Effects of Soil Compaction on Height Growth of a California Ponderosa Pine Plantation

Abstract

Abstract An analysis was made of the extent to which observed variability in plantation height growth could be explained by variability in soil surface characteristics that are modified by harvesting and site preparation activities. The study was done in a 16-year-old ponderosa pine (Pinus ponderosa) plantation in the Sierra Nevada of California. Annual height growth of all 423 trees within a 0.48 ha area was measured together with soil bulk density, A-Horizon thickness, and shrub competition. Soil organic carbon and mineralizeable nitrogen were measured on a subsample of 72 trees. Trees in areas of highest bulk density grew 43% less at age 1 and 13% less at age 15 than those in areas of lowest bulk density. Annual shoot growth was markedly reduced for 4 consecutive years following 2 years of below-normal precipitation, especially in trees growing in soils of lowest bulk density. Bulk density, A-Horizon thickness, and shrub cover accounted for only 13 to 23% of variability in height growth of the 423-tree sample. These same variables, plus organic carbon and mineralizeable nitrogen, accounted for 31% of variability in height growth of the 72-tree sample. West. J. Appl. For. 1:104-108, Oct. 1986.