Tropical forest canopies and their relationships with climate and disturbance： results from a global dataset of consistent field-based measurements

Background： Canopy structure, defined by leaf area index （LAI）, fractional vegetation cover （FCover） and fraction of absorbed photosynthetically active radiation （fAPAR）, regulates a wide range of forest functions and ecosystem services. Spatially consistent field-measurements of canopy structure are however lacking, particularly for the tropics. Methods： Here, we introduce the Global LAI database： a global dataset of field-based canopy structure measurements spanning tropical forests in four continents （Africa, Asia, Australia and the Americas）. We use these measurements to test for climate dependencies within and across continents, and to test for the potential of anthropogenic disturbance and forest protection to modulate those dependences. Results： Using data collected from 887 tropical forest plots, we show that maximum water deficit, defined across the most arid months of the year, is an important predictor of canopy structure, with all three canopy attributes declining significantly with increasing water deficit. Canopy attributes also increase with minimum temperature, and with the protection of forests according to both active （within protected areas） and passive measures （through topography）. Once protection and continent effects are accounted for, other anthropogenic measures （e.g. human population） do not improve the model. Conclusions： We conclude that canopy structure in the tropics is primarily a consequence of forest adaptation to the maximum water deficits historically experienced within a given region. Climate change, and in particular changes in drought regimes may thus affect forest structure and function, but forest protection may offer some resilience against this effect.

Rapid ongoing decline of Baird’s tapir in Cusuco National Park, Honduras

During the International Tapir Symposium 16-21 Oct 2011,the conservation of Baird's tapir(Tapirus baindi)in Honduras received a boost with the signing of a memorandum of understanding between the Minister Direc-tor of the Honduran Instute of Conservation and Forestry(CF)and the Tapir Specialist Group(TSG)Despite this agreement,accelerating levels of hunting and habitat loss contimue to pose a threat to Baird's tapir in Hon-duras.An ongoing study in Cusuco National Park in northwestern Honduras has been monitoring changes in population dynamics of Baird's tapir since 2006 through the collection of occupancy data.The study has iden-tified an increase in hunting pressure,coinciding with a drastic decline in the encounter rate with Baird's tapir spoor.Here,we examine the significance of a range of demographic variables on Baird's tapir occupancy in Cu-suco National Park using the software PRESENCE,and simulate the effects of different management strategies on the fiuture dynamics of the population using the stochastic simulation software VORTEX The predictions of the theoretical population models are compared to observed changes in occupancy levels.We found that non-intervention resulted in the local extinction of Baird's tapir within a very short time fiame,but that various in-tervention models enabled the population to recover to near carrying capacity.Occupancy and extinction prob-ability were shown to respond marlkedly to the increase in hunting pressure;and occupancy models supported the fiuture population predictions generated by VORTEX.Our study suggests that immediate intervention is re-quired to reduce hunting pressure to near historical levels to prevent the imminent 1ocal extinction of the species.