Information Center for the Environment

Assessing dominant land cover change is critical to understanding the terrestrial consequences of climate change. This study created digital maps from a portion of a heritage vegetation survey of California, the Wieslander Vegetation Type Map survey of the 1930s. Digital maps were produced for a 30,236 km2 area of the Sierra Nevada. These historical data were compared with CalVeg, a 1996 vegetation map produced by the US Forest Service. In addition, the extent of Pinus ponderosa forests on the Placerville quadrangle was compared to a historical map from 1850 as well as the 1934 map.At low elevations, blue oak (Quercus douglasii) and foothill pine (Pinus sabiniana) areas have largely converted to grasslands. At about 1000 meters elevation, the lower edge of the “Yellow Pine Belt” (dominated by Pinus ponderosa) has retreated upslope about 180 meters between 1934 and 1996, and by 526 meters since 1850. Grazing, competition by nonnative grasses, and fire occurred on only 42% of the total area of change.The authors hypothesize failure of conifer seedling establishment due to earlier Sierra snowmelts caused by warmer temperatures. The lower edge of the Sierran conifer belt appears to be sensitive to climate change, a conclusion with implications for the water‐holding capacity of the mountains.