Aboveground net primary production and leaf-area index in early postfire vegetation in Yellowstone National Park

Aboveground net primary production (ANPP) and leaf-area index (LAI) of lodg epole pine (Pinus contorta var. latifolia Engelm. ex Wats.) saplings and ab oveground productivity of herbaceous vegetation components were determined 9 years after the 1988 fires in Yellowstone National Park (YNP). Measuremen ts were made in four sites representing a wide range of early postfire vege tation present in YNP, including high-density lodgepole Dine, low-density l odgepole pine, and two nonforest stands. LAI of the pine saplings and total ANPP (trees plus herbs) generally increased with increasing sapling densit y, from 0.002 m(2) m(-2) and 0.25 Mg ha(-1) year(-1) in the infertile nonfo rest stand (100 pine saplings ha(-1)) to 1.8 m(2) m(-2) and 4.01 Mg ha(-1) year(-1) in the high-density pine stand (62,800 saplings ha(-1)). Abovegrou nd herbaceous productivity was not strongly correlated with sapling density , but appeared to be influenced by soil fertility. In the high-density pine stand, tree ANPP and LAI were within the lower range of values reported fo r similar mature coniferous forests. This finding suggests that at least so me ecosystem processes (related to ANPP and LAI) may have nearly recovered after only 9 years of postfire succession, in at least some of the young fo rests developing after the 1988 Yellowstone fires.