Spatial and Temporal Relationships of Old-Growth and Secondary Forests in Indiana, USA
We examined the spatial pattern of forests in Indiana to: (1) determine the extent, connectivity and percent edge of all forests, (2) examine the change in connectivity among these forests if all riparian zones were replanted to forest or other native vegetation, (3) determine the location, spatial dispersion and percent edge of current old-growth forest remnants, (4) predict future changes in area and spatial distribution of old-growth forests based on current land management plans of public agencies and (5) discuss biological implications of different edge widths, patch sizes and spatial configurations of forests in Indiana.. To achieve this, we produced a map of forested riparian zones using a Geographic Information System (GIS) buffering function and developed GIS models to predict locations of potential old-growth forests on lands designated in public agency management plans as preserves or unmanaged forests. A proximity index (PX) was used as a quantitative measure of effective connectivity of forest patches. PX values ranged from 0 to nearly 3,000, where a value of 0 is effectively isolated and a value of 3,000 is very well connected. For the 9,508 patches and 2,026,716 ha of all forests in both Indiana and the surrounding area, the average PX was 19.49. Adding a 200-m forest buffer to both sides of all non-forested riparian areas resulted in a decreased number of fragments to 3,634 and an increase of 1,724,664 ha of forest (the buffer). A 20-m buffer would add 172,466 ha of forest. The PX was not used to analyze riparian areas because it was not appropriate for the dendritic pattern formed when riparian areas were revegetated. Total area of old-growth forests ³ 4 ha held in public trust in Indiana is 362 ha divided among 19 forests. An additional 8 sites ³ 4 ha in private ownership contain 215 ha. Most old-growth forests are isolated within an agricultural matrix. The percentage of old-growth forest area located within 40 m, 200 m, 400 m and 600 m of a non-forest edge was 23%, 75%, 89% and 93% respectively. PX values for all 19 old-growth sites were 0 implying that they are very isolated sites. If current public forest management plans are followed, the area and number of old-growth forests will increase and their relative isolation will decrease. Potential future old-growth forests consisted of 137 patches and 82,520 ha with an average PX of 1.8. Of this amount 27,297 ha were within Hoosier National Forest purchase boundaries but are currently in private ownership.