Browsing by Author "Golladay, Stephen W."

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    Assessment of Nutrient Limitation in Floodplain Forests with Two Different Techniques
    Neatrour, Matthew A.; Jones, Robert H.; Golladay, Stephen W. (Hindawi, 2008-05-15)
    We assessed nitrogen and phosphorus limitation in a floodplain forest in southern Georgia in USA using two commonly used methods: nitrogen to phosphorus (N:P) ratios in litterfall and fertilized ingrowth cores. We measured nitrogen (N) and phosphorus (P) concentrations in litterfall to determine N:P mass ratios. We also installed ingrowth cores within each site containing native soil amended with nitrogen (N), phosphorus (P), or nitrogen and phosphorus (N + P) fertilizers or without added fertilizer (C). Litter N:P ratios ranged from 16 to 22, suggesting P limitation. However, fertilized ingrowth cores indicated N limitation because fine-root length density was greater in cores fertilized with N or N + P than in those fertilized with P or without added fertilizer. We feel that these two methods of assessing nutrient limitation should be corroborated with fertilization trials prior to use on a wider basis.
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    The effects of forest disturbance on stream stability
    Golladay, Stephen W. (Virginia Polytechnic Institute and State University, 1988)
    This project was designed to examine the stability of stream ecosystems in response to forest disturbance and subsequent succession. Stability was defined as the ability of streams to retain particulate organic matter and nutrients during storms. I hypothesized that forest streams are least stable during the intermediate stages of forest succession because particulate organic matter accumulations in streams are lowest at that time. This hypothesis was tested by examining stream stability in relation to forest succession. Stream surveys indicated fewer debris dams and organic matter accumulations in streams draining early and intermediate successional forests compared to reference sites. The abundance of large wood declined within 10 years of forest disturbance and continued to decline for at least 30-40 years through the intermediate stages of forest succession. Comparisons of inputs with standing stocks of organic matter indicated that streams draining early and intermediate successional sites receive less litter from their watersheds and processed it faster. Decreases in stream obstructions combined with changes in litter inputs and processing resulted in relatively high storm transport of fine organic matter from disturbed streams. Storm organic matter export from disturbed streams averaged 4.22 g AFDW/m² and from reference streams averaged 1.83 g AFDW/m². Storm nutrient budgets, constructed by measuring nutrient inputs (soil water, throughfall) and outputs (stream discharge) during individual storms indicated that streams draining early and intermediate successional forest were less retentive of nitrogen and phosphorus than reference sites. Nitrogen loss from disturbed streams averaged 58.04 mg/m²/storm and from reference streams averaged 16.52 mg/m²/storm. Phosphorus loss from disturbed streams averaged 32.52 mg/m²/storm and from reference sites averaged 7.14 mg/m²/storm. A majority of the nitrogen and phosphorus loss was in association with organic particles. There was no difference between disturbed and reference streams in potassium, calcium, or sulfate retention during storms. However, disturbed streams tended to lose more particulate organic potassium and calcium than reference sites. These results indicate that forest disturbance has a Iong-term impact on stream ecosystems by reducing their stability for many years following forest clearing.
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    Factors affecting root system response to nutrient heterogeneity in forested wetland ecosystems
    Neatrour, Matthew Aaron (Virginia Tech, 2005-04-21)
    Soil nutrients are often heterogeneously distributed in space and time at scales relevant to individual plants, and plants can respond by selectively proliferating their roots within nutrient-rich patches. However, many environmental factors may increase or decrease the degree of root proliferation by plants. I explored how soil fertility, nitrogen (N) or phosphorus (P) limitation, and soil oxygen availability affected root system response to nutrient heterogeneity in forested wetland ecosystems of southeastern United States. Fine root biomass was not correlated with soil nutrient availability within wetland ecosystems, but was related to ecosystem-scale fertility. Root systems generally did not respond to P-rich patches in both floodplain (nutrient-rich) and depressional swamps (nutrient-poor) swamps, but results were inconclusive because the growth medium (sand) potentially hindered root growth. In floodplain forests, roots proliferated into N-rich patches but not P-rich patches, even though litterfall N:P ratios were > 15, which suggested that these ecosystems were P-limited. The combination of nutrient and oxygen heterogeneity affected root proliferation and biomass growth of three common floodplain forest species (Liquidambar styraciflua, Fraxinus pennsylvanica, and Nyssa aquatica) in a potted study, which was related to species' flood tolerance. My results suggest that the environmental context of plants can affect roots system response to nutrient heterogeneity in forested wetland ecosystems and highlights the need for field studies that investigate this phenomenon. Learning how environmental conditions affect plant response to nutrient heterogeneity at a fine-scale will provide better predictions of nutrient cycling, plant competition and succession, and forest productivity, which are important factors that determine carbon sequestration and timber production.