Ashesh Kumar Das

Conservation of Plant Diversity in Rural Homegardens with Cultural and Geographical Variation in Three Districts of Barak Valley, Northeast India1

Conservation of Plant Diversity in Rural Homegardens with Cultural and Geographical Variation in Three Districts of Barak Valley, Northeast IndiaHomegardens are recognized worldwide as sustainable agroforestry systems that are repositories of species and genetic diversity. Species diversity and composition of homegardens are influenced by a number of environmental, socioeconomic, and cultural factors. The present study examines the tree species diversity in the homegardens of different cultural groups of Barak Valley, Assam, Northeast India. Complete enumeration was done for diversity analysis in 181 homegardens from 38 villages in the three districts of the Valley. Factors affecting plant diversity were analyzed, and the floristic composition of the homegardens was found to vary with garden size, ethnicity of the homegarden owners, and geographical parameters such as location and altitude. Results indicate high plant diversity, with a total of 161 tree species identified from 47 families. Tea garden labor communities were comparatively found to hold more diversity in their homegardens. Similarity and cluster analysis revealed the distinctness of the majority of the homegardens, and seven groups of homegardens with very low distance were revealed. Homegardens were also found to maintain considerable conservation value as repositories of many underutilized, wild, and rare plant species. Biodiversity conservation in the homegardens was found to be linked to the multiple values of the different plant species to the homegardeners and further highlight the concept of the “conservation through use” approach. For the preservation of such traditional agroforestry systems, which also have the potential to provide options for adaptation to climate change, proper documentation of traditional knowledge concerning the different plant species and the human-nature interaction in the homegardens is necessary before such systems are completely lost.

Comparing tree diversity and population structure between a traditional agroforestry system and natural forests of Barak valley, Northeast India

We studied population structure, composition and diversity in a traditional Indian agroforestry system, called paan jhum, in comparison to natural forests of the Barak valley, Assam, northeast India. The phytosociological data from these forests were analysed quantitatively, to determine species richness, diversity, importance value, stand density and the basal area. The analysis showed that species richness and diversity were higher in paan jhum than in natural forests, in all three study sites. A total of 47, 37 and 48 tree species were recorded in paan jhum, compared with 35, 32 and 42 species in natural forests of the three study sites, respectively. Paan jhum had higher stand density (790, 934 and 763) and basal area (74.05, 41.60 and 55.88 m2 ha−1), whereas natural forests had lower stand density (775, 865 and 522) and basal area (68.75, 40.50 and 48.04 m2 ha−1) in all the study sites, respectively. An F-test showed significant differences in the variance in species richness, basal area and the stand density at 95% confidence level in the two forest categories. Paan jhum might become a component of a forested landscape that is valued for contributing to resource production, other ecosystem services and biodiversity conservation.

Structural and compositional variations in undisturbed and disturbed tropical forests of Bhuban hills in south Assam, India

The present study describes the structure, composition and regeneration of tree species in undisturbed and disturbed tropical forests in Bhuban hills in southern Assam, India. The study area is part of one of the globally recognized biodiversity hot spots and in spite of the increasing human activities in these forests, so far no information is available on their impacts on plant assemblages in the area. In each forest, the vegetation was analysed through 50 quadrats (10 m × 10 m) in a belt transect of 500 m × 10 m. A total of 49, 47 and 42 tree species were recorded in disturbed forests and 62, 61 and 60 species in undisturbed forests. The average tree density and basal area were significantly higher in undisturbed forests (708.67 and 42.01 m2 ha−1, respectively) than disturbed forests (443.33 and 18.44 m2 ha−1, respectively). The population structure of tree species in disturbed forests showed a fluctuating curve, and in undisturbed forests, it was a reversed J-shaped curve. The present study reveals that the species richness, diversity, density and basal area have significantly declined (P < 0.01) due to anthropogenic disturbances. As reflected from the population structure, most of the tree species in disturbed forests showed poor regeneration status. If degradation of these forests continues at the present pace, several of these species which are providing various ecosystem services to the local human communities may disappear in the very near future.

Ecological implications of village bamboo as global climate change mitigation strategy

Purpose – The present study seeks to evaluate the role of village bamboo management in the rural landscape of North East India in global climate change mitigation.Design/methodology/approach – A set of 100 home gardens and 40 bamboo groves were selected from Irongmara and Dargakona village, in Cachar district, Assam, North East India through random sampling. Sampling was done mostly for smallholders. Culm growth, carbon storage, carbon sequestration and carbon in litter floor mass and soil of bamboo growing areas in homegarden was explored from 2003‐2007.Findings – Culm growth extension revealed the brief periodicity of culm growth in a single growth period. Of the total carbon storage soil contributed 84.6 per cent of the total (50.1 Mg ha−1) followed by carbon in above ground vegetation 15 per cent (9 Mg ha−1) and carbon in litter floor mass 0.4 per cent (0.2 Mg ha−1).Practical implications – Bamboo plantation development and its management in home gardens has social, ecological and economical benefits ...

Impact of land use changes on the storage of soil organic carbon in active and recalcitrant pools in a humid tropical region of India

Quantifying soil organic carbon (SOC) dynamics is important in understanding changes in soil properties and carbon (C) fluxes. However, SOC measures all C fractions and it is not adequate to distinguish between the active C (AC) and recalcitrant or passive C (PC) fractions. It has been suggested that PC pools are the main drivers of long term soil C sink management. Therefore, the present study was undertaken with the objective of determining whether or not SOC fractions vary with land use changes under a humid tropical climate in the North East India. A chronosequence study was established consisting of natural forest, Imperata cylindrica grassland and 6, 15, 27 and 34yr old rubber (Hevea brasiliensis) plantations to determine changes in the different fractions of SOC and total SOC stock. SOC stocks significantly varied with soil depth in each land use practice. SOC stocks increased from 106Mgha-1 under 6yr to 130Mgha-1 under 34yr old rubber plantations. The SOC stocks under 34yr old plantations were 20% higher than that under I. cylindrica grassland, but 34% lower than SOC stocks recorded under natural forest soil. The proportion of AC pools decreased with increase in plantation age, AC pools being 59% of SOC stock in 6yr old stands and 33% of SOC stocks in 34yr old plantations. In contrast, the proportion of PC pools increased from 41% of SOC stock in 6yr old plantation to 67% of SOC in 34yr old plantation. In the 50-100cm soil depth, the PC pool under 27-34yr old plantations was comparable with that under natural forest but much higher than in I. cylindrica grassland. Therefore, it is concluded that old rubber plantations can play a significant role in long term soil C sink management.

Vegetative and reproductive phenology of some multipurpose tree species in the homegardens of Barak Valley, northeast India

Traditional homegardens are an important component of the farming systems in many rural communities and have been highlighted considerably due to their sustainability and role in the conservation of biodiversity. However, the functional aspect of the homegardens, which includes the phenological behavior of the dominant tree species in such agroforestry systems, has been undermined till date, and there is a lack of adequate data on this aspect of the traditional homegardens. As a step in this direction the present study was carried out to determine the phenological behavior of important multipurpose trees in the homegardens of the village of Dargakona, Assam, northeast India. The study revealed the dominance of periodic growth deciduous species from a total of 25 tree species selected for phenological observation. The diversity of multipurpose trees in the homegardens is represented by different plant functional types with different phenological behavior which showed significant changes in their responses to inter-annual climatic variations. The diversity of tree species with different phenological behavior has implications for the temporal partitioning of resources, especially during periods of scarcity, thereby resulting in efficient utilization of resources such as water. Also the diverse phenological behavior plays an important role in regulating the food supply for the herbivore population and the year-round availability of products, and such information can be useful in the selection of species for integration into other agroforestry systems which can be sustainable in the long run.

Population status and regeneration of a tropical clumping bamboo Schizostachyum dullooa under two management regimes

Schizostachyum dullooa (Gamble) Majumder ‘dolu bamboo’ is a thin walled sympodial moderate sized to large tufted bamboo, dominant in the successional fallows of northeast India. The impact of resource management on productivity and sustainability of the species was evaluated by investigating the population status and regeneration in Cachar tropical semi evergreen forest under private property resource management (PPRM) and common property resource management (CPRM) regimes. Population status revealed current-year, one-year, two-year and three-year-old culms contribute 54%, 24%, 16% and 6% of the total culms per clump, respectively, under PPRM. Three-year-old culms were absent in CPRM and population status was thus represented by current year (83%), one-year (16%) and two-year (1%) old culms. Net change, rate of change and % gain in population for different age classes showed the prevalence of management practices under CPRM was unscientific. Efficiency of new culm production per clump used as an index of regeneration was 69.7% in PPRM and 59.88% in CPRM. New culms produced under CPRM were small and thin. We conclude that CPRM is inappropriate for a long term economic and ecological sustainability of the species and alternative management protocols are needed for conservation of the species.

Net ecosystem productivity and carbon dynamics of the traditionally managed Imperata grasslands of North East India

There have been few comprehensive descriptions of how fire management and harvesting affect the carbon dynamics of grasslands. Grasslands dominated by the invasive weed Imperata cylindrica are considered as environmental threats causing low land productivity throughout the moist tropical regions in Asia. Imperata grasslands in North East India are unique in that they are traditionally managed and culturally important in the rural landscapes. Given the importance of fire in the management of Imperata grassland, we aimed to assess (i) the seasonal pattern of biomass production, (ii) the eventual pathways for the produced biomass, partitioned between in situ decomposition, harvesting and combustion, and (iii) the effect of customary fire management on the ecosystem carbon cycle. Comparatively high biomass production was recorded during pre-monsoon (154 g m-2 month-1) and monsoon (214 g m-2 month-1) compared to the post-monsoon (91 g m-2 month-1) season, and this is attributed to nutrient return into the soil immediately after fire in February. Post fire effects might have killed roots and rhizomes leading to high belowground litter production 30-35 g m-2 during March to August. High autotrophic respiration was recorded during March-July, which was related to high belowground biomass production (35-70 g m-2) during that time. Burning removed all the surface litter in March and this appeared to hinder surface decomposition and result in low heterotrophic respiration. Annual total biomass carbon production was estimated at 886 g C m-2. Annual harvest of biomass (estimated at 577 g C m-2) was the major pathway for carbon fluxes from the system. Net ecosystem production (NEP) of Imperata grassland was estimated at 91 g C m-2 yr-1 indicating that these grasslands are a net sink of CO2, although this is greatly influenced by weather and fire management.

Fired Bricks: CO2 Emission and Food Insecurity

Abstract Fired bricks are used for construction purposes over the millennia, going back to the Indus Valley Civilization. The traditional brick‐making process involves removal of agriculturally productive topsoil rich in clay and soil organic matter contents. In addition to the removal of the fertile topsoil and accelerated degradation by other processes, the traditional clay brick making process also emits CO2 and other gases into the atmosphere. Therefore, the present study aims to assess the impact of brick making in India on: (i) the magnitude of annual CO2 emission and (ii) the loss of agricultural production. Currently, 0.7 Mha (million hectare) of agricultural land is under brick kilns that produce ≈250 billion bricks annually. It is estimated that soil organic carbon lost through the firing process of 250 billion bricks is 5.58–6.12 Tg (teragram) (20.48–22.46 Tg CO2), and in conjunction with clay burning and coal combustion the process releases 40.65–42.64 Tg CO2 into the atmosphere per annum. Brick kiln also impacts quality of the exposed subsoil, and may also reduce 60–90% agronomic yield. Therefore, brick making from topsoil exacerbates food and nutritional insecurity by degrading soil quality, and increases risks of climate change through increase in gaseous emissions.

Population structure and regeneration status of rhododendrons in temperate mixed broad-leaved forests of western Arunachal Pradesh, India

ABSTRACT This study was conducted to investigate the population structure and regeneration status of Rhododendron tree species in temperate mixed broad-leaved forests in Tawang and West Kameng districts of western Arunachal Pradesh, India. Population structure was determined through densities of seedlings, saplings and adults from the sampling quadrats. Based on density of individuals at the seedling, sapling and adult, the regeneration status of the species was determined. Density and basal area of the selected rhododendrons ranged from 16 individuals ha−1 to 1422 individuals ha−1 and 0.24 m2 ha−1 to 131.30 m2 ha−1, respectively. Rhododendron species (viz. R. arboreum, R. arboreum ssp. delavayi var. delavayi, R. barbatum and R. kesangiae) exhibited reverse J-shaped distribution with the density of sapling less than seedling and adult population. Density of selected Rhododendron species is found to be higher between the girth classes 10-30 cm to 130-150 cm and decreased with the increase of girth in all the study stands. About, 90% degrees of disturbances recorded due to cooking and space heating purposes. Among the regenerating species, 77% of the species exhibited fair regeneration, 8% species showed good regeneration while 15% of the species exhibited no regeneration. However, 90% of the tree species showed fair regeneration in disturbed stands than the undisturbed stands. Selected Rhododendron species exhibited fair regeneration in their respective stands. Inadequate regeneration status and population structure of tree species, including rhododendrons, are observed as the density of sapling less than seedling and adult population. Anthropogenic disturbances resulted to be declined in populations of Rhododendron and may lead many species to endangered, rare and threatened categories. Therefore, proper conservation and management initiatives with active involvement of local people are urgent need to protect this keystone plant species in their habitat particularly in western Arunachal Himalaya.