My research concentrated on the analysis of spatial patterning and process in ecological systems, and soil-vegetation relationships in various ecosystems as affected by a range of human and natural disturbances. Ecosystems investigated include temperate deciduous and mixed coniferous forest (Montane US), grassland/forest ecotones (front range CO), mediterranean chaparral and grassland (CA), and high elevation grassland (PRC). Human disturbances studied include grazing, land use changes, and introduced species. Natural disturbances include climate fluctuation, treefall/blowdown, mass movement, and fire. Research addresses factors that determine species diversity of ecosystems, and how fine scale process can be used to predict coarse scale change. Investigating the impacts and mechanisms of exotic species invasion in forested ecosystems areas is a current research priority.