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GAP SIZE AND SUCCESSIONAL PROCESSES IN SOUTHERN APPALACHIAN FORESTS
Citation:
Shure, D. J., D L. Phillips, AND P. E. Bostick. GAP SIZE AND SUCCESSIONAL PROCESSES IN SOUTHERN APPALACHIAN FORESTS. Plant Ecology. Springer Netherlands, , Netherlands, 185:299-318, (2006).
Impact/Purpose:
We used clearcut logging in a southern Appalachian hardwood forest to examine the long-term effects of disturbance size on plant community structure, biomass accumulation, aboveground net primary productivity, and mode of recovery.
Description:
We used clearcut logging in establishing four replicated sizes of canopy openings (0.016, 0.08, 0.4, and 2.0 ha) in a southern Appalachian hardwood forest in 1981 to examine the long-term effects of disturbance size on plant community structure, biomass accumulation, aboveground net primary productivity (NPP), and mode of recovery. The reestablishment of NPP and biomass following logging was 6¿7-fold greater in large than small openings by 17 years. Total biomass in the 2.0 ha openings (127.3 Mg ha¿1) recovered 59.5% as NPP (19.7 Mg ha¿1 yr¿1) reached 225% of precut forest levels. Biomass accumulation was 2.6¿3.6-fold greater in interior than edge locations of all but the 0.016 ha gaps. The absence of significant patch size or edge vs. interior differences in tree densities suggests that growth rates of individual trees were enhanced in more insolated microenvironments. Sprouting (86¿95% of tree NPP) was much more important than advance regeneration (4¿10%) or seedling germination (<2%) during early recovery in all opening sizes. Canopy dominant Quercus and Carya trees exhibited limited sprouting following disturbance. Instead, shade-intolerant Robinia pseudoacacia and Liriodendron tulipifera were major sprouters that used N-fixation (Robinia) and rapid growth (Liriodendron) in attaining 7.4 and 5.9 fold greater biomass accumulation, respectively in 2.0 ha than 0.016 ha opening sizes. Seedling germination and understory production were extensive in all openings following logging, but declined rapidly as the young tree canopy began closing by 4¿6 years. The relative importance of shade-intolerant tree biomass approximately doubled over 17 years as shade-tolerant tree seedlings, herbs, and shrubs gradually regained importance under the emerging canopy. Sprouting caused the persistence of a tree species composition in all openings that remained relatively similar to the precut forest. Large disturbances on mountain slopes of the southern Appalachians generally promote sprouting and rapid recovery, whereas small disturbances in low-elevation cove forests lead to a gradual recovery through seedling germination and/or advance regeneration. Continued logging in the southern Appalachians will increase the relative size and frequency of large disturbances, further the importance of sprouting of shade-intolerant species, and lead to more even-aged forest stands throughout the region.