Dr. Avi Bar-Massada
Department of Biology and Environment
One of the basic questions in ecology concerns the driving forces behind the distribution of ecological phenomena (and organisms in particularly) in space and time. Our research has been focused on understanding the different mechanisms (natural and anthropogenic) that affect the abundance and distribution of species, as well as the structure and composition of ecological communities, at different spatial scales from local to continental. Some of our main lines of research are: Addressing a fundamental question in community ecology: which forces drive community assembly at different geographical locations, and how can we explain variations in the structure of communities across environmental gradients. We used a modeling approach to reveal the effect of habitat heterogeneity on the relative roles of niche versus neutral processes in driving species assembly in communities (here). We then focused on another key pattern in community ecology, species co-occurrence, to quantify how species interactions depend on environmental conditions and habitat heterogeneity (here). We then used both models and empirical data on tree communities to reveal that species co-occurrence patterns change along environmental gradients (here), which could have profound implications on our ability to predict future species distributions under environmental change. In an ongoing study, we analyze how do climate, land-cover, and land-use interact to affect bird community composition along a sharp rainfall gradient along the Jordan River Rift Valley. Investigating the ubiquitous ecological relationship between species richness and environmental heterogeneity. In recent years, we showed that the shape of the richness – heterogeneity relationship depends on the choice of environmental variable as well as the type of habitat (here). A theoretical study revealed how the pattern of this relationship also depends on species traits (here). At present, we are analyzing how the spatial configuration of the environment interacts with species traits and habitat composition to dictate the richness – heterogeneity relationship in modeled and real landscapes. Quantifying the effects of disturbances (mostly traditional agro-pastoral activities such as grazing and shrub removal) on the spatial patterns of woody vegetation (here), on herbaceous community composition and dynamics (here), and on reptile communities in Israel’s Mediterranean landscapes (ongoing PhD research by Roy Talbi). Livestock grazing has profound effect on vegetation structure in Mediterranean landscapes, which facilitates its usage as a management tool to preserve biodiversity and minimize wildfire risk. At the same time, Mediterranean herbaceous communities undergo considerable spatial and temporal turnover in species composition as the outcome of both by grazing and changes in rainfall amounts. Our ongoing research on reptile communities reveals that they are strongly affected by cattle grazing, and most surprisingly, we found that Cattle Egrets, which accompany cattle in many Mediterranean landscapes, exert a strong predatory pressure on many reptile species. Wildfire is a catastrophic ecological phenomenon that has profound effects on natural ecosystems and human settlements alike. Our collaborative applied research into the processes behind wildfire initiation, spread, and outcomes focuses on the spatial aspects of these processes. Past studies included statistical analyses of ignition patterns in the US (here), developing mapping methods to quantify where settlements are more likely to be affected by wildfire (here), and revealing how urban development patterns can have a significant impact on wildfire risk to houses (here). At present, we are working on a collaborative study that focuses on developing new remote sensing algorithms for mapping wildfire risk (as well as vegetation structure) in Mediterranean Israel using VENuS, a new satellite sensor.