­­Estimating Forest Management Units from Road Network Maps in the Southeastern U.S.

Abstract:

The most important factor affecting forest structure and function is the type of management undertaken in forest stands. Owners manage forests using appropriately sized areas to meet management objectives, which include economic return, sustainability, recreation, or esthetic enjoyment. Thus, the socio-environmental unit of study for forests should be the management unit. To study the ecological effects of different kinds of management activities, we must identify individual management units. Road networks, which provide access for human activities, are widely used in managing forests in the southeastern U.S. Coastal Plain and Piedmont (SEUS). Our research question in this study is: How can we identify individual forest management units in an entire region? To answer it, we hypothesize that the road network defines management units on the landscape.

Road-caused canopy openings are not always captured by satellite sensors, so it is difficult to delineate ecologically relevant patches based only on remote sensing data. We used a reliable, accurate and freely available road network data, OpenStreetMap (OSM), and the National Land Cover Database (NLCD) to delineate management units in a section of the SEUS defined by Landsat Wprldwide Reference System (WRS) II footprint path 17 row 39. The spatial frequency distributions of forest management units indicate that while units < 0.5 Ha comprised 64% of the units, these small units covered only 0.98% of the total forest area. Management units ≥ 0.5 Ha ranged from 0.5 to 160,770 Ha (the Okefenokee National Wildlife Refuge). We compared the size-frequency distributions of management units with four independently derived management types: production, ecological, preservation, and passive management. Preservation and production management had the largest units, at 40.5 ± 2196.7 (s.d.) and 41.3 ± 273.5 Ha, respectively. Ecological and passive averaged about half as large at 19.2 ± 91.5 and 22.4 ± 96.0 Ha, respectively. This result supports the hypothesis that the road network defines management units in SEUS. If this way of delineating management units stands under further testing, it will provide a way of subdividing the landscape so that we can study the effects of different management on forest ecosystems.