Functional diversity changes during tropical forest succession

Functional diversity (FD) ‘those components of biodiversity that influence how an ecosystem operates or functions’ is a promising tool to assess the effect of biodiversity loss on ecosystem functioning. FD has received ample theoretical attention, but empirical studies are limited. We evaluate changes in species richness and FD during tropical secondary forest succession after shifting cultivation in Mexico. We also test whether species richness is a good predictor of FD. FD was calculated based on a combination of nine functional traits, and based on two individual traits important for primary production (specific leaf area) and carbon sequestration (wood density). Stand basal area was a good predictor of successional changes in diversity and FD, in contrast to fallow age. Incidence-based FD indices increased logarithmically with stand basal area, but FD weighted by species’ importance values lacked pattern with succession. Species richness and diversity are strong predictors of FD when all traits were considered; linear relationships indicate that all species are equally functionally complementary, suggesting there is little functional redundancy. In contrast, when FD was calculated for individual traits and weighted for abundances, species richness may underestimate FD.Selection of functional trait(s) critically determines FD, with large consequences for studies relating biodiversity to ecosystem functioning. Careful consideration of the traits required to capture the ecosystem process of interest is thus essential.     

Aquatic insect diversity in a tropical Vietnamese stream in comparison with that in a temperate Korean stream

A comparative investigation on aquatic insect diversity was conducted in a tropical stream in Southeast Asia (the Dak Pri stream in southern Vietnam; stream orders II–V, two sites per stream order) with a reference temperate stream in Northeast Asia (the Gapyeong stream in central Korea) in March 2001 and April 2000, respectively. The numbers of aquatic insect taxa in Dak Pri stream (268 species, mostly undescribed, 230 genera, 91 families, and 9 orders; 110.5 ± 17.1 species per site) were about twice those in Gapyeong stream (133 species, 98 genera, 51 families, and 8 orders; 60.3 ± 8.5 species per site). Coleoptera, Trichoptera, Ephemeroptera, and Diptera were the major aquatic insect orders with high taxonomic richness, and Coleoptera, Odonata, and Hemiptera contributed to the higher degree of aquatic insect diversity in Dak Pri stream. The species diversity indices of Dak Pri stream (4.37 ± 0.19) were higher than those of Gapyeong stream (3.73 ± 0.42), whereas the dominance indices of Dak Pri stream (0.195 ± 0.046) were lower than those of Gapyeong stream (0.346 ± 0.113). Collector-gatherers were predominant in both streams; shredders were more abundant in Dak Pri stream while scrapers were more abundant in Gapyeong stream. Factors affecting the higher degree of aquatic insect diversity in Dak Pri stream are discussed.     

Abundance and diversity of Homoptera in the canopy of a tropical forest

Abstract. 1. A series of samples of Homoptera was obtained by fogging the canopy of Luehea seemannii trees in tropical forest in the Panama Canal Zone at three different times of the year.
2. The peak of abundance occurs around July (at least 11.8 individuals/m²), in the early wet season, at a time when most of the trees in the forest, including Luehea are producing new leaves.
3. Minimum abundance occurs in March (at least 3.5 individuals/m²), in the late dry season.
4. The samples obtained are some 35% richer in species per given number of individuals than light trap samples taken simultaneously in a similar forest some 6 km away from the present sampling site.
5. The data show that the effect of intensive light trapping on the populations of Homoptera in the forest is virtually negligible.
6. For a given sample size the tropical samples are many times richer in species than samples from temperate areas.     

Endemism, diversity, and the threat of tropical moist forest extinctions

Extinction rates have risen to perhaps 10⁴ the background rate. Much of this increase is due to projected influences of habitat loss on regions of the world with tropical moist forest. This ecosystem, home to a disproportionate amount of global biodiversity and a major regulator of regional and global climate, also faces disproportionately severe threats. In this study, we collect diversity and endemism data for tropical forested countries of the world, along with areal and socioeconomic data. While a correlation between overall numbers of species and endemic species per country is expected, we demonstrate that endemism patterns among birds and mammals remain very strongly convergent even after statistically rendering all countries equal in size and overall species richness and after adjusting for spatial autocorrelation. On a per country basis, mammals are generally more threatened than birds in these tropical moist forested countries. Human population growth rates and rising debt among these nations should be viewed as priorities for amelioration by the developed countries. Reserve network extent is not related to numbers of endemic mammals or birds at this large spatial scale.     

Recurrent landslides affect the functional beta diversity of a megadiverse tropical forest

Background: Natural disturbance is an important factor that contributes to structuring plant communities. In tropical mountain areas, landslides are frequent and could enhance the diversity in mountain forests. However, the spatial scale in which landslide affect diversity is not known.

Aims: To investigate whether landslides affect taxonomic and functional diversity at different spatial scales. We tested if: (1) taxonomic and functional α-diversity were lower in areas with landslide history; (2) the taxonomic β-diversity was high while the functional β-diversity was low in landslide-affected areas; and (3) plants in areas with landslide history would have, on average, smaller and thicker leaves, with greater pubescence, lower specific leaf area and higher dry matter content.

Methods: At five sites in the Atlantic Forest, we sampled five 5 m × 5 m plots in areas with recent landslide history (from 2 to 39 years) and in adjacent control areas. We identified all juvenile trees (30–100 cm in height) and measured their leaf traits.

Results: Taxonomic α-diversity and functional β-diversity and the occurrence of leaves with trichomes were greater in areas affected by landslide.

Conclusion: The habitat heterogeneity in areas subject to recurrent landslides influenced the functional dispersion and the structuring of plant communities.     

The effects of forest disturbance on diversity of tropical soil nematodes

We provide the first account of the effects of forest disturbance on species richness of nematodes in tropical forest soils, from 24 sites along gradients of disturbance and regeneration in the Mbalmayo Forest Reserve, Cameroon. Species richness was very high. Samples of 200 nematodes from individual soil cores contained a maximum of 89 and an average of 61 species; in total we recorded 431 species and approximately 194 genera. The model of Siemann et al. (1996), predicting that species richness scales as the number of individuals I ^0.5, underestimates nematode diversity 4–6 fold in these samples. Over 90% of specimens cannot be assigned to known species. Although nematode species richness declined with forest disturbance, statistically significant effects were detectable only under the most extreme conditions (active slash-and-burn agriculture and complete mechanical forest clearance) and even here remained at 40% of the richness of near primary sites. Impacts on trophic structure were also small, and there were no significant changes in the maturity index (MI) (Bongers 1990) with disturbance (mean MI across all treatments was very high, at 3.58). In the light of this study, the problems of completing reliable all-taxon inventories in tropical forests are briefly discussed. Received: 22 July 1996 / Accepted: 3 April 1997     

Drivers of beta diversity of macroinvertebrate communities in tropical forest streams

1. There has recently been increasing interest in patterns of beta diversity but we still lack a comprehensive understanding of these patterns in various regions (e.g. the tropics), ecosystems (e.g. streams) and organism groups (e.g. invertebrates). 2. Our aim was to investigate the patterns of beta diversity of stream macroinvertebrates in relation to key environmental (i.e. stream size, pH and habitat degradation) and geographical variables (i.e. latitude, longitude, altitude) in a tropical region. We surveyed a total of 8–10 riffle sites in each of 34 streams (altogether 337 riffle sites were sampled) in Peninsular Malaysia to examine variation in macroinvertebrate community composition at within‐stream and among‐stream scales. 3. Based on test of homogeneity of dispersion, we found that the streams studied differed significantly in within‐stream variation in community composition (i.e. among‐site variation of within stream beta diversity). The patterns were similar based on Bray–Curtis coefficient on abundance data, Sorensen coefficient on presence–absence data and Simpson coefficient on presence–absence data. We also found that within‐stream beta diversity was significantly related to stream size, pH and latitude, with each of these variables individually accounting for around 20% of the variation in beta diversity in simple regressions, while the total variation explained by the three significant variables amounted to around 50% in multiple regressions. By contrast, habitat degradation, longitude and altitude were not significantly related to beta diversity. We also found that the factor drainage basin accounted for much of the variation in beta diversity in general linear models, suppressing the effects of environmental variables. 4. We concluded that within‐stream beta diversity is mainly related to a combination of the identity of a drainage basin and stream environmental factors. Our findings provide important background for stream environmental assessment and conservation planning by emphasising that (i) macroinvertebrate communities within streams are not homogeneous, but show considerable beta diversity, (ii) streams differ in their degree of within‐stream beta diversity, (iii) stream size and water pH should be considered in applied contexts related to within‐stream beta diversity and (iv) historical effects may be different in different drainage basins and may affect present‐day patterns of within‐stream beta diversity.     

海南岛坝王岭热带天然要植物物种多样性研究

采用植物群落学和植物种群学的研究方法,从数量和质量 特征两个方面研究了海南岛坝王岭热带天然林的植物物种多样性。结果表明：⑴该地区不同植物群落的优势种类组成差别较大,彼此之间的物种相似性水平低;⑵相对于低地雨林而言,该地区的山地雨林物种数量较多,物种均匀度较高,主要优势种的优势程度较弱;⑶在优先考虑物种稀有性的前提下,根据各物物种在群落中所处的位置及其分布情况,可将该地区的植物物种分为珍稀濒危种、特     

Spatial pattern of diversity in a tropical rain forest in Malaysia

The diversity of trees (species richness, abundance and Shannon diversity) in a tropical rain forest of Malaysia has been studied from the point of view of its spatial organization in order to formulate hypotheses about the origin of the observed spatial patterns. The question that motivated this study is whether tropical forests communities are in a state of equilibrium or non-equilibrium. Three aspects have been examined: (1) changes in diversity were studied with respect to sampling area and sampling designs. A minimum area of 5–10 ha is recommended by the species–area curves, while 2–5 ha seem appropriate based on the Shannon diversity–area curves. Different sampling designs significantly affect the species–area curves. The power function, which can be derived under the equilibrium assumption, is not appropriate to fit the observed diversity–area curves. (2) The spatial features of diversity variables were then studied. Variograms showed that there are dominant short-range effects (around 150 m), obvious anisotropic distribution, and high random variation in the diversity data. (3) Partitioning the variation of the diversity measures into environmental (topographic) and spatial components indicated that the spatial organisation of that community was mostly unpredictable. There may be many processes controlling the formation of the spatial patterns in the tropical rain forest. Unidentified causes, affecting mainly the small-scale processes (<20 m), seem responsible for the large amount of undetermined variation in the diversity data sets. The study suggests that the Pasoh forest of Malaysia may not be in a state of equilibrium.     

Polypore fungal diversity and host density in a moist tropical forest

In a moist tropical forest in Panama, the wood-decay polyporefungi comprise many rare species (more than half found only once) andexhibit diversity that exceeds that of the supporting tree community.The most abundant fungal species were non-specialists, each found onseveral host species from multiple plant families. In diverse fungalcommunities, each of many species should infect a given host species ina density-dependent manner, so that the infected proportion of a hostpopulation should increase with host density. Applied across hostspecies, hosts with denser populations should support greater fungaldiversity. For 10 tree species, fungal incidence and diversity increasedwith abundance of the host in the community, consistent withacross-species density-dependent infection. Fungal diversity associatedwith individual trunks did not, however, vary with host-species density.Both host density and persistence of decaying logs may be important indetermining fungal diversity associated with tree species.     

Tree species diversity of tropical forest vegetation in Xishuangbanna, SW China

Tree species diversity of four tropical forest vegetation types was investigated in Xishuangbanna, southwestern China. These are: tropical seasonal rain forest, tropical montane rain forest, evergreen broad-leaved forest and monsoon forest over limestone. A total of 17 samples were taken and four species diversity indices were calculated: Shannon-Wiener's H, the complement of Simpson's index, d, Fisher's and evenness index E. The results reveal the long-tailed rank/abundance diagrams of these forests. However, this feature is greatly reduced in the samples of monsoon forest over limestone. Tropical seasonal rain forest shows the highest tree species diversity of all four vegetation types. Owing to the variation of microenvironment, diversity values within the same vegetation type vary between the samples from different patches. The tree species diversity of single-dominant rain forest is not significantly lower than that of mixed rain forest, because the dominant species of some single-dominant rain forests are principally in the emergent layer. This is composed of sparse and huge trees of one species and, consequently, creates a unique canopy architecture and more heterogeneous microenvironments for the more diversified species composition under the emergent layer. The occurrence of tree species with small population sizes, particularly of species represented by only one individual, is highly correlated with the tree species diversity of the local forest vegetation. They are crucial elements in the richness of local biodiversity.     

population dynamics of some tropical trees that yield non-timber forest products

The population biology ofAquilaria malaccensis, one source of gharu, and Cinnamomum mollissimum, one source of wild cinnamon, was studied in a 50 ha permanent plot of primary rain forest in Malaysia. Median diameter growth rates of 0.22 cm yr^-1 and 0.1 cm yr^-1 should not be prohibitive of economic exploitation, and suggest that the trees could be grown commercially. However, the natural densities were between 2 and 3 trees over 1 cm d.b.h. per ha, which is roughly the median for all trees in the plot, would preclude economic exploitation of these natural populations. The economics of harvesting natural populations is considered in a preliminary fashion by allowing favorable assumptions of quantity and quality of production. The price likely to be fetched from either a first time extraction (on the order of US$10.00 per ha) or from sustained production (on the order of USThe population biology ofAquilaria malaccensis, one source of gharu, and Cinnamomum mollissimum, one source of wild cinnamon, was studied in a 50 ha permanent plot of primary rain forest in Malaysia. Median diameter growth rates of 0.22 cm yr^-1 and 0.1 cm yr^-1 should not be prohibitive of economic exploitation, and suggest that the trees could be grown commercially. However, the natural densities were between 2 and 3 trees over 1 cm d.b.h. per ha, which is roughly the median for all trees in the plot, would preclude economic exploitation of these natural populations. The economics of harvesting natural populations is considered in a preliminary fashion by allowing favorable assumptions of quantity and quality of production. The price likely to be fetched from either a first time extraction (on the order of US10.00 per ha) or from sustained production (on the order of US10.00 per ha) or from sustained production (on the order of US0.10 per ha per yr), are too small to be of interest as single-product schemes, and are negligible compared to the extraction of multi-species crops of timber. However, it is possible that by combining multiple products under a “High Diversity Forestry” scheme, one could increase the density of harvestable products, reduce the unit cost of labor and improve the economic portrait. La poblacion dinamica de algunos arboles tropicales. La población biológica deAquilaria malaccensis, un original de gharu, yCinnamomum mollissimum, un original del cinnamon salvage, ha sido estudiado en 50 ha en un terreno primario permanente de lluvia tropical en. Con un índice de crecimiento de medio dimetro 0.22 cm yr^-1 0.1 cm yr^-1 no deberia prohibirse la explotación económica, y se segiuere que los árboles pueden ser cultivados comercialmente. De cualquier manera, la densidad natural siendo aproximadamente entre 2 y 3 árboles per encima de 1 cm dbh per ha, lo cúal es un promedio de todos los árboles en el terreno, esto representa un impedimento a la explotacion económica de la población natural. La economía de la población natural de recolección de la cosecha está considerada como una moad preliminar por permitirse favorablemente la supuesta cantidad y calidad de productión. Los precios problemente alcanzen, bien sea, la primera vex de su extracción sobre el pedido de US10.00 per ha o desde una continua productión ininterrumpida, (sobre un pedido US10.00 per ha o desde una continua productión ininterrumpida, (sobre un pedido US0.10 per ha per yr), siendo demassiado peque?o para ser de interés tal proyecto comoproducto-unico, y son insignificantes comparados con la extracción de multiples especies de semillas de madera. De caulquier manera esposible que sepueda combinar los multiple productos en el proyecto de “Alta Diversidad Forestal,” uno puede la un puede incrementar la densidad de la productión de la cosecha, reduciendo el costo de mano de obra por unidad y mejorando la imagen económica.     

Habitat specificity and diversity of tree species in an African wet tropical forest

Niche differentiation with respect to habitat has been hypothesized to shape patterns of diversity and species distributions in plant communities. African forests have been reported to be relatively less diverse compared to highly diversed regions of the Amazonian or Southeast Asian forests, and might be expected to have less niche differentiation. We examined patterns of structural and floristic differences among five topographically defined habitats for 494 species with stems ≥1 cm dbh in a 50-ha plot in Korup National Park, Cameroon. In addition, we tested for species–habitat associations for 272 species (with more than 50 individuals in the plot) using Torus translation randomization tests. Tree density and basal area were lowest in areas with negative convexity, which contained streams or were inundated during rainy periods and highest in moist well-drained habitats. Species composition and diversity varied along the topographical gradient from low flat to ridge top habitats. The low depression and low flat habitats were characterized by high diversity and similar species composition, relative to slopes, high gullies and ridge tops. Sixty-three percent of the species evaluated showed significant positive associations with at least one of the five habitat types. The majority of associations were with low depressions (75 species) and the fewest with ridge tops (8 species). The large number of species–habitat associations and the pronounced contrast between low (valley) and elevated (ridgetop) habitats in the Korup plot shows that niche differentiation with respect to edaphic variables (e.g., soil moisture, nutrients) contributes to local scale tree species distributions and to the maintenance of diversity in African forests.     

Crop diversity and fallow management in a tropical deciduous forest shifting cultivation system

Shifting cultivation is important to many of the inhabitants of tropical forest regions. Much scientific research has been conducted on this form of agriculture in the humid tropics, but the drier portions of the tropics remain less studied. The shifting cultivation system practiced in the tropical deciduous forests of western Guerrero, Mexico, provides insight into such production systems, especially with regard to crop diversity and fallow characteristics. This system is characterized by low crop diversity, based primarily on maize (Zea mays)cultivation, and a general lack of fallow management. The farmers also utilize several strategies not common to many other regions, including highly seasonal labor allocation patterns, varying fallow cycle lengths, and the occasional application of chemical inputs.     

Structure,diversity, and regeneration of tropical dry deciduous forest of northern India

This study examined the impact of disturbance on the pattern of diversity, forest structure and regeneration of tree species in the Vindhyan dry tropical forest of India. A total of 1500 quadrats distributed over five, 3-ha permanent plots in five sites, differing in degree of disturbance, were used to enumerate and measure the tree species. A total of 65 species with 136,983 individuals were enumerated in the total 15-ha area for stems 30 cm height. The number of species and number of stems ranged from 12 to 50 and 8063–65331 per 3-ha area. The number of species and stems for trees 10 cm dbh ranged from 3 to 28 species, with a mean value of 16 species ha^–1, and from 16 to 477 stems, with a mean value of 256 stems ha^–1, respectively. The adult based PCA ordination indicated uniqueness of sites in terms of species composition and habitat characteristics. PCA ordination also showed uniqueness of sites in terms of seedling composition, but the seedling and adult distributions were not spatially associated. The distinct species composition at the different sites and at the two life-cycle stages on the same site is indicative of marked spatio-temporal dynamics of the dry tropical forest. The density–diameter semi-logarithmic curves ranged from a near linear to an overall concave appearance with a limited plateau in the mid-diameter ranges. The -diversity and its components decreased with increasing disturbance intensity, reflecting enhanced utilization pressure with increasing disturbance. The site-wise and species-wise regression analyses of the number of individuals in different stages of the species revealed that both the level of disturbance and the nature of species strongly affect the regeneration. In conclusion, although the forest is relatively species-poor, the differential species composition on different sites and the temporal dynamics lend a unique level of diversity to the tropical dry deciduous forest.     

Liana diversity and host relationships in a tropical evergreen forest in the Indian Eastern Ghats

In tropical evergreen forest in the Kolli Hills of the Indian Eastern Ghats, four 2 ha (100 m × 200 m) replicate plots (two plots each in undisturbed and human-impacted sites), were inventoried for species diversity of lianas 5 cm girth at breast height (g.b.h.) and their relationships with 30 cm g.b.h. host trees. Liana diversity included 26 species from 18 families and 24 genera. The population density and basal area of lianas in the study plots were 48 individuals ha^–1 and 0.23 m² ha^–1, respectively, while those of the trees were 478 stems ha^–1 and 43.6 m² ha^–1, respectively. As the lianas and their hosts had often been cut in the disturbed sites, their diversity was less there than in the undisturbed sites. Five (19%) liana species were common to all four sites. Three lianas, Hiptage benghalensis (Malpighiaceae), Elaeagnus indica (Elaeagnaceae) and Gnetum ula (Gnetaceae) were dominant. The twining mechanism (54% of liana species and 71% of individuals) and zoochorous diaspores (73% of species and 77% of individuals) predominated. A total of 336 trees from 39 species, 34 genera and 22 families hosted 345 lianas. The ratio of liana : host for species was 1 : 1.5 and for individuals was 1 : 1. Liana preferences for certain host trees, host girth classes and trellis heights were evident.     

Local effects of forest fragmentation on diversity of aquatic insects in tropical forest streams: implications for biological conservation

The influence of forest fragmentation (habitat isolation) on biological and ecological diversity of aquatic insects was investigated in streams of fragmented forests in Hulu Gombak (6 streams) and Gunung Angsi (5 streams) and un-fragmented forest of Berembun (6 streams) in peninsular Malaysia. Several environmental parameters including canopy cover, DO, temperature and pH differed significantly among the three catchments (P < 0.05). We found that taxonomic richness in Berembun forest was significantly different from Gunung Angsi (P < 0.05), but not with Hulu Gombak forests (P > 0.05). Nestedness pattern that measures the effect of habitat isolation on taxonomic assemblages showed that aquatic insect’s community in un-fragmented forest (Berembun) was less nested (T = 54.4), indicating high diversity compared to highly nested (less diverse) in the two fragmented forests (Hulu Gombak, T = 30.45 and Gunung Angsi, T = 35.45). Taxa similarity in Berembun streams was negatively correlated with the geographical distance among streams (Mantel test, r = ? 0.462, P < 0.05). Such correlation was absent in both Gunung Angsi and Hulu Gombak streams. Forest fragmentation in Hulu Gombak and Gunung Angsi measured as the distance of the forests from the nearest forested area had negative effect on aquatic insects diversity (r ² = ? 0.149, P < 0.05), but not on their abundances (r ² = 0.003, P > 0.05). We concluded that local habitat conditions were the most important in shaping the aquatic insects community among streams of both unfragmented and fragmented forests.     

Amphibian species and functional diversity as indicators of restoration success in tropical montane forest

Tropical forest restoration is increasingly seen as an activity that may counteract or reduce biodiversity loss. However, few studies monitor fauna or consider measures of functional diversity to assess restoration success. We assessed the effect of a tropical montane forest restoration program on species and functional diversity, using amphibians as the target group. We compared amphibian assemblages in three types of land use: restoration areas, tropical montane cloud forest (TMCF; reference ecosystem) and cattle pastures (degraded ecosystem) in southern Mexico. We also described microclimate, microhabitat heterogeneity, woody vegetation structure and diversity for each type of land use, and their relationship to amphibian species and functional diversity. Compared to TMCF, restoration areas had similar environmental conditions. However, amphibian species richness was similar in the three types of land use and abundance was lower in the restoration areas. In TMCF, the amphibian assemblage was dominated by forest-specialist species, the pastures by generalist species, and the restoration areas by a combination of both species types. Interestingly, functional richness, functional evenness and functional divergence did not vary with land use, though the number of functional groups in restoration areas and TMCF was slightly higher. Overall, the results suggest that after seven years, active restoration provided habitat heterogeneity and recovered woody vegetation capable of maintaining amphibian species and functional groups similar to those inhabiting TMCF. Forest fragments adjacent to restoration areas seem to facilitate fauna recolonization and this emphasizes the importance of the conservation of the reference ecosystems to achieving restoration success.