A general account of the findings of a joint USDA Forest Service/University of Alaska research project studying taiga ecosystems, especially the black spruce type [see FA 42, 5305; 43, 3427]. Black spruce forests are the most nutrient poor and least productive forest type, with stands of 120-150 yr old having a m.a.i. of approx. 110 g/m2 compared with an av. 460 g/m2 for white spruce, Betula papyrifera, Populus tremuloides and P. balsamifera. Ecosystem differences in productivity and degree of nutrient limitation are controlled mainly by soil and forest-floor temp. Periodic fires affect nutrient cycling as well as largely controlling the vegetation pattern to produce a mosaic of black spruce, white spruce and broadleaves.