RAPID VEGETATION TRANSITIONS AND THEIR POSSIBLE IMPACT ON SOIL INFILTRATION

Old field succession, the ecological succession of formerly managed fields, affects many aspects of the underlying soil. Our previous work (see reprints at the base of this poster) has already determined that old field succession creates measurable changes in depression storage and impacts carbon dynamics. This study investigates the effect that old field succession has on saturated conductivity. Since managed fields are often plowed, driven over, and mowed, soil characteristics are far from natural. If this same field is allowed to go native, chemical, meteorological, and ecological forces will change the soil. Changes in vegetation cover are the most abrupt alteration, with dramatic deviation in root depth, root density, leaf litter, soil shading, and plant diversity occurring within a few years of old field succession’s introduction. Tunneling caused by worms and small mammals, held in check on maintained fields by mowing and raking, may become a dominant factor in soil hydrology as fields go native. Our hypothesis is that saturated conductivity increases as old field succession progresses, chiefly due to soil matrix disruption by plant roots, worms, and small mammals. Infiltration rates were collected on a land parcel where geology, soil, and slope are constant, but vegetation and management practices vary. Double ring infiltrometers with inner ring diameters of 30.5 cm were used to measure saturated conductivity. Measurements were collected in a Palmyra stony soil with a slope of 3% on a land parcel that was originally un-mowed old field grassland. Data was extracted within a 40 year old planted pine forest, with the remainder of the data taken from an adjacent field, mowed occasionally to a depth of approximately 10 cm. Root density was greater (but shallower) in the mowed grassland. The infitrometer results suggest that median saturated hydrologic conductivity has increased from 31.5 cm/hr in the mowed field to 113.0 cm/hr in the pines. Based on a 2-sample Mann-Whitney test with 7 degrees of freedom, this increase was significant at the 0.11 level. We are actively seeking funding to collect infiltration data from other fields that are undergoing vegetation and management transitions in order to test this hypothesis.