The effects of forest fuel-reduction treatments in the United States

The current conditions of many seasonally dry forests in the western and southern United States, especially those that once experienced low- to moderate-intensity fire regimes, leave them uncharacteristically susceptible to high-severity wildfire. Both prescribed fire and its mechanical surrogates are generally successful in meeting short-term fuel-reduction objectives such that treated stands are more resilient to high-intensity wildfire. Most available evidence suggests that these objectives are typically accomplished with few unintended consequences, since most ecosystem components (vegetation, soils, wildlife, bark beetles, carbon sequestration) exhibit very subtle effects or no measurable effects at all. Although mechanical treatments do not serve as complete surrogates for fire, their application can help mitigate costs and liability in some areas. Desired treatment effects on fire hazards are transient, which indicates that after fuel-reduction management starts, managers need to be persistent with repeated treatment, especially in the faster-growing forests in the southern United States

Variation in Recruitment and Early Demography in Pinus Rigida Following Crown Fire in the Pine Barrens of Long Island, New York

Following severe, stand-replacing fires in 1995, we quantified emergence, growth and survival in Pinus rigida seedlings in eight stands in three areas of the pine barrens of Long Island, New York, USA, and examined factors contributing to spatial and temporal variation in recruitment. We followed 6431 marked seedlings in the first cohort following fire, as well as additional cohorts in subsequent years, for 7 years to assess the effects of fire intensity, soil characteristics, intraspecific density, interspecific competition and facilitation on variation in early demography at three different scales. We found substantial variation in many of the demographic parameters measured between plots within stands (10–50 m apart), among stands within areas (600– 1500 m apart), and among forest areas (5 –30 km apart), as well as among years. Almost all adult P. rigida in most of the stands studied were killed by the 1995 fires and population recovery therefore depended upon recruitment from seed. Initial recruitment appears to be largely determined by seed limitation, which was affected by fire intensity combined with serotiny and other factors. Subsequent seedling survival and growth were determined largely by inherent differences among areas and sites in factors including cover of the shrub Quercus ilicifolia and soil texture and composition. Initial seedling density, and subsequent survival and growth, varied among plots within sites, among sites within areas, and among areas. Early survival was negatively correlated with intraspecific seedling density, but was enhanced by neighbouring Q. ilicifolia, although these shrubs inhibited later seedling growth. Early demographic variation may determine many of the differences observed among mature populations in this landscape. Variation in demographic parameters across space and time, and over a hierarchy of scales, may have critical consequences at the population, community and landscape levels. A comprehensive evaluation of the nature and extent of such demographic variation across different systems would have major implications for understanding vegetation patterns at the population, community and landscape levels