An Investigation on Spatial Variability of Selected Soil Parameters of Landscape under Mahogany in Wet Zone of Sri Lanka

Abstract

Soils show a wide variability in their macro and micronutrient contents and distribution. Thespatial distribution of soil nutrients and physical parameters can be largely attributed tophysical, chemical, and biological processes that undergo in different rates and differentintensities in different localities. The availability of nutrients and the degree of interactionbetween these nutrients and the soil ultimately influence the vegetation that grows on aparticular soil. Although past literature has investigated the spatial variability of soilparameters and correlation of soil parameters with various agricultural crops, few studieshave examined such relationships in forest plantation landscapes. GIS has emerged as avaluable tool in visualizing and understanding spatial variability of soil parameters. Such soilparameter maps of large landscapes improve our understanding of the nature and extent ofnutrient problems, as well as aid in exploring their possible relationships with various sitefactors such as slope, physical features, moisture and temperature etc.

The present study examined the spatial dependency of selected soil organic matters andnutrients on a 34-acre 8-year old mixed Mahogany stand in Wet Zone of Sri Lanka. Soilparameters of pH, Total Organic Carbon, Total Nitrogen, Ammonium Chloride extractable K,Ammonium Chloride extractable Mg, Ammonium Chloride extractable Ca was analysedusing soil samples collected following a systematic grid point sampling method (50m x 50mgrid).Accordingly, data from 44 soil sampling points were analysed using geostatistics andGIS techniques. Spatial distribution maps of above soil parameters were prepared in ArcMap9.3 environment. The relationships of above soil parameters with various site specificattributes such as elevation, soil texture, proximity to drainage systems/streams werestatistically examined.Results revealed that soil parameters tested show spatial heterogeneityalong the landscape while showing correlations with selected site attributes. Implications ofthe findings in management of Mahogany forest crop are also discussed.