B. Mohan Kumar

Diversity, structure and standing stock of wood in the homegardens of Kerala in peninsular India.

A survey was conducted in 17 selectedthaluks (revenue sub-divisions) of Kerala state to elucidate the floristic structure, composition and the extent of similarities and diversities in the composition of homegardens of Kerala, with particular reference to small (below 0.4 ha), medium (0.5 to 2 ha) and large (>2.0 ha) holding size categories. Besides attempts wer also made to characterize the potential of homegardens to supply commercial timber and fuelwood. Two hundred and fifty two farmers were selected through a stratified random process. In addition to gathering general information on crop and livestock production enterprises, all scattered trees and shrubs (≥15 cm girth at breast height) on the homestead and border trees except palms and rubber were enumerated.There was tremendous variability both in the number of trees and shrubs present and species diversity of the selected homesteads in different provinces. The small, medium and large sized holdings also exhibited profound variability in the number of woody taxa and individuals present. In total, 127 woody species (Girth at Breast Height (GBH) ≥15 cm) were encountered. The mean number of woody taxa found in the homegardens ranged from 11 for Pathanapuram to 39 in Perinthalmanna. Floristic diversity was higher in the smaller homesteads. It decreased with increasing the size of holdings. Mean Simpsons diversity index for the homesteads ranged from 0.251 (Kochi) to 0.739 (Kottarakkara) suggesting that floristic diversity of homegardens was moderate to low compared to a value over 0.90 for the species-rich evergreen forests of the Western Ghats. The Sorensens similarity indexes suggested a moderately high degree of similarity for the different tree species encountered in the homesteads of Kerala.No clear cut planting pattern was discernible in the homegardens of Kerala. The homegarden trees and shrubs were either scattered throughout the homestead or on farm boundaries. Farmers tend to prefer timber trees such as ailanthus (highest frequency) and teak besides fruit trees such as mango, jack, cashew and the like. Major homegarden species were represented in all diameter classes. The diameter structure, however, exhibited a slightly skewed (+) distribution pattern, having the highest frequency in the 20–30 cm classes ensuring adequate regeneration status and in that process making homegardens a sustainable as well as dynamic land use system.Standing stock of timber and firewood in the homestead of differentthaluks are presented. Average commercial standing stock of homesteads ranged from 6.6 to 50.8 m3 ha−1 and fuel wood volume was of the order of 23 to 86 m3 ha−1. Implicit in the high commercial timber volume and fuel wood volume is that a substantial proportion of the societys wood demands are met from the homesteads. Palms, however, constituted the dominant component of standing commercial timber and fuel wood volumes accounting as much as 63% and 72%, respectively, of the total wood in these categories.

Vegetation responses along edge-to-interior gradients in a high altitude tropical forest in peninsular India

A study was conducted in a high altitude tropical forest (shola forest) in peninsular India to examine the changes in floristic composition (mainly woody species regeneration) along an edge to interior gradient in relation to changes in edaphic and microenvironmental factors. Species inventory was taken in 25 m2 plots, established at 10 m intervals along edge to interior transects. The measured soil variables included pH, organic carbon, total nitrogen, available phosphorus, and soil moisture. Microenvironmental factors including light transmittance, relative humidity, and air and soil temperatures also were monitored. Both edaphic and microenvironmental factors exhibited strong patterns along the edge to interior gradient. Forest edges were characterized by higher light transmittance, higher air and soil temperatures, and lower relative humidity. Soil variables including pH, organic carbon, total nitrogen, available phosphorus, and moisture increased toward the forest interior. Significant increases in organic carbon (53.9%), total nitrogen (47%), and soil moisture (55%) indicated a relatively fertile forest interior compared with the forest edge. A definite floristic compositional pattern also was observed along the edge to interior gradient which was correlated to the edaphic and microenvironmental variables as revealed by canonical correspondence analysis. It appears that edge effects in these high altitude forests penetrate to a distance of 15–30 m. Further, edaphic factors have an important influence on woody species regeneration, perhaps much more than microenvironmental factors. This indicates that any disturbance that significantly exposes theforest floor, thus lowering soil moisture and altering soil nutrient status, can adversely affect the regeneration of many of the shola species.

Comparison of biomass production, tree allometry and nutrient use efficiency of multipurpose trees grown in woodlot and silvopastoral experiments in Kerala, India

Abstract In woodlot and silvopasture experiments involving a total of three age-sequences, the rates of biomass accumulation and nutrient accumulation by multipurpose trees were evaluated. The woodlot experiment included nine multipurpose trees (Acacia auriculiformis, Ailanthus triphysa, Artocarpus heterophyllus, Artocarpus hirsutus, Casuarina equisetifolia, Emblica officinalis, Leucaena leucocephala cv. K8, Paraserianthes falcataria and Pterocarpus marsupium) and the silvopastoral experiment involved a subset of four trees (Acacia auriculiformis, Ailanthus triphysa, Casuarina equisetifolia and Leucaena leucocephala cv. K8). Both plantings were maintained at Thiruvazhamkunnu, Kerala, India. Trees in the woodlot experiment were felled (partially) at 8.8 years of age and that of the silvopastoral experiment both at 5 years and 7 years of age. Rate of biomass accumulation and nutrient accumulation was highest for Acacia and the least for Leucaena. Allometric relationships linking above ground biomass with DBH and/or total height gave reasonable predictions. A comparison between species and among tissue types within species indicated that nutrient use efficiency for N, P and K varied widely. Implications for nutrient export from the site through whole tree harvesting systems involving fast growing multipurpose tree species are discussed.

Litter production and decomposition dynamics in moist deciduous forests of the Western Ghats in Peninsular India

Abstract A field study was conducted in the moist deciduous forests of the Western Ghats (India) to test the following three hypotheses: (1) Litter production in tropical forests is a function of the floristic composition, density, basal area and disturbance intensity; (2) Decay rate constants of tropical species is an inverse function of the initial lignin/nitrogen ratio; (3) Decomposition rates in tropical forests are faster than temperate forests. Litter fall was estimated by installing 63 litter traps in the moist deciduous forests of Thrissur Forest Division in the Western Ghats at three sites. Litter fall followed a monomodal distribution pattern with a distinct peak during the dry period from November–December to March–April.Dillenia pentagyna, Grewia tiliaefolia, Macrosolen spp.,Xylia xylocarpa, Terminalia spp.,Lagerstroemia lanceolata, Cleistanthus collinus, Bridelia retusa, andHelicteres isora were the principal litter producing species at these sites. The annual litter fall ranged from 12.18 to 14.43 t ha−1. Structural attributes of vegetation such as floristic composition, basal area, density and disturbance intensity did not directly influence litter fall rates. Leaf litter decay rates for six dominant tree species were assessed following the standard litter bag technique. One hundred and eight litter bags per species containing 20 g samples were installed in the forest floor litter layer at the same three sites selected for the litter fall quantification exercise. The residual litter mass decreased linearly with time for all species. In general, less disturbed sites and species adapted to higher nitrogen availabilities exhibited relatively higher decay rate coefficients (k). The rapid organic matter turnover observed in comparison with published temperate forest litter decay rates confirms that tropical moist deciduous forest species are characterised by faster decomposition rates. Mean concentrations of N, P and K in the litter were profoundly variable amongst the dominant species. Initial nitrogen content of the leaf litter varied from 0.65 to 1.6%, phosphorus from 0.034 to 0.077% and potassium from 0.25 to 0.62%.C. collinus, an understorey shrub consistently recorded the lowest litter concentrations for all nutrients. The overriding pattern is one of higher nutrient levels in the overstorey leaf litter and lower concentrations in the understorey litter. Furthermore, as decomposition proceeded, the nitrogen concentration of the residual biomass increased.

A density management diagram for teak plantations of Kerala in peninsular india

Abstract A density management diagram was constructed using stand inventory data from 193 teak ( Tectona grandis L.f) plantations in Western Ghats of peninsular India. The diagrams utility in predicting and displaying the consequences of stand density manipulations is illustrated with two alternative density management regimes.

Root competition for phosphorus between the tree and herbaceous components of silvopastoral systems in Kerala, India

Root competition in polyculture systems involving combinations of four tree species and four grass species was evaluated based on 32P recovery by each species in mixed and sole crop situations. The tree species were: Leucaena leucocephala, Casuarina equisetifolia, Acacia auriculiformis and Ailanthus triphysa, and the grass species were: Pennisetum purpureum (hybrid napier), Brachiaria ruziziensis (congo signal), Panicum maximum (guinea grass) and Zea mexicana (teosinte). Four lateral distance (25 and 50 cm) and depth (15 and 50 cm) treatments were included in the study to characterize the relative fine root distribution of trees. Absorption of 32P was monitored through radioassay of leaves. Regardless of the species, 32P uptake from 50 cm soil depth was lower than that of 15 cm depth. Absorption of 32P from 50 cm lateral distance was also less than that of 25 cm distance in Acacia and Casuarina. Grass species in sole crop situations absorbed more 32P than in mixed systems. None of the grass species when grown in association with tree components affected the absorption of 32P by trees. All grass species exerted a complementary effect on 32P absorption by Casuarina. Leucaena also benefited in the same way when grown in association with congo signal and/or teosinte. Of the tree species, Acacia and Leucaena adversely affected the 32P uptake by grass species.

Fuelwood characteristics of tree species in homegardens of Kerala, India

Indiscriminate use of natural resources in the past has lead to fuelwood shortages in many parts of the tropical world. To surmount this domestic energy crisis, not only degraded sites must be planted with trees having high fuel value potential, but also agroforestry promoted on arable lands. To enable choice of species for such energy plantations/agroforests in the humid tropics of peninsular India, we assessed the heat of combustion and physical properties that determine combustion of phytofuels, such as ash content, specific gravity and moisture content. Bark and wood samples of 45 multipurpose tree species in the homegardens of Kerala, India and three fuel materials of local importance (coconut [Cocos nucifera] endocarp, dried coconut spathe and dehiscent rubber [Hevea braziliensis] pericarp) were evaluated. Variations abound in the calorific values and physical properties of species and tissue-types. In general, heat of combustion and specific gravity followed the sequence: heartwood > sapwood > bark, while mean ash percentage followed a reverse order (bark > sapwood > heartwood). Ash content had a negative correlation with heat of combustion, but specific gravity exerted a positive influence. Furthermore, ash content and wood specific gravity were inversely related. Although green moisture content increased in the order: bark < heartwood < sapwood, it failed to show any predictable relationship with heat of combustion.

Structural, floristic and edaphic attributes of the grassland-shola forests of Eravikulam in peninsular India

Abstract The high elevation shola-grassland vegetation types of the Western Ghats apparently remained in a stable equilibrium for many decades, implying that both vegetational types are highly developed and attained stability under the same climatic regime. Several authors considered these two distinct vegetation formations occurring in juxta-position, as climax formations. According to the Clementsian view of climatic climax, however, two distinctly different vegetation types cannot form climatic climaxes under the same regional climate. Possibly some edaphic or biotic factors are responsible for rendering stability to the grassland in this system. We tested the following three hypotheses in this context. (1) The physico-chemical properties of the soil such as depth, organic matter, nutrient status and water holding capacity are more favourable in the depressions than in the exposed surfaces, which in turn might be responsible for the development of the woody vegetation in the depressions. (2) The shola forests exhibits similar structural attributes and a higher floristic diversity compared with the medium and low elevation wet evergreen forests of the Western Ghats region. (3) The shola trees are characterized by a low regeneration capacity, thus probably making it a shrinking resource base. With its characteristic deep fertile soil and high moisture holding capacity, the shola forests may remain in the same steady climax state, provided anthropogenic and other catastrophic disturbances do not destroy them. The grasslands were, however, characterised by generally shallow soils, low water holding capacity and low site nutrient capital. Hence, the assumption that grasslands are steady state vegetations maintained by edaphic factors, holds good. Structural and floristic elements of the shola forest revealed a very high floristic richness and diversity, probably the highest in the Western Ghats region. A total of 942 stems of at least 10 cm girth at breast height (GBH) and belonging to 53 species were encountered in the 5000 m 2 sampling area (basal area 48 m 2 ha −1 ). Contrary to the widely held dogma that shola forest does not possess adequate regeneration potential, the present study reveals that under the forest cover, profuse regeneration of almost all of the overstorey species occur. However, regeneration characteristics were different along the margins and in open grasslands, possibly as a result of differences in ecological conditions.

Litter dynamics and cumulative soil fertility changes in silvopastoral systems of a humid tropical region in central Kerala, India

SUMMARY Litter dynamics and associated nutrient turnover were studied in 4–5 yr-old silvopastoral systems involving four fast growing multipurpose tree species (Leucaena leucocephala, Casuarina equisetifolia, Acacia auriculiformis and Ailanthus triphysa). Our objectives were to characterise the variations in amount and quality of litter, decay rates and release of nutrients through litter decomposition, and to evaluate the possible cumulative influence on soil physico-chemical properties. Annual addition of litter ranged from 1.92–6.25 Mg ha-1. Leucaena showed the highest NPK levels in leaf litter and Ailanthus the least. Results of a litter bag study revealed that residual litter mass declined either exponentially or linearly with time. Casuarina and Leucaena litter decomposed completely within 6-7 months. Regardless of species, K remaining in the decomposing litter mass showed an exponential decline over time while both N and P had brief accumulation phases during the course of decomposition. Five years...

Comparative performance of four multi-purpose trees associated with four grass species in the humid regions of Southern India

The results of a field trial conducted at the Livestock Research Station, Thiruvazhamkunnu, Kerala to study the compatibility of different components in a silvo-pastoral system revealed that growth and yield of fodder species were significantly influenced by the tree components only after tree canopy formation. The fodder species such as Pennisetum purpureum Schum., Panicum maximum Jacq., Brachiaria ruziziensis Griseb. and Euchlaena mexicana Schrad. grown in association with Casuarina equisetifolia J. R. & G. Forst. and Ailanthus malabarica DC recorded comparatively higher forage yield even after canopy formation. However, forage crops grown in combination with Acacia auriculiformis A. Cunn. ex Benth. and Leucaena leucocephala (Lam.) de Wit. registered relatively lower values for growth and yield. Increased light infiltration into the understorey due to the cladophyllous canopy can be attributed as reason for the higher fodder productivity under Casuarina. Due to the combination of crown size and shape, tree height and spacing the amount of light intercepted by Ailanthus also was very low. Among the four multi-purpose trees used, Acacia recorded the maximum growth rate followed by Casuarina, Ailanthus and Leucaena. Forage productivity of the four species was in the order: Pennisetum purpureum > Panicum maximum > Brachiaria ruziziensis > Euchlaena mexicana. Casuarina with Pennisetum/ Panicm were found to be optimal tree — forage combinations for silvo-pastoral systems.