Tropical Ecology最新文献

Abstract

The composition of species, as well as their population and regeneration status of tree species, provide an important ecological foundation for assessing the current state and rate of ecosystem degradation. Therefore, the present study aimed to determine the plant species composition with population and regeneration status of the 40 different tree species in peri-urban vegetation of Ranchi, eastern India using 52 belt transects each of 0.10 ha. A total of 58 different plant species of 49 genera and 26 families were recorded with the majority (86%) of native Indian origin species. The 14% of exotic origin species included dominant invasives in herb, shrub, and tree layers viz., Mesosphaerum suaveolens (L.) Kuntze. (2949 ind. ha⁻¹), Lantana camara L. (1667 ind. ha⁻¹), and Acacia mangium Willd. (33 ind. ha⁻¹), respectively. On the other hand, 59% of the total plant species were IUCN Red-listed including Endangered (Tectona grandis L.f.), Near Threatened (Aegle maremlos (L.) Corrêa), Data Deficient (Mangifera indica L.), and Least Concern (Dalbergia sissoo Roxb. ex DC). Total adult tree density and basal cover were 541 ind. ha⁻¹ and 24.93 m² ha⁻¹, respectively and Shorea robusta C.F.Gaertn. was the most dominant tree (295 ind. ha⁻¹) recorded in the majority of the studied patches (87%) where adult tree density (ind. ha^{− 1}) ranged from 10 to 1520 with a mean of 363 ± 49 (SE) signifying that the majority of the studied urban vegetation was Sal dominated forest patches. The total density of tree seedlings (22,627 ind. ha⁻¹) was highest in the studied peri-urban vegetation of Ranchi followed by total tree saplings density (2677 ind. ha⁻¹) and adult tree (GBH ≥ 10 cm) density (541 ind. ha⁻¹) signifying good regeneration status (density of seedlings > saplings > adults) of the peri-urban vegetation of Ranchi. was the most common human disturbance observed in 31% of the total studied patches. No regeneration of 56% of the total tree species, the prevalence of human disturbances in the 48% studied patches, and the occurrence of invasives in all three layers of vegetation in the studied peri-urban vegetation signify the ongoing biotic and abiotic pressure on the survival of different plant species at various growth stages. Besides, the predominance of plant species of rare and very rare occurrences (56.9%), IUCN Red-listed (59%) with a total of 84% native Indian origin species demonstrated the importance of the studied peri-urban vegetation and warrants for immediate conservation measures to protect it from further depletion.

Macroinvertebrate assemblages associated with six aquatic macrophyte species were investigated in Nigeen Lake of Kashmir valley, Jammu and Kashmir. Across the lake surface, four locations were selected for collection of the aquatic macrophytes. The macrophytes were collected in plastic bags, labelled, and brought to laboratory for further analysis. The samples were sieved using a 0.5 mm mesh, sorted, and identified. During the study period, 18 macroinvertebrate species were recorded from 6 macrophytes. The macroinvertebrates belonged to eight families, seven orders, and extend over three phyla, viz.: Mollusca, Arthropoda, and Annelida. Phylum Arthropoda comprised of highest number (11) of species, followed by Mollusca (4), and Annelida (3). Maximum number of individuals was found attached to Myriophyllum verticillatum (75 ind./m²), Potamogeton crispus (71 ind./m²), Trapa natans (60 ind./m²), Potamogeton natans (57 ind./m²), Ceratophyllum demersum (38 ind./m²), and least for Potamogeton lucens (19 ind./m²). Principal component analysis (PCA) of the data resulted in two principal components (PCs) with eigenvalues > 1, explaining 86% of variance. Investigation of the factor loadings of macroinvertebrate assemblages linked with aquatic macrophytes on the first two PCs of the dataset revealed that relationship exhibit habitat gradients potentially affecting associated macroinvertebrates. The study demonstrated that macroinvertebrates differed with different vegetation types in terms of both density and diversity, and that plant structure plays a significant role in determining this variation. Macroinvertebrate communities benefit from increased macrophyte productivity. The study concludes that the certain taxa of macroinvertebrates are more comfortable to the high pollution loads and nutrient enrichment in the Nigeen lake.

Frugivores and seed dispersers are important in maintaining biodiversity and ecosystems. Yet, these agents receive less attention, in particular from ubiquitous or garden-cultivated species like Amorphophallus paeoniifolius and Alocasia odora. Despite extensive ecological studies carried out across the distribution regions of both species in tropical and subtropical, the only known disperser of A. paeoniifolius is the bird-of-paradise that was reported from Papua New Guinea. Meanwhile, there are reports of Pycnonotus and Eudynamys being the dispersers for both wild and cultivated Amorphophallus in India. Despite this, the frugivores and dispersal agents for both A. paeoniifolius and A. odora, in general, are not known and may be different in other parts of the world. In this study, I set up camera traps at five sites (two for A. paeoniifolius and three for A. odora) between 2017 and 2019 at the Xishuangbanna Tropical Botanical Garden to observe the frugivores and dispersal agents for these two ubiquitous cultivated aroid species. Apart from morphological observations on the infructescence of A. paeoniifolius and A. odora, the size of berries were measured and number of seeds per berry were counted. Six frugivores (Pycnonotus aurigaster, Copsychus saularis, Alophoixus pallidus, Niltiva davidi, Orthotomus sutorius, and Pycnonotus jocosus) were identified as potential dispersal agents, attracted to the colourful, succulent, and smaller (< 2 cm) berries. Pycnonotus aurigaster visited both A. odora and A. paeniifolius. The latter four frugivores visited A. paeniifolius, whereas P. jocosus visited only A. odora. All frugivores demonstrate endozoochory, and consumed the entire berries without showing any peculiar behaviour patterns. The berries are red-yellowish on ripening, with an average size of 1.63 cm ± 0.23 cm × 0.88 cm ± 0.19 (L × W) for A. paeniifolius, and 1.04 ± 0.09 cm × 0.67 ± 0.09 cm for A. odora. This study provides insight into how frugivores may depend on and connect to their regions of distribution as well as the distributions of plant taxa. Similar studies could be comparatively expanded into different distribution localities of A. paeoniifolius and A. odora for a wider understanding of their relationship linkage to the dispersal agents.

Abstract

The present paper describes the phenological pattern of 73 tree species from tropical zone of Andaman and Nicobar Islands (ANIs), India. The study exhibits two flowering peaks (dry season and wet season) among the studied tree species. The dry season peak flowering was immediately followed by peak fruiting during pre-monsoon dry period just prior to onset of wet season. Peak flowering in March was significantly correlated with changes in temperature, this synchronized flowering in the dry season also affects the insect’s floral visits on the plant. Ripening of fruits during early wet season may offer post dispersal advantage for seeds to germinate and thereby ensuring offspring survival. The finding indicates that both temperature and rainfall strongly influence the seasonality in reproductive phenology of trees of this archipelago. The study supports the “optimal time of reproductive phenology” and suggests that a strong seasonality exists with respect to reproductive phenology (flowering and fruiting) in tree species of tropical evergreen forests of Andaman and Nicobar Islands.

For sustainable management of urban forests, information regarding species-specific responses of urban trees is essential to determine suitable trees for planting and to maintain the existing trees amid the worsening climate. One approach is to study plant growth and water use and their changes with weather variations in various tree species and sites. Here, we measured leaf photosynthesis (A), transpiration (E), and stomatal conductance (g_s) of Samanea saman, Tabebuia rosea, and Millingtonia hortensis, which were found in a new and an old park in Bangkok. Additionally, we investigated how these parameters and water-use efficiency (WUE), the ratio between A and E, varied with atmospheric conditions, represented by leaf-to-air vapor pressure deficit (VPD_LA). Results indicated decreasing gas exchange rates with increasing VPD_LA in all species, signifying stomatal closure under drying air. In all cases, changes of A and E with VPD_LA were similar to those in g_s, except for E of T. rosea in the new park that showed no response. Of all species, only M. hortensis displayed similar response patterns with VPD_LA across sites, implying its capacity to adapt to various settings. Interestingly, regardless of the periods since establishments of the parks, WUE of these species responded similarly to VPD_LA. This finding may imply that, regardless of their sizes, these trees may retain the capacity of carbon dioxide absorption provided the same unit of water use, despite the changing climate. Nevertheless, further investigations involving more species and sites with various periods since establishment should be performed to confirm these results.

Land uses may shift soil biota community composition, and soil chemical traits. Our aims were to assess if the land uses may influence the soil biota community composition and soil chemical traits; if there are differences into soil biota biomass as influenced by land uses; and what are the plant-soil feedback among the land uses, soil biota, and soil chemical traits. We have collected soil samples and extracted soil biota individuals from four different land uses (e.g., natural ecosystem, conventional farming system, agroecological farming system, and fruticulture). Our results have revealed that land uses have influenced soil biota abundance (from 59.0 to 210.12 ind. trap^− 1 in the natural ecosystem and fruticulture system, respectively), richness (from 6.5 to 10.5 in the fruticulture system, and natural ecosystem, respectively), diversity (from 1.01 to 1.75 in the conventional farming system, and natural ecosystem, respectively), dominance (from 0.52 to 0.71 in the natural ecosystem, and conventional farming system, respectively), and its biomass. The studied land uses have decreased the soil organic carbon when compared with the natural ecosystem (5.75 g kg^− 1). SOC, soil pH, Olsen’s available P, Mg²⁺, K⁺, and Na⁺ were the main factors contributing to the variance of the samples accounting for 78% of the data variance. The results of our study highlight the importance of considering land uses as key factors influencing soil biota community and soil chemical traits. Thus, long-term experiments considering land uses (e.g., conventional farming system, fruticulture, and agroecological farming system) may exploit negative effects of land uses on soil biota abundance on the one hand, while positive effects on soil chemical traits on the other hand.

Human population is becoming increasingly urbanized, and in this context, private gardens (home gardens) constitute an important component of urban biodiversity and provide access to ecosystem services. This study aims at identifying spatial patterns to understand the socio-ecological processes that influence the urban landscape.

In our study, we analyze private gardens in one of the main urban agglomerations of Argentina to understand whether socio-economic structure or spatial distribution is more strongly influencing the species composition of private gardens.

We selected 50 gardens from the urban area of Gran San Miguel de Tucumán. We surveyed the sociodemographic characteristics of garden owners and we performed vegetation censuses in each of the gardens. In the survey, we also evaluated the main mechanisms of plant acquisition. We used the species composition of each garden to perform a non-metric multidimensional scaling, which reflected the botanical distance between gardens. We used Mantel tests to correlate these botanical distances with the geographic and socio-economic distances between gardens to determine which variable controls the ecological attributes of the garden. To spatially characterize the socio-economic level, we used data from the national population census.

The species composition of the gardens is more strongly associated with socioeconomic conditions than with geographical distance. The exchange of species is the main method of obtaining plants.

Our study permits understanding how socio-economic structure influences the construction of private gardens, which are important components of the landscape and urban ecology. Our results could be explained by the willingness to belong to certain socio-economic groups but also by the interchange of propagules, which may reinforce social ties. Our results highlight the importance of addressing social issues to understand private decisions and design strategies toward a fair distribution of urban vegetation services.