Tropical Ecology最新文献

In the socio-ecological landscapes of tropical mountains, including the highly diverse Eastern Himalaya, fragments of natural forests have been traditionally managed as part of different agriculture systems. Recent studies have recognized their role as important biodiversity repositories outside protected areas. However, basic information on forest structure and composition of these forests outside protected areas is still limited in the Himalaya. In the current study, diversity, structure, composition, and regeneration status of non-protected forests were studied across 15 spatially different sites in the socio-ecological landscapes of Darjeeling-Sikkim, Eastern Himalaya, across an approximate elevation range of 500-2300 m above sea level. Quadrats (20 m × 5 m) were used to enumerate woody species in the study area. Enumeration of 156 quadrats (= 1.56 ha) resulted in a total of 249 woody species, of which species such as Schima wallichii, Alnus nepalensis, and Engelhardtia spicata were found to dominate the existing stand of trees. The vegetation structure of these forests was found to be almost comparable with that of protected forests, as assessed by prior studies in the same landscape. Species composition of woody plants in the study area were found to be primarily influenced by elevation. Assessment of regeneration patterns found the forests to have a high regeneration potential, however, the most dominant tree species of the area had relatively fewer saplings, indicating probable replacement of localized species of large trees by disturbance-adapted species. The current study adds to the literature on the structure and composition of non-protected forests in the tropical mountains.

Characterizations of meiofauna, as well as of Nematoda assemblages, are rare in oceanic islands due to logistical difficulties and, until now, no study on the vertical distribution of this fauna has been conducted in these environments. Therefore, this study shows vertical distribution patterns in the meiofauna community and Nematoda assemblage on two beaches with different sediment characteristic (volcanic and carbonate) of Trindade Island, a remote oceanic island in the Atlantic Ocean. Samples were collected in December 2014 at Príncipe and Portugueses beaches in three intertidal zones (high, mid-, and low) at two sedimentary column depths (0–10 and 10–20 cm). Overall, meiofauna was comprised of seven major groups, with Oligochaeta (57%) and Nematoda (12%) as the most abundant. Higher density and richness of meiofauna and Nematoda assemblage were found at Portugueses beach with the carbonate sediment. Nematoda assemblage was mainly comprised of non-selective deposit-feeders, with a total of 27 genera and 12 families; Cyatholaimidae and Xyalidae were the most abundant and had the highest diversity. Composition and density of meiofauna and Nematoda assemblage showed similar vertical distribution where the surface layer (0–10 cm) presented lower densities. Sediment characteristics (grain size, sorting, and composition) were primarily responsible for the regulation of the structure and distribution of meiofauna and Nematoda assemblage in Trindade Island beaches.

This study underscores the critical importance of assessing the performance of the Upper Ganga Canal (UGC) and its minors, Harchandpur and Naserpur. The UGC serves as a lifeline, providing water for both agricultural and non-agricultural purposes in the region, making it vital for food security, rural economies, and environmental sustainability. The uniqueness of this study lies in its comprehensive evaluation of the efficiency of UGC using a multifaceted approach, encompassing meteorological data, field observations and remote sensing. The monetary aspects of the irrigation system performance, which were often ignored in previous studies, have also been included in this study. The study, conducted from 2012 to 2018, assesses various performance indicators. The findings reveal that the capacity of UGC to meet peak irrigation requirements highlights the potential for increased crop production. However, it also demonstrates a concerning decreasing trend in the availability of water, driven by rising non-agricultural water demands. Several performance indicators, such as relative irrigation supply (RIS), relative water supply (RWS), depleted fraction (DF), and crop water deficit (CWD), expose inefficiencies in the system, especially during the sugarcane growth period. Despite supplying ample water, sugarcane exhibits a water deficit, possibly due to the annual maintenance closure of the UGC. This calls for a revision of irrigation scheduling to address changing agricultural practices. Future research can expand this work to include climate change impact assessment, economic analyses, advanced technologies, and socio-economic factors. In summary, this study provides critical insights into the performance of UGC, highlighting the need for modernization and equitable water distribution to meet evolving agricultural demands while addressing the challenges of decreasing water availability and the changing climate.

The demand for the fruits of Phyllanthus emblica, an important tree species with a long history of medicinal use, has risen tremendously in recent years. The rapid decline in the distribution of the species can be attributed to habitat loss, climate change, invasive species, extensive harvesting, and various other anthropogenic disturbances. In the present study, we modelled the potential habitat distribution of Phyllanthus emblica (Indian gooseberry) across Asia. The current and future climatic scenarios are predicted using Representative Concentration Pathway (RCP) and the latest climate model Shared Socio-economic Pathway (SSP). The model constructed using Representative Concentration Pathway had the mean value of Area Under Curve (AUC) 0.970 and 0.975 for the Shared Socio-economic Pathway. The study indicated that some of the highly suitable habitats in Asia could become unsuitable and climatic variables combined with human activities could significantly impact species distribution in near future.

Numerous studies involving tree rings have been conducted in the Himalayas on a wide variety of species for paleoclimate reconstructions. Each species responds differently to precipitation and temperature variability in different ecological settings. Therefore, an improved understanding is required to reconcile the mechanisms behind the different responses of tree growth with changing climate regimes. The review is focused primarily on the studies undertaken in the field of dendrochronology in the western Indian Himalayan region (WIH) and explores the relationships between climate and forest response. The study embraces a dual strategy by surveying the literature of tree-ring studies conducted in WIH and using metadata to synthesize results and their global implications. Our review reveals that 553 years (A.D. 1452–2004) long tree-ring chronologies from high altitudes in WIH have indicated anomalous higher tree growth in the recent past strongly associated with warming trends over the region. Correlation and response function analysis between tree-ring widths and climatic parameters have shown a significant negative correlation with pre-monsoon March–April–May (MAM) temperature and a positive correlation with precipitation during the same period in the region influenced mainly by Indian summer monsoon (ISM). However, a positive correlation with winter months’ temperature has also been observed owing to the availability of water from snowmelt due to increased warming trends. Of all the potential datable tree rings, Cedrus deodara was the most studied tree species followed by Pinus spp. while Betula utilis was the least studied.

Abstract

The leaf area index (LAI) provides valuable input for modeling climate and ecosystem processes. However, ground-based observations are necessitated across various phenophases from dense tropical forests for a better understanding in terms of their contribution to carbon fixation. In this study, Digital Hemispherical Photography (DHP) was used for LAI observation from Similipal Biosphere Reserve, and to predict high-resolution LAI using Random Forest Machine Learning approach. Observations were taken from ninety-three Elementary sampling units (ESUs) corresponding to the beginning and end of leaf fall seasons across moist deciduous, dry deciduous, and semi-evergreen forests. LAI demonstrated high values for dry deciduous, followed by semi-evergreen and moist deciduous forests for the start of the leaf fall season, whereas moist deciduous forests demonstrated high values during the end of the leaf fall season. Satellite-based spectral reflectance bands of Sentinel-2 and vegetation indices (VIs) were used as predictor variables, wherein the band-7, band-8, band-12, enhanced vegetation index (EVI), and Red-edge based EVI were evaluated as the most dominant responsive variables for LAI estimation. Random Forest (RF) model provided good accuracy (R² = 0.64, RMSE = 0.62) with observed DHP-based LAI. However, a comparison of RF model-based predicted LAI with global LAI products (MOD15A2H and VNP15A2H) provided a moderate correlation. Such studies demonstrate the potential of site or region-specific case studies to evaluate coarser-resolution global LAI products for possible improvement.

Considering the medicinal and conservational significance of Saraca asoca, the present study employed three different geographical ranges for building ecological niche models. The vifstep procedure detected multicollinearity among 10 out of 19 predictor variables. The selected subset included mean diurnal range, isothermality, mean temperature of wettest quarter, mean temperature of driest quarter, annual precipitation, precipitation of driest month, precipitation seasonality, precipitation of warmest quarter, and precipitation of coldest quarter. The performances of machine learning and regression approaches were compared. Machine learning algorithm RF outweighed all other algorithms in performance. Following RF, model algorithms viz., Maxent, BRT, GLM, FDA, and Bioclim performed better in the declining order. Machine learning algorithms performed better than regression and profile-based approaches. The weighted average of True skill statistic was used to develop ensemble models. Potential habitats in native and introduced ranges in present and future conditions were identified. Introduction potential in unintroduced areas where herbal medicines were in greater use was also assessed. With rise in emissions, range of S. asoca may prefer an eastward expansion in native range and northward expansion in Andaman Nicobar Islands. If S. asoca is planted in recommended potential ranges in African and Latin American continents, eastward expansion in West Africa and westward expansion in Latin America may occur if temperature rises. The present study could develop a robust evidence-based hypothesis for ecologists, conservationists, herbal medicine manufactures, government agencies, and forest departments at national/international level to establish plantations for growing S. asoca.

Arbuscular mycorrhizal (AM) fungi are keystone species in the terrestrial ecosystem. Application of AM fungi play a critical role in forestry or ecological restoration. Chamaecyparis formosensis is endemic to Taiwan and threatened by habitat loss and over-cutting. How to protect and increase their populations has become an important issue to be addressed. An efficient ecological strategy was to applicate native mycorrhizal community for afforestation programs, such as mycorrhizal inoculation in the seedling stage. Therefore, it is important to know the native AM fungal community associated with C. formosensis. In this study, we investigated the diversity of AM fungi associated with C. formosensis along an altitudinal gradient (1200–2500 m) in their natural habitat by observing and identifying the spores from soil. A total of 1071 spores belonging to 26 AM fungal species were isolated and identified. AM fungal species diversity and spore density were not correlated with the altitude of the study sites. However, spore composition of AM fungi changed responding to area and altitudes significantly. Acaulospora laevis, Sclerocystis rubiformis and Acaulospora morrowiae distributed widely and were especially abundant occurring in 35.0%, 21.0% and 8.9% of all spores, respectively. Acaulospora koskei prefer the medium and high elevation whereas Acaulospora mellea prefer low elevation. The diversity of AM fungi associated with C. formosensis along an altitudinal gradient was presented. This data provides avenues for the protection and cultivation of C. formosensis in different area and elevations.

Abstract

Monodominant woody species are frequent in the Pantanal. Monodominant forests of Erythrina fusca (Fabaceae) occur in Northern Pantanal, but little is known about the environmental factors that influence this dominance. This work investigated the relationship between flooding and soil characteristics and the E. fusca monodominance. We hypothesized that the dominance of E. fusca is mainly associated with extended flooding periods and lower soil fertility, factors frequently related to monodominance. We sampled 16 sites within the study area of 115 km². We sampled three 50 × 5 m vegetation plots in each site, for species composition and abundance in multispecies forests and E. fusca monodominant forests. Soil samples were taken in each plot, and the duration of flooding was determined. We performed Canonical Correspondence Analysis and Regression Trees to verify the variation of species composition along environmental gradients and to identify which environmental factors influence this monodominance. We observed that flooding is the main factor driving E. fusca dominance, where higher flooding duration led to higher dominance. Further, the dominance of E. fusca is related to low soil fertility and higher concentration of sulfur and organic matter, than multispecies forests. Our findings confirm the hypothesis that dominance of E. fusca is associated with high flooding regimes with low soil fertility, which together act as a strong filter for other riparian forest species, thus favoring the dominance of E. fusca.

Ants of the genus Solenopsis are highlighted as the potential nest predators of many crocodilian species. During a study on the aspects of the natural history of the broad-snouted caiman in a protected area of Atlantic Rainforest in Pernambuco, North-eastern Brazil, a predation event was documented during nest visiting activities related to reproduction monitoring. The predation of a Caiman latirostris neonate by red fire ants Solenopsis sp. was observed, a dead neonate C. latirostris hatchling was found partially out of its shell, soon after hatching, still in the nest and covered in red fire ants.