SAMPLING STRATEGIES IN FOREST SOILS

Many studies have revealed the high variability of soil properties, es pecially on the forest floor. Sampling techniques have been developed to reduce this variability so as to obtain more precise mean values. L ittle attention has been paid to the frequency distributions of variab les, even though they could provide information on factors that contro l variability. This paper addresses the selection of the sampling stra tegy considering the type of study. For the characterization of ecosys tems, stratified sampling or systematic sampling is proposed, dependin g on previous knowledge of the study area. To study processes, two cas es were considered: processes that occur within the ecosystem, such as organic matter decomposition, and processes that concern the whole ec osystem, such as fire. In the first case subjective sampling was usefu l, since it reduced the extrinsic variability of the processes. In the second case, both stratified and systematic sampling were very effect ive. Frequency distribution analysis was proposed as a tool to detect some factors that control litter accumulation.