MODIFICATION OF TEXAS CLEAR-CUT ENVIRONMENTS WITH LOBLOLLY-PINE SHELTERWOODS

The near-surface (within 0.30 m of the surface) environments of a clear-cut and a loblolly pine (Pinus taeda L.) shelterwood in east Texas were instrumented to determine treatment effects on the radiation, thermal, humidity and wind components of microclimate. The shelterwood produced lower net radiation and photosynthetically-active radiation loads, lower daytime air temperatures, the same or slightly lower daytime vapor pressures and lower wind speeds than the clear cut. Although sunfleck incidence in the shelterwood allowed net radiation and photosynthetically-active radiation (PAR) to increase briefly to levels similar to those measured in the clear cut, seedlings within the shelterwood were subjected to sunflecks for only a short period of time before the sunfleck dissipated and shade returned. Air temperature differences between treatments were not great and soil temperature differences were negligible. The influence of the shelterwood on all environmental factors was primarily due to the partial overstory canopy, which dissipated incident radiation before it reached the near-surface environment where it could significantly alter the microclimate.