Evaluating Success and Function of Marsh (Juncus roemerianus) Restoration (2006-2011)

While many restoration efforts have been conducted, there have been few comparisons of relative success between different restoration designs, especially with J. roemerianus. Here we present two restoration designs for evaluation, a full density restoration design and a half density restoration design. Full density restorations represent the more expensive and labor intensive option. Several parameters will be compared between these two designs relative to the adjacent natural marsh to determine how the individual plants within these treatments perform. Several measurements have and will continue to be taken as proxies of plant health including: total shoot length, percent living tissue length, shoot growth, leaves per shoot, chlorophyll content , and chlorophyll fluorescence. Evaluation of these parameters should yield information on the relative health of restored marsh plants as compared to natural marsh plants. No studies were found that evaluated the colonization rates of J. roemerianus or the cost effectiveness of any aspect of J. roemerianus marsh restoration. We hope to evaluate the effectiveness of 2 restoration designs to produce colonizing shoots and compare these observed shoot counts to the associated cost for each design. We will also transform these counts into rates, extrapolating coverage areas over certain time periods for both designs and also run a cost effective analysis on these rates. Also if differences in rates exist between exterior and interior colonization shoot lengths will be used to determine if varying energy allocation strategies are apparent between interior and exterior shoots. The determination of shoot colonization rates between restoration designs as well as cost analysis for each design based on these rates will prove very useful for managers who need to balance cost and results for restoration projects. An estimate of groundwater N partitioning and the capacity of marsh systems to attenuate the ever increasing groundwater derived N loads into marshes is a pressing need for managers. On the US Gulf Coast, J. roemerianus is a dominant marsh plant that is a prime candidate for restoration projects and is relatively understudied with regards to nutrient filtration capabilities. In this project we aim to quantify the amount of groundwater introduced NO3- that can be attenuated within 2 different restoration designs of a J. roemerianus marsh as well as trace the processes that contribute to the attenuation. A high [NO3-] groundwater plume will be continuously pumped through the 2 J. roemerianus restoration designs and 1 unvegetated control for 31 days. Subsequent measurements of several N species concentrations, δ15N value (N species, plants, animals) and conservative tracers will be taken to determine the magnitude and primary pathways of N removal from this groundwater plume. Spatial and temporal variability will be taken into account by measurements being taken at multiple distances from plume injection point on several sampling days. The exact location and frequency of these measurements differ according to the target measurement. Knowledge of the regulatory mechanisms, specifically top-down, and its response to fertilization is needed for J. roemerianus dominated marshes. In this study we try to alleviate the unknowns regarding potential grazer responses to fertilization and the subsequent regulation of J. roemerianus through field and lab experiments. We will determine if grazers preferentially choose fertilized areas of marsh and what potential fertilization level triggers increased grazing through both field and lab experiments. Also a potential trophic cascade will be tested in which insectivorous marsh birds regulate insect grazer abundances thus reducing grazing pressures exerted on J. roemerianus. Overall the goals of the project are to understand if top-down control by grazing insects is occurring in a J. roemerianus marsh and what potential mechanisms contribute to the enhancement or reduction of this control.