the increment of forest biomass and nutrient content on walker branch watershed, tennessee, from 1967 to 1983 was interrupted by two insect outbreaks. an outbreak of the southern pine beetle in the early 1970s and an outbreak of the hickory borer in the late 1970s to early 1980s killed a number of shortleaf pine (pinus echinata) and hickory (carya spp.), respectively. yellow-poplar (liriodendron tulipifera) growth increased over this 16-year period, especially in response to the mortality of shortleaf pine. the net result of these events was little change in total biomass but a substantial shift in species composition (from pine to yellow-poplar) in the pine forest type over this period. no species has yet responded to the mortality of hickory. due to the shift in species composition in the pine type, calcium and magnesium accumulation rates in biomass increased but foliage biomass decreased over the inventory period. there was little change in foliage biomass or nutrient content in other forest types, despite hickory mortality, since mortality occurred primarily among large trees having low foliage-to-woody-biomass ratios. the insect attacks, combined with apparently natural self-thinning, caused a large increase in standing dead biomass and in nutrient return via tree fall. this increased rate of return will substantially alter forest floor nutrient content and availability, especially with regard to calcium (where the calcium content of standing dead currently equals forest floor calcium content) and nitrogen (where inputs of woody litter will substantially alter carbon