||Site index for common tree species in North Carolina. Site index is (a) A relative measure of forest site quality based on the height (in feet) of the dominant trees at a specific age (usually 25 or 50 years, depending on rotation length). Site index information helps estimate future returns and land productivity for timber and wildlife. (b) Height of a tree at a specified index or base age. Used as an indicator of site quality.Dataset was created using data from NRCS National Soil Survey. Data is based on "soil map units," which NRCS defines as a set of geographic areas for which a common management strategy is suitable. The range in size of a soil map unit varies depending on the level of detail at which the survey was conducted. In a typical survey area, which is mapped at an approximate scale of 1:24000, map units can range from approximately two acres to thousands of acres in size. A map unit is the smallest delineation that appears on a soil map.A map unit is typically composed of one or more “map unit components”. A map unit component is either some kind of soil, or some kind of non-soil entity like “rock outcrop”. For each component of a map unit, a percent composition is recorded. Although map units contain components, those components are not delineated within the map unit. The majority of attributes (such as forest site index) are attributes of a map unit component, and a map unit may be composed of more than one component. We have to somehow come up with a single value to represent a map unit as a whole, from multiple component values. The process of reducing multiple component values to a single value to represent the corresponding map unit is what we refer to as “aggregation”.This dataset uses the aggregation method "Dominant Component," which returns the attribute value associated with the component with the highest percent composition in the map unit. If more than one component shares the highest percent composition, the corresponding "tie-break" rule determines which value should be returned. The "tie-break" rule indicates whether the lower or higher attribute value should be returned in the case of a percent composition tie. This dataset uses the higher attribute value.This dataset uses the most recent soil surveys available as of August 2012.