Forty Years of Vegetation Changes on the Pumice Desert, Crater Lake National Park, Oregon

摘要

The Pumice Desert is a pumice flat occupying about 640 ha along the northern portion of Crater Lake National Park. It is surrounded by lodgepole pine (Pinas contorta var. murrayana) forest. The purpose of the study was to identify the factors maintaining the open, barren nature of the area and to monitor vegetation changes. The initial vegetation survey on the Pumice Desert was conducted in 1965. Nine 0.04-ha strip plots and one rectangular 40.5-ha plot were marked with iron rods to monitor herbaceous plants and lodgepole pine. The plots were resurveyed in 1977, 1995, 2000, and 2005. Only 14 species were initially found in the 0.04-ha plots; an additional species was found in 2005. Plant numbers varied in the 0.04-ha plots during four surveys spanning 40 years. Vegetation was sparse with about 5% coverage. However, the number of trees in the 40.5-ha plot nearly tripled in the 40 years the area has been monitored. This paper documents the changes that have taken place over 40 years and offers rationale for the slow speed of plant succession. It also documents the predominance of multiple-trunked lodgepole pine within the study area and evaluates possible causes.