Quantifying tree carbon stock in historically conserved Seminary Hills urban forest of Nagpur,India

Urban forests help regulating flow of ecosystem services and are efficient to sequester atmospheric carbon. Tree carbon stock in urban forests and green spaces can help improving human well-being. Nagpur being one of the fastest growing urban agglomerate in India that has faced rapid loss of green spaces in last three decades. Present study assessed tree biomass carbon storage potential of a historically conserved large (67.41 ha) Seminary Hills Reserve forest of Nagpur. A total of 150 quadrats of 100 m² were laid to understand the vegetation structure and tree biomass storage. Overall structure and composition of the forest was assessed while, non-destructive biomass estimation was carried out using tree volume eqs. A total of 27 tree species belonging to 12 plant families were observed from the forest with only 6 tree species being dominant and remaining 21 being rare in occurrence. The maximum tree carbon storage was observed in dominant tree species of Hardwickia binata (76.30 t C ha^?1) followed by 17.04 t C ha^?1 in Tectona grandis and 1.19 t C ha^?1 in Boswellia serrata. Carbon stock in other co-dominant species was reported in Terminalia bellirica (76.57 kg C ha^?1), Gardenia resinifera (1118.6 g C ha^?1) and Terminalia arjuna (84.8 g C ha^?1). Total carbon stock of dominant tree species present in Seminary Hills urban forest was 94.53 ± 39.6 t C ha^?1. The study intends to bring focus ecosystem benefits from Urban Forests in growing urban sprawls of India and the need to include their vital role in urban planning.     

Species diversity and community structure in sal (<Emphasis Type="Italic">Shorea robusta</Emphasis>) forests of two different rainfall regimes in West Bengal,India

Knowledge on the structure and composition of the plant communities has enormous significance in conservation and management of forests. The present study aimed to assess the community attributes, viz., structure, composition and diversity in the moist and dry sal (Shorea robusta) forests in the West Bengal province of India and compare them with the other sal forests of India. The phytosociological data from these forests were quantitatively analysed to work out the species richness, diversity, evenness, dominance, importance value, stand density and the basal area. The analysis showed that plant richness and diversity in moist sal forests of northern West Bengal are higher than the dry sal forests of south-west Bengal; a total of 134 tree (cbh ≥30 cm), 113 shrub and 230 herb species were recorded in the moist sal forest compared to 35 tree, 41 shrub and 96 herb species in dry sal forest. Papilionaceae was observed to be the dominant family. Dry sal forests had higher tree dominance (0.81) and stand density (1,006 stems ha⁻¹) but lower basal area (19.62 m²ha⁻¹) while moist sal forest had lower tree dominance (0.18) and stand density (438 stems ha⁻¹) but higher basal area (56.52 m²ha⁻¹). Tree species richness and stem density across girth classes in both the types decreased from the smallest to largest trees, while the occurrence rate of species increased with increase in girth class. A t-test showed significant differences in species richness, basal area and the stand density at 95% confidence level (p = <0.05) in the two forest types. The CCA indicated very low overall match (canonical correlation value = 0.40) between the two sets of variables from moist and dry sal types. The differences in these forests could be attributed to the distinct variations in climatic conditions- mainly the rainfall, disturbance regimes and the management practices.     

Diversity and spatial clustering of shade trees affect cacao yield and pathogen pressure in Costa Rican agroforests

The importance of the spatial organisation of individuals in explaining species coexistence within a community is widely recognised. However, few analyses of spatial structure have been performed on tropical agroforests.The main objective of this study was to highlight the links between spatial organisation of shade trees on the one hand, and shade tree species richness and cacao yield on the other, using data from 29 cacao agroforests in Costa Rica.A method of spatial statistics, Ripley's K-function, was used to analyse the spatial organisation of shade and cacao trees in the study plots. For each stand, the X and Y coordinates of ≥2.5-m-tall trees were recorded. In each plot we also assessed shade tree species richness and cacao yield (with total number of pods = number of pods damaged by frosty pod rot + number of healthy pods).Three types of stands were identified: the first was characterised by significant clustering of shade trees, the highest shade tree species richness (S = 6), and the highest number of damaged pods (139 pods ha^?1 year^?1). The second type was characterised by random spatial organisation of shade trees. The third type showed a trend towards regular organisation. Species richness of shade trees did not differ significantly between the last two types (S = 4 for both), nor did the number of damaged pods (56 pods ha^?1 year^?1 and 67 pods ha^?1 year^?1 respectively).Although the trends were not statistically significant for all the variables in our data set, the clustered spatial structure appears to favour a synergy between environmental (tree species richness), and provisioning (cacao production) services.     

Biomass,carbon density and diversity of tree species in tropical dry deciduous forests in Central India

Tropical dry deciduous forests play a significant role in regulating the biogeochemical cycles. Present study assesses the carbon stock of tropical dry deciduous forests varying in tree density, basal cover, and diversity located in Singrauli district of Madhya Pradesh in Central India. Field sampling was carried out in six forest sites viz., Chitrangi, East Sarai, Gorbi, Renukoot, West Sarai, and Waidhan, of Singrauli. A total of 29 tree species belonging to 18 families were recorded across the forest ranges where tree density, basal area and diversity values varied from 702 (Gorbhi Range) – 1671 (East Sarai range) individuals ha^?1; 15.43 (Renukhund range) – 71.76 m² ha^?1 (Chitrange range) and 0.69 (West Sarai range) – 2.52 (Gorbi range), respectively. Total biomass estimated ranged from 103.32 (Renukhund range) – 453.54 Mg ha^?1 (Chitrange range) while the total tree carbon density varied from 48.97 to 214.97 Mg C ha^?1. The variation in carbon storage in the studied ranges was found dependent on density of trees in different diameter and age classes and tree species diversity. Diospyros melanoxylon, Butea monosperma, Shorea robusta, Senegalia catechu, Spondias pinnata, and Lagerstroemia parviflora were the dominant species at different study sites (forest ranges) and contributed towards higher carbon storage in respective forest ranges. Study endorses field-based approach for carbon estimations based on above and belowground assessments as a more realistic approach to understand sink potential of natural forests.     

Carbon of Chaillu forests based on a phytosociological analysis in Republic of Congo,more than meets the eye?

The objectives were to quantify aboveground, belowground and dead wood carbon pools near Mayoko in the Chaillu massif of Republic of Congo and explore relationships between carbon storage and plant diversity of all growth forms. A total of 190 plots (25 m by 25 m) were sampled (5072 stems, 211 species) and data analysed using recommended central-African forest allometric equations. Mean stem diameter at breast height was 33.6 cm, mean basal area 47.7 m² ha⁻¹ and mean density of individuals 407 ha⁻¹. Mean aboveground carbon (AGC) ranged from 13.93–412.66 Mg C ha⁻¹, belowground carbon from 2.86–96.97 Mg C ha⁻¹ and dead wood from 0.00–7.59 Mg C ha⁻¹. The maximum AGC value recorded in a plot was 916 Mg C ha⁻¹. The analysis performed using phytosociological association as basis rather than broad vegetation type is unique. AGC values for undisturbed terra firme forest sites featured among the highest recorded for African tropical forests. Considering only tree diversity, a weak, yet significant, relationship existed between AGC and species richness, Shannon-Wiener index of diversity and Fisher's alpha. However, if diversity of all plant growth forms is considered, no relationship between carbon and plant diversity existed.     

Stand density and species richness affect carbon storage and net primary productivity in early and late successional temperate forests differently

How stand density and species richness affect carbon (C) storage and net primary productivity (NPP) changes with forest succession is poorly understood. We quantified the C storage of trees and the aboveground NPP in an early successional secondary birch forest (birch forest) and a late successional mixed broadleaf-Korean pine (Pinus koraiensis) forest (mixed forest) in northeastern China. We found that: 1) tree C storage in the mixed forest (120.3 Mg C ha^?1) was significantly higher than that in the birch forest (78.5 Mg C ha^?1), whereas the aboveground NPP was not different between the two forest types; and 2) only stand density had a positive linear relationship with tree C storage and aboveground NPP in the birch forest. In the mixed forest, both tree C storage and aboveground NPP were significantly affected by the combination of the stand density and species richness. The tree C storage to stand density and species richness relationships were hump-shaped. The aboveground NPP increased with increasing stand density, but its relationship to species richness was hump-shaped. We conclude that the effect of stand density and species richness on tree C storage and aboveground NPP was influenced by forest stand succession, and such effects should be considered in studying stand density- and species richness- ecosystem function (e.g., C storage and NPP) relationships in temperate forest ecosystems.     

The effects of environmental variables and human disturbance on woody species richness and diversity in a bamboo–deciduous forest in northeastern Thailand

Variations in species richness and diversity at a local scale are affected by a number of complex and interacting variables, including both natural environmental factors and human-made changes to the local environment. Here we identified the most important determinants of woody species richness and diversity at different growth stages (i.e. adult, sapling and seedling) in a bamboo–deciduous forest in northeast Thailand. A total of 20 environmental and human disturbance variables were used to determine the variation in species richness and diversity. In total, we identified 125 adult, 111 sapling (within fifty 20 × 20-m plots) and 89 seedling species (within one hundred and twenty 1 × 1-m subplots). Overall results from stepwise multiple regression analyses showed that environmental variables were by far the most important in explaining the variation in species richness and diversity. Forest structure (i.e. number of bamboo clumps and canopy cover) was important in determining the adult species richness and diversity (R ² = 0.48, 0.30, respectively), while topography (i.e. elevation) and human disturbance (i.e. number of tree stumps) were important in determining the sapling species richness and diversity (R ² = 0.55, 0.39, respectively). Seedling species richness and diversity were negatively related to soil phosphorus. Based on our results, we suggest that the presence of bamboos should be incorporated in management strategies for maintaining woody species richness and diversity in these forest ecosystems. Specifically, if bamboos cover the forest floor at high densities, it may be necessary to actively control these species for successful tree establishment.     

Heterogeneity of tree diversity and carbon stocks in Amazonian oil palm landscapes

ABSTRACT

Background: Quantitative effects of large-scale oil palm expansion in the Neotropics on biodiversity and carbon stocks are still poorly documented.

Aims: We evaluated differences in tree species composition and richness, and above-ground carbon stocks among dominant land cover types in Pará state, Brazil.

Methods: We quantified tree species composition and richness and above-ground carbon stock in stands in remnant primary rain forest, young secondary forest, oil palm plantation and pastures.

Results: We sampled 5,696 trees with a DBH ≥ 2 cm, of 413 species in 68 families, of which 381 species were recorded in primary forest fragments. We found significant differences in species richness and carbon stock among the four land cover classes. Carbon stocks in remnant primary forest were typically over 190 Mg ha^?1, while those in other land cover types were typically less than 60 Mg ha^?1.

Conclusion: Oil palm plantations have a species-poor tree community given active management; old plantations have a standing carbon stock which is comparable to that of secondary forest and far greater than that of pastures. Private forest reserves within oil palm company holdings play an important role in preserving primary forest tree diversity in human-modified landscapes in Amazonia.     

Plant species diversity,community structure and invasion status in insular primary forests on the Sekimon uplifted limestone (Ogasawara Islands)

Native forests on oceanic islands are among the most threatened ecosystems. The forests formed on Sekimon uplifted limestone in Haha-jima Island (Ogasawara Islands) have not yet been destroyed by human activities and remain as primary forests harboring several narrow endemic endangered plants. In this paper, we described the plant species diversity, community structure, and status of invasion by alien plants in the mesic forests of Sekimon. The Sekimon forest was characterized by low tree diversity (37 species), high stem density (1731 ha^?1), and high basal area (63.9 m² ha^?1), comparing with natural forests in world islands. The forests were dominated in the number of stems by the sub-tree Ardisia sieboldii followed by the trees Pisonia umbellifera and Elaeocarpus photiniifolius. The invasive tree Bischofia javanica ranked fourth for basal area and third for the number of stems (DBH?≥?10 cm), and its distribution expanded, especially near a past plantation site. Surveys of forest floor vegetation revealed that species richness of vascular plants was 109 species and that many alien plants had already invaded the forests. Despite the low species richness of alien (16% for vascular flora and 8% for trees), the high frequency of aliens on the forest floor suggests that they have colonized successfully in the Sekimon forest. Extrapolation analysis based on the rarefaction curves predicted that the vascular plants in the Sekimon (25 ha) accounted for 135 species (29.9% of the vascular flora of the Ogasawara Islands) and endemic plants were 85 species (62.0%). The fact that the 39 vascular species recorded in our plots were listed in Japanese Red List suggests that the Sekimon forest should be conserved as a sanctuary of biodiversity. Because alien plants are invading the forests without apparent anthropogenic disturbance, immediate action to eradicate these invaders is highly needed.     

Litterfall production, decomposition and nutrient use efficiency varies with tropical forest types in Xishuangbanna, SW China: a 10-year study

Litterfall production, decomposition and nutrient use efficiency in three different tropical forest ecosystems in SW China were studied for 10 years. Annual mean litterfall production in tropical seasonal forest (TSF) (9.47?±?1.65 Mg ha^?1) was similar to that in man-made tropical forest (MTF) (9.23?±?1.29 Mg ha^?1) (P?>?0.05) but both were significantly lower than that in secondary tropical forest (STF) (12.96?±?1.71 Mg ha^?1) (P?<?0.05). The annual variation of litterfall was greater in TSF (17.4%, P?<?0.05) than in MTF (14.0%) or STF (13.2%). The annual mean decomposition rate of litterfall increased followed the order of MTF (2.72)?<?TSF (3.15)?<?STF (3.50) (P?<?0.05), which was not correlated with annual precipitation or annual mean temperature, but was rather related to litter quality. The nutrient use efficiency was found to be element-dependent and to vary significantly among the three forest types (P?<?0.05). These results indicate that litterfall production and decomposition rates in different tropical forest systems are related to plant species composition and are influenced strongly by coexisting species and their life stage (age) but less so by the species richness. Constructing multi-species and multistory man-made tropical forest is an effective way to enhance biological productivity and maintain soil nutrients on degraded tropical land.     

Does forest restoration using taungya foster tree species diversity? The case of Afram Headwaters Forest Reserve in Ghana

The taungya agro‐forestry system is an under‐researched means of forest restoration that may result in high tree diversity. Within a forest reserve in Ghana, the forest core and its surrounding Teak‐ and Cedrela‐taungya on logged, cropped and burned land were mapped with ALOS satellite imagery. Native trees, seedlings and saplings were enumerated in 70 random, nested plots, equally divided between forest and taungya. The native tree regeneration was assessed by species richness (SR), Shannon‐Wiener Index (SWI), Shannon Evenness Index (SEI) and species density (SeD) for seedlings, saplings and trees separately and combined and subsequently correlated with canopy covers (CC) in taungya. As anticipated, the taungya diversity was lower than the forest diversity but higher than reported from nontaungya exotic plantations. In the forest, the diversity of native trees increased from seedlings through saplings to trees. The reverse was found in the taungya. Taungya seedling diversity was not significantly different from the forest, while the sapling and tree diversity were significantly lower. Weak correlations of CC with SR, SWI, SEI and SeD were found. Our results suggest the need for treatment to maintain the tree diversity beyond the seedling stage in the taungya.     

Influence of soils and topography on Amazonian tree diversity: a landscape‐scale study

Question: How do soils and topography influence Amazonian tree diversity, a region with generally nutrient‐starved soils but some of the biologically richest tree communities on Earth? Location: Central Amazonia, near Manaus, Brazil. Methods: We evaluated the influence of 14 soil and topographic features on species diversity of rain forest trees (≥10 cm diameter at breast height), using data from 63 1‐ha plots scattered over an area of ～400 km². Results: An ordination analysis identified three major edaphic gradients: (1) flatter areas had generally higher nutrient soils (higher clay content, carbon, nitrogen, phosphorus, pH and exchangeable bases, and lower aluminium saturation) than did slopes and gullies; (2) sandier soils had lower water storage (plant available water capacity), phosphorus and nitrogen; and (3) soil pH varied among sites. Gradient 2 was the strongest predictor of tree diversity (species richness and Fisher's α values), with diversity increasing with higher soil fertility and water availability. Gradient 2 was also the best predictor of the number of rare (singleton) species, which accounted on average for over half (56%) of all species in each plot. Conclusions: Although our plots invariably supported diverse tree communities (≥225 species ha^?1), the most species‐rich sites (up to 310 species ha^?1) were least constrained by soil water and phosphorus availability. Intriguingly, the numbers of rare and common species were not significantly correlated in our plots, and they responded differently to major soil and topographic gradients. For unknown reasons rare species were significantly more frequent in plots with many large trees.     

Effects of experimental nitrogen additions on plant diversity in an old‐growth tropical forest

Response of plant biodiversity to increased availability of nitrogen (N) has been investigated in temperate and boreal forests, which are typically N‐limited, but little is known in tropical forests. We examined the effects of artificial N additions on plant diversity (species richness, density and cover) of the understory layer in an N saturated old‐growth tropical forest in southern China to test the following hypothesis: N additions decrease plant diversity in N saturated tropical forests primarily from N‐mediated changes in soil properties. Experimental additions of N were administered at the following levels from July 2003 to July 2008: no addition (Control); 50 kg N ha^?1 yr^?1 (Low‐N); 100 kg N ha^?1 yr^?1 (Medium‐N), and 150 kg N ha^?1 yr^?1 (High‐N). Results showed that no understory species exhibited positive growth response to any level of N addition during the study period. Although low‐to‐medium levels of N addition (≤100 kg N ha^?1 yr^?1) generally did not alter plant diversity through time, high levels of N addition significantly reduced species diversity. This decrease was most closely related to declines within tree seedling and fern functional groups, as well as to significant increases in soil acidity and Al mobility, and decreases in Ca availability and fine‐root biomass. This mechanism for loss of biodiversity provides sharp contrast to competition‐based mechanisms suggested in studies of understory communities in other forests. Our results suggest that high‐N additions can decrease plant diversity in tropical forests, but that this response may vary with rate of N addition.     

Does using species abundance data improve estimates of species diversity from remotely sensed spectral heterogeneity?

Different approaches for the assessment of biodiversity by means of remote sensing were developed over the last decades. A new approach, based on the spectral variation hypothesis, proposes that the spectral heterogeneity of a remotely sensed image is correlated with landscape structure and complexity which also reflects habitat heterogeneity which itself is known to enhance species diversity. In this context, previous studies only applied species richness as a measure of diversity. The aim of this paper was to analyze the relationship of richness and abundance-based diversity measures with spectral variability and compare the results at two scales. At three different test sites in Central Namibia, measures of vascular plant diversity was sampled at two scales – 100 m² and 1000 m². Hyperspectral remote sensing data were collected for the study sites and spectral variability, was calculated at plot level. Ordinary least square regression was used to test the relationship between species richness and the abundance-based Shannon Index and spectral variability. We found that Shannon Index permanently achieved better results at all test sites especially at 1000 m², Even when all sites where pooled together, Shannon Index was still significantly related with spectral variability at 1000 m². We suggest incorporating abundance-based diversity measures in studies of relationships between ecological and spectral variability. The contribution made by the high spectral and spatial resolution of the hyperspectral sensor is discussed.     

Large-Scale Wind Disturbances Promote Tree Diversity in a Central Amazon Forest

Canopy gaps created by wind-throw events, or blowdowns, create a complex mosaic of forest patches varying in disturbance intensity and recovery in the Central Amazon. Using field and remote sensing data, we investigated the short-term (four-year) effects of large (>2000 m²) blowdown gaps created during a single storm event in January 2005 near Manaus, Brazil, to study (i) how forest structure and composition vary with disturbance gradients and (ii) whether tree diversity is promoted by niche differentiation related to wind-throw events at the landscape scale. In the forest area affected by the blowdown, tree mortality ranged from 0 to 70%, and was highest on plateaus and slopes. Less impacted areas in the region affected by the blowdown had overlapping characteristics with a nearby unaffected forest in tree density (583±46 trees ha⁻¹) (mean±99% Confidence Interval) and basal area (26.7±2.4 m² ha⁻¹). Highly impacted areas had tree density and basal area as low as 120 trees ha⁻¹ and 14.9 m² ha⁻¹, respectively. In general, these structural measures correlated negatively with an index of tree mortality intensity derived from satellite imagery. Four years after the blowdown event, differences in size-distribution, fraction of resprouters, floristic composition and species diversity still correlated with disturbance measures such as tree mortality and gap size. Our results suggest that the gradients of wind disturbance intensity encompassed in large blowdown gaps (>2000 m²) promote tree diversity. Specialists for particular disturbance intensities existed along the entire gradient. The existence of species or genera taking an intermediate position between undisturbed and gap specialists led to a peak of rarefied richness and diversity at intermediate disturbance levels. A diverse set of species differing widely in requirements and recruitment strategies forms the initial post-disturbance cohort, thus lending a high resilience towards wind disturbances at the community level.     

Variation in structural diversity and regeneration potential of tree species in different tropical forest types of Similipal Biosphere Reserve,Eastern India

Understanding the regeneration potential of tree species in natural forest ecosystems is crucial to deliver suitable management practices for conservation of biodiversity. We studied the variation in structural diversity and regeneration potential of tree species in three different tropical forest types, namely: Dry Deciduous forest (DDF), Moist Deciduous forest (MDF) and Semi-evergreen forest (SEF) of Similipal Biosphere Reserve (SBR), Eastern India. Random sample plots were laid for studying the diversity and distribution pattern of tree, sapling, and seedling stages of the tree species. A total of 84 species belong to 73 genera and 35 families were recorded from the study area. The highest species richness was reported for tree (54 species) in DDF, sapling (24 species) in MDF and seedling (22 species each) in SEF and DDF. The overall density of trees with GBH (Girth at Breast Height) ≥ 10 cm was 881 individuals/ha. The regeneration potential of tree species was poor in DDF (39%) where as it was fair in SEF (43%) and MDF (49%). Most of the dominant tree species at each forest type performed good regeneration. The species such as Ehretia laevis Roxb., Bridelia retusa (L.)A.Juss., Mitragyna parviflora (Roxb.) Korth., Terminalia tomentosa Wight & Arn., Terminalia chebula Retz., Terminalia bellirica (Gaertn.) Roxb.etc. had either no regeneration or poor regeneration potential need immediate attention for conservation measures. The diversity of standing trees did not correlate with seedling or sapling diversity in all the cases but there was significant correlation among seedling and sapling diversity found in DDF (r = 0.67, p ≤ 0.05) and SEF (r = 0.83, p ≤ 0.05). Further, the diversity of tree species increased with their age (trees > saplings > seedlings) and the stem density decreased with their age (trees < saplings < seedlings) in all three forest types. The results of our study would be helpful in understanding the structural attributes, diversity and regeneration potential of different tropical forest types of India for their better conservation and management.     

Tree population changes in a tropical dry evergreen forest of south India over a decade (1992–2002)

Changes in species composition and density of trees >10 cm gbh in a tropical dry evergreen forest in Puthupet, south India are interpreted for the period between 1992 and 2002. A 1-ha plot was inventoried in 1992 and was recensused in 2002. During the 10-year interval tree taxa diversity as well as stand density increased, but the basal area value decreased. Tree species richness increased by 21% (from 24 to 29 species) by an addition of eight species and local extinction of three species. The tree density increased just by eight individuals (from 1330 stems ha⁻¹ in 1992 to 1338 ha⁻¹ in 2002), but the basal area decreased by 8% (from 37.5 to 34.5 m² ha⁻¹). Many species (11 numbers) have increased in abundance rather than decreased. Many surviving species seem to have considerable stability in abundance at the local scale. The density of smaller stems (10 29 cm gbh) increased by 15.3%, while that of the larger trees decreased drastically (81.6%). Ninety percent of the missing stems were from the middlestorey of the forest. Tree density changes among the three ecological guilds revealed a decrease in stem density and an increase in basal area in the lowerstorey; while the middlestorey exhibited a reverse trend. Family-wise, tree density changes revealed that the majority of families (67%) showed an increase in stem density. Long-term studies on tree population changes are essential to estimate tree mortality and recruitment rates, which will provide a greater insight in tropical forest dynamics.     

Diversity and composition of arboreal beetle assemblages in tropical pasture afforestations: effects of planting schemes and tree species identity

Timber tree plantations are considered for rehabilitating forest biodiversity in the tropics, but knowledge on determinants of faunal diversity patterns in such human-modified forest landscapes is scarce. We quantified the composition of beetle assemblages on three native timber species (Anacardium excelsum, Cedrela odorata and Tabebuia rosea) planted on former pasture to assess effects of tree species identity, tree species diversity, and insecticide treatment on a speciose group of animals in tropical plantations. The beetle assemblage parameters ‘abundance’, ‘species richness’, ‘Chao1 estimated species richness’ and ‘Shannon diversity’ were significantly reduced by insecticide treatment for each tree species. Shannon diversity increased with stand diversification for T. rosea but not for A. excelsum and C. odorata. Species similarity was highest (lowest species turnover) between beetle assemblages on T. rosea, and it was lowest (highest species turnover) for assemblages on insecticide-treated trees of all timber species. Considering trophic guilds, herbivorous beetles dominated on all tree species and in all planting schemes. Herbivores were significantly more dominant on T. rosea and C. odorata than on A. excelsum, suggesting that tree species identity affects beetle guild structure on plantation trees. Insecticide-treated stands harbored less herbivores than untreated stands, but exhibited a high abundance of predator beetle species. Our study revealed that even young pasture-afforestations can host diverse beetle assemblages and thus contribute to biodiversity conservation in the tropics. The magnitude of this contribution, however, may strongly depend on management measures and on the selected tree species.     

Forest vegetation of the Himalaya

This review deals with the forest vegetation of the Himalaya with emphasis on: paleoecological, phytogeographical, and phytosociological aspects of vegetation; structural and functional features of forest ecosystem; and relationship between man and forests. The Himalayan mountains are the youngest, and among the most unstable. The rainfall pattern is determined by the summer monsoon which deposits a considerable amount of rain (often above 2500 mm annually) on the outer ranges. The amount of annual rainfall decreases from east to west, but the contribution of the winter season to the total precipitation increases. Mountains of these dimensions separate the monsoon climate of south Asia from the cold and dry climate of central Asia. In general, a rise of 270 m in elevation corresponds to a fall of 1°C in the mean annual temperature up to 1500 m, above which the fall is relatively rapid. Large scale surface removals and cyclic climatic changes influenced the course of vegetational changes through geological time. The Himalayan ranges, which started developing in the beginning of the Cenozoic, earlier supported tropical wet evergreen forests throughout the entire area (presently confined to the eastern part). The Miocene orogeny caused drastic changes in the vegetation, so much so that the existing flora was almost entirely replaced by the modern flora. Almost all the dominant forest species of the Pleistocene continue to maintain their dominant status to the present. Presently the Himalayan ranges encompass Austro-Polynesian, Malayo-Burman, Sino-Tibetan, Euro-Mediterranean, and African elements. While the Euro-Mediterranean affinities are well represented in the western Himalayan region (west of 77°E long.), the Chinese and Malesian affinities are evident in the eastern region (east of 84°E long.). However, the proportion of endemic taxa is substantial in the entire region. A representation of formation types in relation to climatic factors, viz., rainfall and temperature, indicates that boundaries between the types are not sharp. Formation types often integrate continuously, showing broad overlaps. Climate does not entirely determine the formation type, and the influence of soil, fire, etc., is also substantial. The ombrophilous broad leaf forests located in the submontane belt (< 1000 m) of the eastern region are comparable to the typical tropical rain forests. On the other extreme, communities above 3000 m elevation are similar to sub-alpine and alpine types. From favorable to less favorable environments, as observed with decreasing moisture from east to west, or with decreasing temperature from low to high elevations, the forests become increasingly open, shortstatured and simpler, with little vertical stratification. Ordination of forest stands distributed within 300–2500 m elevations of the central Himalaya, by and large indicates a continuity of communities, with scattered centers of species importance values in the ordination field. Within the above elevational transect, sal (Shorea robusta) and oak (Quercus spp.) forests may be designated as the climax communities, respectively, of warmer and cooler climates. The flora of a part of the central Himalayan region is categorized as therohemigeophytic and that of a part of the western Himalayan region as geochamaephytic. An analysis of population structure over large areas in the central Himalaya, based on density-diameter distribution of trees, suggests that oldgrowth forests are being replaced by even-aged successional forests, dominated by a few species, such asPinus roxburghii. Paucity of seedlings of climax species, namelyShorea robusta andQuercus spp. over large areas is evident. The Himalayan catchments are subsurface-flow systems and, therefore, are particularly susceptible to landslips and landslides. Loss of water and soil in terms of overflow is insignificant. Studies on recovery processes of forest ecosystems damaged due to shifting cultivation or landslides indicate that the ecosystems can recover quite rapidly, at least in elevations below 2500 m. For example, on a damaged forest site, seedlings of climax species (Quercus leucotrichophora) appeared only 21 years after the landslide. In the central Himalaya, the biomass of a majority of forests (163-787 t ha^?1) falls within the range (200-600 t ha^?1) given for many mature forests of the world, and the net primary productivity (found in the range of 11.0–27.4 t ha^?1 yr^?1) is comparable with the range of 20–30 t ha^?1 yr^?1 given for highly productive communities of favorable environments. In most of the forests of this region, the litter fall values (2.1-3.8 t C ha^?1 yr^?1) are higher than the mean reported for warm temperate forests (2.7 t C ha^?1 yr^?1). Of the total litter, the tree leaves account for 54–82% in the Himalayan forests. The rate of decomposition of leaves in some broadleaf species of submontane belt (0.253-0.274% day^?1) are comparable with those reported for some tropical rain forest species. Because of the paucity of microorganisms and microarthropods in the forest litter and soil, high initial C:N ratio and high initial lignin content in leaves, the rate of leaf litter decomposition inPinus roxburghii is markedly slower than in other species of the central Himalaya. The fungal species composition of the leaf litterof Pinus roxburghii is also distinct from those of other species. A greater proportion of nutrients is accumulated in the biomass component of the Himalayan forests than in the temperate forests. Although litter fall is the major route through which nutrients return from biomass to the soil pool, a substantial proportion of the total return is in the form of throughfall and stemflow. Among the dominant species of the central Himalaya, retranslocation of nutrients from the senescing leaves was markedly greater inPinus roxburghii than inQuercus spp. andShorea robusta. Consequently, the C:N ratio of leaf litter is markedly higher inPinus roxburghii than in the other species. Immobilization of nutrients by the decomposers of the litter with high C:N ratio is one of the principal strategies through whichPinus roxburghii invades other forests and holds the site against possible reinvasion by oaks. Observations on the seasonality of various ecosystem functions suggest that Himalayan ecosystems are geared to take maximum advantages of the monsoon period (rainy season). Most of the human population depends on shifting-agriculture in the eastern region and on settled agriculture in the central and western regions. Either of these is essentially a forest-dependent cultivation. Each unit of agronomic energy produced in the settled agriculture entails about seven units of energy from forests. Consequently, forests with reasonable crown cover account for insignificant percentage of the land. Tea plantations and felling of trees for timber, paper pulp, etc., are some of the major commercial activities which adversely affected the Himalayan forests.