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SCSB# 395

Chapter Contents

• Introduction
• Map
• Areal Extent of MLRAs Included

Introduction
The United States has been divided by the NRCS (1983) into categories of major land resource regions and major land resource areas (MLRA). MLRAs are geographically associated land resource units and have been used in state, regional and national agricultural planning and in natural resource assessment. A major land resource region combines those MLRAs that can be grouped regionally. MLRAs are useful as a basis for making decisions about national and regional agricultural concerns, identification of research needs and resource inventories, a broad base for extrapolating the results of research within national boundaries, and serve as a framework for organizing and operating resource conservation programs (NRCS 1981).

The map of the MLRAs for the southern region of the United States was developed from the patched version of the STATSGO digital database of the United States. The STATSGO database was designed primarily for regional, multi-state, watershed, state and multi-county resource planning, management, and monitoring. The digital file containing the MLRAs was reclassed based on the individual MLRAs selected in this work. A mask of each MLRA was developed to partition each MLRA from other areas. The areal extent of each MLRAs in the southern region was approximated by developing a report with the respective mask using the GIS software GRASS.

Locations of the major land resource regions and MLRAs for the southern region of the United States are shown in Fig. 1. Seven major land resource regions were identified in the southern region of the United States. The areal extent of the 20 MLRAs in which data are reported in this bulletin and the states in the southern region in which they occur are presented in Table 1. The three most extensive MLRAs are 133A, 136 and 133B. The Southern Coastal Plains (MLRA 133A) occupies about 275,000 km² and occurs in eight states in the region. The Southern Piedmont (MLRA 136) is the second most extensive MLRA and occupies about 167,000 km² in the five states adjacent to MLRA 133A. The third largest MLRA is the Western Coastal Plains (MLRA 133B) which occupies about 137,000 km² and occurs in four states in the western portion of the region. The list also includes five MLRAs that occupy less than 25,000 km². These relatively small MLRAs include the Nashville Basin in Tennessee, the Blackland Prairies in Alabama, Mississippi, and Arkansas, the Sand Hills in North Carolina and South Carolina, the Sand Mountains in Alabama and Georgia, and the Texas Claypan area in Texas. Collectively, the MLRAs chosen in this work occupy almost 1.45 million km² and about 65.8% of the land area in the southern region of the United States.