Floristic Composition and Diversity of Freshwater Swamp Forests in the Niger Basin of Nigeria

AimsTo describe the structural and floristic diversity of New Caledonian mixed tropical rain forest and investigate its environmental determinants.LocationNew Caledonia (SW Pacific), a biodiversity hotspot.MethodsStructural (stem density, basal area) and floristic characteristics (composition, species richness and dissimilarity) were investigated along environmental gradients (elevation, rainfall and slope) on different substrates (ultramafic and non‐ultramafic) through the New Caledonian Plant Inventory and Permanent Plots Network (NC‐PIPPN, 201 plots each measuring 20 m x 20 m).ResultsA total of 28,640 trees (DBH ≥5 cm) belonging to 749 species, 240 genera and 92 families were inventoried in the NC‐PIPPN. The New Caledonian mixed rain forest studied was characterized as having high stem density, basal area and species richness, and many small stems (60% of the trees <10 cm DBH and almost a quarter of species did not exceed this threshold). More than one‐third of the species were rare (i.e. inventoried in less than three plots or represented by fewer than three individuals) in the plot network and floristic dissimilarity was high (Bray–Curtis index >0.70). The presence of ultramafic (UM) and non‐ ultramafic substrates (non‐UM) combined with altitudinal and rainfall gradients were the main drivers of floristic dissimilarity, whereas the effect of geographic distance between the plots was surprisingly low. Floristic dissimilarity was very high between UM and non‐UM substrates from species up to family level. About 75% of the species occurred on a single substrate type. The mixed rain forest on UM and non‐UM substrates differed in floristic composition but not in structure.ConclusionsNC‐PIPPN proved to be an effective tool for investigating the woody species richness of New Caledonia as containing ca. 46% of its non‐herbaceous species. However, the network's design, and more specifically its small plots, restricts its capacity to capture beta diversity and forest structure. High species richness and floristic dissimilarity confirm that New Caledonian mixed rain forest is exceptionally rich.

The Lienhuachih Forest Dynamics Plot (FDP), measured 500 m by 500 m square, is located in central Taiwan. The collected data, followed a unified method adopted for the worldwide FDP network, were analyzed for floristic composition, size-class structure, and species diversity. In total, the censused trees and shrubs belonged to 144 species in 86 genera and 39 families. The most dominant families were the Fagaceae, Lauraceae, Rubiaceae, Euphorbiaceae, and Melastomataceae. In total, 153268 (6131 ha^(-1)) individuals were recorded, and the total basal area was 34.77 m^2 ha^(-1). Of the 144 species, the most abundant were Randia cochinchinensis and Blastus cochinchinensis. Pasania nantoensis had the highest basal area (8.38%), followed by Engelhardtia roxburghiana (8.12%) and Schefflera octophylla (7.23%). Calculation of the importance value (IV, incorporating relative values of abundance and basal area) showed that R. cochinchinensis, B. cochinchinensis, S. octophylla, Cryptocarya chinensis, and E. roxburghiana were the most dominant species with the highest IV values in the plot. The sum of the 30 top species' IV reached 83.06% of the whole. Although the 1st 2 species were understory and very dominant due to the large number of individuals, certain numbers of rare species however increased the floristic diversity in the plot. Based on the species composition, the forest is characteristic of the Machilus-Castanopsis forest zone of Taiwan, with certain dominant understory species and possessing 2 pioneer species in the major canopy composition. For the size-class structure, 102 (each with total stems ≥ 25) species showed 4 patterns of size-class distribution: L-shaped, inverse J-shaped, fluctuating, and bell-shaped. The former 3 patterns in a total of 98 species, including a great number of small-sized individuals, imply that most current species in this study site can display good recruitment with rich resources of saplings. The woody plant richness of the Lienhuachih FDP is the highest among low-elevation FDPs in Taiwan. Compared to other Center of Ttropical Forest Science forest dynamics plots on islands, Fisher's alpha diversity (ha^(-1)) index of the subtropical Lienhuachih FDP was similar to that of the Luquillo FDP in Puerto Rico but much lower than that of other FDPs in the tropics.

Abstract. The long‐term growth dynamics of natural forest stands on the island of Hokkaido were described on the basis of an analysis of data from 38 permanent plots spanning 15–22 yr. Stand structure was characterized by basal area, stem density and tree size variability. To detect trends in stand structure, regression models for recruitment rate (per ha per yr), mortality rate and the rate of change in stem density and tree size variability were developed by a stepwise method using initial basal area, stem density, tree size variability, species composition summarized by LNMDS ordination, altitude, annual mean temperature, annual precipitation, type of understorey vegetation, topography and slope aspect as candidates for predictor variables. The same analyses were conducted for basal area increment (net growth) and its components: survivor growth = basal area gain by growth of surviving individuals and mortality = basal area loss by death of individuals.Stem density remained generally unchanged; recruitment was relatively low even in very sparse stands. Stand basal area generally increased as survivor growth was approximately double the mortality.Recruitment rate was strongly affected by the presence of dwarf bamboo (Sasa spp.) vegetation on the forest floor which inhibited tree regeneration. Mortality rate was density‐dependent; dense stands had higher mortality than sparse stands. Density change rate (recruitment rate ‐ mortality rate) was, therefore, determined by both the type of understorey vegetation and stem density. Survivor growth was high in stands with high stem density and basal area. Mortality was dependent on basal area and altitude. Net basal area increment (net growth) was dependent only on stem density with other factors that influenced survivor growth and mortality omitted. Tree size variability decreased in stands with high tree size variability whereas it increased in stands with low size variability. Based on the obtained models for density change rate and net basal area increment, trajectories of stands were illustrated on a log‐log diagram of stem density and basal area. The predicted differences in trajectories as affected by the understorey vegetation type indicated the importance of dwarf bamboo vegetation for forest dynamics on Hokkaido.

We examined the variation in forest structure, species diversity and floristic composition of trees for different minimum sizes (≥ 4.8 cm and ≥ 10 cm stem diameter) in six 0.25-ha plots of a tropical montane forest (1600 m above sea level) on Mount Kinabalu, Sabah, Malaysia. Four plots are parts of a 2.74-ha plot, and two are located 75 m and 200 m apart from the others. In all, the six plots are distributed in an area of approximately 8 ha (450 m × 175 m) on similar topography (sideslopes). Forest structure (e.g. stem density, basal area and estimated aboveground biomass) appeared to be similar among the six plots. Tree species richness per plot varied little (91-102 for stems ≥ 4.8 cm diameter and 60-72 for stems ≥ 10 cm diameter). Several indices of species diversity (or evenness) were also within narrow ranges, correlated with species richness. The dominance of species varied greatly among the six plots, but that of genus and family was relatively consistent. Analysis based on the 2.74-ha plot suggested that this reflected different habitat associations with microtopography among congeneric or confamilial species and intraspecific aggregation. Similarity indices based on presence/absence of species (e.g. Jaccard and S.rensen indices) were negatively correlated with spatial distances between plots (for stems ≥ 4.8 cm diameter), but those based on relative abundance of species were not. Indices of species diversity (or evenness) and similarity based on basal area were correlated between two minimum sizes (≥ 4.8 cm and ≥ 10 cm diameter), but those based on number of stem or presence/absence of species were not. We concluded that variations in forest structure, tree species diversity and floristic composition at genus and family levels were small at this spatial scale, and that the results obtained in any single 0.25-ha plot can be reasonably extrapolated to the other stands on similar topography in this area except dominance of species.

Knowledge on the structure and composition of the plant communities has enormous significance in conservation and management of forests. The present study aimed to assess the community attributes, viz., structure, composition and diversity in the moist and dry sal (Shorea robusta) forests in the West Bengal province of India and compare them with the other sal forests of India. The phytosociological data from these forests were quantitatively analysed to work out the species richness, diversity, evenness, dominance, importance value, stand density and the basal area. The analysis showed that plant richness and diversity in moist sal forests of northern West Bengal are higher than the dry sal forests of south-west Bengal; a total of 134 tree (cbh C30 cm), 113 shrub and 230 herb species were recorded in the moist sal forest compared to 35 tree, 41 shrub and 96 herb species in dry sal forest. Papilionaceae was observed to be the dominant family. Dry sal forests had higher tree dominance (0.81) and stand density (1,006 stems ha -1 ) but lower basal area (19.62 m 2 ha -1 ) while moist sal forest had lower tree dominance (0.18) and stand density (438 stems ha -1 ) but higher basal area (56.52 m 2 ha -1 ). Tree species richness and stem density across girth classes in both the types decreased from the smallest to largest trees, while the occurrence rate of species increased with increase in girth class. A t-test showed significant differences in species richness, basal area and the stand density at 95% confidence level (p = \0.05) in the two forest types. The CCA indicated very low overall match (canonical correlation value = 0.40) between the two sets of variables from moist and dry sal types. The differences in these forests could be attributed to the distinct variations in climatic conditions- mainly the rainfall, disturbance regimes and the management practices.

Abstract. Hernandez JO, Ata JP, Combalicer MS. 2022. Long-term changes in floristic diversity, composition and stand structure in Acacia auriculiformis plantation in Mount Makiling Forest Reserve, Philippines. Biodiversitas 23: 3631-3638. There have been continuous debates about whether exotic tree plantation facilitates vegetation succession. In the Philippines, the potential for the re-establishment of native plant communities and improvement of the plant community structure under exotic tree plantations has not yet been evaluated adequately. Thus, the study investigated the dynamics in floristic diversity, composition and stand structure of a reforested area using Acacia auriculiformis Benth. in Sitio Kay Inglesia, Mount Makiling Forest Reserve (MMFR), Philippines. The changes in basal area, stem density, biomass growth, species diversity, species evenness and richness, and canopy closure were determined between two study periods, i.e., 1993-2008 and 2009-2019. Results revealed significant changes in stem density (i.e., 1324 to 2135 trees ha-1) and canopy closure (i.e., 18% to 10%) for mature trees and seedlings/saplings in 2009-2019. The changes in basal area and aboveground biomass were not significant between the two study periods. The species richness was significantly higher in 2009-2019 (i.e., 55 species) than in 1993-2008 (i.e., 22 species). The species diversity also significantly increased from low (i.e., H' = 1.99, S = 23) to moderate (i.e., H' = 2.88, S = 55). Moreover, the number of exotics decreased (i.e., 60 to 40% or 15 to 9 species) as the number of native ones increased (i.e., 27 to 72% or 15 to 40 species). Therefore, the findings of the present study show that re-establishment of native species is possible when restoring degraded land with A. auriculiformis plantation. However, monitoring studies on other key ecosystem attributes (e.g., ecosystem functionality, external exchanges, structural diversity) of the plantation are recommended to enhance our understanding of the species' potential for restoration.

Tropical forest ecosystems are generally seen as diverse ecosystems with rich biodiversity. However, how this applies to the freshwater swamp forests (especially in West Africa) is largely unknown. To verify how diverse this ecosystem is and how its structure varies in an intact forest landscape, one hectare forest plots were set up at 8 different points. This was used to collect information on the diversity and structure of the ecosystem. Consistent with the findings from other freshwater swamp forests, the ecosystem was seen to have a low species occurrence which ranged from 4 to 19 (mean value = 11 species) across the forest plots. Its diversity was equally low (mean = 1.66), unlike other tropical forest ecosystems. Stem heights varied as in mature tropical forest ecosystems; with the middle stratum recording the highest proportion of trees (54.63%) and the emergent layer having the least (0.83%). Its basal area, biomass and relative density were similar with other tropical ecosystems and equally had its highest species contribution from Leguminosae as in some other ecosystems as well. The ecosystem was seen to have features and characteristics that were common and similar with other tropical forest ecosystems, apart from its low diversity. Ensuring that effective and appropriate forest-tree species conservation measures are enhanced across the landscape are vital steps to securing the already existing (few) species and preventing species extinction across the ecosystem.

Management strategies and floristic diversity in agroforestry practices of northwestern Ethiopia

ABSTRACTFuelwood is an essential forest product for small-holder farmers in the tropics, but fuelwood harvesting may cause forest degradation and impact ecosystem services. Understanding tree species composition, diversity and biomass changes in forests with active fuelwood collection is important for informing sustainable forest harvesting. In the miombo woodlands of southern Malawi, using forest plots, we investigated: 1) if forests with fuelwood harvesting (n = 50) have different tree, sapling and seedling stem density, species diversity, species composition, and aboveground biomass (AGB) than forests with minimal use (n = 36); and 2) if forest product harvesting pressure and access are predictors of tree stem density, diversity and AGB. We found a significant reduction in tree diversity and AGB but not stem density, and different species composition in areas with fuelwood harvesting compared to reference sites. For saplings, stem density was higher and species composition was different in fuelwood harvesting sites. Seedling Shannon index and Simpson’s diversity were lower in fuelwood harvesting sites. Harvesting pressure and access were predictors of AGB and tree stem density. The reduced AGB and tree species diversity may hinder collection of fuelwood and other forest products, and may reduce ecosystem functioning. Exploring the possibility of forest landscape restoration in the area could be beneficial.

How micro-topography affecting plant communities classification and species composition at one stand-level was investigated through the plant communities and species composition varied across fine-scale environmental heterogeneity at the 25-ha Lienhuachih broad-leaved forest dynamics plot (FDP). All free-standing woody plants with diameter at breast height ≧ 1 cm were identified, measured, tagged and mapped. Four plant communities were identified and represented with dominant and indicating species based on two-way indicator species analysis (TWINSPAN). Type I, Pasania nantoensis - Randia cochinchinensis, locating on the ridge and the highest elevation was with the highest stem density; Type II, Mallotus paniculatus - Engelhardtia roxburghiana, locating on the upper slope was an ecotone between type I and type III, with the middle stem density and basal area among four plant community types; Type III, Diospyros morrisiana - Cryptocarya chinensis, locating on the lower slope and stream side was with lower stem density but the highest species heterogeneity; and Type IV, Machilus japonica var. kusanoi - Helicia formosana locating on west stream side was with the lowest stem density and basal area. Detrended Correspondence Analysis (DCA) results showed nearly 27.11% of the plant species composition was attributable to micro-topographic variables. Ridge distance, stream distance and convexity were the most important factors effected the changes of plant community and species composition. Classification and regression tree (CART) method was also used to examine the relationship between each single specie and micro-topographic variables. Over 70% species had more than 27.11 % variations which explained by DCA results. To conclude, our results support the existence of habitat association and niche divergence related to micro-topography in a subtropical evergreen broad-leaved forest.

The science of ecology fundamentally aims to understand species and their relation to the environment. At sites where hurricane disturbance is part of the environmental context, permanent forest plots are critical to understand ecological vegetation dynamics through time. An overview of forest structure and species composition from two of the longest continuously measured tropical forest plots is presented. Long-term measurements, 72 years at the leeward site, and 25 years at windward site, of stem density are similar to initial and pre-hurricane values at both sites. For 10 years post-hurricane Hugo (1989), stem density increased at both sites. Following that increase period, stem density has remained at 1400 to 1600 stems/ha in the leeward site, and at 1200 stems/ha in the windward site. The forests had similar basal area values before hurricane Hugo in 1989, but these sites are following different patterns of basal area accumulation. The leeward forest site continues to accumulate and increase basal area with each successive measurement, currently above 50 m2/ha. The windward forest site maintains its basal area values close to an asymptote of 35 m2/ha. Currently, the most abundant species at both sites is the sierra palm. Ordinations to explore variation in tree species composition through time present the leeward site with a trajectory of directional change, while at the windward site, the composition of species seems to be converging to pre-hurricane conditions. The observed differences in forest structure and composition from sites differently affected by hurricane disturbance provide insight into how particular forest characteristics respond at shorter or longer time scales in relation to previous site conditions and intensity of disturbance effects.

Soil microbial biomass and activity in tropical riparian forests

Much of the world's tropical forests have been affected by anthropogenic disturbance. These forests are important biodiversity reservoirs whose diversity, structure and function must be characterized across the successional sequence. We examined changes in structure and diversity along a successional gradient in the lowlands of New Guinea. To do this, we measured and identified all stems ≥5 cm diameter in 19 0.25 ha plots ranging in age from 3 to >50 yr since disturbance. We also measured plant functional traits related to establishment, performance, and competitive ability. In addition, we examined change in forest structure, composition, species diversity, and functional diversity through succession. By using rarefaction to estimate functional diversity, we compared changes in functional diversity while controlling for associated differences in stem and species density. Basal area and species density increased with stand age while stem density was highest in intermediate secondary forests. Species composition differed strongly between mature and secondary forests. As forests increased in basal area, community‐weighted mean wood density and foliar carbon increased, whereas specific leaf area and proportion of stems with exudate decreased. Foliar nitrogen peaked in medium‐aged forests. Functional diversity was highest in mature forests, even after accounting for differences in stem and species diversity. Our study represents one of the first attempts to document successional changes in New Guinea's lowland forest. We found robust evidence that as succession proceeds, communities occupy a greater range of functional trait space even after controlling for stem and species density. High functional diversity is important for ecological resiliency in the face of global change.

Igapó forests are a key part of the Amazon.  And so, it is important to know their floristics and physical structure, and how they may be influenced by their soil.  The floristics and physical structure of 16 primary [1o] and secondary [2o] igapó forest plots in Loreto Province, Peru was described and linear regressions were computed to explore whether soil bulk density could predict structural parameters. In the 1o forest, Fabaceae, Malvaceae and Rubiaceae were the most common families and Calycophyllum spruceanum, Ceiba samauma, Inga spp., Cedrela odorata, Copaifera reticulata, Phytelephas macrocarpa, Guazuma rosea, and Piptadenia pteroclada were the most common species. And as flooding increased, bulk density, stem density, stem size, species richness, Fishers α, basal area and above-ground biomass all decreased. In the 2o forest, Urticaceae, Rubiaceae and Euphorbiaceae were the most common families and Cecropia membranacea, Sapium glandulosum, Pourouma guianensis and Byrsonima arthropoda were the most common species. The number of stems was greatest in the island 2o forest and lowest in the 1o forest under water for more than four months, and mean stem size, species richness, Fishers α, basal area and above-ground biomass was lowest in the sandy beach 2o forest and highest in the 1o forest under water one to two months. Soil bulk density predicted mean stem size, species richness and Fishers α well, where all three decreased as soils became more sandy. I conclude that as soil becomes less sandy with more clay content there is an increase in forest structural complexity, unpredictable flooding in 2o forests reduces structure more than the predictable flood pulse 1o forests receive, and soil bulk density may have a causal role for diversity in igapó forests.

Effects of extractive disturbance on bird assemblages, vegetation structure and floristics in tropical scrub forest, Sariska Tiger Reserve, India