Changes in Understory Vegetation and Soil Characteristics Following Silvicultural Activities in a Southeastern Mixed Pine Forest1

Abstract

A silvicultural chronosequence was studied in upland pine stands of Fort Benning, Georgia, to assess understory vegetation and soil characteristics following silvicultural disturbance activities. Hypotheses regarding patterns of understory vegetation distribution and abundance, and the impact of disturbance on soil properties were evaluated in 32 forest stands. The chronosequence encompassed various times following clear-cut regeneration: stand age (0–3 yrs), (8–10 yrs), (18–20 yrs), and (30–80 yrs). Soil pH, total carbon (C) and nitrogen (N) contents, soil texture, and bulk density were used to characterize soil conditions across the chronosequence. Foliar cover by species was used to characterize vegetation across this same chronosequence. Canonical correspondence analysis (CCA) was performed to determine the relationship between understory vegetation pattern and measured soil gradients and stand age. CCA identified stand age as the most important factor influencing distribution and abundance of understory vegetation. Herbaceous species composition and cover varied more with stand age than did understory woody species. Aside from a decrease in bulk density soil variables did not vary with recovery time. Indicator analysis identified Gaylussacia mosieri (Small) and Carya spp. as the only significant woody indicators of age class. Cyperus croceus (Vahl) and Bulbostylis barbata (Rottb.) C. B. Clarke were identified as herbaceous indicators of the 0–3 age class. Andropogon virginicus (L.), Dichanthelium sp. and Sporobolus junceus (Beauv.) Kunth were significant indicators of the 8–10 year age class. Significant indicators of the 15–20 year class were Pityopsis sp. and Tridens flavus (L.) A. S. Hitchc. Andropogon ternarius (Michx.), Schizachyrium scoparium (Michx.) Nash, Desmodium sp., Hieracium sp., and Rhynchosia tomentosa (L.) Hook. & Arn. were indicators of 30–80 year age class. Major changes in understory vegetation cover and composition continued for at least 15–20 years post clear-cut regeneration.