Soil-site productivity indices and tree growth in loblolly pine (Pinus taeda L.) plantations [electronic resource] /
Abstract (Summary)This research investigates soil variables relevant to growth in loblolly pine (Pinus taeda L.) plantations in the Piedmont of Georgia, USA. Under conditions of complete competing vegetation control, soil-site productivity relationships were investigated to test whether nitrogen (N) availability indexes and descriptive soil-site variables were correlated to stand growth. In addition, relationships between soil N availability and the soil organic matter light fraction (LF) were investigated. I hypothesized that: 1) under simplified forest conditions due to complete competition control, indices of soil available N will be strong predictors of pine growth and 2) indices of soil available N will be positively correlated to the amount of LF in the soil. In plots on Udults, and Udifluvents that received herbicide (H) and herbicide plus fertilization (HF) treatment resin extractable N, and potentially mineralizable N in long-term laboratory incubations were estimated. Resin extractable and laboratory estimates of N mineralization were correlated to stand growth and to the quantity of LF. In addition, plots(N=66) under experimental treatment combinations of Control (C), Fertilization (F), H, and HFwere evaluated for changes in soil nutrients and carbon. Resin extractable N was found well correlated (R²=0.7) to mean annual increment (MAI) for 13 out of 17 sampling dates. Based on four sampling dates, resin core estimates of N availability were also significantly correlated (R²=0.5) to the corresponding laboratory estimates of soil potentially mineralizable N. Another significant relationship was found between the LFpool and resin core estimates of N mineralization (r=0.63, n=25). Finally, the factorial analysis indicates that H, F, and HF treatments can alter the quantity of nutrients other than N with a clear effect of H treatments on soil carbon and exchange capacity. On a regional scale, when controlling for understory competing vegetation on N limited soils, it is possible to improve on soil-site productivity relationships. The significant correlation between soil potentially mineralizable nitrogen and resin core estimates of N availability suggests that both techniques are valuable tools for the prediction of growth on N limited soils and that the LF is an important variable affecting N availability.
School:The University of Georgia
School Location:USA - Georgia
Source Type:Master's Thesis
Date of Publication: