Mapping and Assessing Fire Damage on Broadleaved Forest Communities in Big Cypress National Preserve

Within Big Cypress National Preserve (BICY), oak-dominated forests and woodlands as well as tropical and temperate hardwood hammocks are integral components of the landscape and are biodiversity hotpots for both flora and fauna. These broadleaved forest communities serve as refugia for many of the Preserve’s wildlife species during prolonged flooding and fires. However, both prolonged flooding and severe fires, which are important and necessary disturbance vectors within this landscape, can have deleterious effects on these forested communities. This is particularly true in the case of fires, which under extreme conditions associated with drought and elevated fuel loads, can burn through these forested communities consuming litter and understory vegetation and top killing most, if not all, of the trees present.

Human disturbance and forest diversity in the Tansa Valley, India

We assessed the diversity of woody plants at 15 forested sites in the Tansa Valley of Thane District, in Maharashtra, India. The fewest species (11) were seen at a degraded mangrove site near the river mouth, and the greatest number (150) in the rich semi-evergreen forest on Tungar Hill. For all sites there were 141 tree, 25 shrub and 15 liana species, a total of 181 species. Excluding the mangrove site, which had no species in common with the other 14 sites, we analyzed the species distributions in detail. 2 These sites ranged in area from 4 to 30 km each, had woody floras of 89 6 6 species, and varied in intensity of human impact. Despite a history of exploitation and substantial reduction in biomass from firewood collecting, set fires and illicit tree felling, considerable plant diversity remains in the area.We found a modest increase in species richness in transects away from two villages. We observed the exploitation of the forest by the principal users, primarily of the Warli Tribe. They exploited a wide variety of forest resources (92 species), for medicines, foods, construction materials, household goods, manure and other purposes. They collected 15 items for sale. By far the single most important item collected was firewood, which dramatically reduced forest biomass within 2 km of villages. The species distributions in these forest remnants are strongly nested, mostly due to varying degrees of disturbance at individual sites. The high species diversity on Tungar Hill is most likely a relict of the earlier character of forests throughout much of the valley. It merits the highest priorities for preservation, as a refuge for Western Ghat species at the northern limits of their distributions.

Population viability analyses of Chamaecrista keyensis (Leguminosae: Caesalpinioideae), a narrowly endemic herb of the lower Florida Keys: Effects of seasonal timing of fires and the urban -wildland interface

This research first evaluated the effects of urban wildland interface on reproductive biology of the Big Pine Partridge Pea, Chamaecrista keyensis, an understory herb that is endemic to Big Pine Key, Florida. I found that C. keyensis was self-compatible, but depended on bees for seed set. Furthermore, individuals of C. keyensis in urban habitats suffered higher seed predation and therefore set fewer seeds than forest interior plants. ^ I then focused on the effects of fire at different times of the year, summer (wet) and winter (dry), on the population dynamics and population viability of C. keyensis. I found that C. keyensis population recovered faster after winter burns and early summer burns (May–June) than after late summer burns (July–September) due to better survival and seedling recruitment following former fires. Fire intensity had positive effects on reproduction of C. keyensis. In contrast, no significant fire intensity effects were found on survival, growth, and seedling recruitment. This indicated that better survival and seedling recruitment following winter and early summer burns (compared with late summer burns) were due to the reproductive phenology of the plant in relation to fires rather than differences in fire intensity. Deterministic population modeling showed that time since fire significantly affected the finite population growth rates (λ). Particularly, recently burned plots had the largest λ. In addition, effects of timing of fires on λ were most pronounced the year of burn, but not the subsequent years. The elasticity analyses suggested that maximizing survival is an effective way to minimize the reduction in finite population growth rate the year of burn. Early summer fires or dry-season fires may achieve this objective. Finally, stochastic simulations indicated that the C. keyensis population had lower extinction risk and population decline probability if burned in the winter than in the late summer. A fire frequency of approximately 7 years would create the lowest extinction probability for C. keyensis. A fire management regime including a wide range of burning seasons may be essential for the continued existence of C. keyensis and other endemic species of pine rockland on Big Pine Key. ^