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Abstract Small features in ecological systems are often underrepresented in conservation monitoring, management and policy. Tree cavities and other forms of refuge play disproportionately large ecological roles due to their importance for shelter and rearing vulnerable offspring. Giant panda (Ailuropoda melanoleuca) cubs are highly altricial, and dependent on dens. In Fengtongzai—a reserve with cavity-containing old growth forest—we measured 19 structural and microhabitat variables in potential tree dens. We also established data loggers in rock cavities in Foping Nature Reserve (which due to logging does not contain old growth) and tree cavities in Fengtongzai to monitor temperature and humidity inside and outside dens to evaluate microclimatic buffering. Fengtongzai pandas selected tree dens that were better concealed, with large interiors and entrances but smaller entrance to interior ratios. Microclimate inside dens differed dramatically from ambient conditions outside: in cold weather dens were warmer, in hot weather dens were cooler, dens were less humid and dens had more stable microclimates. Dens used by maternal pandas were warmer, drier and less variable than tree and rock cavities that were not used. Tree dens showed better capacity to buffer against extremes of temperature and humidity than did cave dens. Our findings have important conservation implications, including the value of den sites and the need for better monitoring and management. Specifically, management practices that preserve large old trees may increase carrying capacity and any experimentation with artificial dens as a conservation intervention should reference our findings on structural and microclimatic characteristics of preferred den sites. [ABSTRACT FROM AUTHOR]

Coastal rainforests of southeast Alaska have relatively simple species composition but complex structures with high diversity of tree ages, sizes and forest canopy layers, and an abundant understory plant community. Wildlife and fisheries resources also play an important role in the ecological functioning of forest and aquatic systems. Clearcutting has greatly altered these forest ecosystems with significant decreases in structural diversity of forest stands and greatly reduced wildlife habitat. This paper synthesizes information on management options in older forests that have never been actively managed, and in younger forests to increase diversity of stand structures and their associated effects on biodiversity. Light to moderate levels of partial cutting in old-growth forests can maintain the original diversity of overstory stand structures and understory plant communities. In younger forests that develop after clearcutting, mixed alder-conifer stands provide more heterogeneous structures and significantly higher understory biomass than in pure conifer forests. Research has shown that red alder increases diversity and abundance of understory plants, and provides forage for deer and small mammals. Results also show a clear linkage between alder and improved invertebrate diversity in aquatic systems. A combination of light partial cutting in older forests along with inclusion of red alder in conifer-dominated forests could provide the greatest amount of diversity and maintain the complex stand structures that are an important component of these forest ecosystems. [Copyright &y& Elsevier]

Backcross breeding has provided a viable means to restore American chestnut (Castanea dentata (Marsh.) Borkh.) to eastern North American forests, where the foundation species was essentially extirpated by an introduced pathogen. With the prospect of American chestnut reintroduction imminent, it is critical to formulate restoration strategies based on the ecology and silvics of the species, operational confines, social or policy limitations, and ecological implications. American chestnut was apparently adapted to a relatively wide range of site conditions, has evolved a capacity to survive for prolonged periods beneath forest canopies yet respond rapidly to disturbance, and demonstrates extraordinary growth and competitive ability. These characteristics are discussed in reference to operative planting techniques and potential for migration of regeneration from hybrid chestnut plantings into forests of the original American chestnut range. The use of hybrid trees for American chestnut reintroduction may generate social and policy ambiguities that require conciliation. Additionally, potential long-term ecological implications associated with reintroduction of American chestnut to the original species range, or introduction to areas outside its original range, must be realized and integrated into reintroduction strategies. Limitations in genetic fitness, potential for disease mutation, and threats from other exotic insects and pathogens may serve as continual challenges to American chestnut restoration. This paper helps establish preliminary guidelines for restoration plantings and creates awareness of imposing ecological issues and barriers that must be overcome to successfully restore American chestnut to its natural range, while simultaneously maintaining ecological integrity and ensuring conservation benefits to eastern North American forests. [Copyright &y& Elsevier]

Abstract: Over-exploitation and fragmentation are serious problems for tropical forests. Most sustainable forest management practices avoid clear-cuts and apply selective logging systems focused on a few commercial species. We applied a simulation model to estimate the impact of such selective logging scenarios on the genetic diversity and demography of four tropical tree species from French Guiana. The simulations used data on genetic and demographic composition, growth, phenology and pollen and seed dispersal obtained for Dicorynia guianensis, Sextonia rubra, Symphonia globulifera and Vouacapoua americana at the experimental site in Paracou. Whereas Symphonia globulifera serves as a model for a species with low logging pressure, the other three species represent the most exploited tree species in French Guiana. In simulations with moderate logging, typical for French Guiana, with large cutting diameter (>60cm diameter) and long cutting cycles (65 years), the two species V. americana and Sextonia rubra were not able to recover their initial stock at the end of the rotation period, with a large decrease in the number of individuals and in basal area. Under a more intensive logging system (cutting diameter >45cm diameter, cutting cycles of 30 years) that is common practice in the Brazilian Amazon, only Symphonia globulifera showed no negative impact. Generally, the differences between the genetic parameters in the control scenarios without logging and the logging scenarios were surprisingly small. The main reasons for this were the overlapping of generations and the effective dispersal ability of gene vectors in all species, which guarantee relative homogeneity of the genetic structure in different age classes. Nevertheless, decreasing the population size by logging reduced the number of genotypes and caused higher genetic distances between the original population and the population at the end of the logging cycles. Sensitivity analysis showed that genetic changes in the logging scenarios were principally determined by the growth, densities and cutting diameter of each species, and only to a very small extent by the reproductive system including factors such as pollen and seed dispersal and flowering phenology. [Copyright &y& Elsevier]