TEXTURE ANALYSIS OF SURFACE SOILS IN THE LUQUILLO MOUNTAINS OF NORTHEASTERN PUERTO RICO

Parent rock and the biogeochemical processes associated with decomposition of parent material are important factors influencing soil texture. Soil texture strongly influences soil water holding capacity, carbon and nutrient holding capacity and the vegetation that can be established on the soils.

This study sampled and analyzed texture for soils at a depth of 20-50 cm across the Luquillo Experimental Forest (LEF) in NE Puerto Rico in a balanced design that were sampled by forest type (tabonuco, Colorado, palm), parent rock (volcaniclastic oxisols, quartz diorite inceptisols), and three topographic positions. Samples were analyzed using a density fractionation method and sieve analysis to determine the percentage of sand, silt and clay in each of these samples. A total of 24 sites (72 samples) were analyzed.

Results indicate that oxisols have on average 40-50% silt and 30-40% clay, while inceptisols contained an average of 60-80% sand. A comparison of the topography showed that valleys contained more sand than their ridge and slope counterparts, but much less clay and silt.

These patterns and associated statistical models are then used to create predictive models and maps.