Vegetation Communities in Intensively Established Loblolly Pine Plantations at Crown Closure.

The potential effects of increasing herbicide use on vegetation communities and wildlife habitat have implications for biodiversity conservation and sustainability. We examined the response of understory vegetation to a gradient of plantation establishment intensity 6-8 years after planting in southern Mississippi, USA. Treatments were combinations of mechanical site preparation, chemical site preparation, and banded or broadcast herbaceous weed control. We compared species richness, coverage, and diversity indices for seven vegetation growth forms. Increasing pine coverage appeared to be the primary driver of vegetation change during this period. Herbaceous vegetation coverage declined each year in concert with increasing slash and litter coverage. Vines and woody species comprised most understory vegetation cover; woody species richness and coverage increased each year in all treatments. Mechanical site preparation maintained greater vegetation diversity and coverage than chemical site preparation at crown closure; the effects of different herbaceous weed control regimes were no longer detectable. Our results suggest that the influence of intensive stand establishment regimes, particularly chemical site preparation, can persist to crown closure. However, effects on wildlife habitat quality during this period were slight, and managers interested in promoting biodiversity should concentrate on managing for a variety of early succession communities. [ABSTRACT FROM AUTHOR]