Although young forests may be net carbon sources, this is largely the result of soil and vegetation disturbance associated with harvesting the previous forest, and the accompanying changes in microclimate (Cropper and Ewel 1984; Johnson 1992), neither of which apply to the same degree to afforestation. Mid- to late-rotation forests are generally net carbon sinks (Cropper and Ewel 1984). It is reasonable to assume that agroforests and plantations will display this same general pattern of increasing rate of carbon accretion in woody biomass and soil litter into middle age. Substantial amounts of carbon may be accumulated in the “duff” layer of semi-decomposed needles under old stands of conifer trees (Alban 1982). Our trees were่ just beginning to shed sufficient needles for this layer to begin to accumulate. Since needle production in young Douglas-fir stands is exponentially related to tree size (Gholz et al 1979), needle fall should become an important carbon sink in both our agroforests and plantations in future years. Since conifers grow proportionately to their initial size, greater current tree size in agroforests relative to plantations should increase differences in net carbon accretion both in tree mass and in needle fall in the future.