Changes in plant communities after planting and release of conifer seedlings: Early findings

Plant diversity, density, and development data from an extensive research program in conifer plantations in northern California suggest changes in plant community composition after site preparation and many kinds of release. Based on 17 studies, the average number of species per study area after 10 years was 25 with composition of 1 conifer, 1 hardwood, 8 shrubs, 12 forbs, and 3 graminoids. Species ranged from 13 to 46. Density, foliar cover, and height varied by treatment and type of vegetation present. Density in a mixed shrub community, for example, ranged from 902 to 18,168 plants/acre after 10 years and in a mixed shrub-grass community from 147,400 to 254,900 plants/acre. Additional data are presented on the fate of a serious invader, side-by-side develop- ment comparison of two vigorous shrubs, and changes in species composition in several vegetation density classes in a plantation after 27 years.