Related literatures

Saha, S., Nair, P.K.R., Nair, V., Kumar, B.M., 2009. Soil carbon stock in relation to plant diversity of homegardens in Kerala, India. Agroforestry Systems 76, 53-65.

Abstract

Conservation of biodiversity and mitigation of global warming are two major environmental challenges today. In this context, the relationship between biodiversity (especially plant diversity) and soil carbon (C) sequestration (as a means of mitigating global warming) has become a subject of considerable scientific interest. This relationship was tested for homegardens (HG), a popular and sustainable agroforestry system in the tropics, in Thrissur district, Kerala, India. The major objectives were to examine how tree density and plant-stand characteristics of homegardens affect soil C sequestration. Soil samples were collected at four depths (0–20, 20–50, 50–80, 80–100 cm) from HG of varying sizes and age classes, and their total C content determined. Tree density and plant-stand characteristics such as species richness (Margalef Index) and diversity (Shannon Index) of the HG were also determined. Results indicated that the soil C stock was directly related to plant diversity of HG. Homegardens with higher, compared to those with lower, number of plant species, as well as higher species richness and tree density had higher soil carbon, especially in the top 50 cm of soil. Overall, within 1 m profile, soil C content ranged from 101.5 to 127.4 Mg ha⁻¹. Smaller-sized HG (<0.4 ha) that had higher tree density and plant-species density had more soil C per unit area (119.3 Mg ha⁻¹) of land than larger-sized ones (>0.4 ha) (108.2 Mg ha⁻¹). Soil C content, especially below 50 cm, was higher in older gardens. The enhanced soil-C storage in species-rich homegardens could have relevance and applications in broader ecological contexts.

Kumar, B.M., Nair, P.K.R., 2004. The enigma of tropical homegardens. Agroforestry Systems 61-62, 135-152.

Abstract

Tropical homegardens, one of the oldest forms of managed land-use systems, are considered to be an epitome of sustainability. Although these multispecies production systems have fascinated many and provided sustenance to millions, they have received relatively little scientific attention. The objective of this review is to summarize the current state of knowledge on homegardens with a view to using it as a basis for improving the homegardens as well as similar agroforestry systems. Description and inventory of local systems dominated the ‘research’ efforts on homegardens during the past 25 or more years. The main attributes that have been identified as contributing to the sustainability of these systems are biophysical advantages such as efficient nutrient cycling offered by multispecies composition, conservation of bio-cultural diversity, product diversification as well as nonmarket values of products and services, and social and cultural values including the opportunity for gender equality in managing the systems. With increasing emphasis on industrial models of agricultural development, fragmentation of land holdings due to demographic pressures, and, to some extent, the neglect – or, lack of appreciation – of traditional values, questions have been raised about the future of homegardens, but such concerns seem to be unfounded. Quite to the contrary, it is increasingly being recognized that understanding the scientific principles of these multispecies systems will have much to offer in the development of sustainable agroecosystems. Research on economic valuation of the tangible as well as intangible products and services, principles and mechanisms of resource sharing in mixed plant communities, and realistic valuation and appreciation of hitherto unrecognised benefits such as carbon sequestration will provide a sound basis for formulating appropriate policies for better realization and exploitation of the benefits of homegardens.



Kumar, B.M., 2011. Species richness and aboveground carbon stocks in the homegardens of central Kerala, India. Agriculture, Ecosystems & Environment 140, 430-440.
  
Abstract

Tropical homegardens with high agrobiodiversity have high potential for carbon (C) sequestration, especially under changing environments. Floristic diversity, richness, and aboveground C stocks and how size of homegardens influence agrobiodiversity and C sequestration potential were assessed in the Kerala homegardens. A total of 839 homegardens in 28 panchayaths (lowest unit of local self-government) of Thrissur, Palakkad, and Malappuram districts were surveyed through a stratified random process. Information was gathered on holding size, floristic composition, plant height, and girth at breast height (GBH) of all trees and shrubs (>20 cm GBH). Aboveground C stocks of trees were computed using allometric relationships, assuming C as 50% of biomass. The homegardens were also classified into small (<0.4 ha), medium (0.4–1.2 ha), and large (>1.2 ha). In total, 473 species were recorded, of which 208 were trees (>20 cm GBH), 86 shrubs, and 179 herbs. Simpson's floristic diversity index (0.64, 0.41, and 0.46 for a subset of small, medium, and large homegardens, respectively), species richness, and tree density (per hectare) were highest for small-sized holdings. Large-sized homegardens, however, had more stems per garden. Average aboveground standing stocks of C ranged from 16 to 36 Mg ha⁻¹, with small homegardens having higher C stocks on unit area basis than large- and medium-sized ones. Implicit in this is the potential for C sequestration and agrobiodiversity conservation, especially by small homegardens.



Kumar, B.M., Nair, P.K.R., Saha, S., Stein, T., Andreu, M., 2011. The Socioeconomic Context of Carbon Sequestration in Agroforestry: A Case Study from Homegardens of Kerala, India. In: Kumar, B.M., Nair, P.K.R. (Eds.), Carbon Sequestration Potential of Agroforestry Systems. Springer Netherlands, pp. 281-298.
  
Abstract

While the biological and ecological role of agroforestry (AF) on climate change mitigation has received considerable research attention lately, the role of socio-psychological factors in this context has been left largely unexplored. Socio-psychological variables such as culture, demography, economy, and social values play important roles in farmers’ decision making with the land management, which in turn influence the ability of AF systems to sequester carbon (C). This chapter presents a case study from Thrissur, Kerala, India, which examined how different socio-psychological factors influence soil C sequestration through land management decisions in tropical homegardens (HGs), a popular agroforestry system in the tropics. This study used the Theory of Planned Behavior (TPB) as the theoretical framework to understand homegarden owners’ perceptions on the adoption of five land management practices (i.e., tillage, tree planting, plant residue incorporation, manure usage, and fertilizer applications), which are known to impact C sequestration. Data collected using focus group and household interviews were analyzed by regression statistics. Results indicated that farmers’ decision making processes were most influenced by factors such as ancestors and education, followed by peers, financial condition, and economic importance of the AF land holding. The results of this case study will not only benefit researchers and extension practitioners, but can also contribute to the policy platform to recognize the role of socio-psychological factors in agricultural decision making.

P. Saikia, B.I. Choudhury and M.L. Khan (2012) Floristic composition and plant utilization pattern in homegardens of Upper Assam, India. Tropical Ecology 53(1): 105-118

Abstract

Homegardens of Upper Assam, northeastern India are diverse and species-rich. We conducted vegetation survey of 80 homegardens in 17 villages of Golaghat and Jorhat districts of Upper Assam. Structure, diversity and plant uses were analyzed. Altogether, 294 plant species representing 217 genera and 92 families were encountered. Of these, 260 species were economically important and were categorized into seven use categories. The remaining 34 species were weeds and grasses. Aquilaria malaccensis Lam., an endangered and red listed species of India, was the most dominant tree (1,414 trees ha-1). This species contributes significantly to the economy of the region. Principal Component Analysis (PCA) using frequency data showed two groups for each of the tree, shrub and herb layers. The high floristic diversity and presence of many rare/endangered species in the homegardens reflect the ways how owners utilize and conserve plant diversity. However, genetic diversity of such rare species of forest origin could be affected in managed ecosystems due to limited gene flow, inbreeding and selection pressure. Therefore, studies on genetic diversity of rare/endangered species in homegardens are required so that potential of homegardens for their conservation can be assessed.



Saha, S., Ramachandran Nair, P.K., Nair, V., Mohan Kumar, B., 2010. Carbon storage in relation to soil size-fractions under tropical tree-based land-use systems. Plant Soil 328, 433-446.

Abstract

The extent of carbon (C) sequestration in soils under agroforestry systems in relation to soil types (fraction sizes) and vegetation structure remains largely unexplored. This study examined soil C storage, an indicator of C sequestration potential, in homegardens (HGs), natural forest, and single-species stands of coconut (Cocos nucifera), rice (Oryza sativa)-paddy, and rubber (Hevea brasiliensis), in Thrissur district, Kerala, India. Soil samples collected from four depth zones up to 1 m were fractionated to three size classes (250 – 2000 µm, 53 – 250 µm,  < 53 µm) and their total C content determined. Total C stock (Mg ha⁻¹) was highest in forests (176.6), followed by managed tree-based systems, and lowest in rice-paddy field (55.6). The results show storage of higher amounts of C in the  < 53 µm fraction, the most stable form of C in soil, up to one- meter depth, in land-use systems with high stand density of trees such as forests and small-sized HG. Although the results do not allow comparison of changes in soil C stock in different land-use systems, they show higher C storage in soils under tree-based land-use systems compared with the treeless (rice-paddy) system, especially in lower soil depths, suggesting the higher soil C sequestration potential of tree-based systems, and thereby their role in reducing atmospheric concentration of carbon dioxide.