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Theses

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2015 - 20174
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Subject: Agroforestry × Author: KAU × End date: 2017 × Start date: 2015 ×
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    ThesisItemOpen Access
    Diversity, structure and standing stock of timber in the homegardens of Thrissur district, Kerala
    (Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2017) Subu, R Unnithan; KAU; Kunhamu, T K
    Tropical homegardens are time-tested land use systems which have evolved through generations of crop intensification. Homegardens of Kerala are traditional agricultural systems that were closely related to the livelihood and nutritional security of small and marginal farmers of Kerala. A study was carried out to investigate the functional and structural status of the homegardens in Thrissur District, Kerala. Study was conducted in selected homegardens of 10 panchayths and one peri urban area of Thrissur district. The study was based on comparison of homegardens of three size classes such as small (<0.2 ha), medium (0.2-0.4 ha) and large (>0.4 ha) from three eco regions (highland, midland and coastal land) and one peri urban area (municipality). A total of 330 homesteads were selected from selected panchayths based on a stratified random sampling. There was a great variability in diversity, abundance and standing stock of different tree species belongs to different use categories among three homegarden size classes and across different eco regions. There were 163 total species present in the entire Thrissur district that included 122 trees species and 41 agricultural crop species. Contrary to earlier studies, consistent decline in diversity was observed with decrease in homegarden size. Highest number of taxa was observed from large homegardens (102 species) which was followed by medium (95 species) and small (85 species). Population pressure and skewed land availability may have negatively affected the species diversity in homegardens. Most abundant functional group of trees found in surveyed homegardens were medicinal trees (62 species) followed by timber species (53 species). Economically important functional groups such as timber, fodder, fuel, green manure and other MPTs were abundant in large homesteads. Eco-region wise comparison of tree diversity suggested high diversity in the midland and highland regions while lower in coastal land and peri-urban areas. Mangifera indica was the predominant timber tree species in terms of abundance and standing stock in Thrissur district with a total stand number and standing stock projected to the Thrissur district as 15,98,849 and 18,84,356.3 m3 respectively. Other dominant timber trees in terms of standing stock were Artocarpus heterophyllus, Tectona grandis, Swietenia macrophylla, etc. Standing stock per hectare of total timber species identified in Thrissur district was 55.12 m3 ha-1 and projected standing stock of all timber species in the district was 81,38,931.6 m3. Vertical diversity of the studied homegardens suggested high species richness associated with middle storey. Also all three strata of large homegardens were more diverse than medium and small homegardens irrespective of eco-region. In total there were 41 species of agricultural crops and medicinal plants identified from selected homegardens. Musa sps., Areca catechu and Cocos nucifera were the predominant species of all size holds. Simpson Index and Shannon Diversity Indices of agricultural crops of all size holds showed no large difference. Attempts to study the socio-economic factors of homegarden functioning revealed land fragmentation as the principal agent of their decline. The most frequent constraints of homegardens included high wage of the labourers involved in homegarden maintenance, less labour availability, large expense/less profit, pest and disease, etc. Wood quality assessment of Tectona grandis, Artocarpus heterophyllus and Swietenia macrophylla using NDT showed that oven dry specific gravity (SPGo.d) has no influence on eco-regions and tree size classes. The dynamic modulus of elasticity (MOEdyn) showed significant differences for Artocarpus heterophyllus and Swietenia macrophylla across eco-regions. However, this was not prominent for Tectona grandis. On the whole, the functional and structural analysis of the homegardens in Thrissur district of Kerala revealed their potential contribution to the agro-biodiversity. However concerted efforts are required to revitalize these unique traditional agricultural practices in terms of their ecological and economic viability.
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    ThesisItemOpen Access
    Fine root dynamics and associated carbon and nutrient flux in 12 year old acacia mangium at varying stand densities
    (Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2017) Delphy Rocha; KAU; Kunhamu, T K
    Fine root production has been estimated to account for up to 33% of global annual Net Primary Production, NPP (Gill and Jackson, 2000). Thus, fine root turnover has important implications for individual plant growth, plant interactions, and below-ground carbon and nutrient cycling. Direct and indirect methods for measuring fine root production and turnover in 12 year old Acacia mangium Willd. at varying stand densities were studied. Fine root production estimated ranged from 3.8 - 5.75 Mg ha-1 with a turnover of 4 yr-1. It was estimated that through fine root decomposition about 1.36-2.39 Mg C ha-1, 34.56- 102.52 kg N ha-1, 1.46-3.3 kg P ha-1 and 19.94-33.60 kg K ha-1 is released to soil. Even though fine root constitutes only 1.7-2.14% of the total tree biomass its contribution to the system productivity is very high. Attempts were also made to relate fine root production with various growth variables and in general most of the variables (DBH, basal area per tree, volume per tree, aboveground biomass per tree and leaf area per tree) gave good correlation (R>8**) with fine root production when considered on per tree basis. Average annual litter production was estimated to a range of 9.99-11.69 Mg ha-1. Interestingly, annual litter production had a high correlation (R=0.9**) with fine root production. Through litter decomposition, 1.4-2.07 Mg C ha-1, 36-48 kg N ha-1, 1- 4 kg P ha-1 and 3-6 kg K ha-1 is released to the soil. Total soil carbon stock up to 1m soil depth was estimated and it was significantly different across different density regimes. Invariably the SOC concentration was relatively lower in treeless plot compared with A. mangium at different density regimes. Soil C sequestration was 15.96 - 34.58 Mg C ha-1 and the nutrient content of soil estimated as 2343.811-948 kg N ha-1, 13.12-21.92 kg P ha-1, 313.52-261.25 kg K ha-1. Total system C content estimates in the ranges from 148.93 -263.79 Mgha-1. So Density manipulation plays a significant role on productivity in 12 year old A. mangium. Hence, management objectives should be based on assessment of their impact on various productivity attributes
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    ThesisItemOpen Access
    Performance of selected medicinal herbs under typical homegarden and pure coconut plantation
    (Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2015) Niyas, P; KAU; Kunhamu, T K
    A field research was undertaken at Vellanikkara, Kerala to assess the understorey productivity of coconut and homegarden through intercropping with three selected herbaceous medicinal crops viz. Zingiber officinale (ginger), Curcuma longa L. (turmeric) and Kaempferia galangal L. (galangal). These landuse systems by virtue of spatial and temporal advantages offer good scope for integrating shade tolerant crops and thereby offer supplementary returns to the farmer. The biochemical changes in the understorey crops and the biophysical attributes influencing the productivity of the land management systems were studied. Additionally soil carbon sequestration in both the given land use systems and a treeless open plot was estimated. The intercrop growth considerably varied among the land use systems both in vegetative growth and rhizome yields. Growth observations at various sampling period revealed considerably higher plant heights of ginger and turmeric in shaded condition than treeless open. As regards leaf spread galangal performed well in the coconut garden followed by homegarden and treeless open. All the intercrops exhibited higher root length in treeless open plots, except galangal for which coconut was the best. Invariably root production was lowest in homegarden. Tiller production at final stages showed highest in treeless open. Contrary to the plant height growth trends, homegarden recorded lowest tiller production at final stages of sampling. Understorey productivity for ginger in terms of rhizome yield at final harvest followed the order treeless open (3.45 Mg ha-1), coconut (2.86 Mg ha-1), and homegarden (1.49 Mg ha-1). Turmeric rhizome production showed considerable variation with intercropping system with highest yield from open area (7.01 Mg ha-1) and the lowest from homegarden (1.77 Mg ha-1). Highest Galangal yields were reported in the treeless open (3.05) while homegarden represented lowest production (2.04 Mg ha-1). Understorey photosynthetically active radiation (PAR) transmittance presumed to have a cardinal influence on intercrop growth which was highest for coconut (37%) and lowest under homegarden (17%). Turmeric and galangal showed strong positive correlation with understorey PAR. Regression equation relating PAR with rhizome yields showed statistical soundness with high value of coefficient of determination (r2). Leaf Area Index varied between the homegarden and coconut considerably with higher value for homegarden (3.84) while the same for pure coconut plantation was considerably low (2.21). The oleoresin concentration in all the intercrops was found to be greatest in homegarden followed by coconut and treeless open. Soil physico-chemical attributes were assessed at periodic intervals in all the landuse system and results indicate overall better condition prevailed in the homegarden in terms of organic carbon content, soil bulk density, total N, available P and exchangeable K which however registered lowest values in the treeless open. Similar was the trend in soil carbon sequestration with homegarden giving higher values (67.45 Mg ha-1) followed by coconut (59.65 Mg ha-1) lowest by treeless open soil (55.1 Mg ha-1). Result converges to the generalisation that despite better soil physico-chemical attributes, understory productivity in the homegarden is by and large decided by the PAR availability. Hence there is need to develop stand structure that optimize the productivity in homegarden through judicious stand density regulation and tree management practices.
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    ThesisItemOpen Access
    Diversity, structure and standing stock of timber in the homegardens of Thrissur district, Kerala
    (Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2017) Subu, R Unnithan; KAU; Kunhamu, T K