Forest Harvesting Influence on Water Table Dynamics in a Florida Flatwoods Landscape

Abstract

Flatwoods are an important ecological plant community in the southeastern Coastal Plain with approximately one‐third of Florida's flatwoods in timberland. This study was conducted to investigate hydroperiod changes in the water table of both hydric and nonhydric soils following harvest in a Florida cypress [Taxodium distichum (L.)]–pine (Pinus elliottii var. elliottii Engelm.) flatwoods landscape. Shallow water‐table wells were established on a 42‐ha area and divided into three harvesting treatments containing mature slash pine plantations and pine–cypress swamps: control, clearcut (both hydric and nonhydric soils harvested), and cypress swamps only harvested (hydric soils only harvested). Water‐table measurements were obtained at 2‐wk intervals for 6 yr. Harvesting treatments occurred 2 yr into the study. Regression equations created from preharvest water‐table data between the control block and harvested blocks allowed us to predict uncut water‐table responses in the cut areas. These predicted values were compared with the actual postharvest observations. The water‐table level increased 48 and 49 cm and 19 and 21 cm in the hydric and nonhydric soils in the clearcut and cypress swamps only cut, respectively, during the first 126 d after harvesting. Significant differences (P < 0.10) in water‐table depth because of harvesting occurred throughout the four postharvest years, but the differences were less than seen initially, and the pattern was seasonal. Compared with the predicted uncut condition, water tables tended to be lower (drier) during the growing season and higher (wetter) during the nongrowing season. These seasonal fluctuations were presumably driven by changes in evapotranspiration rates resulting from differences in leaf area of the pine canopy and understory.