Browsing by Author "Mohankumar, B"

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Biomass production and resource partitioning in silvi-pastoral systems
(College of Forestry, Vellanikkara, 1993) Suman Jacob George; Mohankumar, B
A randomized block design experiment involving factorial combinations of four fodder species : Pennisetum purpureum (hybrid napier), Brachiaria ruziziensis (congo signal), Panicum maximum (guinea grass) and Zea Mexicana (Teosinte) and four tree species (Leucaena leucocephala, Casuarina equisetifolia, Acacia auriculiformis and Ailanthus triphysa initiated in June 1988 was used for the present investigations. The study was pursued with the objective of quantifying the biomass production potential of selected forage species grown in association with tree components after canopy closure, comparing the productivity of different tree components grown in silvopastoral systems; characterizing the micro-site enrichment and nutrient cycling aspects of silvopastoral systems, analysis the partitioning of solar radiation among the different components of the system and elucidate influence regarding the nature of root interactions in silvopastoral systems. The tree attributes such as biomass, height, DBH and crown diameter were in the order acasia > leucaena>casuarinas>ailanthus and the fodder biomasses were in the order hybrid napier> guinea grass > congo signal>teosinte. The concentration of N,P and K in the above ground portion decreased in the order: leaves >Branches >bole. The N-fixing trees, in general, had lower nutrient – use efficiencies. Amount of photosynthetically active radiation interception by the tree canopy was a cardinal factor effecting the herbage yield a direct correspondence was lacking. All the three N-fixing species had markedly higher soil nitrogen status. Soil organic matter, K and P were also higher under the tree canopy. Recovery pattern of 32p isotope injected in the soil revealed that 65 to 85 percent of the fine roots responsible for water and nutrient absorption were concentrated in the 0-15 cms layer of the soil profile. However, 32P recovery from the tree monocultures was generally low suggesting stimulatory effect of nutrient absorption by trees in presence of an associated field crop. The rate of litterfall amount of detritus produced ranged from 1.92 Mg ha-1 yr-1 (ailanthus) to 6.2 Mg ha-1 yr-1 (acacia). Relatively lower contents of nitrogen and phosphorus in the litter recorded during the dry period (March-April). Regarding the inter – specific variations with regards to litter decomposition rates, casuarina and leucaena litter decomposed at a faster rate than acacia and leucaena. The nitrogen and phosphorous contents of the decomposing litter increased during the one – year decay period for all the species. Although widely accepted and yield initial N, lignin or initial lignin/nitrogen could not be directly related to decay rate coefficients in the present study.
Effect of different levels of Nitrogen,Phosphorus and Potassium on Growth and yield of Cowpea,(Vigna sinensis Savi) variety P.118
(Department of Agronomy, College of Horticulture, Vellanikkara, 1978) Mohankumar, B; Balakrishna Pillai, P
An experiment was conducted at the Instructional Farm, Vellanikkara, during the second crop season of 1977 to study for effect of different levels of nitrogen, phosphorus and potassium on the growth and yield of cowpea, variety P. 118. The experiment was laid out in a 33 confounded factorial design confounding N P2 K and NP2 K2 in replications I and II, respectively. The study revealed that plant height increased with incremental doses of nitrogen. Nitrogen at 20kg/ha level contributed to increased nodulation which in turn favorably increased the grain yield. Phosphorus also had significant positive effect on nodulation. Nitrogen at 20 kg/ha and phosphorus at 40 kg P2O5 /ha exerted significant positive influence on the total dry matter production of the crop at harvest. Through their increased response in terms of number of pods per plant, number of seeds per pod and length of pods, nitrogen, at 20 kg ha and P2O5 at 40 kg/ha increased the grain yield per hectare significantly. Application of nitrogen at 30 kg/ha registered the maximum haulm yield. The grain haulm ratio was maximum for the combination of 20 kg nitrogen and 40 kg P2O5/ha Nitrogen at 21.6 kg/ha was found to be the optimum level for maximum grain production. The optimum level of phosphorus could not be estimated since the crop exhibited a linear response beyond the maximum level tried. Nitrogen application increased the plant content as well as the grain content of the element. Similarly application of phosphorus and potassium increased the plant contents of phosphorus and potassium, respectively. The uptake by nitrogen and phosphorus was significantly influenced by the 20 kg/ha and 40kg P2O5 /ha The protein content of grain increased with increasing levels of nitrogen. Applied potassium did not exhibit any significant influence on the yield components and most of the growth attributes.
Evaluation of fuelwood characteristics, physical and mechanical properties of selected agroforestry tree species
(Department of Silviculture and Agroforestry, College of forestry, Vellanikkara, 2001) Shanavas, A; Mohankumar, B
An experiment to evaluate the fuelwood value, and physical and mechanical properties of selected agroforestry tree species was conducted at the College of Forestry, Vellanikkara. The study involved determination of the fuelwood value of 48 species/materials and assessment of the physical and mechanical properties of three promising multipurpose trees having local importance, viz., Acacia auriculiformis, Acacia mangium and Grevillea robusta. Variations abound in the calorific values of agroforestry species and their tissue-types. Ash content, specific gravity, chemical composition and moisture content of tissues are primary factors affecting calorific value; while species and tissue-types, may exert a secondary control. Ash content and moisture content had a negative correlation with calorific value, whereas specific gravity exerted a positive influence. Based on the range in calorific values and fuelwood value indices obtained, different species and tissue-types could be broadly divided into three categories: high, medium and low. Calorific value of different tissue fractions decreased in the order: heartwood> sapwood > bark. Mean ash percentage of tissue-types followed the order: bark> sapwood > heartwood. Variations of ash content along bole height followed the order: branchwood > top > bottom > middle. Mean specific gravity of tissue-types followed the order: heartwood> sapwood > bark. For sample positions it followed the sequence: bottom> middle> top> branchwood. Wood moisture content increased from bottom to top along tree height and for tissue-types, it followed the order: bark < heartwood < sapwood. Coconut shell recorded the highest fuel value index (FVI) which was approximately 25 times greater than the highest value for tree species (Casuarina equisetifolia). Physical and mechanical properties of Acacia auriculiformis was significantly supenor to that of Acacia mangium and Grevillea robusta. The physical and mechanical properties were affected by both species and sample positions. Wood specific gravity increased from inner to outer sample positions along radial direction except for Grevillea robusta, which followed the order: outer < inner < middle. Moisture content decreased from inner to outer sample positions in Acacia mangium; while Grevillea robusta exhibited a divergent trend. Variations in shrinkage along radial direction followed the same trend as that of moisture content but was inconsistent with that of specific gravity. Most of the strength properties followed a trend similar to that of specific gravity. On a final note, specific gravity, work to limit of proportionality in static bending, work to maximum load in static bending, compressive stress at limit of proportionality in parallel to grain, compressive stress at limit of proportionality in perpendicular to grain and end-hardness of Acacia auriculiformis were greater than the values reported for teak. The physical and mechanical properties of Acacia mangium and Grevillea robusta except for shrinkage were less than that of teak.
Field testing of leucaena germplasm for their relative susceptibility to infestation by the Psyllids
(Kerala Agricultural University, 1992) Suresh Babu, K V; Mohankumar, B; Thomas Mathew
Functional dynamics of an agrisilvicultural system involving coconut palms, multipurpose trees and kacholam
(Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 1997) Sureshkumar, S; Mohankumar, B
Productivity of ailanthus (Ailanthus triphysa) under different fertilizer regimes and population densities N
(Department of Sivilculture and Agroforestry, College of Forestry, Vellanikkara, 2001) Naveed Shujauddin; Mohankumar, B
Regeneration status of some important moist deciduous forest trees in the Trichur forest division
(College of Forestry, Vellanikkara, 1988) Narayanan Illath Valappil; Mohankumar, B
Sustained management of forests depends on their ability to regenerate. The pace at which the older trees are replaced by younger ones, is very important in this respect. The details of sylvigenesis is little known, especially of the moist deciduous forests. To get a general idea of the regeneration behaviour of the moist deciduous forests eight localities of varying levels of disturbance were sampled in the Trichur Forest Division. Enumeration of trees and their regeneration were done and data were analysed at three levels of organization, viz. ecosystem level, stratum level and species level. Physiognomically the moist deciduous forests comprise three vertical strata namely, upper, middle and the lower. The middle stratum is richest in species. Most of the species represented in the upper stratum are commercially important. Five species, Dillenia pentagyna, Grewia tiliifolia, Lagerstroemia microcarpa, Terminalia paniculata and xylia xylocarpa, occupying the upper stratum, possess higher values of basal area, relative basal area, density per hectare, relative density and importance value index, and are the dominant ones. The average growing stock of desirable commercially important species > = 20 cm DBH per hectare is 149.79. This is slightly lower than the average of 167 trees/ha cited by Seth and Kaul. The growing stock of trees > = 1 cm DBH, of the middle and lower strata decrease exponentially with increasing cover gaps. The upper stratum on the other hand is not much affected by disturbance. In fact, with slight disturbance it increases a little. Relative importance value index of the middle stratum increases where that of the lower straum decreases and vice versa. Frequency distribution statistic for stands and strata conform to the negatively exponential model. Mortality rates are maximum in the lower size classes. Comparison of observed frequencies of unestablished seedlings to the expected frequencies of the commercially important stratum indicates that the reproductive potential of stands is not poor. On the other hand, the growing stock of established seedlings (saplings + poles) is very low. Owing to very low survival probability in the sapling stage acute paucity of poles of the upper stratum is observed. The five dominant species show the same pattern of population structure and distribution of survival probability as the stratum. Regeneration of important species in the moist deciduous forests is under various stresses of which that of human origin is the most hazardous. Grazing, browsing, fire, and illicit cutting are the greatest constraints. Some species like Lagerstroemia microcarpa also show some intrinsic constraints.
Root distribution pattern of bamboo (Bambusa arundinacea (Retz.) Roxb. Gamble) and associated competitive effects
(Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 1999) Divakara, B N; Mohankumar, B
Stand density manipulation and fertilization studies on teak
(College of Forestry,Vellanikkara, 1991) Gawande, S R; Mohankumar, B
With the object of standardizing the density manipulation and fertilization strategies for teak, a study was carried out at Vellanikkara during 1990-91. The experimental variables consisted of high, medium and low site quality classes (classified on basis of tree heights), three thinning intensities (control, 30 per cent density reduction and 50 per cent density reduction) and three fertilizer levels (control, 50:25:25 kg of N, P2 O5 and K2O ha -1 yr-1, 100: 50:50 kg of N, P2 O5 and K2O ha-1 yr-1). The results indicate that mean height of trees was strongly influenced by density manipulation. The combination of high site quality with medium and heavy fertilizer doses also significantly increased the mean height of trees. However quadratic mean diameter, stand basal area, basal area increment and height increment were not substantially different among the thinning site quality and fertilization regimes. Tree biomass, foliage area and leaf weight allometry were examined for the first time in teak. The results suggest that leaf area and the biomass yield are strongly dependent on the allometry of trees. High sites consistently recorded higher values for estimates of leaf area, leaf biomass and tree biomass. Combinations of high site quality with medium and heavy thinning as well as medium and heavy fertilization recorded high tree biomass yield, foliage area and leaf area followed by medium and low site quality classes. Foliar analyses showed a general increase in leaf nitrogen during summer (May) and a gradual decline of the same during the fall season (August). High site quality with medium and heavy fertilization recorded highest nitrogen content. Thinning on higher sites significantly increased foliage phosphorus and potassium levels. In general the trend concerning nutrient contents of different tree organs followed the order leaves> stemwood> branchwood. Branch wood and stem wood N levels were relatively higher on high sites. Potassium content was, however, greatest in the low sites. Soil nutrient analysis did not indicate any substantial changes in the soil physico-chemical properties consequent to thinning and fertilization which incidentally substantiates Miller’s hypothesis on forest fertilization that fertilizers benefits only the trees and not the sites.
Stand density regulation in even aged teak plantations
(Faculty of Agriculture, College of Forestry, Vellanikkara, 1990) Prasoon Kumar; Mohankumar, B
A teak density management diagram was constructed using the stand inventory data on teak collected from Parambikulam, Thrissur and Chalakudy areas. Density management diagram is a graphical representation of the stand growth through time, in terms of density and quadratic diameter, volume, height and Reineke’s stand density index. A size –density based index such as Reineke’s stand density index incidentally provides a good biological basis for the translation of management objective into levels of growing stock. Stand density index (SDI) incidentally is also independent of site quality and age. The data – set also revealed that Parambikulam is a better site for teak followed by Thrissur and Chalakudy. The maximum SDI for teak was found to be 600 which probably covers all possible combinations of size and density included in the data – set. The use of diagram for designing two alternate density management regimes for a hypothetical stand is illustrated. Designing a density management regime requires the translation of management objectives into appropriate levels of growing stock. Maximization of volume production and maximization of individual tree growth are the two alternate but contrasting silvicultural strategies in this context. For maximization of volume per unit area the level of the growing stock should fall in the zone 11 of the Langsaeter’s curve. On the other hand, if the land management objective is to maximize individual tree growth, then trees should not experience much competition (preferably in zone 1 of the Langsaeter’s curve). So, in the former case the levels of growing stock will be naturally higher than that of latter. After fixing the appropriate upper and lower levels of size – density relations the stand is allowed to grow till it reaches upper limit and then thinned down to the lower limit. This process is repeated as many times as necessary. The diagram has diverse utility from designing alternate density management regimes to comparing the results of optimization analyses. However, it suffers from some shortcomings such as lack of memory, prediction of same rotation age irrespective to the path taken by stand, rotation ending before culmination of periodic annual increment, the assumption of single maximum size – density relationship and slight bias of the model with respect to the independent variables outside the range of the data base. However, with more work many of these defects could be over come.