Validating landtype associations using forest inventory and analysis data and neutral landscape models

Abstract

One of the principal uses of land type associations (LTAs) is to provide information on ecological patterns and potentials useful for identifying alternatives and setting vegetation management objectives at landscape and watershed scales. Since LTA identification and delineation is an iterative process involving subjective decisions, it is imperative that LTAs accurately capture measurable distinctions in vegetation. In this study, we provided a framework for validating LTAs in Missouri's. We chose a suite of variables from the Forest Inventory and Analysis database of the US Forest Service, an independent source, to capture a wide range of characteristics of the forest ecosystem. These variables included forest type, species composition, species diversity, species richness, site index, density of all trees 1 inch dbh and greater, and density of all trees 5 inch dbh and greater. First, the appropriateness of grouping LTAs into broader LTA types (identifications) was examined, and results suggest that species composition is more similar within LTA Type than among LTA Types. Second, a neutral model approach was used to evaluate the variables used in the study, and it was shown that forest type and the two density measures validated LTA adjacencies no more often than randomly delineated LTAs. Therefore, these three variables were removed from the analysis. Finally, comparisons of adjacent LTAs using statistical analysis of remaining variables resulted in the validation of 480 of the 623 compared adjacencies, showing a significant difference in at least one variable. Results of this study provide a quantitative measure of Missouri LTAs and reveal LTAs that have less distinction and need further refinements.