GEOSTATISTICAL ANALYSIS OF SOIL PROPERTIES IN A SECONDARY TROPICAL DRY FOREST, ST-LUCIA, WEST-INDIES

Spatial variability of soil properties directly influences forest grow th. However, spatial variation in soil properties has not been studied within tropical dry forests. As such, it is unclear whether soil prop erties, like moisture and N availability, display spatial variation at scales similar to that of other ecosystems. To gain insight into this variation, we established a 56 x 56 m sampling grid in tropical dry f orest on the Caribbean island of St. Lucia. Samples collected at 4-m i ntervals were analyzed for forest floor mass, soil texture, pH, organi c C, net N mineralization, net nitrification and available P. Geostati stical procedures were used to determine spatial autocorrelation of th e aforementioned properties and processes. Semivariogram parameters we re used in a block kriging procedure to produce spatial maps of soil p roperties. At the scale of our study, most soil properties exhibited s patial autocorrelation at distances of 24 m or less. Varying degrees o f similarity were found between patterns of forest floor mass, organic C, net N mineralization, net nitrification and available P. No simila rity was found between soil texture or pH and other properties. Fine-s cale spatial patterns of net N mineralization and net nitrification ar e likely driven by overstory litter inputs, rather than variation in s oil texture and water availability.