PARENT SESSION
Oral Session #15: Ecosystem Ecology. Presiding: J. Jenkins.
Monday, August 6, 2001. 1:00 PM to 4:45 PM. Hall of Ideas F.
Spatio-temporal patterns of available N and P after whole-tree harvest and girdling.
GUO, DALI1, MOU, PAUL2, JONES, ROBERT3, MITCHELL, ROBERT4, 1 2 3 4
ABSTRACT- Spatio-temporal patterns of soil nutrient heterogeneity after disturbance are of great importance in understanding the interactions between soil resources and vegetation regeneration during early secondary succession, and thereafter. Thorough studies on this subject have generally been lacking. Using both conventional statistics and geostatistics, we quantified spatio-temporal patterns of available N and P following two types of disturbances - whole-tree harvest and girdling (to mimic bark-beetle outbreak) in a slash pine (Pinus elliottii Engelm.) forest in the coastal plain of South Carolina, USA. Global variability of available N and P sharply increased in the first year after both disturbance treatments (p<0.05, F-tests) as compared to the reference plot, and declined in the second year following disturbance but remained higher than in the reference plot (p<0.05). Semivariogram analysis revealed marked temporal changes and scale-dependence in spatial dependence patterns, but repeatable seasonal changes and treatment differences in spatial dependence could not be identified. Our results suggested that the disturbances generated not only higher mean levels but also higher variability in available N and P. However, semivariance analysis did not provide sufficient evidence that the removal of the previously homogeneously distributed vegetation and the consequent heterogeneous forest floor patterns could cause finer-scale soil patches in available nutrients.
KEY WORDS: Spatio-temporal Patterns, Nitrogen, Phosphorus , Disturbance