Impacts of periodic and catastrophic disturbance on the plant and terrestrial invertebrate communities of wetland forests.

摘要

In August 1992, Hurricane Andrew uprooted thousands of trees in the Atchafalaya Basin of southern Louisiana. Uprooting resulted in large canopy openings with numerous tip-up mounds and adjacent depressions. I selected 120 mound-depression complexes in two heavily impacted sites in the Atchafalaya River Basin to study the herbaceous and woody plants associated with these unique microhabitats. I conducted vegetation surveys on the mounds and their associated depressions, as well as on the adjacent undisturbed habitat in 1994, 1996 and 1998. At each site, mounds had higher species diversity than the depression or undisturbed habitat in 1994. However, by 1998, the abundance and diversity of herbaceous plants declined on the mounds whereas vines increased in density.; The soil seed bank associated with mound, depression, and undisturbed habitat also exhibited large differences. Mounds and depressions supported higher numbers of germinating plants than the undisturbed habitat. I also discovered that hydrologic conditions played an important role in seed germination, with the greatest success in moderately saturated compared to flooded or dry soils. These results demonstrate the importance of disturbance for enhancing plant abundance and diversity.; Canopy gap formation can have major impacts on wetland forest communities, and in 1996 I initiated a study to quantify canopy gap and undisturbed forest use by aerial homopterans (planthoppers). This three-year project demonstrated that homopteran density and diversity was significantly greater in canopy gaps than in interior forest habitat. Furthermore, I discovered that homopteran abundance plummeted when exposed to long-term floods compared to brief flood or dry periods.