Modeling and Mapping Forest Vegetation Using Soil and Site Variables.

Forest species composition and regeneration dynamics are closely linked to soil and site characteristics related to water and nutrient supply. This is particularly true for many species of oaks (Quercus spp.). Oak regeneration has remained a widespread and persistent problem and research has shown that successful oak regeneration requires an abundance of oak advance reproduction—the seedlings and seedling sprouts in the understory prior to a canopy release. Although it has long been recognized that oak advance reproduction abundance is inversely related to site quality, there has been little effort to model oak advance reproduction abundance as a function of measured levels of light, water, or nutrient supply. Here data from the Sinkin Experimental Forest in southeastern Missouri were used to develop and test models for estimating the abundance of oak advance reproduction as a function soil and site characteristics. Site variables included soil available water holding capacity, pH, photosynthetically active radiation in the understory, forest stocking, terrain shape, and slope-aspect. Oak advance reproduction abundance was successfully predicted with soil pH, available water holding capacity, and slope-aspect. Models for the red oak group species generally exhibited better fit than those for the white oaks. Estimates of soil pH and water holding capacity obtained from the SSURGO database also could be used in these oak advance reproduction models to generate oak advance reproduction density maps. These maps can be used as a planning tool for identifying where oak advance reproduction is lacking and, consequently, where silvicultural interventions are needed to increase the abundance and size of oak advance reproduction.