Limber pine health in the southern and central Rocky Mountains
Date
2014
Authors
Cleaver, Christy, author
Jacobi, William, advisor
Reich, Robin, committee member
Negron, Jose, committee member
Steingraeber, Dave, committee member
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Abstract
White pine blister rust, bark beetles, and dwarf mistletoe are causing decline in health and mortality in limber pine and impacting limber pine seedlings in the central and southern Rocky Mountains. Ecologically valuable limber pines often grow in fragile ecosystems where few other trees can grow. The combined effects of mountain pine beetle, white pine blister rust, dwarf mistletoe, and climate change could greatly impact the biodiversity of these ecosystems. Current condition status and long term monitoring of limber pine trees and seedlings are needed to advise land managers and to implement restoration. Our study objectives were to: (1) assess site, stand, and health characteristics of limber pine trees and seedlings in Colorado, Wyoming, and Montana, (2) determine factors that influence the occurrence and incidence of white pine blister rust, bark beetles, and dwarf mistletoe, and (3) determine factors that impact seedlings, including site, stand, and meteorological characteristics. In 2011 and 2012, we assessed 22,700 limber pines on 508 plots in limber pine-dominated stands in twenty-five study areas in Colorado, Wyoming, and Montana. Mean density of live limber pine was 311 stems/ha. Fifty percent of all standing trees were classified as healthy, 26% were declining or dying, and 24% were dead. White pine blister rust was the primary damage agent and was widespread, occurring in 23 of the 25 study areas with a mean incidence of 26%. Bark beetle-caused mortality occurred in all 25 study areas and 18% of standing limber pines were killed by bark beetles. Limber pine dwarf mistletoe occurred within 20 study areas, on 29% of plots with an average incidence of 9%. In previously monitored study areas, incidence of WPBR increased 6%, bark beetles by 17%, while dwarf mistletoe remained the same. Live limber pine seedling density averaged 141 stems/ha. Of all standing live and dead limber pine seedlings, 1.5% were dying, 4.4% were dead, and white pine blister rust occurred on 5.3% of live seedlings. We used statistical modeling to determine the meteorological, macro, and micro site factors and stand factors that influenced the occurrence and incidence of white pine blister rust, bark beetles, and dwarf mistletoe on limber pines. We also used statistical modeling to determine factors that predict density (stems/ha) of limber pine seedlings and proportion of limber pine seedlings with white pine blister rust. Limber pine stands heavily impacted by mountain pine beetle and white pine blister rust, combined with low seedling density in some study areas suggest that some limber pine stands may not survive. These areas may be in need of additional monitoring so land managers can decide if restoration efforts are warranted.
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Subject
mountain pine beetle
white pine blister rust
seedlings
dwarf mistletoe
limber pine