Community characteristics of old-growth western juniper woodlands

While considerable attention has been given to the areal expansion of junip er (Juniperus sp.) in the western United States, the presence and ecologica l significance of old-growth juniper communities has gone largely unnoted. Increased recognition of these communities has prompted questions about how to recognize old-growth, community structure, ecological importance, and a ppropriate management. As an initial analysis of old-growth western juniper woodlands (Juniperus occidentalis Hook var. occidentalis Vasek) in central Oregon, this study investigated old-growth community structure on eolian-s and derived soils. These woodlands represent the most extensive old-growth western juniper woodlands throughout its range. Nine study plots were estab lished at 7 sites. Within each plot, densities and physical attributes of a ll live trees and large standing and fallen woody detritus were recorded. A dditional measurements for live trees included canopy cover, apparent age c lass (pre- or postsettlement), and a sampling of tree ages. Aging of trees older than 250 years was complicated by extensive heartwood rot. Shrub dens ity and cover were measured by species. Understory cover was measured by sp ecies and functional type. Bare ground, rock, juniper litter, other litter, moss, and cryptogamic crust cover were also measured. Plant cover ranged f rom 11 to 33% for trees, 0 to 10% for shrubs, 3 to 12% for perennial grasse s, 1 to 2% for forbs, and from 0 to 0.1% for annual grasses. The woodlands contained at least 80 trees ha(-1) aged over 200 years. Correlations betwee n tree parameters and understory structure and composition were generally p oor. Differences in plant composition among these stands was primarily attr ibuted to elevation, slope, and percent sand content. Structural characteri stics that distinguished old-growth stands from younger stands included tre e growth form, presence of standing and dead large woody debris, lichen on dead branches, and a relatively open canopy. Results provide a preliminary basis for identifying old-growth Juniperus occidentalis stands, as a prelud e to the development of management plans and further research into the func tional characteristics of the systems, A definition of old-growth juniper w oodlands is presented.