Browsing by Author "Neatrour, Matthew Aaron"

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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.
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    The Role of Floods in Particulate Organic Matter Dynamics of a Southern Appalachian River/Floodplain Ecosystem
    Neatrour, Matthew Aaron (Virginia Tech, 1999-08-20)
    I investigated the role of a flood in particulate organic matter (POM) dynamics of the Little Tennessee river/floodplain ecosystem in western North Carolina, USA. I measured litter inputs, leaf breakdown, floodplain litter, and aboveground herbaceous net primary production at 12 sites. Annual litter inputs (274-625 g m-2 y-1) were typical of a temperate deciduous forest, but lower than other floodplain forests in the eastern United States. Mean aboveground herbaceous net primary production ranged from 61-439 g m-2 y-1 and leaf breakdown rates of 4 tree species ranged from 0.001-0.010 d-1. Following a flood on 8 January 1998, sites were separated into three inundation classes: inundated, partially-inundated, and non-inundated. Sites inundated by a January flood had significantly less forest floor leaf litter and coarse woody debris after the flood. There was no significant change at the partially-inundated or non-inundated sites. In addition, there was no significant difference in herbaceous material between pre- and post-flood collections for any inundation classes. Litter input, leaf breakdown, and floodplain litter standing crop data suggest that flood entrainment of POM from the floodplain of Little Tennessee River is a source of POM to the active channel. The impact of floods on the floodplain POM dynamics, however, is highly dependent on the time of year and magnitude of the flood, and on the structure of floodplain tree assemblages, which is strongly influenced by anthropogenic land use. Compared to direct litterfall and instream primary production, the floodplain may be a small annual source of POM for the river.