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silviculture
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.
Keywords: biodiversity, forest management, herbicide, mechanical, site preparation
Intensive management of southern pine (Pinus spp.) allows increasing yields from fewer acres and is expected to persist across the southeastern United States (Wagner et al. 2006, Miller et al. 2009). Intensive management, including mechanical site preparation to manage logging debris and prepare the soil for planting, herbicide application to control competing vegetation, and fertilization to compensate for inherent nutrient deficiencies, will be especially important if demand for wood products is to be met from a smaller land base (Wear and Greis 2002). Long-term monitoring throughout this region shows that wood volume can increase as much as 200% in intensively managed pine stands at midrotation (Wagner et al. 2006). However, increased pine dominance can alter plant communities and decrease time to canopy closure, which can affect wildlife species that are reliant on early successional communities.
Canopy closure can dictate composition, abundance, and spatial distribution of understory plants and their development (Miller 2001) by affecting available light, moisture, and nutrients (Anderson et al. 1969, Riegel et al....