Tropical Forests Of Asia Research Articles

Response of dholes to prey availability and human disturbance in space and time in Southern India

Understanding spatial and temporal behavior of large carnivores is critical to developing conservation strategies that mitigate the limiting factors of prey availability and human disturbance. Dholes (Cuon alpinus) are endangered, pack-living canids persisting in tropical forests of Asia, yet significant knowledge gaps remain about their basic ecology. We estimated spatial occurrence and temporal activity of dholes relative to prey availability, anthropogenic disturbance, and landscape features using camera traps in two protected areas in Southern India. Estimated detection probability of dholes was 0.14 (95 % CI: 0.11, 0.18), while estimated occupancy probability was 0.33 (95 % CI: 0.26, 0.40). Prey availability was the strongest driver of spatial occurrence of dholes, followed by multiple measures of human disturbance. Dholes responded to human activity and human infrastructure differently in space and time, which appeared to free them to overlap with their primary prey. Dholes avoided roads spatially, avoided livestock in space and time, and avoided human activity temporally. Dholes exhibited high temporal overlap with chital, barking deer, and wild pig activity, which are likely important prey. We recommend regulating livestock presence within protected areas and limiting new road development within habitat occupied by endangered species. A proposed reservoir project to create drinking water and electricity would inundate important forested habitat for dholes along the River Cauvery where occupancy was high. This removal of habitat would significantly impact dhole presence in this landscape. Our findings advance understanding of behavioral responses by an understudied, endangered large carnivore to its primary limiting factors: prey and human disturbance.

Determinants of locals’ willingness to participate in human–elephant conflict management: Evidence from Dong Nai Biosphere Reserve, Vietnam

Human-elephant conflict (HEC) poses a significant threat to the conservation of Asian elephants (Elephas maximus Linnaeus, 1758) and the well-being of local communities in the tropical forests of Asia. As local communities play a crucial role in HEC reduction, their engagement is essential for the success and sustainability of HEC management strategies. This study employs exploratory factor analysis and a logistic regression model to examine the key determinants influencing the participation of locals in HEC management within the Dong Nai Biosphere Reserve (DNBR), Vietnam. The findings indicate that improvements in elephant habitat and land use have the most substantial positive impact on locals' participation in HEC management, followed by policies for HEC reduction, local perception of the benefits associated with elephants, and measures for HEC prevention and mitigation. In terms of demography, individuals' education levels exhibit the highest positive influence on their involvement in HEC management, followed by income, and occupation. These research findings contribute to a broader understanding of human-wildlife conflicts and underscore the significance of community engagement in conservation efforts. By identifying the factors that influence local participation in HEC management, this study aims to inform future initiatives and policies aimed at mitigating conflicts between humans and elephants, while promoting coexistence and sustainable development in the DNBR, Vietnam.

Symbiotic control of canopy dominance in subtropical and tropical forests.

Subtropical and tropical forests in Asia often comprise canopy dominant trees that form symbioses with ectomycorrhizal fungi, and species-rich understorey trees that form symbioses with arbuscular mycorrhizal fungi. We propose a virtuous phosphorus acquisition hypothesis to explain this distinct structure. The hypothesis is based on (i) seedlings being rapidly colonised by ectomycorrhizal fungi from established mycelial networks that generates positive feedback and resistance to pathogens, (ii) ectomycorrhizal fungi having evolved a suite of morphological, physiological, and molecular traits to enable them to capture phosphorus from a diversity of chemical forms, including organic forms, and (iii) allocation of photosynthate carbon from adult host plants to provide the energy needed to undertake these processes.

Dietary Specialization and Habitat Shifts in a Clade of Afro-Asian Colubrid Snakes (Colubridae: Colubrinae)

Speciation through niche divergence often occurs as lineages of organisms colonize and adapt to new environments with novel ecological opportunities that facilitate the evolution of ecologically different phenotypes. In snakes, adaptive diversification may be driven by the evolution of traits relating to changes in their diets. Accordingly, habitat-mediated differences in prey available to ancestral snakes as they colonized and occupied novel dynamic landscapes are likely to have been a strong selective agent behind the divergence and radiation of snakes across the globe. Using an ancestral reconstruction approach that considers the multivariate nature of ecological phenotypes while accounting for sampling variation between taxa, we explored how diet and macro-habitat use coevolved across a phylogeny of 67 species of Afro-Asian colubrine snakes. Our results show that the most recent common ancestor of this clade was likely a dietary generalist that occupied tropical forests in Asia. Deviations from this generalist diet to a variety of specialist diets each dominated by the utilization of single prey types repeatedly occurred as ancestral colubrines shifted from tropical forests to savanna and grassland habitats across Africa. We additionally found that dietary specialist species were on average smaller in maximum length than dietary generalists, congruent with established predator-size, prey-diversity dynamics in snakes. We speculate that adaptive divergence in ancestral colubrines arose as a result of a selective regime that favored diets comprised of terrestrial prey, and that partitioning of different prey types led to the various forms of dietary specialization evident in these lineages today. Our findings provide new insights into the ecological correlates associated with the evolution of diet in snakes, thereby furthering our understanding of the driving forces behind patterns of snake diversification.

Social wasps, crickets and cockroaches contribute to pollination of the holoparasitic plant Mitrastemon yamamotoi (Mitrastemonaceae) in southern Japan.

Mitrastemon yamamotoi is completely embedded within the tissues of its hosts, except during the reproductive stage, when aboveground parts emerge from host tissues. Its highly modified appearance has attracted attention of many botanists, but very little is known about the reproductive system. Floral visitors to M. yamamotoi were observed in southern Japan. Pollination experiments were conducted to determine the plant's self-compatibility and pollen limitation, as well as the contribution of diurnal and nocturnal visitors to fruit set and outcrossing. Mitrastemon yamamotoi is mainly pollinated by social wasps, but previously unnoticed pollinators (i.e. crickets and cockroaches) are also important, based on visitation frequency and pollen loads. Results of the pollination experiments suggest that nocturnal visitors, such as crickets and cockroaches, contribute to geitonogamous pollination, whereas diurnal visitors, such as social wasps, facilitate outcrossing. The unexpected pollinator assemblage of M. yamamotoi might be influenced by multiple factors, including the highly modified flowers that are produced close to the ground in dark understorey environments, the species' winter-flowering habit and the location of the study site (i.e. near the northern limit of the species' range). Considering that M. yamamotoi occurs widely in subtropical and tropical forests in Asia, additional studies are needed to assess pollinator assemblages of M. yamamotoi at other locations.

Resilience of a forest fragment exposed to long-term isolation in Singapore

Background: Fragmentation can fundamentally alter the structure of tropical forests. However, the impacts of fragmentation may vary significantly among regions and lead to different outcomes.Aims: We examined the structure, composition and dynamics of a forest fragment in Singapore to investigate reasons for the apparent resilience of this forest to long-term isolation.Methods: We conducted 5 censuses of 12,688 trees ≥1-cm dbh in a 2-ha plot on the edge of the fragment between 1993 and 2012.Results: Stem density and basal area were not significantly different between 1993 and 2012 and were typical of other south-east Asian forests. However, there were short-term decreases in both variables after droughts in 1997 and 2009, both followed by recovery. Total mortality rate over the 19 years was 3.3% year−1, considerably higher than other tropical forests in Asia, but it was balanced by high recruitment. The 10 most abundant species were primary forest species, pioneer species comprised <5% of all stems, and none of the 338 species in the plot was exotic. However, species abundances changed more than expected by chance for 86 species, and the rank order of the commonest species changed significantly. Species abundance changes were not related to known species traits.Conclusions: Despite the long period of isolation, we found a surprising level of resilience of the Bukit Timah forest. While the forest may be more sensitive to the effects of climatic fluctuations at decadal time scales, there were very few signs of forest degradation in this diverse fragment of tropical forest.

Ecology, Conservation, and Adventure of the Tropical Forests in Asia and New Guinea

Ecology, Conservation, and Adventure of the Tropical Forests in Asia and New Guinea

Spatial and dietary overlap between blackbuck (Antilope cervicapra) and feral horse (Equus caballus) at Point Calimere Wildlife Sanctuary, Southern India: Competition between native versus introduced species

Overgrazing by livestock is a serious threat to the biodiversity in the tropical forests of Asia. Feral horse, an introduced species at Point Calimere Wildlife Sanctuary, is a grazer and overlaps extensively in space and food resources with blackbuck, a native species, and thus could be a potential competitor. We have assessed, between December 2012 and June 2013, if the ecological conditions in the study site favour competition between these two species by assessing their spatial distribution pattern, population density, and dietary overlap. Spatial distribution pattern on direct sighting of both the species across habitats revealed that feral horses ranged mostly in the southern and southeastern parts of the sanctuary, in areas mostly with open grasslands, overlapping extensively in space with blackbuck, a grassland habitat specialist of the sanctuary. Population density estimated using line-transect distance sampling method showed 50 (95% CI 41.6–60.6) blackbucks and 21 (15.2–30.0) feral horses per km2 of the sanctuary. Dietary overlap assessed through site examination of feeding trails revealed that out of 14 plant species identified from blackbuck diet during the study period, 12 (86%) were also consumed by feral horses. Similarly, food plants such as Cloris parpata, a grass species, and herb Desmodiam dryflorae, the principal food of blackbuck, were also the major food plants of feral horses. Further, estimation of food consumption rate showed that feral horse consumed significantly more food per unit time (2.8±0.08g/min) than blackbuck (1.7±0.07g/min). Dietary overlap estimated using Schoener’s Index showed a significant overlap between the two species (overall 89% and habitat-wise 85–90%). An analysis of food preference using Jacob’s Preference Index revealed that all the preferred food plants of the blackbuck were equally preferred by feral horses indicating significant overlap in the diet species composition. Although the density estimate revealed a lesser number of feral horses per capita than blackbuck, the higher food consumption rate of the former coupled with larger body mass, could outweigh the higher density of blackbuck and the same is discussed as an effective ecological competitor. Based on the findings appropriate recommendations are made for the management of blackbuck in the sanctuary.

Seed Dispersal of Vitex Glabrata and Prunus Ceylanica by Civets (Viverridae) in Pakke Tiger Reserve, North-East India: Spatial Patterns and Post-Dispersal Seed Fates

Civets are considered potentially important seed dispersers in tropical forests of Asia, but relatively little is known about spatial patterns of dispersal and post-dispersal fates of civet-dispersed seeds. We explored these aspects of civet seed dispersal for two tree species Vitex glabrata (Lamiaceae), also known as smooth chaste tree and Prunus ceylanica (Rosaceae), in Pakke Tiger Reserve, a tropical forest reserve in north-east India. Pakke has five known species of viverrids: small Indian civet ( Viverricula indica), large Indian civet ( Viverra zibetha), common palm civet ( Paradoxurus hermaphroditus), masked palm civet ( Paguma larvata) and the binturong ( Arctictis binturong). For both tree species, civets as a group dispersed seeds (100% of scats that we found) within 50 meters from fruiting trees and deposited seeds onto multiple substrates including tree branches, forest floor, and fallen logs. However, the distribution of seeds among substrates differed for the two tree species: while most seeds of V. glabrata (&gt; 90%) were deposited onto canopy branches and fallen logs, the majority of P. ceylanica seeds (&gt; 70%) were deposited on the forest floor. For both tree species, seeds deposited on logs experienced higher seed predation than seeds on the forest floor, especially when local seed densities (number of seeds in 1m2 area around the scat and in the scat) were high. Further, seed viability of P. ceylanica was significantly lower on logs (~35%) than on the forest floor (~65%). For both tree species, civets neither dispersed seeds far from fruiting trees nor to sites where seeds experienced either low predation or high survival, suggesting that while civets were legitimate dispersers, they were not especially effective.

Spatial organization and activity patterns of the masked palm civet (Paguma larvata) in central-south China.

Movement and activity patterns are important components of life history, being central to resource acquisition and defense, mating behavior, and individual survival and fitness. Here, we present results from the 1st systematic radiotracking study of the masked palm civet (Paguma larvata), a widespread viverrid found in subtropical and tropical forests of Asia. From June 2004 to November 2007, we radiotracked 12 masked palm civets (5 males and 7 females) in central-south China. Mean individual home-range size based on 95% minimum convex polygons was 192.6 ha ± 42.6 SE (range = 64–451 ha). Although males had larger mean home-range sizes than females (276.8 and 136.5 ha, respectively), these differences were not statistically significant. Males also exhibited greater daily movement distances and extents than females, but we found no evidence of sexual dimorphism in body size. Masked palm civets were predominantly nocturnal, but were active intermittently during the day. No significant seasonal (monthly) differences in daily activity patterns were apparent. We did, however, observe reduced hours of activity—but not continuous inactivity—during winter; consequently, we concluded that our study animals did not hibernate or semihibernate. We speculate that our observations of home-range overlap among individuals may indicate group living in the masked palm civet.

What controls tropical forest architecture? Testing environmental, structural and floristic drivers

AbstractAimTo test the extent to which the vertical structure of tropical forests is determined by environment, forest structure or biogeographical history.LocationPan‐tropical.MethodsUsing height and diameter data from 20,497 trees in 112 non‐contiguous plots, asymptotic maximum height (H AM) and height–diameter relationships were computed with nonlinear mixed effects (NLME) models to: (1) test for environmental and structural causes of differences among plots, and (2) test if there were continental differences once environment and structure were accounted for; persistence of differences may imply the importance of biogeography for vertical forest structure. NLME analyses for floristic subsets of data (only/excluding Fabaceae and only/excluding Dipterocarpaceae individuals) were used to examine whether family‐level patterns revealed biogeographical explanations of cross‐continental differences.ResultsH AM and allometry were significantly different amongst continents. H AM was greatest in Asian forests (58.3 ± 7.5 m, 95% CI), followed by forests in Africa (45.1 ± 2.6 m), America (35.8 ± 6.0 m) and Australia (35.0 ± 7.4 m), and height–diameter relationships varied similarly; for a given diameter, stems were tallest in Asia, followed by Africa, America and Australia. Precipitation seasonality, basal area, stem density, solar radiation and wood density each explained some variation in allometry and H AM yet continental differences persisted even after these were accounted for. Analyses using floristic subsets showed that significant continental differences in H AM and allometry persisted in all cases.Main conclusionsTree allometry and maximum height are altered by environmental conditions, forest structure and wood density. Yet, even after accounting for these, tropical forest architecture varies significantly from continent to continent. The greater stature of tropical forests in Asia is not directly determined by the dominance of the family Dipterocarpaceae, as on average non‐dipterocarps are equally tall. We hypothesise that dominant large‐statured families create conditions in which only tall species can compete, thus perpetuating a forest dominated by tall individuals from diverse families.

Book review: Tackling thorny issues in seasonally dry tropical forests

news and update ISSN 1948‐6596 book review Tackling thorny issues in seasonally dry tropical forests The ecology and conservation of seasonally dry forests in Asia, by William J. McShea, Stuart J. Davies and Naris Bhumpakphan (editors) 2011, Smithsonian Institution Scholarly Press, 418 pp. ISBN: 978‐1‐935623‐02‐1 Price: $69.95 / £44.95 (Hardback); http://www.scholarlypress.si.edu/ Seasonally dry tropical forests: ecology and conservation, by Rodolfo Dirzo, Hillary S. Young, Harold A. Mooney and Gerardo Ceballos (editors) 2011, Island Press, 391 pp.ISBN: 978‐1‐59726‐703‐8/978‐1‐59726‐704‐5 Price: $95.00 (Hardback)/$50.00 (Paperback); http://islandpress.org/ The first difficulty in reviewing (and I presume writing) any book on seasonally dry tropical for‐ ests (SDTF) is to come to some understanding as to what SDTF actually are. I hazard a guess that what is a seasonally dry tropical forest to one per‐ son is a seasonal rain forest to another. I myself have recently treated ‘seasonally dry tropical for‐ est’ formations as various types of ‘seasonal rain forest’ (Ghazoul & Sheil, 2010). What is clear is that aseasonal tropical wet forests grade almost imperceptibly into seasonally dry evergreen for‐ est, variably deciduous forest and, ultimately, xe‐ rophytic woodland at the other extreme. Imposing clear‐cut system definitions is always going to be problematic, but it is the nature (and necessity) of human enquiry to impose some sort of classifica‐ tion system on hopelessly complex realities. In this vein two recent edited books on Neotropical (Dirzo et al.) and Asian (McShea et al.) forests de‐ fine SDTF as tropical forests with predictable, regular dry seasons lasting 4‐6 (Neotropics) or 2‐6 months (Asia), while also recognising variations on this theme. It is not so much the duration or inten‐ sity of the dry season that matters, but rather the seasonal water stress that plants are subjected to, and this is as much a function of local topography, soil and disturbance history as it is of climate. Thus in Asia SDTF can occur alongside wet ever‐ green formations in a mosaic of different vegeta‐ tion types, adding to the complexities of distin‐ guishing and mapping SDTF. Both these books begin similarly, with a couple of chapters on floristic composition and biogeography of seasonally dry tropical forests in each respective region. In the Neotropics Linares‐ Palomino et al. identify close floristic affinities among isolated SDTF regions that are distributed across a formerly hypothesised ‘Pleistocene Arc’ of SDTF that extends from Argentina in the south through Paraguay and across Brazil in the north. The Andean dry forests might represent an exten‐ sion of this arc, although the data on this point are ambiguous. Yet these authors argue that there is little evidence for a wide‐ranging Pleistocene SDTF formation, citing long‐distance dispersal events to explain the distribution of widespread species. The floristic ordination of continental Southeast Asian SDTF conducted by Bunyavejchewin et al. separates formations by elevation, topography, soil chemistry and soil physical features, all of which are related to soil water‐holding capacity, as well as the length of the dry season. A striking feature of SDTF and other tropical forests in Asia is their abundance of trees belonging to the Dip‐ terocarpaceae, yet some formations (e.g. mixed deciduous forests and lower montane forests) are notable by the near absence of dipterocarps. A biogeographic approach might provide some in‐ sights into such patterns because the Asian mixed deciduous and lower montane forests are domi‐ nated largely by families that are thought to have warm‐temperate Eurasian origins (e.g. Fagaceae, Lythraceae), while the dipterocarps originated in the southern hemisphere (Gondwana) and colo‐ nised the Asian tropics via India’s collision with Asia around 50 Mya. A fascinating chapter on the evolution of dry forest gingers by John Kress is unfortunately not placed in the context of the dis‐ tribution of forest formations outlined in the ear‐ lier chapters. The central defining feature – a predictable dry season – shapes phenological, behavioural, © 2012 the authors; journal compilation © 2012 The International Biogeography Society — frontiers of biogeography 3.4, 2012

Allometric equations for biomass estimations in Cameroon and pan moist tropical equations including biomass data from Africa

Moist tropical forests in Africa and elsewhere store large amounts of carbon and need accurate allometric regressions for their estimation. In Africa the absence of species-specific or mixed-species allometric equations has lead to broad use of pan moist tropical equations to estimate tree biomass. This lack of information has raised many discussions on the accuracy of these data, since equations were derived from biomass collected outside Africa.Mixed-species regression equations with 71 sample trees using different input variables such as diameter, diameter and height, product of diameter and height, and wood density were developed to estimate total aboveground biomass and biomass of leaves and branches for a Cameroon forest. Our biomass data was added to 372 biomass data collected across different moist tropical forests in Asia and South America to develop new pan moist tropical allometric regressions. Species-specific and mixed-species height diameter regression models were also developed to estimate heights using 3833 trees.Using only diameter as input variable, the mixed-species regression model estimates the aboveground biomass of the study site with an average error of 7.4%. Adding height or wood density did not improve significantly the estimations. Using the three variables together improved the precision with an average error of 3.4%. For general allometric equations tree height was a good predictor variable. The best pan moist tropical equation was obtained when the three variables were added together followed by the one which includes diameter and height. This study provides height diameter relationships and wood density of 31 species. The pan moist tropical equation developed by Chave et al. (2005), estimates total aboveground biomass across different sites with an average error of 20.3% followed by equations developed in the present study with an average error of 29.5%.

The importance of secondary forest blocks for terrestrial mammals within an Acacia/secondary forest matrix in Sarawak, Malaysia

With the rapid conversion of tropical forests in Asia to plantation forests for timber or biofuel production there is a need to determine if these forests serve any viable role in wildlife conservation. We used infra-red trip cameras to survey for large terrestrial mammals within an Acacia/secondary forest matrix being created for pulpwood production in Sarawak, Malaysia. We detected at least 27 species of mammals within the matrix and 18 species were detected in both Acacia and secondary forest. Using occupancy modeling to determine important covariates for seven mammal species within the project area, six of these species were sensitive to forest type, and most were sensitive to the amount of secondary forest within 1 km of the sample point. For four species (sun bear, Helarctos melayanus; common porcupine, Hystrix brachyura; mousedeer, Tragulus spp.; and pig-tailed macaque, Macaca nemestrina), the mean distance of detection from large secondary forest blocks was significantly closer than expected from the distribution of sample points. Most species used Acacia forest less frequently than secondary forest, possibly for transit or foraging, with the exception of bearded pigs ( Sus barbatus), sambar ( Rucervus unicolor), and civets which were more common in Acacia stands. The amount of secondary forest preserved within forest plantations seems to be the best measure of conservation potential for these industrial forests. Forest plantations can provide a conservation value if managed properly and those retaining significant amounts of secondary forest should be eligible for a base level of certification as they comprise a significant portion of the landscape in this region.

A new species of Lagerstroemioxylon (Lythraceae) from the Pliocene of Yuanmou, Yunnan, China

Lagerstroemioxylon yuanmouensis sp. nov. is established from the Pliocene sediments near Xinhua, Yuanmou Basin, Yunnan, China. Its growth rings are distinct. Pores diffuse, solitary, and in radial multiples; perforation plates simple; intervessel pits alternate, vestured; vessel-ray pits alternate; tyloses thin-walled, abundant in vessels. Septate fibers distinct. Axial parenchyma predominantly paratracheal, narrow vasicentric and marginal. Rays mostly uniseriate, homocellular. The genus Lagerstroemioxylon was reported in the Tertiary sediments of India, Myanmar, Indonesia and Germany, which might indicate that Lagerstroemia living today in tropical forests of Asia and North Australia grew wider during the Tertiary.

Irregular droughts trigger mass flowering in aseasonal tropical forests in asia

General flowering is a community-wide masting phenomenon, which is thus far documented only in aseasonal tropical forests in Asia. Although the canopy and emergent layers of forests in this region are dominated by species of a single family, Dipterocarpaceae, general flowering involves various plant groups. Studying proximate factors and estimating the flowering patterns of the past and future may aid our understanding of the ecological significance and evolutionary factors behind this phenomenon. Here we show that this phenomenon is most likely triggered by irregular droughts based on 10 years of observations. In the aseasonal forests of SE Asia, droughts tend to occur during transition periods from La Niña to El Niño, which results in an irregular 6-7-yr cycle involving a dry period with several droughts and a wet period without droughts. The magnitude of a flowering event also depends on the timing of droughts associated with the El Niño southern oscillation (ENSO) cycle, with the largest events occurring after an interval of several years with no flowering. Because most plant species can only reproduce successfully during large flowering events, changes in the ENSO cycle resulting from global warming, may have serious ramifications for forest regeneration in this region.

The community ecology of Asian rain forests, in relation to catastrophic events

Although natural catastrophic disturbance of tropical forests in Asia can be caused by volcanism and earthquakes climate-induced catastrophes are most widespread. These are prevalent and most diverse at high tropical latitudes because of the single annual dry and wet monsoon. Comparative studies indicate that periodicity of catastrophes may influence forest physiognomy, structure and species richness but long-term research in sample plots suggests that a variety of other factors are locally influential. The importance of accounting for natural catastrophes in silvicultural protocols is stressed, and research priorities identified.

Conserving Eden: The (European) East India Companies and their Environmental Policies on St. Helena, Mauritius, and in Western India, 1660 to 1854

The history of tropical forest change over the last millennium is difficult to chart with any confident degree of accuracy. Indeed, systematic attempts even for the last hundred years have been made only recently. In general, more is known at present about the history of tropical forests in Asia and Southeast Asia than forests in Africa or South America. This lack of knowledge is partly due to the fact that the causal factors behind the erosion of tropical forests area are particularly difficult to disentangle. However, important connections can be made between European expansion, the penetration of capitalist economic forces, and the transformation of tropical environments.Above all, the spread of market relations in the tropics has served to encourage the rapid clearance of forests for agriculture. The history of global deforestation has probably been closely associated at many of its fastest stages with the dynamics of the forces of industrialisation and the expansion of a European-centered world-system.