Biodiversity patterns in disturbed landscapes

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The homogenization of plant communities across space and time, associated with the current biodiversity crisis, is increasingly documented for natural habitats located in urban matrices. Yet, predicting when homogenization will occur and identifying its causes require further investigation for successful conservation planning. My research program aims to understand how natural habitats isolated in anthropogenic landscapes are being transformed. Over the next five years, I will use multiple approaches based on both taxonomic and functional (plant traits) aspects of diversity. First, I will study forests and wetlands to assess whether stress regime, such as waterlogged conditions, can modulate the response of communities to urban development. In districts with low and high urbanization levels, I will compare forests, intact swamps, and swamps that have been affected by drainage, such as those disconnected from their hydrological recharge by road construction. I hypothesize that mesic forest flora will become more homogenized with urbanization, whereas forested wetland flora will diversify. For the latter, the release of environmental stress (waterlogged conditions) will indeed create new conditions for species establishment for which plant propagules will be supplied by the urban matrix. Over time, wetland and mesic forest floras will become more similar. Second, I will compare forests of residential and industrial sectors to assess the impacts of fine variations of urban disturbance types. These sectors may have similar ratios of green vs impervious areas, yet may differ in respect to air quality, pollinator activity, as well as citizens' behavior. In addition to standard plant surveys, I will sample lichens as bioindicators of air pollution. In a phytometer experiment, individuals of three species will be transplanted in several forests of residential and industrial sectors and used as sentinel plants for measuring pollinator activity. Paths will be used as a proxy for detecting citizens' use of forests. I hypothesize that in situ disturbance (citizens' visits) in residential sectors is a stronger driver of taxonomic homogenization than land-use in the surrounding matrix, but that pollution and reduced pollination prevailing in industrial developments are factors associated with functional homogenization. Third, I will use historical data from Baillargeon (1981) to study changes in species composition for a variety of habitats within the Québec City plateau. Replicates of forests, escarpments, railways and Power-line ROW, and coastal marshes will be selected and resurveyed. I hypothesize that homogenization/differentiation will depend on two important gradients across original habitats: original naturalness and environmental stress. This research program addresses crucial questions about biodiversity distribution and aims to increase our ability to effectively guide conservation and management decisions in human-modified landscapes.