PARENT SESSION
Thursday, August 10, 1:30-5:00 pm
COS 103 - Ecology of natural and created wetland ecosystems
Heritage Ballroom I, Marriott
Presiders: G Ervin and S Hoeppner
Effects of disked microtopography on vegetation in mitigation wetlands in Virginia.
Moser, Kurt*,1, Ahn, Changwoo1, Noe, Gregory2, 1 George Mason University, Fairfax, VA2 U.S. Geological Survey, Reston, VA
ABSTRACT- Microtopography, or topographic variation on the scale of individual plants, may influence wetland hydrology, physicochemistry, and plant community composition, but the microtopographic variation found in natural wetland settings is rarely found in created wetlands, unless manipulated, as by disking after grading. This study explores the relationship between microtopography, hydrology, soil nutrients, and plant species richness/diversity for two created wetlands. Microtopography was measured using multiscale (0.5m-, 1m-, 2m-, and 4m-diameter) circular transects in order to determine the appropriate scale for consideration. Measurement data were used to calculate three microtopographic indices: tortuosity, limiting slope, and limiting elevation difference. Steel rod rust depth was used to assess water table depth at 80cm transect intervals. Vegetation surveys at peak growth were used to assess weighted-average wetland indicator status and species richness/diversity, as well as to compare native/invasive and seeded/volunteer species. Results are examined with regard to wetland creation method: grading/disking versus grading only, as well as in relation to measurement scale. Some of the early results show that mean values for tortuosity (T), limiting slope (LS), and limiting elevation difference (LD) are higher for disked wetlands (T=1.015±0.002, LS=0.24±0.03, LD=5.48±0.87 cm) than for undisked wetlands (T=1.003±0.003, LS=0.12±0.05, LD=1.62±1.51 cm). Shannon diversity index (SI) and species richness/density per survey unit (SR) likewise appear higher for disked (SI=1.70±0.11, SR=4.88±0.42) than for undisked wetlands (SI=0.78±0.19, SR=2.70±0.73), thus suggesting positive effects of microtopography on plant diversity.
Key words: created wetland, soil surface disk treatment, microtopography