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Light transmittance estimates under open, heterogeneous woodland canopies such as those of longleaf pine (Pinus palustris Mill.) forests report high spatial and temporal variation in the quantity of the light environment. In addition, light quality, that is, the ratio of red to far-red light (R:FR), regulates important aspects of plant development including stem extension, specific leaf area, and seed germination. We conducted two experiments to document sources of variation in R:FR (using a LI-COR 1800 portable spectroradiometer with a cosine-corrected light sensor) in a 70- to 90-year-old natural longleaf pine woodland in southwest Georgia, USA. The first experiment compared instantaneous measurements of R:FR over a 3-day period (March) with annual estimates of canopy transmittance (using gallium arsenide phosphide photodiodes) across the range of observed overstory abundance. The second experiment examined the effect of wiregrass cover (above or below), sky condition (blue sky or overcast), and solar angle (four sampling periods between October and March) on R:FR using a multifactorial repeated measures design. We found that (1) R:FR was significantly (p < 0.0001) and strongly (R2 = 0.72) related to annual estimates of canopy transmittance (percent photosynthetic photon flux density, %PPFD); (2) R:FR and %PPFD showed significant negative relationships with increasing overstory stocking (R2 = 0.20, p = 0.028 for R:FR, and R2 = 0.87, p < 0.0001 for %PPFD); and (3) R:FR decreased with increasing solar angle from maximum zenith for the study site under blue skies, was greater under overcast skies (0.84 blue sky vs. 1.18 overcast sky), and decreased under wiregrass (Aristida stricta Michx.) canopies (1.10 above vs. 0.98 below). [ABSTRACT FROM AUTHOR]

The article discusses the study on the management of white-tailed deer found at the forest sites of northwestern Pennsylvania which causes damage on forest vegetation, crops, and wildlife habitat. It shows their is no negative effects on vegetation despite of deer densities but species resilient to browsing have indirect effects on plants.

Abstract unavailable [ABSTRACT FROM AUTHOR]