Tropical Ecology最新文献

The relative dominance of life-forms in a riparian forest can be related to the landforms and functional vegetation types and which is considered as the primary requirement for any restoration effort. We examined the functional vegetation types, life-forms and landforms in a riparian forest of tropical river Pamba of Western Ghats by 52 transects (2 km length and 10–30 m width. The riparian forests have 31 pteridophytes, 3 gymnosperms and 545 angiosperms, comprising 16 chamaephytes, 31 cryptophytes, 17 epiphytes, 10 helophytes, 22 hemicryptophytes, 17 hydrophytes, 158 small phanerophytes, 170 large phanerophytes and 138 therophytes. The Canonical Correspondence Analysis (CCA) indicated that life-form distribution largely based on landform and a combined effect of landform features, longevity, elevation and disturbance regime resulted in resister, avoider, endurer and invader functional vegetation types. Therophyte dominance in floodplains indicated flood disturbances and terrain modification. Ochrenauclea missionis, Crataeva magna, Neolamarckia cadamba and Lagerstroemia speciosa prefers floodplain and protect from bank erosion. Leea indica, Pandanus odorifer and Tetrameles nudiflora have prop-roots, stilt roots and buttress formation against inundation. High range trees Actinodaphne wightiana and Persea macrantha prefer hydrochory for recruitment in the midlands and lowlands. The identified species were resister in functional group and prefer floodplain as their landform preference. The research provides baseline data for designing a nature based riparian buffer system with resister and endurer species for restoration.

The Himalayan region harbours a rich biodiversity, with Taxus wallichiana and Taxus contorta (Taxus species) are playing a significant role in its flora. A study was conducted to ascertain the potential range of these plant species in the Indian Himalayan Region by synthesizing species distribution models using MaxEnt for different climate change scenarios. The geocoordinates of Taxus species populations were obtained from various sources, including field visits, scientific literature, and the Global Biodiversity and Information Facility web portal to run the model and the two species were segregated according to their geographic range. Further, the environmental predictors of current and future climate scenarios of four Shared Socioeconomic Pathways (SSP126, SSP345, SSP370, SSP585) were obtained from the WorldClim web portal. The Jackknife test and ROC analysis were used to validate the model. The projected map showed Arunachal Pradesh, Sikkim, Manipur for T. wallichiana under the current climate scenario and Himachal Pradesh, Uttarakhand, and some parts of Jammu & Kashmir as potential distribution regions for T. contorta. In future scenarios, the high potential area for this species decreased the most in 2050s of SSP126 to 4,960.4 km² for T. wallichiana and corresponding maximum decrease for T. contorta was SSP345 to 6,866.7 km² in 2050s; which were however found to be increased the most in 2070s for T. wallichiana, i.e. up to 14,693.5 km² (SSP585) and for T. contorta, an increase of 11,060.69 km² in 2100s (SSP126). The Jackknife test indicated that the climatic variable, Srad 5 and BIO 17 exerted the largest influence on the generated model of the current potential distribution of T. wallichiana and T. contorta respectively. The research findings are significant as they provide insights into the potential range of Taxus species and can help develop conservation and sustainable management strategies for the unique biodiversity of the region.

Forest biophysical and biochemical parameters are critical for assessing forest health. The integration of proximal and remote sensing approaches is becoming more prevalent for plant characterization because of the benefits associated with multi-dimensional data collection and interpretation. This study aims to deduce the biophysical and biochemical parameters of forests in the Behali Reserve Forest (BRF) located in the Eastern Himalayas. Specifically, the red-edge spectral bands of the Sentinel-2A sensor were deployed to derive the Leaf Area Index (LAI), Enhanced Vegetation Index (EVI), and Normalized Difference Red-Edge (NDRE). Furthermore, the Normalized Area Over Reflectance Curve (NAOC) is used to deduce leaf chlorophyll content and leaf nitrogen content. The biophysical parameters analysis showed that the LAI ranged from 0 to 5.5 m²/m². The healthy dense forests showed an LAI of more than 4.5 that comprised 37.5% of the area. The satellite-derived NDRE has a significant positive association with measured leaf chlorophyll and nitrogen contents that exhibited coefficient of determination (R²) of 0.88 and 0.89, respectively. The NAOC-based empirical model leaf chlorophyll content of dense forests ranges between 30 and 45 μg/cm². The leaf nitrogen content of dense forest as demonstrated by the Nitrogen Balance Index (NBI) was estimated between 40 and 70 (unitless). The synergy of near-proximal and remote sensing data has demonstrated a robust and efficient method of monitoring the health of forests in reserve forests. The retrieved biophysical and biochemical parameters have supplied crucial information on forest health which is vital for forest conservation, plantation, monitoring and management.

Land use change threatens the integrity of riparian woodland vegetation. The aim of this study was to investigate the diversity and population structure of riparian plant species in protected and communal areas. A total of 71 transects were sampled from each of the protected and communal areas. Total species richness recorded was 36 and 38 in communal and protected areas, respectively. Species diversity was significantly (p < 0.05) higher in the protected than communal areas. Vachellia tortilis (communal areas) and Croton megalobotrys (both areas) showed a reverse J shaped pattern with more individuals in the lower diameter size classes than in the large ones. Dichrostachys cinerea (both areas), Ziziphus mucronata (communal areas), Combretum imberbe (protected areas), C. hereroense (protected areas), Berchemia discolor (protected areas) and Vachellia erioloba (communal areas) showed a reverse-J distribution pattern, but with missing size classes. Philenoptera violacea (protected areas) was characterized by a bell-shaped distribution with more individuals in the middle size classes than in the lower and upper ones while Combretum hereroense, C. imberbe and B. discolor were characterized by irregular population structure in communal areas. Croton megalobotrys, D. cinerea, C. imberbe, C. hereroense, Z. mucronata, B. discolor and S. erubescens had higher Important Value Indices (IVIs) in protected than communal areas. Comparatively, Vachellia tortilis, P. violacea and V. erioloba had higher IVIs in communal than protected areas. We recommended that species with J-shaped population structure and those with only one size class be protected to enable them to attain healthy population structures.

Analysing land transformation and its driving factors is of utmost importance for the optimal land use planning for development at grassroots level. The south-western zone of Punjab, India is vulnerable in terms of adverse climatic conditions, problem of sand dunes, water logging and brackish ground water for irrigation. Therefore, it was felt imperative to understand the long term land use land cover dynamics in the intensively cultivated region of south-western Punjab having more than 80% area under agriculture. The objective was to study and analyse the conversion of agricultural land to urbanization, industrialization, and other classes, which is of significant concern to food production and security. Change detection for last two decades (2000, 2010 and 2020) was carried out using Landsat archive data to observe distinct land transformation. An increase has been observed in the agricultural land from 86.60 to 88.96% during 2000–2010 whereas it decreased to 87.38% during 2020. In contrast, the area under settlement shows a gradual increase i.e. 4.43, 6.22, 7.57% for 2000, 2010 to 2020, respectively indicating major conversion of agricultural and wastelands to this category. Further, reduction of wastelands from 6.82 to 2.03 to 1.4% can be attributed to ameliorative measures taken up by the government and farmers. The waterlogged areas showed the extent as 1.24%, 1.09%, and 2.0% for 2000, 2010 and 2020, respectively. The results of this study can be effectively utilised to alter the land use practices and policies for south-western region of Punjab, as the study area represents the similar ecological conditions of the entire region.

Naturally, insect herbivore populations are controlled by their plant hosts and predators. These ‘bottom-up’ and ‘top-down’ controls influence leaf area lost to herbivory. Bottom-up control of herbivory may be driven by leaf nutrients and plant defences. Top-down control can be driven by abundance and species richness of natural enemies, host or prey specificity, and predation strategies (e.g., active searching or sit-and-wait ‘ambush’ predation). The relative importance of bottom-up and top-down controls is unresolved but likely to vary spatially and temporally and under different environmental conditions such as changing temperature. We surveyed leaf carbon and nitrogen, leaf area loss, and attacks on plasticine caterpillars across a tropical elevational gradient in Xishuangbanna, Yunnan Provence, China. We show that predatory foraging activity decreases with elevation and temperature, whereas leaf nutrients and leaf area loss from herbivory remains more or less constant. Predation patterns were driven by ants, which are thermophiles and therefore more active, abundant, and diverse at warmer, lower elevations. Leaf nutritional values are important in driving herbivory patterns as herbivory was stable across this gradient, but other factors such as mechanical defences and herbivore-induced plant volatiles demand further study. Elevational studies provide insight into how ecosystem function will shift under climate change. As increasing temperatures following climate change allows predatory groups like ants to exploit higher elevations, top-down control in high elevation habitats could increase, resulting in re-wiring of these ecologically sensitive communities. At the same time, top-down control at lower elevations may be at risk if critical thermal maxima for natural enemies are exceeded.

Long-term biodiversity monitoring studies of restored wetland ecosystems are essential for successful conservation. We studied the bird diversity of century-old Pashan Lake (18.5344°N, 73.7853°E), Pune, Maharashtra, India, after 15 years of restoration. Pashan Lake is an overwintering site for many birds and recently went through a restoration event after eutrophication. Currently, the lake receives heavy sewage water and industrial effluents through a small river Ramnadi. The lake receives heavy monsoon rainwater, and in late winter and summer, hyacinth vegetation covers the entire lake surface. We monitored bird diversity (number of species with abundance) at Pashan Lake throughout the year (June 2021-May 2022) using the point transact method during morning and evening hours. We also recorded physicochemical parameters, including water temperature, pH, dissolved oxygen, conductivity, salt, and TDS (Total Dissolved Solids). We calculated diversity indices for each season, Monsoon (June–September), winter (October-January), and summer (February-May). We recorded a total 81 bird species with the highest bird diversity in the winter season. Omnivorous and insectivorous birds dominate the fauna. Bird community recorded every month was clustered into two groups, June-November and December-May, suggesting the influence of hyacinth vegetation. Bird community was dissimilar among seasons. The study signifies the importance of long-term biodiversity monitoring studies for wetland conservation.

The internal retranslocation of nutrients of senescence leaves is a significant aspect of nutrient dynamics in a forest ecosystems. The present investigation was carried out by considering four types of deciduous tree species (Shorea robusta, Tectona grandis, Schleichera oleosa, and Albizia lebbeck) to assess nutrient resorption efficiency (NuRE) and resorption proficiency (NuRP) of nitrogen (N), phosphorous (P), and potassium (K), as well as seasonal changes of nutrient concentration in green and senescence leaves. Green and senescent leaves were sampled and analysed for NPK concentration by standard methods. Experimental results revealed that the higher nutrition contents were recorded in green leaves than senescence leaves. The highest N and P resorption efficiency (RE) were recorded for S. robusta and lowest for T. grandis (46.74%) and A. lebbeck (37.93%) respectively, whereas T. grandis exhibited the highest resorption efficiency of K (47.67%) and lowest for A. lebbeck (40.29%). Furthermore, the highest percentage of nutrients from mature leaves and soil were transported to the tree body during senescence were 47.0% (S. oleosa), and 21.29% (T. grandis), respectively. Moreover, nutrients were retranslocated from senescent leaves in the order as N > P > K. On the other hand, the nutrient resorption proficiency (NuRP) was highest with respect to N (53.26%) and P (62.07%) for T. grandis and K (59.71%) for A. lebbeck. Similarly, the lowest with respect to N (44.27%) and P (50.91%) for S. robusta, and K (52.33%) for T. grandis. Therefore, it can be concluded that changes in nutrient concentrations in green and senescence leaves could be the possible reason for different retranslocation efficiency.

Graphical abstract

The life history traits of the invasive slug, Deroceras laeve, occurring in the Darjeeling Himalayas, India, were estimated under laboratory conditions using the hatchlings from eggs of field-collected D. laeve. The growth pattern of D. laeve was found to be logarithmic, rapidly increased initially, and reached a stable condition till death. The maximum life span of D. laeve was 138 ± 3.48 days, with slightly higher mortality during the juvenile period, which decreased gradually at older ages. The pre-reproductive period of 37 ± 2.7 days, reproductive period of 100.8 ± 5.2 days, and 5.4 ± 1.72 days post-reproductive period of D. laeve were observed. D. laeve attained sexual maturity during 38 ± 2.7 days, and the age-specific fecundity increased with increasing age. The hatchability of the eggs was observed to be > 75% following the incubation period of 14.25 ± 0.49 days. The net reproductive value (R₀), generation time (T_c), and finite rate of increase (λ) were 40.01, 12.48 weeks, and 1.455, respectively. Apparently, the earlier sexual maturity, high net reproductive rate, and shorter generation time of D. laeve are indicative of its invasive nature as well as prospective range expansion in similar geographic locations.

In recent years, Hainan Eld’s deer (Cervus eldi) population in the Datian Nature Reserve (DNR) has been decreasing. This may be due to predation by Burmese python (Python bivittatus), as the number of Eld’s deer predation events by Burmese pythons has increased since 2013. This poses huge pressure on the DNR that is mainly involved in the conservation of wild Eld’s deer population. We divided the changes in deer population size in the DNR into three time periods (1988–1992, 1999–2003, and 2015–2019) according to changes in the number of Burmese pythons. We analyzed changes of Eld’s deer population in the Wenchang conservation station (WNR) for the period 2010–2018. In the DNR, Eld’s deer population increased from 242 to 349 during 1988–1992 in the absence of Burmese python. When there were few Burmese pythons in the region in 1999–2003, Eld’s deer population increased from 702 to 1075. In 2015–2019, when the number of migrating Burmese pythons captured was the greatest, Eld’s deer population decreased from 306 to 223, and the mean annual growth rate was − 6.21%. As predation by Burmese pythons decreases the survival rate of Eld’s deer fawns in the DNR, the growth rate of Eld’s deer population was significantly affected. Our results indicated that predation by Burmese python is currently a key factor affecting the growth of Eld’s deer population.