Long-term tree population dynamics and their implications for the conservation of the Kakamega Forest, Kenya

Long-term studies of tree population dynamics play an important role in identifying the conservation needs of tropical forest ecosystems. We examined changes in tree population structure and composition over an 18-year period (1981–1999) in three plots located at the center of the Isecheno study site in the Kakamega Forest, Kenya, a forest with a history of logging and other anthropogenic disturbance. DBH size class distribution took the shape of an inverse J curve in both 1981 and 1999 and did not differ significantly between the two study periods. Stem density increased significantly during the study with most of the increase occurring in the smallest stem size class (10–14 cm DBH). Nearly all of the most common species in 1981 remained among the most common in 1999, though the density of pioneer species decreased by 21% during the study. Our results suggest that forest in the study plots remained relatively undisturbed and in good condition over the study period. Forest in the plots also appeared still to be recovering from the selective logging of large trees that took place at Isecheno in the 1940s. In addition to our longitudinal study, we compared tree population parameters at three additional Isecheno sites spread over a distance of 1 km that have experienced different histories of disturbance: (i) a lightly human disturbed site (LHD), (ii) a heavily human disturbed site (HHD), and (iii) a cattle disturbed site (CD). While all three sites were selectively logged in the 1940s, the main signs of disturbance today are footpaths at the LHD site, tree stumps at the HHD site, and wide cattle paths at the CD site. Not surprisingly, of the disturbed sites, the LHD site was in the best condition. Trees at the HHD site exhibited extremely poor recruitment into the small size classes, a condition that can probably be attributed to human exploitation of small trees for poles. The CD site appeared to be at an earlier successional stage than the other disturbed sites with its low mean DBH, high overall stem density, and high pioneer species stem density. Browsing and trampling of vegetation by cattle may be the source of the light gaps that have led to the abundance of pioneer species at this site. We conclude that conservation measures applied to central Isecheno, including the establishment of a forest station nearby and ranger patrols, appear to have succeeded, but that the prognosis for the Kakamega Forest in general is bleak if protection efforts are not increased in other parts of the forest, where anthropogenic disturbance remains high. We also note the considerable variation in tree population structure and composition that can occur within a small area depending on the local history of disturbance.     

Climber species composition, abundance and relationship with trees in a Nigerian secondary forest

Climbers play different roles in forest biology and ecology and are the first to be eliminated during forest clearing but little is known about the species composition, distribution and relationship with tree species of this group of plants of tropical forest. This study thus investigated the species composition, abundance and tree relationship of climbers along altitudinal gradient in four 0.06 ha plots in a secondary forest at Ile‐Ife, Nigeria. All trees ≥10 cm g.b.h were examined for the presence of climbers in the plots. There were 49 climber species consisting of 35 liana and fourteen vine species distributed over 41 genera and 28 families in the forest. Lianas contributed 34% and vines 13.7% of the plant species in the forest. Climber basal area, density, number of species, genera and families increased with altitude. Forty‐two per cent (42%) of the trees in the forest carried climbers. There was significant positive correlation (P ≤ 0.05) between girth sizes of host trees of 31–50 cm with the girths of climbers on them indicating that trees of these girth sizes are highly susceptible to climber infestation. Tree species host density and size are important factors in determining the presence of climbers on a tree.     

Impacts of selective logging on population structure and dynamics of a canopy tree (Olea capensis) in Kakamega forest

This study assessed the impacts of logging on the population structure and dynamics of Elgon teak (Olea capensis), a canopy dominant in Kakamega forest. The objective was to ascertain and determine the regeneration status of this tree species in view of its commercial value. A comparison was made between logged and unlogged sections at three sites in the forest. Pairwise comparisons of the differences in the population structure among three sites and the differences in the mean tree size revealed significant differences in all three study sites. Results also revealed a variation in stem density that was dependent on the block of forest under study. Results of the spatial contagion revealed that O. capensis had a varied clumped distribution in all the study sites. Clumping was highest in the Kisere forest. These results point to logging as the major factor that explains the differences in population structure and stem density in different parts of Kakamega forest. And while intermittent recruitment may explain clumped distribution, logging appears to explain the variation in the degree of clumping.     

Mixed-Forest Species Establishment in a Monodominant Forest in Central Africa: Implications for Tropical Forest Invasibility

Background

Traits of non-dominant mixed-forest tree species and their synergies for successful co-occurrence in monodominant Gilbertiodendron dewevrei forest have not yet been investigated. Here we compared the tree species diversity of the monodominant forest with its adjacent mixed forest and then determined which fitness proxies and life history traits of the mixed-forest tree species were most associated with successful co-existence in the monodominant forest.

Methodology/Principal Findings

We sampled all trees (diameter in breast height [dbh]≥10 cm) within 6×1 ha topographically homogenous areas of intact central African forest in SE Cameroon, three independent patches of G. dewevrei-dominated forest and three adjacent areas (450–800 m apart). Monodominant G. dewevrei forest had lower sample-controlled species richness, species density and population density than its adjacent mixed forest in terms of stems with dbh≥10 cm. Analysis of a suite of population-level characteristics, such as relative abundance and geographical distribution, and traits such as wood density, height, diameter at breast height, fruit/seed dispersal mechanism and light requirement–revealed after controlling for phylogeny, species that co-occur with G. dewevrei tend to have higher abundance in adjacent mixed forest, higher wood density and a lower light requirement.

Conclusions/Significance

Our results suggest that certain traits (wood density and light requirement) and population-level characteristics (relative abundance) may increase the invasibility of a tree species into a tropical closed-canopy system. Such knowledge may assist in the pre-emptive identification of invasive tree species.     

Soil phosphorus and disturbance influence liana communities in a subtropical montane forest

Questions: What are the effects of soil, topography, treefall gaps, tree species composition, and tree density on liana species composition and total liana abundance? Location: A 6‐ha permanent plot in a subtropical montane forest in northwest Argentina. Methods: Multiple regressions were used to quantify associations of liana species composition and total liana abundance with edaphic, disturbance and tree community variables. Gradients in liana and tree species composition were quantified using principal components analysis (PCA). Results: Liana species composition was correlated most strongly with soil phosphorus concentration (R²=0.55). Total liana aanased with phosphorus and the density of recent treefall gaps (R²=0.60). Conclusions: In our study area, liana composition and abundance are most strongly correlated with features of the physical environment, rather than host tree characteristics. Our results support the hypothesis that recent increases in liana abundance in mature tropical forests may be related to increased rates of gap formation.     

Native tree regeneration in native tree plantations: understanding the contribution of Araucaria angustifolia to biodiversity conservation in the threatened Atlantic Forest in Argentina

Deforestation is a global process that has strongly affected the Atlantic Forest in South America, which has been recognised as a threatened biodiversity hotspot. An important proportion of deforested areas were converted to forest plantations. Araucaria angustifolia is a native tree to the Atlantic Forest, which has been largely exploited for wood production and is currently cultivated in commercial plantations. An important question is to what extent such native tree plantations can be managed to reduce biodiversity loss in a highly diverse and vulnerable forest region . We evaluated the effect of stand age, stand basal area, as a measure of stand density, and time since last logging on the density and richness of native tree regeneration in planted araucaria stands that were successively logged over 60 years, as well as the differences between successional groups in the response of plant density to stand variables. We also compared native tree species richness in planted araucaria stands to neighbouring native forest. Species richness was 71 in the planted stands (27 ha sampled) and 82 in native forest (18 ha sampled) which approximate the range of variation in species richness found in the native forests of the study area. The total abundance and species richness of native trees increased with stand age and time since last logging, but ecological groups differed in their response to such variables. Early secondary trees increased in abundance with stand age 3–8 times faster than climax or late secondary trees. Thus, the change in species composition is expected to continue for a long term. The difference in species richness between native forest and planted stands might be mainly explained by the difference in plant density. Therefore, species richness in plantations can contribute to local native tree diversity if practices that increase native tree density are implemented.     

Forest aboveground biomass along an elevational transect in Sulawesi,Indonesia, and the role of Fagaceae in tropical montane rain forests

Aim This study investigates how estimated tree aboveground biomass (AGB) of tropical montane rain forests varies with elevation, and how this variation is related to elevational change in floristic composition, phylogenetic community structure and the biogeography of the dominant tree taxa. Location Lore Lindu National Park, Sulawesi, Indonesia. Methods Floristic inventories and stand structural analyses were conducted on 13 plots (each 0.24 ha) in four old‐growth forest stands at 1050, 1400, 1800 and 2400 m a.s.l. (submontane to upper montane elevations). Tree AGB estimates were based on d.b.h., height and wood specific gravity. Phylogenetic diversity and biogeographical patterns were analysed based on tree family composition weighted by AGB. Elevational trends in AGB were compared with other Southeast Asian and Neotropical transect studies (n = 7). Results AGB was invariant from sub‐ to mid‐montane elevation (309–301 Mg ha^?1) and increased slightly to 323 Mg ha^?1 at upper montane elevation. While tree and canopy height decreased, wood specific gravity increased. Magnoliids accounted for most of the AGB at submontane elevations, while eurosids I (including Fagaceae) contributed substantially to AGB at all elevations. Phylogenetic diversity was highest at upper montane elevations, with co‐dominance of tree ferns, Podocarpaceae, Trimeniaceae and asterids/euasterids II, and was lowest at lower/mid‐montane elevations, where Fagaceae contributed > 50% of AGB. Biogeographical patterns showed a progression from dominant tropical families at submontane to tropical Fagaceae (Castanopsis, Lithocarpus) at lower/mid‐montane, and to conifers and Australasian endemics at upper montane elevations. Cross‐continental comparisons revealed an elevational AGB decrease in transects with low/no presence of Fagaceae, but relatively high AGB in montane forests with moderate to high abundance of this family. Main conclusions AGB is determined by both changes in forest structure and shifts in species composition. In our study, these two factors traded off so that there was no net change in AGB, even though there were large changes in forest structure and composition along the elevational gradient. Southeast Asian montane rain forests dominated by Fagaceae constitute important carbon stocks. The importance of biogeography and species traits for biomass estimation should be considered by initiatives to reduce emissions from deforestation and forest degradation (REDD) and in taxon choice in reforestation for carbon offsetting.     

Diversity and composition of trees and shrubs in Kasagala forest: a semiarid savannah woodland in central Uganda

The diversity and composition of trees and shrubs of ≥5 cm diameter at breast height (DBH) were investigated in Kasagala woodland in central Uganda using 1 ha permanent sample plots. A total of 2745 trees and shrubs with a mean stem density of 686 ha⁻¹ were recorded. These included 69 tree species belonging to 28 families and 47 genera. There was a larger number of small stems compared with that of larger stems. There was significant variation in stem size class distribution between the plots ( F  =   3.14, P  =   0.027). The variation in stem densities (counts) across different size classes was significant ( F  =   8.31, P  <   0.001). Species diversity was higher in the low lands compared with that in the elevated sites in the woodland. The species encountered were unevenly distributed across the plots. Species abundance was not significantly different across the sample plots ( F  =   2.63, P  =   0.053). We suggest that the structure of the forest is typical of any regenerating forest, but other human influences may have played a part in the dominance of size classes <10 cm DBH. The causes of the present status and composition of the woodland require further investigation.     

Seedling regeneration,environment and management in a semi‐deciduous African tropical rain forest

Questions: How is seedling regeneration of woody species of semi‐deciduous rain forests affected by (a) historical management for combinations of logging, arboricide treatment or no treatment, (b) forest community type and (c) environmental gradients of topography, light and soil nutrients? Location: Budongo Forest Reserve, Uganda. Methods: Seedling regeneration patterns of trees and shrubs in relation to environmental factors and historical management types were studied using 32 0.5‐ha plots laid out in transects along a topographic gradient. We compared seedling species diversity, composition and distribution patterns along topographic gradients and within types of historical management regimes and forest communities to test whether environmental factors contributed to differences in species composition of seedlings. Results: A total of 85 624 woody seedlings representing 237 species and 46 families were recorded in this rain forest. Cynometra alexandri C.H. Wright and Lasiodiscus mildbraedii Engl. had high seedling densities and were widely distributed throughout the plots. The most species‐rich families were Euphorbiaceae, Fabaceae, Rubiaceae, Meliaceae, Moraceae and Rutaceae. Only total seedling density was significantly different between sites with different historical management, with densities highest in logged, intermediate in logged/arboricided and lowest in the nature reserve. Forest communities differed significantly in terms of seedling diversity and density. Seedling composition differed significantly between transects and forest communities, but not between topographic positions or historical management types. Both Chao‐Jaccard and Chao‐Sørensen abundance‐based similarity estimators were relatively high in the plot, forest community and in terms of historical management levels, corroborating the lack of significant differences in species richness within these groups. The measured environmental variables explained 59.4% of variance in seedling species distributions, with the three most important being soil organic matter, total soil titanium and leaf area index (LAI). Total seedling density was positively correlated with LAI. Differences in diversity of >2.0 cm dbh plants (juveniles and adults) also explained variations in seedling species diversity. Conclusions: The seedling bank is the major route for regeneration in this semi‐deciduous tropical rain forest, with the wide distribution of many species suggesting that these species regenerate continuously. Seedling diversity, density and distribution are largely a function of adult diversity, historical management type and environmental gradients in factors such as soil nutrient content and LAI. The species richness of seedlings was higher in soils both rich in titanium and with low exchangeable cations, as well as in logged areas that were more open and had a low LAI.     

Assessing the effects of elephant foraging on the structure and diversity of an Afrotropical forest

African forest elephants (Loxodonta cyclotis) are ecosystem engineers that browse and damage large quantities of vegetation during their foraging and movement. Though elephant trail networks and clearings are conspicuous features of many African forests, the consequences of elephant foraging for forest structure and diversity are poorly documented. In this study in northeastern Gabon, we compare stem size, stem density, proportional damage, species diversity, and species relative abundance of seedlings and saplings in the vicinity of seven tree species that produce elephant-preferred fruits (“elephant trees”) relative to control trees that do not. Across 34 survey trees, with a combined census area of 2.04 ha, we recorded data on 26,128 woody stems in three sizes classes. Compared with control trees, the area around elephant trees had the following: (a) a significantly greater proportion of damaged seedlings and a marginally greater proportion of damaged saplings (with 82% and 24% greater odds of damage, respectively); (b) no significant difference in stem density or species diversity; and (c) a significantly greater relative abundance of seedlings of elephant tree species. Increasing distance away from focal elephant trees was associated with significantly reduced sapling stem damage, significantly increased sapling stem density, and significantly increased sapling species diversity. Considered in sum, our results suggest that elephants can affect the structure and diversity of Afrotropical forests through their foraging activities, with some variation based on location and plant size class. Developing a more complete understanding of elephants’ ecological effects will require continued research, ideally with manipulative experiments.     

Evaluating the effects of climate change on tree species abundance and distribution in the Italian peninsula

Question: What is the effect of climate change on tree species abundance and distribution in the Italian peninsula? Location: Italian peninsula. Methods: Regression tree analysis, Random Forest, generalized additive model and geostatistical methods were compared to identify the best model for quantifying the effect of climate change on tree species distribution and abundance. Future potential species distribution, richness, local colonization, local extinction and species turnover were modelled according to two scenarios (A2 and B1) for 2050 and 2080. Results: Robust Random Forest proved to be the best statistical model to predict the potential distribution of tree species abundance. Climate change could lead to a shift in tree species distribution towards higher altitudes and a reduction of forest cover. Pinus sylvestris and Tilia cordata may be considered at risk of local extinction, while the other species could find potential suitable areas at the cost of a rearrangement of forest community composition and increasing competition. Conclusions: Geographical and topographical regional characteristics can have a noticeable influence on the impact of predicted climate change on forest ecosystems within the Mediterranean basin. It would be highly beneficial to create a standardized and harmonized European forest inventory in order to evaluate, at high resolution, the effect of climate change on forest ecosystems, identify regional differences and develop specific adaptive management strategies and plans.     

Effects of repeated burning on Mediterranean communities of the northeastern Iberian Peninsula

Question: In relation to a single fire, do repeated wildfires in Mediterranean type ecosystems (1) reduce plant species richness or diversity; (2) modify patterns of abundance or dominance of plant species or (3) alter plant composition? Location: Pinus halepensis dominated communities of Catalonia, northeastern Iberian Peninsula, western Mediterranean Basin. Methods: Regional, paired design with 14 study sites, each consisting of a once burnt area (1994) and a twice burnt area (1975–1993 and 1994). Ten years after the last fire, we recorded all vascular plant species present in nested plots and quantified their relative abundances on transects. We compared species richness, diversity, dominance and relative abundance and species‐area correlations between paired once and twice burnt areas and assessed their floristic composition similarity. Results: No statistically significant differences were found in species richness or diversity. Slopes of species‐area correlations were higher in once burnt areas. In twice burnt areas, dominance by one or two species was higher. P. halepensis showed lower relative abundance and nanophanerophytes showed higher relative abundance. No differences were found for resprouter, seeder or resprouter‐seeder species. Floristic composition similarity between paired areas tended to be higher in less productive sites. Conclusions: Fire recurrence had contrasting effects on species richness at different spatial scales. Repeated burning reduced the relative abundance of the dominant tree species, which resulted in a higher relative abundance of shrubs. It also promoted the dominance of herbs, particularly Brachypodium retusum. However, it did not change the relative abundance of regenerative groups. Paired areas were more similar as they were more Mediterranean in terms of climatic conditions.     

Orangutan Nesting Behavior in Disturbed Forest of Sabah,Malaysia: Implications for Nest Census

High concentrations of orangutans remain in the multiple-use forests of the Lower Kinabatangan, Sabah, Malaysia. Compared to primary forest, the habitat is highly fragmented, characterized by a low tree density (332 stems/ha), small tree size (83.6% of trees are <20 m high), low basal area (18 m²/ha), abundance of canopy gaps and high level of soil disturbance. The forest structure and composition influence orangutan nesting patterns, and thus directly influence the results of nest surveys used to determine orangutan population size. In logged forests, tall and large trees are the preferred nesting sites of orangutans. The scarcity of suitable nesting sites in the logged-over forests of Kinabatangan, could partly explain the lower daily rate of nest construction (r = 1.00) versus those of other orangutan populations. The nest decay rate t recorded at the study site (average ± SD = 202 ± 151 days) strongly depends on the species of tree in which a nest is built. Our results illustrate that the nest-related parameters used for orangutan censuses fluctuate among habitat types and emphasize the need to determine specific values of r for specific orangutan populations and of t for different tree species in order to achieve accurate analysis of census data.     

Plant Community Structure in Tropical Rain Forest Fragments of the Western Ghats,India1

Changes in tree, liana, and understory plant diversity and community composition in five tropical rain forest fragments varying in area (18–2600 ha) and disturbance levels were studied on the Valparai plateau, Western Ghats. Systematic sampling using small quadrats (totaling 4 ha for trees and lianas, 0.16 ha for understory plants) enumerated 312 species in 103 families: 1968 trees (144 species), 2250 lianas (60 species), and 6123 understory plants (108 species). Tree species density, stem density, and basal area were higher in the three larger (> 100 ha) rain forest fragments but were negatively correlated with disturbance scores rather than area per se. Liana species density, stem density, and basal area were higher in moderately disturbed and lower in heavily disturbed fragments than in the three larger fragments. Understory species density was highest in the highly disturbed 18‐ha fragment, due to weedy invasive species occurring with rain forest plants. Nonmetric multidimensional scaling and Mantel tests revealed significant and similar patterns of floristic variation suggesting similar effects of disturbance on community compositional change for the three life‐forms. The five fragments encompassed substantial plant diversity in the regional landscape, harbored at least 70 endemic species (3.21% of the endemic flora of the Western Ghats–Sri Lanka biodiversity hotspot), and supported many endemic and threatened animals. The study indicates the significant conservation value of rain forest fragments in the Western Ghats, signals the need to protect them from further disturbances, and provides useful benchmarks for restoration and monitoring efforts.     

High butterfly beta diversity between Brazilian cerrado and cerrado–caatinga transition zones

Tropical dry forests are among the most diverse and threatened habitats in the world, yet they are rarely protected and remain poorly studied. In Brazil, dry forests are naturally fragmented and embedded within various biomes, thus making it important to assess biotic homogeneity among geographically separated forest fragments. We sampled 7732 individuals belonging to 48 species to quantify the diversity of fruit-feeding butterfly communities at four Brazilian dry forest sites, and found differences in community structure between northern and central sites. Species richness per plot was the same in both areas, but abundance per plot was higher in northern sites. Species composition differed between sites mostly due to species of Satyrinae. Additive partitioning showed that beta diversity corresponded to 70.1% of all diversity. Rather than species loss, beta diversity primarily represented species turnover that was potentially driven by differences in the surrounding habitats. Butterfly community composition and abundance were influenced by vegetation where abundance increased with tree density and basal area, and decreased with the average tree height. Butterfly species richness and abundance were higher in the wet season than in the dry season, and all species sampled in the dry season were present in the wet season. Differences in community structure across relatively short geographic distances in the same type of habitat highlight the importance of conserving tropical dry forest fragments to ensure the maintenance of butterfly diversity and, presumably, other insects.     

Forest recovery on abandoned logging roads in a tropical montane rain forest of Hainan Island,China

In this study we report the work in recovering forest stands on Hainan Island in South China; we compared the community composition, structure, and plant functional traits (seed mass and wood density) on three positions of abandoned logging roads: road track (RT), road up-slope edge (UE) and road down-slope edge (DE). The results showed that species richness, stem abundance, basal area, stem size, and canopy height were all lowest on the RT among the three road positions. Species richness and abundance of midstorey and canopy trees were higher on the UE than on the DE. The mean stem size was higher on the DE than the UE, but no significant difference existed in canopy height on the two road edges. The different road positions were characterized by varied species assemblages. Indicator species analysis further indicated that 76.9%, 15.4% and 7.7% of the species showed affinity to UE, DE, and RT, respectively. The RT had more small-seeds but less soft-wood trees than the two road edges. The UE and DE had no significant difference in tree seed class distribution. Compared with the DE, however, the UE had a higher and lower proportion of hard wood in terms of species richness and stem abundance, respectively. Our results indicated that the composition and structure of stands on the abandoned logging roads had significantly changed in comparison with the stands around it.     

Structure,composition and diversity of plant communities in FSC-certified,selectively logged forests of different ages compared to primary rain forest

The impact of logging on plant communities was studied in forest that has been logged selectively 1, 5 and 10 years previously (following a certified procedure): diversity was compared with that of primary rain forest in the Berau region of East Kalimantan, Indonesia. Four sets of 20 transects located within an area of 6 ha were sampled for all trees, saplings and seedlings, and records were made of topographic position, structure, composition and species diversity. There was a high level of floristic similarity between primary forests at the study sites compared to primary forest elsewhere in Kalimantan. The impact of logging is therefore likely to be the most important factor determining any differences between the plant communities of the selectively logged and primary forest sites. We found differences in species composition and abundance of most plants between selectively logged and primary forest. Overall, stem densities of trees in the primary forest were higher than in the three selectively logged forest sites. Stem densities of saplings were equivalent in all four forests. Seedling stem densities were higher in the forest site logged 10 years previously than in primary forest. Our results showed that the forests logged selectively under certified regimes still have a high plant diversity, possibly indicating that biodiversity values may be conserved by following certification procedures.     

Differential susceptibility of tree species to oviposition by periodical cicadas

Abstract 1. Periodical cicadas occur widely in deciduous forests of eastern North America and represent the largest insect emergences in the world. Their effects on forest community dynamics, via oviposition damage and root feeding, are potentially great but not well understood. If tree species vary in their susceptibility to cicada oviposition and root colonization, then periodical cicadas may affect ecological interactions among tree species and forest composition. 2. We measured oviposition damage on 63 tree species at 52 sites in southern Indiana, U.S.A. for two broods of periodical cicadas. We compared oviposition damage among different sites, habitats, and tree species. We also measured cicada emergence rates in mature and successional forest habitats and from beneath different tree species. 3. Certain tree species received significantly more oviposition damage than others, and the most and least damaged species were consistent between the two broods. For some species, oviposition damage varied between mature and successional sites. Despite the differences in oviposition rates among species, there was no difference in emergence rates from beneath different tree species, suggesting that initial differences in cicada density among tree species are not maintained through the nymphal life cycle. 4. Cicadas oviposited more at successional sites, but emerged more in mature forest stands, suggesting that successive generations of cicadas represent a shifting mosaic between forests of different ages. As tree species consistently vary in their susceptibility to oviposition damage, periodical cicadas could alter local competitive interactions and therefore affect forest dynamics.     

A common allometric equation for predicting stem weight of mangroves growing in secondary forests

The allometric relationship for stem weight Ws is usually expressed as a function of stem diameter and height, similar to the variable d.b.h.²H, which equals the squared diameter at breast height multiplied by tree height. However, this relationship often differs between tree species, and this segregation of the relationship by species forces the researcher to do a tremendous amount of field work to determine a series of allometric equations for all tree species in the forest. In this study, we examined the segregation in the d.b.h.²H–Ws allometric relationship for five mangrove species. We examined the overall stem shape and the specific gravity of stem relating to the allometric relationships. The difference in the specific gravity was found to be the main cause of the segregation in the d.b.h.²H–Ws relationship. By taking into consideration the specific gravity of stem, we established a common equation for the five mangrove species.