The tundra biome is the dominant terrestrial ecosystem of the circumpolar north, and its fate in a rapidly changing climate is of high scientific and socioeconomic concern. One of those concerns is that the majority of caribou herds throughout the circumpolar north are declining, perhaps as a result of climate change. The principal objective of this research is to reveal the connections between soil nutrient cycling, forage quality and caribou habitat selection. This framework is underpinned by the concept that tundra ecosystem productivity is ultimately driven by the thermodynamics of the system induced by climate. In winter, soil microbial processes drive N mineralization and thus N available for plant growth in spring, but ambient temperature and the dynamics of the snowpack strongly modulate this process. In summer, temperature and soil moisture likewise drive soil-plant processes, and these set constraints on herbivore productivity. Importantly, the mechanistic framework includes the feedbacks that occur between all three trophic levels to determine overall ecosystem function and productivity.
