Disturbance effects on species richness of herbaceous plants in a semi-arid habitat

Maintaining or increasing plant species diversity is often a goal of habitat managers in semi-arid environments. The author compared herbaceous species richness on disced and untreated plots for 5 years after treatment. Effects of discing once, twice, thrice, and annually (October 1994; October 1990 and 1994; October 1990, 1992, and 1994; and October 1990–1994) during a 5-year period on species richness during the first growing season after the final discing treatment was also determined. Total species richness during spring was 108% and 100% greater on disced plots in the 4th and 5th years post-treatments, respectively, on Delmita fine sandy loam, but species richness between treatments was similar on Ramadero loam. In October 1995, total species richness was 100% greater on plots disced only once than on plots disced annually on Delmita fine sandy loam. Plots disced once had greater species richness than all other treatments on Ramadero loam in October 1995. Discing temporarily increases herbaceous species richness, but results are not consistent in part because of the confounding effects of rainfall patterns, soil series, and season of the year.