The landscape of interaction: scaling up from local plant-plant and plant-soil relationships

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My research program investigates how plant community diversity and composition are structured by interactions among plants and between plant and soil communities. My short-term (5 year) objectives for this proposal are to scale up from local-scale (millimetre-metre) plant competition and multitrophic plant-microbial interactions to landscape-scale (metre to kilometre) patterns of plant and soil microbial community composition. I will utilize a spatially explicit multi-year field study of plant competition and plant and soil microbial community composition to characterize the among plants and the cross-trophic level landscape of plant soil feedback. Through this program, I will test 1) the relative importance of competition as a mechanism structuring both local-scale and landscape-level patterns of plant community diversity and composition, 2) whether well understood rhizosphere plant-microbe linkagesare an important mechanism structuring landscape-scale plant and microbial community diversity and composition, and 3) how fine-scale soil nutrient heterogeneity influences plant-soil interactions under field conditions. My research program will support three graduate students, a MSc. student focused on plant competition, a PhD. student focused on plant-soil linkages, and a MSc. student focused on experimentally linking plant competition, root foraging dynamics, and plant-soil microbe interactions. This research program will bridge the gaps between well studied and fundamentally local plant – plant and plant-soil interactions occurring at scales of millimeters to centimeters and landscape level patterns of plant and soil community structure. There is substantial evidence for variation in the strength and importance of competition and plant-soil relationships along environmental gradients, yet few studies have examined these patterns from a landscape perspective. Scaling up to landscape level patterns and processes is challenging because the relative importance of multiple interacting ecological mechanisms need to be assessed, but new analytical tools make this possible. This research program will be the first to bridge these scales, developing clear links between the fine-scale of plant-plant and plant-soil interactions, meso-scale patterns relevant to many pressing issues in ecology, conservation biology, and community assembly, to broad-scale community structure. In this research program, I will work across scales by characterizing a conceptual topography, the “landscape of interaction”, where variation in the strength and importance of local-scale ecological processes are mapped across a grassland landscape. This conceptual tool is key to understanding larger scale patterns in plant and soil communities. Using a spatially explicit sampling design to characterizing patterns of competition between individual plants will allow me to make cross-scale tests of the importance of competition as a mechanism structuring local-scale and landscape level patterns of plant community diversity and composition. Similarly by characterizing the linkages between plant root, soil eubacteria, archaea, and fungal communities across scales, will allow me to test the role of these multitrophic relationships in structuring plant and soil community diversity and composition. Finally, by characterizing rooting patterns in relation to fine-scale soil nutrient heterogeneity and microbial community structure, I will be among the first to investigate the factors that influence plant root foraging patterns under field conditions.