Uma Shankar

Tree species diversity and stand structure along major community types in lowland primary and secondary moist deciduous forests in Tripura, Northeast India

Tree species diversity and population structure at different community types were described and analyzed for primary and secondary lowland moist deciduous forests in Tripura. Overall 10,957 individual trees belonging to 46 family, 103 genera and 144 species were counted at ≥30 cm DBH (diameter at breast height) using 28 permanent belt transects with a size of 1 ha (10 m × 1000 m). Four different tree communities were identified. The primary forests was dominated by Shorea robusta (mean density 464.77 trees·ha−1, 105 species) and Schima wallichii (336.25 trees·ha−1, 82 species), while the secondary forests was dominated by Tectona grandis (333.88 trees·ha−1, 105 species) and Hevea brasiliensis (299.67 trees·ha−1, 82 species). Overall mean basal area in this study was 18.01m2·ha−1; the maximum value was recorded in primary Shorea forest (26.21 m2·ha−1). Mean density and diversity indices were differed significantly within four different communities. No significant differences were observed in number of species, genera, family and tree basal cover area. Significant relationships were found between the species richness and different tree population groups across the communities. Results revealed that species diversity and density were increased in those forests due to past disturbances which resulted in slow accumulation of native oligarchic small tree species. Seventeen species were recorded with <2 individuals of which Saraca asoka (Roxb.) de Wilde and Entada phaseoloides (L.) Merr. etc. extensively used in local ethno-medicinal formulations. The present S. robusta Gaertn dominated forest was recorded richer (105 species) than other reported studies. Moraceae was found more speciose family instead of Papilionaceae and Euphorbiaceae than other Indian moist deciduous forests. Seasonal phenological gap in such moist deciduous forests influenced the population of Trachypithecus pileatus and capped langur. The analysis of FIV suggested a slow trend of shifting the population of Lamiaceae group by Moraceae species in secondary T. grandis L. dominated community.

Evaluating second year cropping on jhum fallows in Mizoram, north-eastern India—Phytomass dynamics and primary productivity

Cropping on jhum fallows in north-eartern India is predominantly done for one year in a jhum cycle. If second year cropping is done, expanse of the forest land required for slashing and burning could be reduced significantly. We tested this hypothesis in a young (6 yr) and an old (20 yr) jhum fallow. We also evaluated if the productivity during second year cropping could be alleviated by auxiliary measures such as tilling the soil or application of fertilizers (chemical or farm-yard manure or both in combination). The results demonstrate that the ecosystem productivity (total dry matter production) and economic yield (rice grain production) decline with shortening of jhum cycle. Second year cropping causes a further decline in ecosystem productivity in old jhum field, but not in young jhum field. Economic yield from second year cropping in its traditional form (without any fertilizer treatment) is not much lower than that in the first year, and can be improved further by manuring the soil. Tilling of soil improves neither ecosystem productivity nor economic yield. Different fertilization treatments respond differently; while inorganic manuring enhances ecosystem productivity, a combination of inorganic and organic manuring improves economic yield

Evaluating second year cropping on jhum fallows in Mizoram, north-eastern India: Soil fertility

Changes in soil fertility were evaluated on young (6 year) and old (20 year) jhum fields in Mizoram, north-eastern India in response to various operations involved injhum such as slashing and burning of vegetation, cropping period, and intervening fallow period between first and second year cropping. The results demonstrate that the soil is richer in nutrients in old than young field prior to the start of jhum cultivation. Slash burning depletes soil acidity, carbon and nitrogen but elevates phosphorus and cations. Soil fertility declined during first cropping phase, and further declined during second cropping phase. After two cropping years, soil fertility of old field was almost at par with that of young field, signifying that the loss of soil fertility was more in old than young field. A short intervening fallow period between first and second year of cropping did not show any pronounced improvement in soil fertility, though it provided some biomass for second burning. Tilling caused maximum loss to soil fertility. The fertilizer treatments ended with comparable or better soil fertility in comparison to no-treatment plot. There seems to be none of the fertilizer treatments superior over others from the standpoint of ending soil fertility. The unifying conclusions of this series of investigations support the hypothesis that the second year cropping holds promise to reduce the demand for forested land for jhum, and lengthen the jhum cycle substantially.

Nutrient cycling in an excessively rainfed subtropical grassland at Cherrapunji

Cycling of six mineral elements (N, P, K, Na, Ca and Mg) was studied in a humid subtropical grassland at Cherrapunji, north-eastern India during 1988–1989. Elemental concentrations in the shoot of four dominant grass species,viz., Arundinella khaseana, Chrysopogon gryllus, Eragrostiella leioptera andEulalia trispicata were very low, and none of the species appears suitable for fodder use. Among different vegetation compartments, live root was the largest reservoir of all the nutrients (except Ca) followed by live shoot, dead shoot, litter and dead root. For Ca, live shoot was the major storage compartment. The total annual uptake (kg ha-1) was 137.3, 10.4, 51.1, 5.5, 8.7 and 18.2 for N, P, K, Na, Ca and Mg, respectively. In an annual cycle 98% N, 77% P, 49% K, 109% Na, 87% Ca and 65% Mg returned to the soil through litter and belowground detritus. A major portion of N, P and Na was recycled through the belowground system, whereas nearly half of K, Ca and Mg was recycled through the shoot system. Precipitation acts as the source of N and P input, but at the same time causes loss of cations.

Evaluating second year cropping on jhum fallows in Mizoram, north-eastern India: Energy and economic efficiencies

Energy and economic efficiencies were evaluated on young (6 year) and old (20 year) jhum fields in Mizoram, north-eastern India during second year of cropping, and were compared with those in the first year. The effect of auxiliary measures such as tilling the soil or application of fertilizers (chemical or farm-yard manure or both in combination) was also examined on energy and economic efficiencies. The results indicated that traditional jhum cultivation is labour intensive and energy efficient, producing almost 15–20 times of energy invested. Energy and economic efficiencies decline with shortening of jhum cycle. These efficiencies decline further from first to second year of cropping. Tilling is not useful to improve either energy or economic efficiency. Fertilizer application, which is though profitable from the point of view of economic efficiency, is highly energy inefficient. Application of fertilizers during second year cropping can be encouraged. Organic manuring may be a better option than others to alleviate energy efficiency. However, a combination of organic and inorgamic manuring could be the best option to enhance economic efficiency.

Trends in Tree Diversity and Stand Structure during Restoration: A Case Study in Fragmented Moist Deciduous Forest Ecosystems of Northeast India

Ecological implications for the conservation of fragmented forests to managed local plant diversity have recently drawn much attention of most conservationists. Present study investigates the importance of fragmented forests using different quantitative measures of species diversity and stand structure as indicators of natural restoration from past disturbances. Eleven independent 500 m × 10 m belt transects (5.5 ha) were established within fragmented low land moist deciduous forests of Tripura. All woody plants ≥10 cm girth at breast height (GBH) were measured. A total of 7,134 individuals with mean density of 648.55 stems ha−1 and 16.36 m2 ha−1 of basal area were recorded, which represented 134 species, 93 genera, and 43 families of woody plants. Diversity-dominance curve showed that maximum number of species were ranked >10 due to low abundance value. Maximum distributions of stems (>50%) were recorded at lowest girth class (10–30 cm) as an indication of advanced regeneration and significantly declined towards upper girth (; ) and height (; ) classes, which also indicated that some plants were adopted with ongoing disturbances through both seeded and nonseeded regeneration. Species richness (; ), dominance (; ), and density (; ) were significantly increased at different disturbance intensities. Disturbances strongly influenced typical community association and structure by increasing diversity and population at certain magnitude and thereby showed declining trend towards maturation. Fragmented moist deciduous forests seek immediate attention as they represent spatial habitat for many economical or ecological important species, thus sustaining local biodiversity for livelihoods.

Patterns of species dominance, diversity and dispersion in ‘Khasi hill sal’ forest ecosystem in northeast India

BackgroundThe ‘Khasi hill sal’ forest ecosystem in Meghalaya, India represents the easternmost limit of sal distribution. We tested if tree diversity and compositional heterogeneity of this ecosystem was higher than other sal-dominated forests due to moister environment.MethodsVegetation was sampled in 11 transects of 10 m width and up to 500 m length covering 5.2 ha area. All stems ≥ 10 cm girth at breast height were enumerated.ResultsWe found a pattern of mixed dominance of Shorea robusta (sal) and Schima wallichii and co-dominance of Pinus kesiya and Careya arborea. The Shannon’s diversity index (H′) was 3.395 nats. This value is remarkably high and competitive to that of moist sal forests of eastern Himalayan foothills and sal-dominated forests of Tripura. A high value of H′ was manifested by: a) high species richness (S = 123), b) good equitability (70.6%), c) ‘fair’ resource apportionment, and d) abundance of rare species (84% species with less than one per cent of total individuals, 67% species with two or less individuals ha−1 and 59% species with one or less individuals ha−1). The compositional heterogeneity was ‘fair’ (Whittaker’s βw = 3.15). The presence of Fagaceae with six species commanding 4.3% of importance value (IVI) and of a pine (P. kesiya) in sal forest was remarkable. As many as 58 species showed ‘low density (≤ 10 individuals ha−1), uniform dispersion’, five species achieved ‘higher density (> 10 individuals ha−1), uniform dispersion’ and six of the top 10 species were ‘clumped’. The forest showed an exponential demographic curve illustrating ‘good’ regeneration of an expanding community. Vertical stratification was simple with a poor canopy and fair subcanopy, which together with low basal area (15.65 m2 · ha−1 for individuals ≥ 10 cm gbh) indicated logging of mature sal trees in the past.ConclusionsThe ‘Khasi hill sal’ forest ecosystem is richer in alpha and beta diversity than most sal-dominated forests, but past logging has reduced basal area. Selective removal of small timber and firewood, slash-and-burn agriculture and recurrent burning of forest floor are the principal anthropogenic factors controlling forest structure and regeneration of species.

Lower altitudinal variation in habitat associations, tree diversity and co-dominant population structures along moist deciduous forests dominated by sal (Shorea robusta) in Northeast India

We used line transects of 10 × 500 m size to analyze the patterns of sal associations, diversity and population structure at lower elevation (<100 meters above mean sea level) of moist deciduous forests dominated by sal (Shorea robusta) in Tripura, Northeast India. Overall 216 woody species with 898.56 ha−1 mean density and 33.21 m2 ha−1 mean basal area were recorded using 32 line transects of 0.5 ha size sampled by measuring sal forests at ≥10 cm girth at breast height. Five different sal associations were recognized by cluster analysis, where sal typically associated with Terminalia bellirica, Careya arborea and Schima wallichii in moist deciduous habitats. Rare associations of sal with Artocarpus chama and Dipterocarpus turbinatusa were also identified. Species diversity (p < 0.001) and dominance (p < 0.0001) was significantly different across the sal associations; species richness was recorded higher in S. robusta – S. wallichii association with 152 species than in S. robusta – T. bellirica association with 85 species. Existing habitat disturbances and intensity of sal effects on diversity and structure were significant (p ≤ 0.05), as observed by the changes in species richness and abundance of most abundant, least abundant and unique species along the associations. Population trends and regeneration potential of sal and its most associated trees were predicted using steepness and negative slope values in regression of size class distributions of tree density per hectare at 10 girth classes for each sal association. The present investigation helps in the understanding of broad ecological aspects in lowland sal habitats, particularly when this ecosystem is shifting to these regions in relatively wetter and plain areas due to climate change.

Temporal patterns of extraction of non-timber forest products in Chel range of Darjeeling Himalaya.

ABSTRACT Data on the collection of non-timber forest products (NTFPs), e.g., bamboo, rattan, leaves, broom heads, thatch, fuelwood, and fodder, between 1930 and 1990 in the Chel range of Darjeeling Himalaya, India were abstracted from the daily transactions recorded in the cashbooks of the Forest Department and analysed for ternporal patterns. Unlike in many forests of India, the Forest Department controlled the collection of NTFPs in Chel and earned revenues by virtue of their land rights. The people employed in NTFP collection were those who had been settled in forest villages to supply labour and allowed to farm areas allocated to them and permitted to keep cattle. Therefore, their cash income did not depend on selling NTFPs though they extracted them for their own use. The intensity of the collection of NTFPs either increased (fuelwood and fodder) or decreased after an initial increase (rattan, bamboo and thatch) over time due to variation in the resource stock, demand of the end user and cultural changes. The extraction of some NTFPs ceased on account of diminishing demand and rising production costs (leaves and baskets). Conversely, some NTFPs (broom heads and stone boulders) entered the commercial extraction domain on escalating demand. There is an integral but complex relationship between the extraction intensity and the resource base of NTFPs that may vary with the product as well as with other social, economic and policy factors.

Rainforests north of the Tropic of Cancer: Physiognomy, floristics and diversity in ‘lowland rainforests’ of Meghalaya, India

The lowland rainforests of Meghalaya, India represent the westernmost limit of the rainforests north of the Tropic of Cancer. These forests, on the Shillong plateau, are akin to Whitmores ‘tropical lowland evergreen rainforest’ formation and exhibit striking similarities and conspicuous differences with the equatorial rainforests in Asia-Pacific as well as tropical seasonal rainforests in southwestern China near the Tropic of Cancer. We found these common attributes of the rainforests in Meghalaya: familial composition with predominance of Euphorbiaceae, Lauraceae, Meliaceae, Moraceae, Myrsiticaceae, Myrtaceae and Rubiaceae; deciduousness in evergreen physiognomy; dominance of mega- and mesophanerophytic life-forms; abundance of species with low frequency of occurrence (rare and aggregated species); low proportional abundance of the abundant species; and truncated lognormal abundance distribution. The levels of stand density and stand basal area were comparable with seasonal rainforests in southwestern China, but were lower than equatorial rainforests. Tropical Asian species predominated flora, commanding 95% of the abundance. The differences include overall low stature (height) of the forest, inconspicuous stratification in canopy, fewer species and individuals of liana, thicker understory, higher proportion of rare species, absence of locally endemic species and relatively greater dominance of Fagaceae and Theaceae. The richness of species per hectare (S) was considerably lower at higher latitudes in Meghalaya than in equatorial rainforests, but was comparable with seasonal rainforests. Shannons diversity index (H′ = 4.40 nats for ≥10 cm gbh and 4.25 nats for ≥30 cm gbh) was lower on higher latitudes in Meghalaya in comparison to species-rich equatorial rainforests, but it was the highest among all lowland rainforests near the Tropic of Cancer.