Tall grass restorations influence communities in the Upper Green River watershed

The Conservation Reserve Enhancement Program (CREP) is replacing pastures with native tall grass fields in the upper Green River watershed in Kentucky. To determine the influences of the restoration on community composition, we conducted a series of surveys. In each of 10 sample sites, vegetation sampling was conducted in one control treatment plot (pasture) and in one experimental treatment plot (CREP).Vegetation sampling was performed in 1-m² quadrats spaced every tenth meter along transects. Ten quadrats were sampled in each plot for a total of 200 quadrats. Presence of all vascular plant species rooted in each quadrat was recorded to estimate site composition and species richness. In addition, number of stems, culms, pedicels, or peduncles at each of three heights (25cm, 75cm, and 100cm) was recorded in each 1-m² quadrat to assess structural heterogeneity within sites. Experimental plots (CREP) are higher in total plant species richness and native plant species richness than are control plots (pastures). Structural heterogeneity also differed considerably between control and experimental treatment plots. Control and experimental treatment plots both displayed relatively low structural heterogeneity in spring and high structural heterogeneity in summer. However, in fall, structural heterogeneity was relatively low in control plots and high in experimental plots. Temporal differences in structural diversity between the two treatment groups is attributable to the differing flowering phenologies of nonnative C₃ perennial grasses (dominant in pasture plots) and native C₄ perennial grasses (dominant in restoration plots).