Boreal forests are the second largest terrestrial biome and arc among the few that are circumpolar. Boreal forests arc characterized by extremely short growing seasons, low species richness, and extreme contrasts in the functional attributes of species that are important in ecosystem processes. Like tundra ecosystems (Chapin and Korner, Chapter 2, this volume), their diversity is therefore characterized by low richness and low redundancy, and thus any loss of diversity has a high potential to affect ecosystem processes. In the boreal forest, many species respond to and affect resource availability, food supply for herbivores and disturbance regimes in very different ways, and the presence of a particular species may alter ecosystem properties to either reinforce or weaken its role in the community. The diversity of plant tissue chemistry among taxonomic units, from subspecies to genera, appears to be one mechanism integrating species diversity with ecosystem properties. Tissue chemistry - particularly concentrations of nitrogen, resin, secondary compounds and lignin - controls decomposition and nutrient availability, payability to herbivores and fiammabiĆ¼ty, and is correlated with other functional plant traits such as life form, growth rates, longevity, etc. The effect of human activities (particularly changes in climate and precipitation chemistry, as well as alterations of disturbance regimes through fire suppression and logging) on the ecosystem consequences of diversity will be mediated through these feedbacks between organisms and ecosystem processes. A full understanding of the ecosystem consequcnces of biodiversity in boreal regions of sufficient power for policy analysis will be achieved only through synthesis of long-term observations and surveys, experiments and theoretical models.

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