A catastrophic tropical drought kills hydraulically vulnerable tree species.

Drought-related tree mortality is now a widespread phenomenon predicted to increase in magnitude with climate change. However, the patterns of which species and trees are most vulnerable to drought, and the underlying mechanisms have remained elusive, in part due to the lack of relevant data and difficulty of predicting the location of catastrophic drought years in advance. We used long-term demographic records and extensive databases of functional traits and distribution patterns to understand the responses of 20 to 53 species to an extreme drought in a seasonally dry tropical forest in Costa Rica, which occurred during the 2015 El Niño Southern Oscillation event. Overall, species-specific mortality rates during the drought ranged from 0% to 34%, and varied little as a function of tree size. By contrast, hydraulic safety margins correlated well with probability of mortality among species, while morphological or leaf economics spectrum traits did not. This firmly suggests hydraulic traits as targets for future research

Ecological fingerprinting of ecosystem succession: Estimating secondary tropical dry forest structure and diversity using imaging spectroscopy

We evaluated the use of EO-1 Hyperion hyperspectral satellite imagery for mapping structure and floristic diversity in a Neotropical tropical dry forest as a way of assessing a region's ecological fingerprint. Analysis of satellite imagery provides a means to spatially appraise the dynamics of the structure and diversity of the forest. We derived optimal models for mapping canopy height, live aboveground biomass, Shannon diversity, basal area and the Holdridge Complexity Index from a dry season image. None of the evaluated models adequately estimated stem or species density. Due to the dynamic nature of the leaf phenology we found that for the application of remote sensing in Neotropical dry forests, the spectro-temporal domain (changes in the spectral signatures over time-season) must be taken into account when choosing imagery. The analyses and results presented here provide a means for rapid spatial assessment of structure and diversity characteristics from the microscale site level to an entire region

Prospects for predatory mirid bugs as biocontrol agents of aphids in sweet peppers

In recent years, biological control strategies to control many major horticultural pests have been successfully implemented in the Eastern Mediterranean basin. However, the management of some pests, such as aphids in sweet pepper crops, can still be improved. The goal of this study was to examine the potential of the omnivorous predatory mirids Nesidiocoris tenuis, Macrolophus pygmaeus, and Dicyphus maroccanus as biocontrol agents of aphids in sweet pepper crops. First, the capacity to detect Myzus persicae-infested and un-infested plants was studied in a Y-tube olfactometer. Females of the three species of predatory mirids were strongly attracted to the odor of infested M. persicae plants. Second, the prey suitability of young and mature nymphs of M. persicae for these three mirid species was studied. The three species actively preyed on M. persicae, although D. maroccanus resulted the most voracious species preying both young and mature nymphs. Finally, the capacity of the three omnivorous predators to reduce M. persicae in heavily infested plants was determined in semi-field conditions. The three species of mirids could reproduce on aphids and establish on sweet pepper plants. Mirids significantly reduced the number of M. persicae per leaf, reaching levels of aphid reduction close to 100 % when compared to the untreated control. These results suggest that mirids might play a major role in aphid management in sweet peppers. The potential implementation methods of predatory mirids for the biological control in sweet peppers are discussed

Important role of forest disturbances in the global biomass turnover and carbon sinks

Forest disturbances that lead to the replacement of whole tree stands are a cornerstone of forest dynamics, with drivers that include fire, windthrow, biotic outbreaks and harvest. The frequency of disturbances may change over the next century with impacts on the age, composition and biomass of forests. However, the disturbance return time, that is, the mean interval between disturbance events, remains poorly characterized across the world’s forested biomes, which hinders the quantification of the role of disturbances in the global carbon cycle. Here we present the global distribution of stand-replacing disturbance return times inferred from satellite-based observations of forest loss. Prescribing this distribution within a vegetation model with a detailed representation of stand structure, we quantify the importance of stand-replacing disturbances for biomass carbon turnover globally over 2001–2014. The return time varied from less than 50 years in heavily managed temperate ecosystems to over 1,000 years in tropical evergreen forests. Stand-replacing disturbances accounted for 12.3% (95% confidence interval, 11.4–13.7%) of the annual biomass carbon turnover due to tree mortality globally, and in 44% of the forested area, biomass stocks are strongly sensitive to changes in the disturbance return time. Relatively small shifts in disturbance regimes in these areas would substantially influence the forest carbon sink that currently limits climate change by offsetting emissions