Nutrient pools and patterns of nutrient availability and use in oak-hickory dominated forests
Abstract
The studies described in this dissertation were designed to quantify nitrogen (N) and phosphorus (P) pools in oak-hickory forests representing various levels of potential site productivities with potential site indices for oak ranged from approximately 17 m to 27 m. The selected stands exhibited a wide range of soil moisture and soil N and soil P availability. Interspecific and intraspecific differences in N and P retranslocation efficiencies were determined in Chapter 2. Nitrogen retranslocation was indepedent of soil N availability while P retranslocation was inversely related to soil P availability. In-situ rates of N mineralization in undisturbed and disturbed Central Hardwood Forest Ecosystems were determined in Chapter 3. In the undisturbed forest systems, N mineralization rates exhibited wide temporal variation with rates dependent upon soil temperatures, moisture availability, and the inherent substrate characteristics produced at a given site. Following forest floor disturbances, rates of N mineralization were significantly enhanced over the control. Chapter 4 examines fine root decomposition rates, and patterns of N and P immobilization and mineralization for the indigenous mix of fine roots and individual species commonly found in Central Hardwood Forest stands. The influence of site environmental factors (soil temperatures, soil moisture availability, and soil nutrient status) as factors controlling decomposition dynamics of common substrate sources were examined. Wide interspecific differences in fine root decomposition rates and patterns of nutrient retention and release were evident. Common litter types incubated at sites of differing soil nutrient status and soil moisture availability demonstrated similar decomposition rates and N and P dynamics indicating that site characteristics indirectly control fine root decomposition rates by influencing the species composition of a stand. Fine root growth in these Central Hardwood Forests is limited by suboptimal soil temperatures and soil moisture availability and is also partly controlled by physiological developmental stages within the tree itself (Chapter 5). Chapter 6 determines fine root production and turnover rates in Central Hardwood Forest stands and the quantity of N and P allocated to these belowground processes. Root production ranged from approximately 1000 kg/ha to over 4000 kg/ha/year. Root longevity ranged from approximately 1.3 to 4.4 years leading to large differences in belowground organic matter, N and P inputs in the different forest stands.
Degree
Ph.D.
Advisors
Pope, Purdue University.
Subject Area
Forestry|Ecology|Biogeochemistry
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.