Chapter 8 Investigating causes of bishop pine decline on California's north coastThis article is part of a larger document. View the larger document here.
This project seeks to understand the causes of a dramatic decline of bishop pine (Pinus muricata) stands on the northern California coast in Mendocino and Sonoma Counties. The northern bishop pine forest is designated by the State of California as a sensitive vegetation type with a global rank of G2 (endangered) and a State rank of S2.2 (threatened) (Sawyer and others 2009). Stand decline and high mortality levels have been reported, especially in mid- to northern Mendocino County, since the early to mid-2000s; a drive along U.S. Highway 1 through these two counties or even a cursory examination of Google Earth imagery confrms the severity of the problem. Coupled with reported declines of bishop pine in the southern part of its California range, this northern decline may imperil the future not only of the species, but also of the unusual forest ecosystems it supports and the people who depend on them.1 However, this decline is not yet represented in the scientifc literature, nor does it show up in aerial survey records or Forest Inventory and Analysis (FIA) plots because of its coastal position. Our project proposed to remedy this need by collecting a set of systematic observations throughout the range of the decline. We investigated the decline using a twofold approach: (1) the application of dendroecological methods to a subset of trees in several stands to determine stand age structure, growth, and regeneration trends within the past century; and (2) an inventory of pest (pathogen and insect) problems present in these stands to gauge their prevalence and identify any that appear to be primary causes of the decline.