Soil Chemistry Patterns In An Edaphic Endemism Hotspot: The Pebble Plains of the San Bernardino Mountains, California

Abstract Pebble plains are a unique edaphic environment known only from the high valleys of the San Bernardino Mountains, California. The pebble plains have long been celebrated for the high vascular plant diversity they support, including at least six taxa endemic to the San Bernardino Mountains. Past research has shown that pebble plains soils differ most notably from nearby non-pebble plains soils in terms of their high clay content and loose, stony structure, especially in their upper-most horizon and on the soil surface. The stony upper horizon is probably the result of frost-heaving and erosion of soil particles by wind; the resulting accumulation of stone fragments at the soil surface is what inspired the name “pebble plains.” The combined effects of a friable, rocky surface, heavy lower horizons, frost heaving, high solar insolation, and desiccating winds are thought to limit recruitment of shrubs and trees and foster the persistence of a unique pebble plains flora consisting of herbaceous annuals...