Our major research interests focus on the current challenges that plant communities are facing in the context of global change, i.e. climate change, invasive species, and landscape fragmentation. These challenges are interconnected as they form the novel environment under which plants are growing. The fact that forest communities are highly dependent on recruitment dynamics makes the study of early demographic stages critical for understanding the impact of global change on the natural ecosystems around us. To isolate these phenomena, we have directed our research at the recruitment of dominant tree species, from seed production to the sapling stage, including seed dispersal, germination, establishment and survival during the first years. This line of research covers a gap on the study of vegetation response to global change, where most work done has been on the basis of correlative approaches, e.g., climate envelopes. By focusing on the actual demographic responses of plant species to a changing environment, results from our work will be essential to forecast reliable vegetation changes under future climate scenarios.
We are particularly interested in the effects of climate change on the structure of natural communities. Climate, as one of the major drivers of species distributions, is already altering the life cycles of many plant and animal species. Quantifying the range of possible responses plant species have to changing conditions is indispensable for developing vegetation models that predict the outcome of global change. Responses of contemporary plant communities to current climate change are arguably the most relevant indication of climate sensitivity, and we can use these observations to anticipate potential consequences of climate change.
Because the study of forests is integral to understanding climate change, in our research we have explored the combinations of factors that tend to place tree species at risk of local extinction, especially the constraints related to species recruitment of new individuals. We have also addressed the identification of sources of potential immigrants for a particular region. A change in climate may select for a combination of characteristics that are not represented in the species pool that currently resides within the migratory reach. If native species were to reduce their abundance and insufficient new species were unable to colonize a region, one would expect major consequences to the local ecosystems, such as reductions in biomass and carbon sequestration, an impact on plant production, soil fertility, watershed conservation, and ultimately on ecosystem stability.
Many plant species are expected to shift their distributional ranges in response to global warming. These changes will then influence the future composition and structure of most communities. The ecological consequences of such changes could be enormous and have serious implications for conservation of local biodiversity and also for preservation of relevant ecosystem functions (e.g. soil erosion prevention, replenishment of water table, carbon storage). Regions that will be particular affected are those where different biomes come together (e.g., temperate and boreal forests), as these areas comprise the distributional limits of numerous species and will likely experience the largest shifts in species compositions.
It is important to consider that in addition to climate, many other factors will also shape the future composition of plant communities. In particular, plant-soil feedbacks will likely have a large impact on colonization success of migrant plant species as these may be released from their natural soil pathogens and/or deprive of key symbiotic organisms. In our work we evaluate the role that soil-plant interactions may play on the migratory potential of dominant temperate tree species at the northern limit of their distributional range in the Great Lakes region.
Contemporary plant invasions have been taking place during the last few decades of climate change and in a human-altered landscape. Thus, recent patterns of plant invasions can help us determine which native species will be successful expanding their ranges under global change and the migratory patterns they may follow. In addition, controlling and preventing the spread of invasive species are common goals among ecologists and natural resources managers. However, reliable forecasts of the spread of newly introduced species are rare. The idiosyncratic nature of the invasion process, where both historical and local conditions affect the likelihood of establishment, makes the generalization of the invasion process very difficult. This, in turn, hampers our ability to generate guidelines for the early control of potentially invasive species and their newly arrived populations.
Anthropogenic drivers of global change, ranging from land-use and fragmentation to changing climatic regimes, are affecting forest composition and functioning across the landscape. In the case of tree species, their long generation time together with a highly fragmented landscape will likely prevent them from being able to naturally track global warming at the rate required to cope with current climate change. Thus, the in situ responses of the current forest communities to the new environment, i.e., their resilience, will be critical to forecast the structure and functioning of future forests. At the same time, reforestation programs taking place after logging or disturbance events will be common, and managers will have the opportunity to select species best suited to the future climate. To better predict the outcome of future forests and plantations research efforts should build a body of work focusing on species performance under forecasted climate scenarios and in particular under drought conditions. Even if most forest species will be able to tolerate changes in mean climatic conditions it is not clear they will be able to withstand the effects of extreme weather effects like drought. Drought conditions can have tremendous effects on forest ecosystems and the incidence of droughts has been predicted to increase in Great Lakes forests. In this study we will assess the resilience to drought of dominant tree species in forests of the Great Lakes region.The goal of this study is to determine if tree species-specific growth rates (our proxy for resilience) are affected by land use, drought or a combination of the two drivers of change.
Additional Research Interests
Statistical modeling - In most of our work, we have encountered statistical challenges common to ecology, including missing observations, nonlinear processes, data sets that are spatially and temporally structured, commonly at different scales, and in some cases, data came from different sources. We have found hierarchical Bayesian methods particularly useful in dealing with these issues. For example, we developed a series of hierarchical Bayes models to quantify the effects of environmental variability on seedling establishment. The inferential models that we developed accommodated many unmeasurable factors that affected demographic processes and the data that derived from them. In our current work on invasive species, we are also devising a hierarchical framework specific to the ecosystems in question. We plan to continue the implementation of this modeling approach and are therefore committed to investigating how new developments in ecological modeling and statistical analysis can contribute to our research program.