Water Depth In An Oxbow Lake-Wetland And Its Influence On Soil Chemistry, Cypress Tree Growth, And Groundwater Recharge

Author(s): Lahiri, C.; Davidson, G.; Threlkeld, S.

Sky Lake, MS, is an oxbow lake-wetland that was once part of the ancestral Ohio-Mississippi River system. It hosts some of the largest and oldest cypress trees in the state, with several trees exceeding 40 ft in circumference. An elevated boardwalk recently built into the heart of the wetland now allows unique access to the public and has provided a platform for mounting experimental equipment to monitor several environmental parameters pertinent to managing wetlands and water resources. An ongoing study along the boardwalk is currently monitoring changes in water level, water and soil chemistry (pH, Eh, DO, conductivity, temperature), and atmospheric parameters (precipitation, temperature, relative humidity), and relating the data to tree growth (sap flow rates, trunk expansion) and to changes in groundwater level in a monitoring well located inside the meander loop. Preliminary data indicate that both the flow and chemistry of water within the root zone is highly variable over short distances, likely caused by physical heterogeneity created by fallen and buried tree limbs in various stages of decomposition. Substantial changes in soil zone Eh, an indicator of the redox potential that can influence nutrient uptake by plant roots, were observed over time with no significant correlation between measurement locations. This means that single measurements of soil chemistry at point locations in this wetland environment are not necessarily representative of the conditions for the system as a whole. Measurements at multiple locations are required to adequately assess the chemical conditions that contribute to the health of wetland flora. Groundwater levels measured in the monitoring well rose and fell over a several month period corresponding to high and low water levels in the wetland, respectively, suggesting a possible surface-groundwater connection. Digital cameras set up with dendrometer bands are allowing collection of daily changes in the circumference of four different trees that will allow correlation with sap flow and the monitored environmental variables.

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