John A. Anhold

Stand Conditions Associated with Roundheaded Pine Beetle (Coleoptera: Scolytidae) Infestations in Arizona and Utah

Abstract Stand conditions associated with outbreak populations of the roundheaded pine beetle, Dendroctonus adjunctus Blandford, in ponderosa pine, Pinus ponderosa Dougl. ex Laws., forests were studied in the Pinaleno Mountains, AZ, and the Pine Valley Mountains, UT. Classification tree models to estimate the probability of infestation based on stand attributes were built for both study areas using growth rate and ponderosa pine basal area information. Cross-validation estimates of correct classification were 0.60 for the Pinaleno Mountains and 0.58 and 0.78 for the Pine Valley Mountains. Regression tree and linear regression models to estimate amount of mortality caused by the beetles were also built for both sites using growth rate, ponderosa pine basal area, and trees per hectare information. The occurrence and mortality levels caused by the roundheaded pine beetle are positively related at both the stand and tree scale with reduced growth rates caused by high stocking densities.

Within-stand spatial distribution of tree mortality caused by the Douglas-Fir beetle (Coleoptera: Scolytidae)

Abstract The Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, causes considerable mortality in Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, forests. Within-stand distribution of mortality was examined in affected stands using geostatistical techniques. A 10 × 10 m grid was established in two 4-ha study sites. Live and beetle-killed host basal area was measured at each node. In a 16-ha stand, a variable-resolution grid was established and the same information collected. The relationship between Douglas-fir basal area and Douglas-fir basal area killed was examined using non-spatially explicit and spatially explicit linear regression models. A positive linear relationship was observed between the variables. Significant spatially explicit models suggest that the relationship is also true at fine scales. Relative variograms were constructed for Douglas-fir basal area before and after the Douglas-fir beetle outbreaks. For the 4-ha sites, increased spatial dependency in the distribution of Douglas-fir basal area was observed as a result of the Douglas-fir beetle outbreak. For the 16-ha site, kriging was used to estimate live Douglas-fir basal area before and after the outbreak to a 10-m resolution and the stand rated for potential mortality illustrating the potential applicability of geostatistical techniques to rating a stand for potential mortality. Cross-validation analysis indicated that although the potential exists for large estimation errors, the majority of the estimates were within acceptable ranges. The study suggests that geostatistical approaches may be suitable to extend our understanding bark beetle ecology and improving the application of extent of mortality models.

Evaluation of Funnel Traps for Characterizing the Bark Beetle (Coleoptera: Scolytidae) Communities in Ponderosa Pine Forests of North-Central Arizona

Abstract Lindgren funnel traps baited with aggregation pheromones are widely used to monitor and manage populations of economically important bark beetles (Coleoptera: Scolytidae). This study was designed to advance our understanding of how funnel trap catches assess bark beetle communities and relative abundance of individual species. In the second year (2005) of a 3-yr study of the bark beetle community structure in north-central Arizona pine (Pinus spp.) forests, we collected data on stand structure, site conditions, and local bark beetle-induced tree mortality at each trap site. We also collected samples of bark from infested (brood) trees near trap sites to identify and determine the population density of bark beetles that were attacking ponderosa pine, Pinus ponderosa Douglas ex Lawson, in the area surrounding the traps. Multiple regression models indicated that the number of Dendroctonus and Ips beetles captured in 2005 was inversely related to elevation of the trap site, and positively associated with the amount of ponderosa pine in the stand surrounding the site. Traps located closer to brood trees also captured more beetles. The relationship between trap catches and host tree mortality was weak and inconsistent in forest stands surrounding the funnel traps, suggesting that trap catches do not provide a good estimate of local beetle-induced tree mortality. However, pheromone-baited funnel trap data and data from gallery identification in bark samples produced statistically similar relative abundance profiles for the five species of bark beetles that we examined, indicating that funnel trap data provided a good assessment of species presence and relative abundance.

Variables associated with the occurrence of Ips beetles, red turpentine beetle and wood borers in live and dead ponderosa pines with post‐fire injury

Recently, wildfires and prescribed burning have become more frequent in conifer forests of western North America. Most studies examining the impacts of insects on trees with post‐fire injury have focused on contributions to tree mortality. Few studies have examined fire‐caused injuries to estimate the probability of attack by insects. Scant data quantifying insect associations with one another, or with live and dead fire‐injured trees, are available. We examined live and dead trees with varying levels of fire injury in wildfires in Colorado, Montana, Arizona and the Black Hills aiming to determine fire injury associated with insect infestation, co‐occurrence between insects and insect association with live and dead fire‐injured trees. Bole scorch height estimated the likelihood of attack by Ips spp. Diameter at breast height, bole scorch height and crown scorch height estimated the likelihood of attack by Dendroctonus valens LeConte. Diameter at breast height and bole scorch height estimated the likelihood of attack by wood borers. Ips spp., Dendroctonus valens and wood borers were associated with one another. Ips spp. beetles and wood borers were associated with dead fire‐injured trees, whereas D. valens was often associated with live fire‐injured trees. Focusing on certain fire‐caused injuries may identify trees targeted by Ips spp. beetles, Dendroctonus valens and wood borers.

Development of post-fire crown damage mortality thresholds in ponderosa pine

Previous research has shown that crown scorch volume and crown consumption volume are the major predictors of post-fire mortality in ponderosa pine. In this study, we use piecewise logistic regression models of crown scorch data from 6633 trees in five wildfires from the Intermountain West to locate a mortality threshold at 88% scorch by volume for trees with no crown consumption. For trees with 440% crown consumption volume, linear regression indicates 485% mortality, but for trees with crown consumption volume o40%, there is a statistically significant, linear relationship between increasing crown scorch and increasing probability of mortality. Analysis of an independent 600þ tree dataset from Colorado produced similar results and supports the analysis approach. Crown scorch volume (485%), crown consumption volume (440%), and crown consumption between 5 and 40% combined with crown scorch volume 450% mortality thresholds could be incorporated into post-fire marking guidelines for forest management goals. Additionalkeywords: crown consumption,crown scorch,logisticregression, markingguidelines,piecewise regression, Pinus ponderosa, statistical models, wildfire.