Modeling bird communities and ecosystem properties in northern forests

[The authors] simulated changes in plant community composition, ecosystem properties, and bird habitat quality across soil moisture and climatic gradients in the Lake Superior region using LINKAGES. LINKAGES is an individual-tree based forest simulation model that includes limitations of climate, soil moisture, and nitrogen on tree growth. Habitat relationships for ten passerines were derived from a seven year data base on species abundances in relation to the same plant community characteristics that LINKAGES simulates. Productivity and nitrogen cycling increased along gradients of increasing temperature from Ontario to Michigan and increasing soil moisture from sand to clays. Concurrently, bird populations oscillated in cold dry forests because of high tree mortality and gap-phase replacement, but these oscillations became damped in more productive forests.