Abstract
<p> </p><p><strong> </strong></p><p> </p><p><strong>Background. </strong>Carbon lost in form of carbon dioxide contributes to climate change corresponding to altered soil chemical properties and plant growth. Land-uses that minimize carbon loses are highly encouraged. Unfortunately, in the Kakamega-Nandi Forest Complex, the Kenyan government continues to promote shamba systems (now Plantation Establishment for Livelihood Improvement Scheme) where the forest adjacent communities are allocated bush land plots to provide land for small-scale agriculture, cash crop farming and planting of tree seedlings for a specified period of time inside the forest. <strong>Objective. </strong>This study analyzed six land-uses and their effect on the dynamics of soil chemical parameters using landsat images and recent soil geochemical surveys. <strong>Methodology. </strong>Land cover and vegetation changes were determined using a series of multispectral Landsat images. A total of seven sets of image datasets were downloaded from the Glovis web portal (<a href="http://glovis.usgs.gov/">http://glovis.usgs.gov/</a>) for the years 1985 to 2015 with the cloud cover ranging from 1 to 10% taken in the dry season. The land-use/cover classification scheme adopted was based on expertise knowledge and literature of land-use/cover activities. <strong>Results. </strong>The results show that (i) small-small agriculture has increased while bush-land has decreased between 1985 and 2015; (ii) smallholder farming of maize, pasture and sugarcane depleted soil organic carbon whereas perennial tree plantations (regenerated forests) increased soil carbon stocks; (iii) nitrogen decreased in all tested land-uses except in maize plantations; (iv) phosphorus remained unchanged in all land-uses, potassium significantly decreased in tea plantations while sugarcane and regenerated forests land-uses had decreased soil calcium stocks. <strong>Implications. </strong>The study provides evidence for the review of the shamba system. <strong>Conclusion. </strong>The study has shown that land-use changes through the application of the shamba system alter the dynamics of soil chemical parameters key among them are soil organic carbon, nitrogen and calcium. Cultivation of annual crops decreases soil carbon stocks which may lead to an influx of carbon dioxide in the atmosphere and increased vulnerability to climate change.</p>
Highlights
An estimated 1.6±0.8 petagrams (Pg) of soil organic carbon (SOC) is lost per year in the tropics through cultivation and conversion of land-uses (Smith, 2008)
Carbon lost as carbon dioxide (CO2) contributes to climate change corresponding to altered soil chemical properties and plant growth
The central hypothesis is that cultivation of annual crops in shamba system depletes soil nutrients leading to massive influx of carbon dioxide in the atmosphere which contribute to climate change
Summary
An estimated 1.6±0.8 petagrams (Pg) of soil organic carbon (SOC) is lost per year in the tropics through cultivation and conversion of land-uses (Smith, 2008). The participants of the system, popularly known as shamba system or PELIS (Plantation Establishment for Livelihood Improvement Scheme), are serving and retired forest workers, landless peasant farmers and those living within the immediate vicinity of the forests (Oduol, 1986). These “farmers” are contracted to work for 9 months each year to clear indigenous bush land to prepare the land (shamba) for cultivation of perennial trees and subsistence crops such as maize, potatoes and cabbages. The central hypothesis is that cultivation of annual crops in shamba system depletes soil nutrients leading to massive influx of carbon dioxide in the atmosphere which contribute to climate change
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