Forests of the western Olympic Peninsula: Understory plant species diversity, forest policy, and landscape pattern (Washington).

摘要

Forest management policies affect the spatial distribution of seral stages and the plant and animal species that are associated with them. Forest policies have historically been developed for a single ownership, with little thought to transboundary implications. Understanding forest policy impacts on ecosystems however, requires analysis at broad spatial and temporal scales that encompasses all ownerships.; In this study, I quantified the current spatial distribution of four forest age categories: regeneration (age 0–19 years), young (20–79 years), mature (80–199 years) and late seral (≥200 years). I characterized the understory plant species diversity in each category. I projected future conditions under three alternative management scenarios across all landowners of the western Olympic Peninsula. Finally, I quantified the resulting landscape structure.; Spatial analysis of current conditions revealed that late seral forest was the most limited in spatial extent and was the most fragmented of the four age categories. Distribution of late seral forest was strongly related to ownership. Currently, 91% is located on public ownerships, and less than 1% is found on private lands. Species richness and abundance, and the distribution of exotic species varied significantly with age category. Richness was highest in regenerating stands, however 20% of the species were exotic. Diversity of native species was highest in late seral stands. Lowest diversity levels were found in the young category, which comprises more than 80% of the current landscape. Because of the isolation and limited spatial extent of late seral forest, late seral understory species are uncommon in some portions of the landscape.; Simulation results revealed that management plans currently in effect for each landowner will change the distribution of forest age categories in the future. The proportion of late seral forest will increase from 8% in the current landscape (all landowners combined) to roughly 40% of the future landscape. Late seral forest will be more evenly distributed, although approximately 80% will lie on public lands. Management efforts aimed at conservation of late seral species at broad spatial scales will need to consider the lack of contiguity of late seral forests and the role of ownership in its distribution.