by the degree of disturbance. We conclude that environmental factors have an overarching effect on forest species composition across the broader range of climatic, geologic and topographic conditions and larger geographic scales, while land-use history influences subtropical secondary forest species assemblages within a specific climatic zone or set of relatively narrow environmental conditions.     

Ecological integrity of remnant montane forests along an urban gradient in the Sierra Nevada

Urban development typically has extensive and intensive effects on native ecosystems, including vegetation communities and their associated biota. Increasingly, urban planning strives to retain elements of native ecosystems to meet multiple social and ecological objectives. The ecological integrity of native forests in an urbanizing landscape is challenged by a myriad of impacts, such as forest management and invasive species. Environmental protection efforts in the Lake Tahoe basin, spanning the California/Nevada border in the Sierra Nevada mountains, over the past half century have resulted in the retention of thousands of parcels of remnant native forest located throughout the urbanizing landscape. The basin landscape provides an opportunity to evaluate the effects of land development on the composition and structure of remnant native forests along a gradient of urbanization. We sampled 118 sites located in remnant forests in the lower montane zone surrounded by 0–70% development. We also sampled forest structure in the landscape surrounding 75 of these sites to evaluate the contribution of remnant forests to the retention of native forest elements in the larger landscape. We characterized plant species composition and cover, vertical structure, and the density of trees, snags, and logs, as well as levels of ground disturbance and human activity. We found that remnant native forests retained much of their compositional and structural character along the development gradient, including large tree density, total canopy cover, and plant species richness. Notable exceptions were reductions in the density and decay stage of snags and logs, and the density of understory trees. We also observed increases in the richness and cover of herb and grass species and increases in the number of exotic plant species. In contrast, structural complexity was reduced in the landscape surrounding forest remnants in all measures except large tree density. We conclude that remnant native forests contribute significantly to maintaining native species in an urbanizing landscape, and that land conservation practices have an important role to play in protecting native forest ecosystems.     

Exotic earthworms of great lakes forests: A search for indicator plant species in maple forests

The invasion of exotic earthworms in previously earthworm-free northern deciduous forests has been linked to the disappearance of forest floor litter, declines in plant species richness, and the development of monotypic stands of Carex pensylvanica. However, the impact of exotic earthworms on the regeneration of trees and understory plants is largely unknown. We examined the relationships between earthworm density, plant species richness, leaf litter accumulation, number of tree (Acer) seedlings, and cover of C. pensylvanica at 14 sites in mesic hardwood forests of the Chequamegon-Nicolet National Forest in northern Wisconsin. Earthworm biomass, especially of the genera Lumbricus, Aporrectodea, and Octolasion was negatively associated with leaf litter mass and number of Acer seedlings. Nine plant species, including two spring ephemerals (Dicentra cucullaria and Osmorhiza claytonii), a sedge (Carex deweyana), and an invasive mint (Galeopsis tetrahit) were negatively correlated with exotic earthworm densities. Dryopteris intermedia and Allium tricoccum, on the other hand, were associated with high earthworm densities. The activities of exotic earthworms appear to have significant impacts on Acer regeneration and the persistence of many herbaceous plants. Our findings suggest that the effects of exotic earthworms on litter mass are strongly related to the observed effects on species composition. Sensitive species can be used as indicators of high and low earthworm densities and might be useful for identifying forests of high conservation value where future invasions of exotic earthworms should be prevented.     

Patterns of exotic plant invasions in Pennsylvania’s Allegheny National Forest using intensive Forest Inventory and Analysis plots

Intensive Forest Inventory and Analysis (FIA) plot data collected in the Allegheny National Forest (ANF), Pennsylvania, between 1999 and 2006 were evaluated for their ability to predict ANF’s vulnerability to invasion by exotic plants. A total of 26 variables classified by biotic, abiotic, or disturbance characteristics were examined. Likelihood of colonization by invasive exotic and non-invasive exotic plants was analyzed using a logistic regression model. Approximately, 11% of the 449 species documented in these plots were exotic, which is higher than has been found in other northeastern forested plots. Only 1% of the ANF flora was invasive exotic plants and these were at low abundance, confirming that most invasions are still at an early stage of establishment. Sites richer in native or non-invasive exotic plants and with more alkaline soils were more likely to be invaded. Younger forests, forests with non-forest patches present, and forests rich in native species were more likely to be colonized by exotic (invasive or non-invasive) plants. Frangula alnus, which is starting to spread locally, differed from the other invasive exotic species in terms of its association with high sapling density to tree density ratios, high soil nitrogen levels, and the presence of fire. Variables representing mortality due to beech bark disease and distance to the nearest exotic planting manifested counterintuitive results. In both cases, the combined occurrence of mortality due to beech bark disease or a close (less than 500 m away) known propagule source and the presence of an invasive or non-invasive exotic plant was rare. We encourage increased use of intensive sampling for FIA in the U.S.A. and similar monitoring programs in other countries, but suggest adding a step to the plot selection phase that would allow forest-wide or regional stratified sampling of typically coarse-scale variables, such as historic or predicted defoliation or fire events, and forest or land type. A more accurate picture of the importance of disturbance variables in defining forest vulnerability to plant invasion may be achieved.     

Ecological consequences of an exotic fungal disease in eastern U.S. hardwood forests

Exotic pests and pathogens can cause extensive mortality of native species resulting in cascading effects within an ecosystem. As ecosystems lose species to exotic enemies, ecosystem function may be disrupted if the ecological roles are not filled by the remaining species. To illustrate this concept, this paper examines the impacts of an exotic fungus (Discula dectructiva) on flowering dogwood (Cornus florida), historically a common understory tree species in eastern U.S. hardwood forests. Recent studies indicate that dogwood plays an important role in the health and ecological integrity of forest ecosystems throughout the eastern U.S. by increasing the availability of calcium in the biota-rich surface horizons of forest soils. However, Discula destructiva causes a disease, dogwood anthracnose, which can rapidly kill dogwood trees. This paper also illustrates how past fire has increased dogwood density and improved tree health in areas infected with anthracnose, suggesting that prescribed fire may offer a tool for land managers to maintain dogwood as a component in eastern U.S. hardwood forests by shifting the “ideal” disturbance regime of this previously fire-intolerant species.     

Distance to flood meadows as a predictor of use of <Emphasis Type="Italic">Nothofagus pumilio</Emphasis> forest by livestock and resulting impact,in Patagonia,Argentina

Seedling browsing by livestock has been indicated as major threat for forest sustainability use. Nothofagus pumilio forests are part of the livestock raising system in Patagonia, but because of the sparse understory cover, livestock graze mainly on flood meadows within the forest matrix. The complexity of the environment under study (forests and flood meadows) means that an adaptive predictor is needed to evaluate the intensity of resource use by livestock in order to assess its effect on the forest. Distance to flood meadows was evaluated as a predictor of the use intensity of the forest by livestock and its effect on the understory. The study was conducted at three sites in Chubut Province, Patagonia–Argentina. We established transects in the forest 320 m long, starting at the edge flood meadow-forest. In these transects, the livestock presence indicators (soil compaction, density of feces and trails) and composition of the understory were evaluated. Generalized Linear Model for repeated measures for longitudinal data were used. The indicators showed that distance is efficient for estimating forest use intensity by livestock. The understory varied with distance, the cover of exotic herbaceous was higher near the flood meadow. Far from the flood meadow, the cover was entirely composited of native species. The results support the use of distance to flood meadows as a tool for decision making in livestock and forest management in N. pumilio forests, and for further research on livestock effect on the forest.     

Floristic and structural recovery of a laurel forest community after clear-cutting: A 60 years chronosequence on La Palma (Canary Islands)

We analyzed a post-clearcut chronosequence (0.5 to 60 years after harvesting) in the laurel forest of La Palma island (Canarian Archipelago) to determine the recovery of the stands with respect to species composition, richness, life strategies and structural parameters of the canopy. Multivariate analysis showed that exotic species, as well as annual ruderal species were confined to early-successional stages, while native perennials, typical of laurel forests, dominated the late-successional stages. Total species richness decreased significantly with time after clear-cutting. The relative fast recovery of understory native species may be due to low forest floor disturbance during harvesting. Shade-intolerant pioneer, pioneer-remnant and shade-tolerant late-successional species were the main life strategies of native tree species. Most structural parameters showed a continuous and monotonic increase (basal area, biomass) or decrease (density, percentage of photosynthetic biomass) during succession. Once clear-cutting, here performed with an interval of 8 years, is abandoned, the recovery of the laurel forest seems possible due to careful logging that protects the soil and a rapid asexual regeneration of native tree species, revealing this to be a sustainable management practice.     

Understory diversity and composition after planting of teak and mahogany in Yogyakarta,Indonesia

ABSTRACT

Forest rehabilitation is when a desired tree species is planted in degraded forests or lands. Rehabilitation by planting a single tree species is a common way to restore exploited forests to maintain ecological processes. We compared woody and herbaceous understory vegetation between forests rehabilitated by mahogany (N = 12) or teak (N = 12) planted from 1941 until 2003 in Yogyakarta, Indonesia. Understory vegetation of these areas was compared with that of three native forests. Species richness, species diversity, density of plants and proportion of native plants did not differ between the rehabilitated areas and the native forest. Recently rehabilitated areas were different from the native forests while 41–74 yr after rehabilitation, characteristics of understory vegetation approached those of native forest. We described species composition using ordination, and found it to differ between areas rehabilitated with teak and with mahogany and, particularly, between the rehabilitated areas and the native forests. Time since rehabilitation and tree species planted were important for the species composition of understory vegetation. We conclude that the selection of species for rehabilitation and letting rehabilitated areas mature are important for understory development and species diversity.     

A review of the roles of forest canopy gaps

Treefall gap, canopy opening caused by the death of one or more trees, is the dominant form of disturbance in many forest systems worldwide. Gaps play an important role in forest ecology helping to pre- serve bio- and pedo-diversity, influencing nutrient cycles, and maintain- ing the complex structure of the late-successional forests. Over the last 30 years, numerous reviews have been written describing gap dynamics. Here we synthesize current understanding on gap dynamics relating to tree regeneration with particular emphasis on gap characteristics consid- ered critical to develop ecologically sustainable forest management sys- tems and to conserve native biodiversity. Specifically, we addressed the question： how do gaps influence forest structure？ From the literature re- viewed, the size of gaps induces important changes in factors such as light intensity, soil humidity and soil biological properties that influence tree species regeneration and differ in gaps of different sizes. Shade- tolerant species can colonize small gaps; shade-intolerant species need large gaps for successful regeneration. Additionally, gap dynamics differ between temperate, boreal, and tropical forests, showing the importance of climate differences in driving forest regeneration. This review summa- rizes information of use to forest managers who design cutting regimes that mimic natural disturbances and who must consider forest structure, forest climate, and the role of natural disturbance in their designs.     

肯尼亚泰塔山区东部弧形山云层森林的外来森林与本土森林树种多样性、丰富度和相似性比较(英文)

对肯尼亚东南部泰塔(Taita)山区的3片破碎的森林进行了树种生物多样性评估,比较外来的松树、柏树、桉树人工林的物种多样性以及外来树种森林和本土森林物种多样性。研究地点为Ngangao(120 hm2)、Chawia(86 hm2)和Mbololo(185 hm2)。采用Y型设计设立32个样区,包含65个小样区。按树种记录每个小样区胸高直径5cm和5cm以上的幼树,同时也记录了各树木的更新情况(幼苗和树苗)。用 Shannon-weiner指数计算了物种的多样性和均匀度。导处的 Shannon指数被进一步转化成有效的数值,用于展示物种多样性的差别幅度。为了评估物种多样性的差别,进行单因素方差分析,为了分离均值,分别用Tukey HSD法和Duncan检测法验证偶数和奇数样品。采用Jaccard相似指数评估物种的类似性。共有58个树种的林木密度变化在每公顷10到2000棵树之间。森林类型和立地之间的物种多样性存在显著差异。本地森林的物种多样性比外来树种森林高;Chawia立地的物种多样性比Nganga和Mbololo立地高,且更新的树种数量也比其他2个立地多,包括野柠檬木(Xymalos monospora)、黑皮密花木(Rapanea melanophloeos)、和(几内亚蒲桃(Syzygium guineense),这些树种具有低干扰属性。这些发现说明,本地森林物种多样性比较高,正如热带地区所预期。Chawia立地的物种多样性高说明此地经历干扰比其他2个立地大。在Chawia地区发现有低干扰树种更新,说明有长期土壤种子库的存在。在Nganga和Mbololo地区发现的外来树种样地上的更新较差情况,可能是缺少种子库所致,因为很多人工林是造在裸地上(如Nganga地区),或者是因为某些树种固有的生理特性(相生相克)抑制了其他树种的更新。     

Liana abundance in a Puerto Rican forest

Liana (woody vine) abundance varies among tropical forests and is often high in disturbed forests. In two areas of subtropical wet forest in Puerto Rico, El Verde and Bisley, we recorded the density of liana stems ≥1 cm dbh, and the percent of tree crowns (trees ≥10 cm dbh) that lianas infested. Both study areas have been disturbed by hurricanes several times in the past century; however, sample plots in each area were divided between plots that were less disturbed and those that were more disturbed, by both hurricanes and humans. The mean density and basal area of liana stems at El Verde were significantly higher in the less disturbed plots than in the more disturbed plots. The percent tree crown infested by lianas was higher on certain tree species and on larger trees, both of which characterized the less disturbed forest. Results at Bisley were similar to those at El Verde. Liana density and tree crown infestation in these Puerto Rican forests were low compared with most other tropical forests, contrasting especially with high values in other disturbed forests. Liana abundance varies among forests for complex reasons, including differences in disturbance, biogeography, seasonality, and tree host features.     

Successional process of Picea crassifolia forest after logging disturbance in semiarid mountains: A case study in the Qilian Mountains,northwestern China

Selective logging is the most widely employed method of commercial timber production in Asia, and its impact on forest structure, composition, and regeneration dynamics is considerable. However, the successional processes in forest communities after logging in semiarid mountains are poorly understood. To provide more information on these processes, we used data from tree rings, direct and indirect age determinations, and field measurements of stand structure to reconstruct the historical disturbance regime, stand development patterns, and successional processes in a natural Picea crassifolia forest community in the Qilian Mountains of northwestern China. The results showed that the density of P. crassifolia forest increased significantly after logging. The densities of second growth forests 30 and 70 years after logging disturbance had increased to 2874% and 294% of primary forest's density, respectively. Logging disturbance did not alter tree species composition of logged stands. However, the diversity of understory species changed significantly among the successional phases. Logging disturbance decreased the spatial heterogeneity of second growth forest. The spatial distributions of recruitment were affected by the location of the remaining trees. There was less recruitment near the remaining trees than near forest that had been cut. In addition, logging disturbance also induced a growth release for the trees on the sites sampled. Our results imply that the succession and regeneration of P. crassifolia forest may be improved if the remaining trees could be retained relative uniform distribution pattern, thinning or selective logging could be performed to height density, exotic shrubs could be removed or the shrubs cover could be reduced during the earlier successional stages.     

Bird use of logging gaps in a subtropical mountain forest: The influence of habitat structure and resource abundance in the Yungas of Argentina

Selective logging is one of the main economical activities in tropical and subtropical forests. While most of the effects of this activity on bird communities have been studied by comparing exploited vs. non-exploited areas; the use of human-created treefall gaps by birds is relatively unknown. We studied habitat structure, resource abundance (fruits, flowers and arthropods) and bird activity in logging gaps of different age (1-year-old and 10- to 20-year-old) in a mountain forest (Yungas) of northwest Argentina in both dry and wet seasons. In less than a year after creation, short herbs colonize logging gaps increasing the abundance of arthropods in the ground and the activity of understory insectivores. During dry seasons recently created gaps become an important source of resources for understory frugivores-insectivores. Later on in succession logging gaps are invaded by exotic graminoid vegetation and tall herbs (dispersed through extraction tracks) which can impede the colonization and development of pioneer trees and natural regeneration. Probably as a consequence of a high abundance of fruits and flowers in the understory and a very low abundance of these resources in the canopy, old gaps were mainly used by understory frugivores-insectivores while arboreal frugivores were rare. Because arboreal frugivores disperse most tree seeds in tropical and subtropical forests, the low activity of this guild in logging gaps contribute to the low observed regeneration. Sustainable timber harvest in tropical and subtropical forests should include gap and logging track management to minimize the invasion by exotic graminoid vegetation and facilitate natural succession.     

Do mature pine plantations resemble deciduous natural forests regarding understory plant diversity and canopy structure in historically modified landscapes?

We compared the structure of the arboreal layer and the diversity and species composition of the understory vegetation of three types of mature forest communities: oak (Quercus pyrenaica) and beech (Fagus sylvatica) forests and Scots pine (Pinus sylvestris) plantations. Our main aim was to determine whether differences in these variables existed and were due to the identity of the dominant tree species. We selected four stands or replicates per forest type located geographically close and with relatively similar conditions. We found no differences in the arboreal structure of oak and beech forests, which were characterised by great variability in tree size, while in case of plantations, this variability was lower at both the intra-stand (estimated by the coefficient of variation) and inter-stand (i.e. the four replicates harboured trees of similar sizes) scales. However, the highest variability in the canopy layer of natural forests was not consistently linked to greater understory species richness. Indeed, the lowest plant species richness was found in beech forests, while oak forests harboured the highest value at either the sampling unit (per m²) or stand scales. The greatest negative correlation between plant diversity and the environmental variables measured was found for litter depth, which was the highest in beech forests. The results obtained by the CCA indicated that the four replicates of each forest type clustered together, due to the presence of characteristic species. We concluded that pine plantations did not approach the environmental conditions of native forests, as plantations were characterised by singular understory species composition and low arboreal layer variability, compared to natural woodlands.     

Development of equations for predicting Puerto Rican subtropical dry forest biomass and volume

Carbon accounting, forest health monitoring and sustainable management of the subtropical dry forests of Puerto Rico and other Caribbean Islands require an accurate assessment of forest aboveground biomass (AGB) and stem volume. One means of improving assessment accuracy is the development of predictive equations derived from locally collected data. Forest inventory and analysis (FIA) measured tree diameter and height, and then destructively sampled 30 trees from 6 species at an upland deciduous dry forest site near Ponce, Puerto Rico. This data was used to develop best parsimonious equations fit with ordinary least squares procedures and additive models fit with nonlinear seemingly unrelated regressions that estimate subtropical dry forest leaf, woody, and total AGB for Bucida buceras and mixed dry forest species. We also fit equations for estimating inside and outside bark total and merchantable stem volume using both diameter at breast height (d.b.h.) and total height, and diameter at breast height alone for B. buceras and Bursera simaruba. Model fits for total and woody biomass were generally good, while leaf biomass showed more variation, possibly due to seasonal leaf loss at the time of sampling. While the distribution of total AGB into components appeared to remain relatively constant across diameter classes, AGB variability increased and B. simaruba and B. buceras allocated more carbon into branch biomass than the other species. When comparing our observed and predicted values to other published dry forest AGB equations, the equation developed in Mexico and recommended for areas with rainfall >900 mm/year gave estimates substantially lower than our observed values, while equations developed using dry forest data from forest in Australia, India and Mexico were lower than our observed values for trees with d.b.h. <25 cm and slightly higher for trees with d.b.h. >30 cm. Although our ability to accurately estimate merchantable stem volume and live tree AGB for subtropical dry forests in Puerto Rico and other Caribbean islands has been improved, much work remains to be done to sample a wider range of species and tree sizes.     

The potential of hinoki (Chamaecyparis obtusa [Sieb. et Zucc.] Endlicher) plantation forests for the restoration of the original plant community in Japan

We estimated the potential of plantation forests for the restoration of the original plant community. We compared the understory vegetation in hinoki (Chamaecyparis obtusa [Sieb. et Zucc.] Endlicher) plantations at the understory re-initiation stage and in adjacent natural forests. To estimate the effect of the original natural forests on the understory species composition of plantation forests, we established study sites in five types of natural forests (mature evergreen broadleaf, mature deciduous broadleaf, mature evergreen coniferous, immature deciduous broadleaf warm-temperate, and immature deciduous broadleaf cool-temperate) and nearby plantation forests. The understory vegetation of the plantation forests had a higher species richness, a higher proportion of early-seral species, and a higher proportion of herb or fern species than the natural forests. The differences between natural and plantation forests varied according to the species composition of the natural forests. The composition of the understory vegetation of the plantations at the understory re-initiation stage was similar to that of the immature deciduous forests. The characteristics of immature, disturbed forests remained in the understory vegetation of the hinoki forests. No great loss of species was observed. Our findings suggest that most of the original forest species still survive in the understory of the plantation forests. These forests have the potential to follow the successional pathway to broadleaf or mixed forests via thinning or clear-cutting without planting.