Response of soil properties to mechanical restoration techniques applied in shrub-encroached wet prairies of the Florida panhandle

Abstract

Shrub encroachment into herbaceous ecosystems is a global concern. Restoration approaches, particularly in oligotrophic wetlands, should address both removal of woody vegetation and associated increases in soil organic matter. In coastal Florida, use of prescribed fire for shrub reduction is not feasible or effective due to surrounding development and saturated soil conditions. As a result, mechanical methods are often used to combat shrub encroachment, but effects on wetland soil properties are unclear. This study compared soil properties among four restoration treatments, non-treated Control, and fire-maintained Reference prairies in the Florida panhandle (6 total treatments). Restoration treatments included mechanical clearing of woody vegetation (C), mechanical clearing and prescribed fire (C + B), mechanical clearing and scraping of accumulated organic material (C + S), and clearing, scraping and burning (C + S + B). Soil samples were collected from each treatment at 2 weeks, 1-year and 2-years following application. All measured soil properties in C + S and C + S + B treatments were significantly different from shrub-encroached wet prairies (Control) but several soil parameters, notably Total N, P, K, available S and SOM, were reduced to levels below reference soil conditions. When all soil parameters were compared simultaneously through multivariate analysis, all restoration treatments were different from shrub-encroached (Control) and fire-maintained herbaceous (Reference) wet prairies, however there was considerable overlap in multivariate space between Reference points and restoration treatments that included scraping (C + S and C + S + B). This highlights the potential of utilizing aggressive mechanical methods to combat shrub encroachment and accumulation of organic material in herbaceous wetlands.