Lowland Tropical Rainforest Research Articles

Standing Herbivory Is Not Affected by Tree Sex or Conspecific Density in a Dioecious Understory Tropical Tree Species

ABSTRACTLeaves are critical to plant photosynthesis and the loss of leaf area can have negative consequences for an individual's performance and fitness. Variation in plant defenses plays a large role in protecting their leaves from attack by insect herbivores. However, trade‐offs in allocation among growth, reproduction, and defense may limit the availability of resources for any one aspect of a plant's life‐history strategy, which would lead to greater herbivory in those plants that allocate more resources to growth or reproduction than to defense. Patterns of sex‐biased herbivory in dioecious plants are well documented yet are known to vary in the direction (female or male) of their bias. A greater concentration of conspecifics may also increase herbivore attack through negative density dependence. In order to test the hypothesis that sex‐biased herbivory varies as a function of conspecific density, we measured standing herbivory on 2350 leaves on 302 trees of the dioecious understory tree Iryanthera hostmannii (Myristicaceae) situated in a large forest dynamics plot in a lowland tropical rain forest in Ecuador. We found no difference in standing herbivory between the 169 male and 133 female trees, nor for focal trees surrounded by higher densities of conspecifics. The slow‐growing, shade‐tolerant growth patterns of I. hostmannii may contribute to suppressed differential expression of secondary sex characters in leaf defenses, leading to similar levels of herbivory between males and females. Considering the factors that most strongly affect herbivory in dioecious species is important in understanding the evolution of sex‐related traits more broadly.

Floristic Composition and Diversity of Plants Across Three Vegetation Zones of Gashaka Gumti National Park, Northeastern Nigeria

Gashaka Gumti National Park (GGNP) is Nigeria’s biggest national park, with an elevation range of 300 m to its highest peak at 2400 m. Although GGNP has a wide range of plant species, particularly woody ones, there is limited information regarding its floristic composition along the vegetation zones. This study examined the floristic composition and species diversity of GGNP by systematically sampling plant species using quadrats of 25 m × 25 m and a point-centered quadrat (PCQ). A total of 228 plant species belonging to 114 genera and 49 families were recorded across the three major vegetation zones. Fabaceae was the most species-rich family (34 species), representing 14.9% of the species, followed by Malvaceae (18 species), representing 7.9%. Other important species include Moraceae and Rubiaceae, 15 species each, representing 6.6% of the species, respectively, while Combretaceae (10 species) represents 4.4% of the species recorded. The Lowland Tropical Rain Forest (LTRF) recorded 137 species in 42 families, and Montane Highland (MH) recorded 146 species in 43 families. In comparison, the Savannah Woodland (SW) recorded 68 species in 28 families. Twenty-five species, which account for 11% of the total, are threatened. Among them, 10 species are Vulnerable, six are Endangered, five are Critically Endangered, and four are Near Threatened, according to the International Union for Conservation of Nature (IUCN) Red List status. Across all plots, average Shannon-Weiner’s species diversity indices of 2.40, 2.40, and 2.25 were recorded for MH, LTRF, and SW, respectively. According to Sorensen’s similarity coefficient, LTRF and SW (33.42%) habitats recorded the highest species similarity, while MH, as against SW habitats, recorded the lowest (18.92%). The importance value indicated that the SW had the most important species based on the importance value (0.581) compared to other vegetation zones. The overall evenness values for LTRF, SW, and MH are 0.77, 0.78, and 0.77, respectively. This study offers significant insights into the flora variety and conservation situation of Gashaka Gumti National Park. It emphasizes the need for more research and conservation initiatives to save its distinct habitats and endangered species.

Diversity of Mangrove Plants in Karimunjawa National Park

Karimunjawa National Park (TNK) area is ± 111,625 hectares covering 27 islands located in Jepara Regency, Central Java at the northern tip of Java Island. Karimunjawa became Karimunjawa National Park (TNK) based on the Decree of the Minister of Forestry and Plantation No.78/Kpts-II/1999 because it has high diversity. The complexity of ecosystems in TNK is interesting to study, such as coral reef ecosystems, mangrove forests, lowland tropical rainforests, seagrass meadows, seaweed, and coastal forests. The mangrove forest in Karimunjawa National Park is a unique ecosystem because it consists of many mangrove species. However, data on the diversity of mangrove species on this island has not been widely described. This study aims to reveal mangrove diversity in Karimunjawa National Park as a rescue strategy and explore the potential of mangrove biodiversity. This research is a descriptive study using the cruising method to explore mangrove species diversity. The location of mangrove diversity exploration is mangrove forest in Karimunjawa National Park. The results found 14 families consisting of 38 mangrove species. Among the 38 species, 24 species are true mangroves, while the other 14 species are associated with mangroves.

Conservation genomic study of Hopea hainanensis (Dipterocarpaceae), an endangered tree with extremely small populations on Hainan Island, China.

Hopea hainanensis Merrill & Chun is considered a keystone and indicator species in the tropical lowland rainforests of Hainan Island. Owing to its high-quality timber, H. hainanensis has been heavily exploited, leading to its classification as a first-class national protected plant in China and a plant species with extremely small populations (PSESPs). This study analyzed genome-wide single nucleotide polymorphisms obtained through restriction site-associated DNA sequencing from 78 adult trees across 10 H. hainanensis populations on Hainan Island. The nucleotide diversity of the sampled populations ranged from 0.00096 to 0.00138, which is lower than that observed in several other PSESPs and endangered tree species. Bayesian unsupervised clustering, principal component analysis, and neighbor-joining tree reconstruction identified three to five genetic clusters in H. hainanensis, most of which were geographically widespread and shared by multiple populations. Demographic history analysis based on pooled samples indicated that the decline in the H. hainanensis population began approximately 20,000 years ago, starting from an ancestral population size of approximately 10,000 individuals. The reduction in population size accelerated approximately 4,000 years ago and has continued to the present, resulting in a severely reduced population on Hainan Island. Intensified genetic drift in small and isolated H. hainanensis populations may contribute to moderate differentiation between some of them, as revealed by pairwise F st. In conclusion, our conservation genomic study confirms a severe population decline and an extremely low level of nucleotide variation in H. hainanensis on Hainan Island. These findings provide critical insights for the sustainable management and genetic restoration of H. hainanensis on Hainan Island.

Soil wetting triggered by selective logging in Bornean lowland tropical rainforests

Aboveground biomass removal and canopy opening by selective logging modifies soil moisture in the main root zone, impacting soil aeration and various biogeochemical processes in tropical production forests. This study investigated the relationship between canopy damage and topsoil (10 cm) moisture in two logged forests in Malaysian Borneo, while simultaneously controlling for logging intensity, time elapsed since historical logging, and spatial autocorrelation. Volumetric soil water content (VSWC), canopy height model (CHM), leaf area index (LAI), and historical logging data were collected from 84 transects placed subjectively in 15 sites exhibiting varying canopies. We generated an index (PC1) quantifying the magnitude of canopy structural degradation from canopy structure metrics (CSM) combining CHM and LAI data within a 20-meter buffer for each transect. PC1 was analyzed for its impact on VSWC across logging periods, and contrasted with topography. Spatial autocorrelation of VSWC was examined regarding to canopy conditions. VSWC was significantly higher in all logged forests (over 0.4 m3 m−3) comparing to non-disturbed forests (0.27 m3 m−3). The immediate wetting could be a result of extracting mature individuals of late-successional species holding large biomass, while the persistent wet condition may be due to retarded canopy and biomass recovery. In the study area, canopy structure was a stronger predictor of soil moisture than topography. The high soil moisture underneath the most degraded canopies presented the largest spatial extent of autocorrelation. This study revealed soil wetting after selective logging in humid tropical forests, driven by reduced transpiration from biomass loss rather than increased evaporative demand resulting from canopy opening. The elevation in soil moisture could have disrupted biogeochemical processes in the below-ground system, which in turn impede forest succession and put stress on the overall vulnerability of disturbed tropical rainforests.

New Cortinariaceae species associated with Dicymbe, Aldina, and Pakaraimaea in Guyana

ABSTRACT Species of the ectomycorrhizal (ECM) family Cortinariaceae (Agaricales, Agaricomycetes, Basidiomycota) have long been considered impoverished or absent from lowland tropical rainforests. Several decades of collecting in forests dominated by ECM trees in South America’s Guiana Shield is countering this view, with discovery of numerous Cortinariaceae species. To date, ~12 morphospecies of this family have been found in the central Pakaraima Mountains of Guyana. Here, we describe three of these as new species of Cortinarius and two as new species of Phlegmacium from forests dominated by the ECM tree genera Dicymbe (Fabaceae subfam. Detarioideae), Aldina (Fabaceae subfam. Papilionoideae), and Pakaraimaea (Cistaceae). Macromorphological, micromorphological, habitat, and DNA sequence data are provided for each new species.

Disguise or surprise: spider antipredator adaptations as a function of the architecture of their webs

Abstract Animals exhibit a variety of strategies to avoid predation; spiders are no exception. We explored whether web-building spiders that differ in the architecture of their webs exhibit morphologies or behaviors suggestive of antipredator strategies that trade-off with the degree of protection offered by their webs. Spiders build webs of 3 types: the more protected tangles and sheet-and-tangles, which are three-dimensional (3D), and the more exposed orbs, which are two-dimensional (2D), both with or without a refuge. We hypothesize that spiders whose webs offer greater protection—a 3D architecture or a refuge—will be less likely to be armored or brightly colored when compared to spiders without these protections. We collected data on 446 spiders and their webs in 2 lowland tropical rainforest sites. We show that 2D web builders with no refuges tended to be brightly colored (background contrasting) and spiny (spiky), whereas those with refuges tended to blend against the background of their refuges. 3D web builders, on the other hand, were neither cryptic nor brightly colored nor armored but were more likely to drop out of the web upon simulated predator contact. These results support the hypothesis that web-building spiders tend to be protected either through the architecture of their webs or their morphology and behavior, suggesting a trade-off between different types of antipredator strategies.

Eksplorasi Mikroflora Alami Cairan Nepenthes mirabilis (Lour) Druce di Kawasan Hutan Penelitian dan Pendidikan Biologi Universitas Andalas

Indonesia is a country that is rich in flora and fauna diversity, one of the unique flora in Indonesia is Nepenthes. This bag serves to trap insects or other small animals, the Biology Education and Research Forest (HPPB) is located in the Andalas Limau Manis University campus area which is classified as lowland tropical rain forest which is the habitat of Nepenthes, in the Biology Education and Research Forest (HPPB) this type of pitcher plant, namely Nepenthes mirabilis. Nepenthes mirabilis is a plant that is able to digest insects trapped in pockets at the ends of its leaf tendrils, so it is classified as a carnivorous plant. Microorganisms play an important role in breaking down organic materials into inorganic ones available to plants. Types of bacteria and bacterial populations greatly determine the decomposition process of animals that have been trapped in the bag as a source of nutrients for Nepenthes plants. This study aims to explore the natural microflora of Nepenthes mirabilis fluids, determine the proportional presence of potential bacteria, and determine the in vitro potential of chitinolytic bacteria from Nepenthes mirabilis fluids. This study used a survey method which was analyzed descriptively. The results showed that Nepenthes mirabilis fluid contained the presence of Fermentative, Amylolytic, Proteolytic, Chitinolytic and Lipolitical bacteria. Nepenthes mirabilis liquid in open bags contained chitinolytic bacteria, the highest presence of chitinolytic bacteria was found in MBB samples (20,104 cfu/ml) and MBA samples (18,104 cfu/ml). .28), fermentative (2.33 and 2.00), amylolytic (1.42 and 1.28), proteolytic (2.00 and 2.00), lipolytic (1.75 and 1.28).

Habitat niches of bird species along a recovery gradient in the Chocó tropical forest

Conservation programs need improved tools to measure the recovery of animal diversity across restoration gradients. We used soundscapes and expert identifications of bird species to calculate niche position (i.e., mean of environmental conditions across all areas a species occupies) and niche breadth (i.e., the standard deviation of the species distribution) along a recovery gradient; from agriculture to early (up to 20 yrs) and late (up to 38 yrs) recovery, to old-growth forests. Our survey included 323 bird species and was conducted in 66 plots in the lowland Chocoan tropical rainforest in Ecuador where less than 11% of the forest remains intact, and large areas are currently undergoing regeneration post-abandonment. First, we validated our niche metrics by contrasting them against independent global categories of forest density dependency. We then explained the niche metrics of the bird species with different ecological traits, gathered from the literature, reflecting species-specific primary diet, morphology and distribution, and accounting for the phylogenetic relatedness of species. Finally, we explored the phylogenetic signal present in bird species’ ecological traits and recovery niche metrics. Niche position and breadth across the recovery gradient closely followed global categories of forest density dependency. However, our approach provided a more fine-scaled sorting of bird species in forest plots categorized as late recovery and old-growth. Granivorous birds occupied niche positions in active cacao and pasture plots and were replaced by frugivorous birds in older regeneration plots. Along the recovery gradient, tail length and handwing index decreased with niche position, supporting previous observations that birds in old-growth forests are less mobile. Birds in old-growth forests had smaller global distribution ranges than birds in agricultural plots. Finally, the latitudinal distribution of birds in the study area averaged south of the equator, with birds in old-growth plots averaging latitudinal centroids in wet forests north of the equator, whereas birds in agriculture plots averaged latitudinal centroids further south of the country, towards the dry and open Tumbesian forest. Frugivores, invertivores and vertivores had broader niche breadths, but these decreased (marginally) with tail length. We suggest these recovery niche metrics as a potentially powerful tool for the rapid assessment of the recovery process, which might support conservation strategies such as biodiversity credits, compensation payments, and strategic land purchases. With the increasing availability of information-intensive models for bird species identification, such as deep learning artificial intelligence, our new niche metrics open the avenue for rapid assessment of tropical biodiversity and new conservation areas at larger scales.

Thermoregulation of understory birds in lowland Amazonia

Understanding the capacity for thermoregulation is critical for predicting organismal vulnerability to climate change, especially in lowland tropical rainforests, where warming conditions combine with high humidity and limited elevational or latitudinal refugia. Here, I focused on nine species of ground‐foraging insectivorous birds in the genus Myrmoderus, Myrmornis, Hylopezus, Myrmothera, Formicarius and Sclerurus – sensitive forest specialists characterized by recently documented population declines in both disturbed and undisturbed forests. Using high‐resolution data from loggers deployed on birds and their environment, I examined whether and how birds used thermoregulation and whether ambient water provided cooling opportunities. Variation in the rate of temperature change over the diel cycle suggested that all species employed behavioral and physiological thermoregulation, but some patterns differed by species' phylogenetic relatedness. All species warmed hours before their environment at sunrise, then experienced lower temperature increases at midday relative to the ambient thermal flux. These morning warming periods peaked around sunrise for all but Sclerurus rufigularis and constituted the diel temperature change maxima for five of the nine species. Six species exhibited pronounced oscillations in temperature change consistent with regular bathing around sunset, possibly for thermoregulatory or other purposes. This oscillation was the most prominent feature in the diel thermal flux for all three Sclerurus species and, to a lesser extent, for Myrmoderus ferrugineus, Myrmornis torquata and Myrmothera campanisona. Local rainfall reduced ambient temperatures, and birds experienced stronger cooling in the wet season and with higher rainfall intensity. However, rain‐induced cooling events were markedly absent in all three Sclerurus spp. These results highlight the fundamental role of water in avian thermoregulation and suggest that terrestrial insectivores attempt to maintain thermal homeostasis throughout the diel cycle. The observed thermoregulatory behaviors highlight a potentially critical aspect of their vulnerability – thermal regimes are profoundly altered by forest disturbance, climate change, and their combination.

The Dynamics of Vegetation Structure, Composition and Carbon Stock in Peatland Ecosystem of Old Secondary Forest in Riau and South Sumatra Provinces

Lowland tropical rainforests provide an abundance of biodiversity as well as dynamic and stable ecosystems. These forests include tropical peat forests in various locations and forest types that have vegetation structure and composition characteristics, and carbon stocks that still need to be explored more deeply. Research on the structure and the composition of the vegetation and carbon stock in the old secondary peat forest was carried out in the protected areas of Bukit Batu, Riau Province, and Muara Merang, South Sumatra Province. Based on a 1-hectare permanent plot established in Bukit Batu and Muara Merang, 25 subplots of 20 m by 20 m were established in each location for measurement purposes. The results showed that Bukit Batu and Muara Merang had 42 and 36 species belonging to 26 and 20 families, respectively. Bukit Batu had a species diversity index (H’) of 2.93, and the dominant tree species were Palaquium xanthochymum with an importance value index (IVI) = 66.27%, Eugenia sp. (IVI = 32.76%), and Litsea sp. (IVI = 18.39%). The Muara Merang location had a species diversity index (H’) of 2.82, and the dominant tree species were Eugenia sp. (IVI = 60.88%), Alseodaphne insignis (IVI = 26.34%), and Adenanthera pavonina (IVI = 22.11%). In Bukit Batu, forest stands with a diameter of ≥10 cm contained a biomass of 178.10 tonnes/ha and carbon stock of 83.70 tonnes C/ha, which is equal to 307.20 tonnes CO2/ha. Meanwhile, in Muara Merang, it was 190.41 tonnes/ha and 89.49 tonnes C/ha, which is equal to 328.44 tonnes CO2/ha. This research, especially that in Bukit Batu, Riau Province, enriches the data and information available to date and is very useful in supporting restoration practices in Riau Province’s Giam Siak Kecil Biosphere Reserve, which was designated by UNESCO as part of the Man and Biosphere Program.

Diel activity patterns of a canopy-inhibiting beetle community (Coleoptera) in a Neotropical rainforest

Diel activity is one main feature of animal‘s behavior and is often an intrinsic trait characterizing distinct taxonomic groups. Abiotic conditions such as temperature may influence the diel activity patterns of arthropod communities associated with a particular ecosystem or habitat. Similarly, biotic factors, such as resource availability, affect arthropod activity. In addition, diel activity is thought to be an important factor in niche partitioning of arthropod communities. As part of a larger beetle survey in a lowland tropical rainforest in southern Venezuela, I analyzed the diel activity of an arboreal beetle community collected from 23 canopy-tree species over a cumulative year. Diel activity was observed in 535 beetle species, comprising 5,948 individuals, using a canopy crane installed in the study area. Of the 535 beetle species, 198 (37%) showed diurnal activity, and 281 (52.5%) showed nocturnal activity. In contrast, the proportions of nocturnal (n = 2,024, 34%) and diurnal (n = 1,983, 33.3%) individuals were balanced. Most of the observed beetles occurred only during the activity phase in their host trees. This particularly applies to extrafloral nectary- and flower-visiting beetle species. Flowering trees attracted different proportions of diurnal and nocturnal species according to flowering syndrome, whereas extrafloral nectaries were mainly visited at night. Thus, the beetle communities associated with single tree species showed distinct compositions of nocturnal and diurnal species.

Population Abundance and Density Estimates of Poorly Documented Near-Threatened Calabar Angwantibo (Arctocebus calabarensis) in Oban Hills Region.

Population abundance and density estimates play important roles in biodiversity conservation assessment and can lead to prioritization of conservation efforts, strategies, and management. The Calabar angwantibo (Arctocebus calabarensis) is a poorly studied, Near-Threatened nocturnal, arboreal mammal species occurring only in the lowland moist tropical rainforest blocks of southeastern Nigeria and southwestern Cameroon. Like other arboreal nocturnal mammals, there are gaps in knowledge of the distribution and abundance of this species, which may be facing population declines due to habitat loss and hunting. In this study, we investigated the abundance and density of A. calabarensis in the Oban Hills Region of Nigeria. We conducted systematic distance sampling survey along 32 transects in different habitats in a 1227 km of survey efforts. A total of 41 sightings of A. calabarensis were detected, resulting in an abundance of 7345 individuals (95% CI = 1.51-4.37) with an estimated density of 2.57 animals/km2. The estimated population abundance is 6515 individuals in closed-canopy forests and 830 individuals in secondary forests, with encounter rates of 0.52 individual/km2 and 0.60 individuals/km2 in the closed canopy and secondary forest habitats. The global estimates encounter rate of A. calabarensis across the habitat types is 0.33 individuals/km2 and population abundance of 4456 individuals. Our findings indicate that the A. calabarensis populations can adapt to low changes in forest habitat modifications resulting from increasing and widespread forest disturbance by human-dominated activity, which is giving way to forest clearance for agriculture cultivation and infrastructural development. Our findings help to fill a knowledge gap regarding this species and may help establish a baseline for future management, population monitoring, and conservation of the cryptic population of A. calabarensis in Cross-Sanaga Forests.

Bees and wasps in the tropical lowland rainforest transformation in Jambi, Sumatra

Bees and wasps are beneficial insects for the stability of ecosystem function. This study aimed to explore the bees and wasps and their relationship with the environmental factors in the three habitats, i.e., oil palm and rubber plantation, jungle rubber and adjacent villages in Harapan Forest, Jambi, Sumatra, Indonesia. Bees and wasps were collected using sweeping method and the environmental factors were recorded during collection time. The correlation between the number of species and environmental factors was analyzed using Principal Component Analysis (PCA). Apis and Tetragonula were the two most common bees in all habitats and villages. The number of bee and wasp species in oil palm and rubber plantations was positively correlated with temperature and light intensity but negatively correlated with humidity. We found a higher number of bee species, i.e., 26 species, compared to seven species of wasps. The highest number of bees and wasps (16 species) was found in the oil palm plantation. Both jungle rubber and adjacent villages showed the lowest number of nine species of bees and wasps. Our study implied the importance of bees and wasps representing the herbivores and predators in these transformation habitats.

An updated infrageneric classification of the pantropical species-rich genus Garcinia L. (Clusiaceae) and some insights into the systematics of New Caledonian species, based on molecular and morphological evidence.

Garcinia L. is a pantropically distributed genus comprised of at least 250 species of shrubs and trees and has centers of diversity located in Africa/Madagascar, Australasia, and Southeast Asia. The genus is notable due to its extreme diversity of floral form, common presence in lowland tropical rainforests worldwide, and potential pharmacological value. Across its entire geographic range, Garcinia lacks a recent taxonomic revision, with the last genus-level taxonomic treatment of Garcinia conducted over 40 years ago. In order to provide an evolutionary-based framework for a revised infrageneric classification of the genus and to investigate in more detail the systematics of New Caledonian species, we conducted molecular phylogenetic analyses using DNA sequence data for the nuclear ITS region on all samples, and for three chloroplast intergenic spacers (psbM-trnD, trnQ-rps16 and rps16-trnK) on a subset of our overall sampling. Our phylogenetic analyses are the most comprehensive to date for the genus, containing 111 biogeographically and morphologically diverse Garcinia species. The analyses support a broad circumscription of Garcinia, including several previously segregated genera (e.g. Allanblackia, Clusianthemum, Ochrocarpos p.p., Pentaphalangium, Rheedia, and Tripetalum). We recovered nine major clades falling within two major lineages, and we delimit 11 sections. We discuss each of the clades, assign them sectional names, discuss their distinguishing morphological features, compare our taxonomic treatment with the most recent sectional treatment, list representative species, note geographic distribution, and highlight some questions that deserve future investigations. We propose nine new nomenclatural combinations, four new names, and three new lectotypes. In New Caledonia (NC), a total of ten, all endemic, species are recognized and were included in our phylogenetic analyses, with several replicates per species (with the exception of G.virgata and G.urceolata, represented by a single accession each). New Caledonian species were retrieved within three separate clades, respectively including 1) G.balansae; 2) G.comptonii, G.neglecta, G.urceolata, G.virgata; and 3) G.amplexicaulis, G.densiflora, G.pedicellata, G.puat, G.vieillardii. Within NC, the phylogenies did not support the distinction between a putative undescribed species and G.balansae. However, it confirmed the distinction between NC species and both G.vitiensis (found in Fiji and Vanuatu) and G.adinantha (found in Fiji), suggesting that all NC species should be considered as endemics.

No evidence of carbon storage usage for seed production in 18 dipterocarp masting species in a tropical rain forest.

Most canopy species in lowland tropical rain forests in Southeast Asia, represented by Dipterocarpaceae, undergo mast reproduction synchronously at community level during a general flowering event. Such events occur at irregular intervals of 2-10years. Some species do not necessarily participate in every synchronous mast reproduction, however. This may be due to a lack of carbohydrate resources in the trees for masting. We tested the hypothesis that interspecific differences in the time required to store assimilates in trees for seed production are due to the frequency of masting and/or seed size in each species. We examined the relationship between reproductive frequency and the carbon accumulation period necessary for seed production, and between the seed size and the period, using radiocarbon analysis in 18 dipterocarp canopy species. The mean carbon accumulation period was 0.84years before seed maturation in all species studied. The carbon accumulation period did not have any significant correlation with reproductive frequency or seed size, both of which varied widely across the species studied. Our results show that for seed production, dipterocarp masting species do not use carbon assimilates stored for a period between the masting years, but instead use recent photosynthates produced primarily in a masting year, regardless of the masting interval or seed size of each species. These findings suggest that storage of carbohydrate resources is not a limiting factor in the masting of dipterocarps, and that accumulation and allocation of other resources is important as a precondition for participation in general flowering.

Variation of Geochemical Properties of Soils in Tropical Lowland Rainforests in Sri Lanka

Tropical lowland rainforests (TLRFs) of Sri Lanka are considered as diverse ecosystems which play a vital role in climate change mitigation. In recent years, increasing deforestation leads to diminishing their potential ecosystem roles. For efficient forest conservation, knowledge of both above- and below-ground characteristics of TLRFs is required. Currently, above-ground information on TLRFs is sufficiently available but the details on the below-ground characteristics are limited. Therefore, this study was carried out to investigate pedo-geochemical properties of lowland rain forests of Kanneliya (KDN) and Pitadeniya, (PTD) in Sri Lanka. Four sampling plots with 1 ha in size (KDN1, KDN2, PTD1 and PTD2) were established, selecting altitudes of 117, 174, 509, and 618 m asl, respectively. Five representative near-surface (up to 25 cm) samples were collected from each plot for the investigation. Soil pH, electrical conductivity (EC), and cation exchange capacity (CEC) were measured while soil organic matter (SOM) content was determined by (i) Walkey-Black (WB) and (ii) Loss on ignition (LI) methods. Data were analysed by ANOVA and means were compared using Duncan‘s test. All measured parameters were significantly different (P<0.05) among the sampling plots. Soil pH and EC values were ranged between 3.43– 3.78 and 0.28–0.44 dS m-1, respectively. The highest CEC was recorded in PTD2 (11.09±3.44 cmol(+)/kg) whereas the lowest was in PTD1 (5.31±1.26 cmol(+)/kg). The highest SOM was recorded in PTD1 (17.71±4.42% in WB, 18.04±3.98% in LI) whereas the lowest was noted in PTD2 (5.81±3.07% in WB, 8.21±2.13% in LI). According to the comparison made between WB and LI methods, LI method recorded higher SOM content. The actual SOM and volatilizable water in hygroscopic mineral fractions might be the reason for the higher values in LI method. All acquired data were compared with standard interpretation data and accordingly, soils of the measured TLRFs are acidic, non-saline and non-reduced with sufficient soil aeration. Even though, TLRF vegetation produce high amount of biomass, soil CEC and SOM contents are low in the study area due to rapid microbial decomposition and absorption of dense vegetation. There was no linear relationship between measured parameters and altitude. Overall, measured soil chemical properties can be considered as ideal indicators of TLRFs conservation and therefore, it needs to be correlated with above-ground properties for understanding the behaviour of TLRFs responding to conservation strategies. 
 Keywords: Forest conservation, Soil chemical properties, Soil organic matter content, Tropical lowland rainforest

Faunal Diversity and the Ecological Aspects of a Community-Based Fragmented Lowland Rainforest Patch in Western Province, Sri Lanka

Wawekale Rainforest Reserve (WRR) is a primary lowland tropical rainforest area in the Western Province of Sri Lanka, established with diversity, but disturbed by human activities such as rubber cultivation, logging, poaching, chemical release, and the collection of firewood. Visual Encounter Surveys (VES) were conducted for 100 hours in the year 2022, which covered wide habitat distribution. The herpetofaunal diversity was measured in the WRR which can indicate broader ecological shifts, environmental changes, or habitat degradation. Water quality was measured in the WRR area to determine the ecosystem health and human impact. The study reports 171 species in 73 families, including two Critically Endangered (1.17%), six Endangered (3.51%), 16 Vulnerable (9.36%), and 14 Near Threatened (8.19%) species according to the IUCN Red List. The study area showed 51 endemic faunal species in Sri Lanka, which represented 29.83% of endemism. Based on the observations conducted on the herpetofauna diversity, the Shannon-Wiener diversity index (H) was calculated and the overall herpetofauna (H’H) showed high diversity within the forest premises. The water quality of the forest fragment had an influence from anthropogenic activities such as removing forest cover, bathing, washing vehicles, and releasing agro-chemical compounds resulting in high water temperature, basic pH level, high electrical conductivity, and high total dissolved solid conditions. The WRR, designated under protection, exhibits the need for immediate remedial actions to mitigate human-induced pollution and deforestation, emphasizing the critical importance of implementing proactive conservation measures to sustain ecological integrity and preserve biodiversity.

Compositional changes at neighborhood and stand scales during recovery of a tropical lowland rainforest after shifting cultivation on Hainan Island, China

Understanding compositional changes during secondary forest recovery is crucial for effective restoration efforts. While previous research has predominantly focused on shifts in species composition at the stand scale, this study delves into the recovery dynamics in three compositional aspects of location (neighbor distances), size (tree diameters), and species (tree species) at both stand and neighborhood scale. The investigation spans nine chronosequence plots within a tropical lowland rainforest ecosystem after shifting cultivation, including three each for young-secondary forests (18–30 years), old-secondary forests (60 years), and old-growth forests (without obvious human interference). The quantification of location, size, and species composition involved categorized neighbor distances (Near, Moderate, Far-distance), tree diameters (Small, Medium, Large-tree), and tree species (Pioneer, Intermediate, Climax-species) into three groups, respectively. Compositional changes at the stand scale (plot) were directly based on these groups, while at the neighborhood scale, assessment involved combination types of these groups within a neighborhood (comprising three adjacent trees). At the stand scale, neighbor distances shifted from Near to Moderate and Far, tree diameters transitioned from Small to Medium and Large, and tree species of Pioneer gave way to Climax. Meanwhile, at the neighborhood scale, there was a notable decline in the aggregations of Near-distance (N), Small-tree (S), and Pioneer-species (P), while the mixtures of Far and Moderate-distance (F-M), Large and Small-tree (L-S), and Climax and Intermediate-species (C–I) experienced a marked increase. The compositional change exhibited a recovery pattern, with the fastest recovery in neighbor distances, followed by tree diameters and tree species. Moreover, compositional recovery in tree diameters and tree species at the neighborhood scale generally lagged behind that at the stand scale. The study suggests that rapid restoration of secondary forest can be achieved by different targeted cutting according to the recovery stages, aimed at reduce the Pioneer-species, Small-tree and Near-distance in neighborhood. Our findings underscore that analyzing the compositional changes in three aspects at two scales not only provides a profound understanding of secondary forest recovery dynamics, but also offers valuable insights for guiding practices in the restoration of degraded forest ecosystems.

The links between wood traits and species demography change during tree development in a lowland tropical rainforest.

One foundational assumption of trait-based ecology is that traits can predict species demography. However, the links between traits and demographic rates are, in general, not as strong as expected. These weak associations may be due to the use of traits that are distantly related to performance, and/or the lack of consideration of size-related variations in both traits and demographic rates. Here, we examined how wood traits were related to demographic rates in 19 tree species from a lowland forest in eastern Amazonia. We measured 11 wood traits (i.e. structural, anatomical and chemical traits) in sapling, juvenile and adult wood; and related them to growth and mortality rates (MR) at different ontogenetic stages. The links between wood traits and demographic rates changed during tree development. At the sapling stage, relative growth rates (RGR) were negatively related to wood specific gravity (WSG) and total parenchyma fractions, while MR decreased with radial parenchyma fractions, but increased with vessel lumen area (VA). Juvenile RGR were unrelated to wood traits, whereas juvenile MR were negatively related to WSG and axial parenchyma fractions. At the adult stage, RGR scaled with VA and wood potassium concentrations. Adult MR were not predicted by any trait. Overall, the strength of the trait-demography associations decreased at later ontogenetic stages. Our results indicate that the associations between traits and demographic rates can change as trees age. Also, wood chemical or anatomical traits may be better predictors of growth and MR than WSG. Our findings are important to expand our knowledge on tree life-history variations and community dynamics in tropical forests, by broadening our understanding on the links between wood traits and demography during tree development.