RESTORING THE COASTAL PRAIRIE: A SOIL STUDY OF THE TEXAS CITY PRAIRIE PRESERVE

Restoration projects in disturbed ecosystems containing invasive plant species require the evaluation of soil composition to establish an action based remediation plan. Situated in Texas City, TX, 42.5 miles from Houston is the Texas City Prairie Preserve (TCPP), a large 2,220-acre coastal grassland restoration property that is managed by The Nature Conservancy. Previously owned by Exxon Mobile, the TCPP (29.4251°N, 94.9583°W) was once a site for oil drilling and production, however, recently it has been established as a restoration site for preserving the ecologically diverse coastal prairie habitat.

Composite soil testing of several plots within the TCPP was initiated in an effort to determine effective coastal restoration practices. In this project we established four representative survey plots (5.3 acres total) to evaluate as potential candidates for coastal vegetation restoration-particularly for the native growth of big bluestem grass (Andropogon gerardii). The soil data we collected using a hand push auger included textural analysis, organic matter, pH, and general mineral elements (N, P, K, Ca, Mg, S, Na).

Despite their close proximity (roughly 23m apart), the test sites showed soil variability in the amounts of macronutrients of nitrogen, phosphorous, magnesium, and sodium contained from plot to plot. The pH of the soil (6.4-7.8) ranged from slightly acidic to moderately alkaline. Additionally, the range of porosity and permeability of soil percentages (sand, silt, and clay) based on USDA classification methods were dissimilar. From our analysis we determined that two sites were considered applicable for restoration without the need for additional soil amendments. The other 2 test plots required specific elements (phosphorous and sodium) to be considered for replanting certain native grasses, such as the big bluestem. The data results suggest from this composite analysis that two out of the four plots studied, needed additional phosphorous which is deemed an essential mineral to coastal grasses. Specially, for successful growth we would suggest the addition of 35lbs2O5/acre at Plot three and 15lbs P2O5/acre at Plot two. We determined that restoration of big bluestem is possible, although some added nutrients may enhance the productivity and project efficiency.