The University of West Florida campus ecosystem study: gopher tortoise and longleaf pine populations in an urban interface

Abstract

College/university campuses comprise a distinct type of urban interface, with their generally expansive spatial pattern of alternating permanent structures, parking lots, and green spaces. The campus of the University of West Florida (UWF) in Pensacola, Florida, was constructed among second-growth longleaf pine stands recovering from extensive logging in the western-most extent of the Panhandle, with the original campus design deliberately carried out to maintain original contours and minimize tree removal. The extended campus includes a fire-excluded, longleaf-dominated landscape with active gopher tortoise populations confined to power line right-of-ways. This study (1) examined burrowing effects on soils and plant communities, and (2) estimated the age of longleaf pine stems (trees) around campus to assess the influence of human activity on population structure. Gopher tortoise sampling was confined to three discrete areas (types) for each burrow: apron (redistributed soil outside burrow), burrow (soil above burrowed cavity), and matrix (unaltered surrounding area). Within one 0.1 m2 quadrat/sample type for each of 16 burrows, density was determined for all vascular species; mineral soil was taken to a 5-cm depth. Air-dried soil was analyzed for pH, organic matter (OM), cation exchange capacity (CEC), extractable macro- and micronutrients, and extractable aluminum. All longleaf stems >2.5 cm diameter at breast height (DBH) were measured for DBH. Stem age was estimated with an allometric equation. Plant density was reduced by burrowing 7-fold on apron versus burrow and matrix sites, which did not vary between each other. Soil variables did not vary between burrow and matrix samples. Apron soils were significantly lower in pH, OM, CEC, and cations. Soil NO3− was ~3-fold higher in apron soils. Age structure of longleaf pine on campus revealed that nearly 2/3 of all stems are between 75 and 125 years old, consistent with the cessation of extensive logging of longleaf in this region.