Plant communities associated with Pinus ponderosa forests in the sky islands of the Davis Mountains, Texas

摘要

Species composition of Pinus ponderosa P.&C. Lawson var. scopulorum Engelm. forests in the sky islands of the Davis Mountains was evaluated and classified using ordination and classification techniques. Twelve study sites were established within Pinusponderosa forests in the summers of 2002 and 2003. Over story (tree) and understory (shrub and herbaceous) vegetation strata were sampled. Thirteen associations were recognized by combining four overstory groups and eight understory groups. The associations reflected a wide range of ecological conditions with Juniperus deppeana associations occupying dry sites and Pinus ponderosa associations occupying wetter sites. The major environmental factors responsible for the differences in vegetation of theseforests were altitude, slope position, slope inclination, and soil moisture.