A. S. Raghubanshi

Tree species composition, dispersion and diversity along a disturbance gradient in a dry tropical forest region of India

Forest inventory data were collected in 1998–2000 from fifteen 1 ha permanent plots along a disturbance gradient in a dry tropical forest region of India. A total of 4033 stems, 49 species, 44 genera and 24 families of adult trees (� 30 cm CBH), occurred in the 15 ha of forest area. The study indicated that the dry tropical forest is characterised by a patchy distribution of species and individuals with mixed species composition, and the sites are represented by different combinations of the dominants and co-dominant species. A PCA ordination indicated that the variation in species composition of the sites is explained by the variation in soil nitrogen as well as the degree of disturbance. About half the analysed species showed changing nature in dispersion along the disturbance gradient. The distribution of Boswellia serrata, Holarrhena antidysenterica and Lannea coromandelica changed from clumped to uniform and the distribution of Butea monosperma, Cassia fistula and Elaeodendron glaucum changed from uniform to clumped as the degree of disturbance increased. The mean stem density was highest (419 stems ha � 1 ) at the least disturbed site and lowest (35 stems ha � 1 ) at the highly disturbed site, and for basal area, the highest value (13.78 m 2 ha � 1 ) was for the second least disturbed forest site and the lowest value (1.30 m 2 ha � 1 ) was for the most disturbed site. The total number of stems, indices of species richness, evenness and a-diversity decreased with disturbance. A strong influence of number of species per individual on b-diversity suggests that for resisting change in floristics due to disturbance, a site must have low species-individual ratio. # 2003 Elsevier B.V. All rights reserved.

Medical ethnobotany of the tribals of Sonaghati of Sonbhadra district, Uttar Pradesh, India.

The present ethnobotanical exploration study presents the folk medicinal uses of certain plants by tribes of the Sonbhadra district in the Uttar Pradesh state of India. One hundred and twenty five plants from 57 families, which are therapeutically used against different diseases, such as cough, cold, dysentery, diarrhoea, ulcers, diabetes, male and female weakness, snake-bite and skin disorders are covered in this report. Part of the plant used, dosage and the mode of drug administration in different ailments are described.

Nitrogen-mineralization in dry tropical savanna : effects of burning and grazing

The effects or burning and grazing on plant available nitrogen (NO3-N + NH4-N) and N-mineralization in a dry tropical savanna were examined. The plant available N ranged from 2.8 to 10.6 μg g−1 with maximum values in the dry period (summer season) and minimum values in the wet period (rainy season). The trend for N-mineralization was opposite to that of the size of the available N pool. N-mineralization rates ranged from 1.8 to 30.6 μg g−1 mo−1 within an annual cycle. On average the pool of available N was 54% higher in the burned treatment and 48% higher in the grazed treatment compared to the protected treatment, similarly the mean annual N-mineralization was 20% higher in the burned and 16% higher in the grazed savanna.

Activity and community structure of methane-oxidising bacteria in a wet meadow soil

The structure and activity of the methane-oxidising microbial community in a wet meadow soil in Germany were investigated using biogeochemical, cultivation, and molecular fingerprinting techniques. Both methane from the atmosphere and methane produced in anaerobic subsurface soil were oxidised. The specific affinity (first-order rate constant) for methane consumption was highest in the top 20 cm of soil and the apparent half-saturation constant was 137-300 nM CH(4), a value intermediate to measured values in wetland soils versus well-aerated upland soils. Most-probable-number (MPN) counting of methane-oxidising bacteria followed by isolation and characterisation of strains from the highest positive dilution steps suggested that the most abundant member of the methane-oxidising community was a Methylocystis strain (10(5)-10(7) cells g(-1) d.w. soil). Calculations based on kinetic data suggested that this cell density was sufficient to account for the observed methane oxidation activity in the soil. DNA extraction directly from the same soil samples, followed by PCR amplification and comparative sequence analyses of the pmoA gene, also detected Methylocystis. However, molecular community fingerprinting analyses revealed a more diverse and dynamic picture of the methane-oxidising community. Retrieved pmoA sequences included, besides those closely related to Methylocystis spp., others related to the genera Methylomicrobium and Methylocapsa, and there were differences across samples which were not evident in MPN analyses.

Effect of topography on selected soil properties and nitrogen mineralization in a dry tropical forest

Abstract Soil nutrients and nitrogen mineralization rates were measured along three topographic sequences in a seasonally dry tropical forest. Soil organic C, total N and P decreased downslope. Accumulation of soil organic C and N was related to the P content which, in turn, was controlled by the proportion of fine particles in the soil. Net N mineralization and nitrification rates ranged from 0 to 33 μg g −1 month −1 and 0 to 19 μg g −1 month −1 , respectively, within the annual cycle and among the topographic positions. Annual mineralization increased from 125 μg g −1 dry soil at the hillbase to 203 μg g −1 dry soil at the hilltop. These differences in mineralization rates were obviously related to the distribution of substrate.

Methane flux from rice/wheat agroecosystem as affected by crop phenology, fertilization and water level

Methane flux was measured for a rice/wheat agroecosystem of Gangetic Plains, with and without application of chemical fertilizer and wheat straw (WS). Three treatments of control, fertilizer application and fertilizer + WS application, were established in a completely randomized block design and measurements were made for two consecutive years (1993 and 1994). CH4 measurements during growth of the rice crop period showed that there were significant difference in flux rates during the two years. Maximum emission occurred at the time of anthesis and minimum at the seedling stage. The flux rates were significantly higher for fertilizer or fertilizer + WS treatments. The effects of the treatments were similar across phenological stages and years. In the subsequent wheat crop and fallow period, the soils consumed CH4. There were significant differences in CH4 uptake rates between the two years. Fertilizer treatments reduced CH4 uptake in both the years. The results suggested that tropical agroecosystems may consume substantial amounts of CH4 and that the methane output can be reduced by lowering the submergence level in rice paddies.

Effect of soil nitrogen, carbon and moisture on methane uptake by dry tropical forest soils

Methane uptake was measured for two consecutive years for four forest and one savanna sites in a seasonally dry tropical region of India. The soils were nutrient-poor and well drained. These sites differed in vegetational cover and physico-chemical features of the soil. There were significant differences in CH4 consumption rates during the two years (mean 0.43 and 0.49 mg m-2 h-1), and at different sites (mean 0.36 to 0.57 mg m-2 h-1). The mean uptake rate was higher (P < 0.05) in dry seasons than in the rainy season at all the sites. There was a significant season and site interaction, indicating that the effect of different seasons differed across the sites. There was a positive relation between soil moisture and CH4 uptake rates during summer (the driest period) and a negative relation during the rest of the year. The results suggested that seasonally dry tropical forests are a strong sink for CH4, and C and N status of soils regulates the strength of the sink in the long term.

Impact of native tree plantations on mine spoil in a dry tropical environment

This study describes the impact of young high-density plantations of two native leguminous (Albizia procera and A. lebbeck) and one non-leguminous timber tree (Tectona grandis) species on the soil redevelopment process during the early phase of mine restoration in a dry tropical environment. There was a general improvement in soil properties due to establishment of plantations. Highest soil organic C values were found in A. lebbeck plantations and lowest in T. grandis plantations. Both A. lebbeck and A. procera substantially increased levels of nitrogen in soil. However, A. procera, with slow decomposing litter, was not as effective in raising N levels in the soil as A. lebbeck, indicating that all N fixers may not be equally efficient in raising soil N levels. Soil microbial biomass and N mineralization rates were always higher in plantations of N-fixer species. A continued increase with age in microbial C:total C ratio indicates these plantations have yet to reach steady state.

Plant functional traits with particular reference to tropical deciduous forests: A review

Functional traits (FTs) integrate the ecological and evolutionary history of a species, and can potentially be used to predict its response as well as its influence on ecosystem functioning. Study of inter-specific variation in the FTs of plants aids in classifying species into plant functional types (PFTs) and provides insights into fundamental patterns and trade-offs in plant form and functioning and the effect of changing species composition on ecosystem functions. Specifically, this paper focuses on those FTs that make a species successful in the dry tropical environment. Following a brief overview, we discuss plant FTs that may be particularly relevant to tropical deciduous forests (TDFs). We consider the traits under the following categories: leaf traits, stem and root traits, reproductive traits, and traits particularly relevant to water availability. We compile quantitative information on functional traits of dry tropical forest species. We also discuss trait-based grouping of plants into PFTs. We recognize that there is incomplete knowledge about many FTs and their effects on TDFs and point out the need for further research on PFTs of TDF species, which can enable prediction of the dynamics of these forests in the face of disturbance and global climate change. Correlations between structural and ecophysiological traits and ecosystem functioning should also be established which could make it possible to generate predictions of changes in ecosystem services from changes in functional composition.

Plant invasions along roads: a case study from central highlands, India.

Road sides provide suitable conditions for the establishment and growth of non-native species. The phenomenon of non-native species spread through roads has further increased due to rapid anthropogenic developments. Here we intend to investigate the status of native and non-native species and how the species richness and diversity change in a perpendicular road transect across the three different road use types in the central highlands of India. Presence of 55 non-native species was recorded, of the total 71 species along the road sides. Non-native species richness significantly increased with increasing road use type. Although, the species diversity significantly decreased from road verges to the forest interior in all the road use types. Indicating the role of non-native propagule spread through the roads into the interior forest landscapes. The study gives a management implication, to restrict the non-native species spread from the road sides to the forest interior, irrespective of road use types.