Ponderosa Pine Mortality Research Articles

Best Predictors for Postfire Mortality of Ponderosa Pine Trees in the Intermountain West

Abstract Numerous wildfires in recent years have highlighted managers' needs for reliable tools to predict postfire mortality of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) trees. General applicability of existing mortality models is uncertain, as researchers have used different sets of variables. We quantified tree attributes, crown and bole fire damage, ground fire severity, and insect presence from a total of 5,083 trees in four 2000 wildfires in four Intermountain states. Crown scorch (percentage) and consumption (percentage) volume collectively accounted for the majority of predictive capacity in all four individual models and in the pooled four-site model. The addition of tree diameter and presence of Ips beetles in the pooled model slightly improved predictive power. Four other statistically significant variables added little to the pooled model's predictive ability. The pooled model correctly classified 3-year postfire mortality of 89.9% of the trees and had a receiver operating characteristic (ROC) score of 0.96. In the external validation step, the model correctly classified 3-year postfire mortality of 96% of 1,361 trees in a 2001 wildfire. Our results and a number of previous studies suggest that a two-variable model using percentage crown scorch volume and crown consumed volume will have applicability beyond the Intermountain West.

Modeling Postfire Mortality of Ponderosa Pine following a Mixed-Severity Wildfire in the Black Hills: The Role of Tree Morphology and Direct Fire Effects

Abstract We examined the relationship among tree size, crown and stem damage, and 5 years of postfire mortality of ponderosa pine (Pinus ponderosa Dougl. ex. P. & C. Laws.) in the Black Hills following a large, mixed-severity wildfire. We measured tree morphology and direct fire effects on 963 trees and assessed individual tree mortality annually from 2001 to 2005. We used logistic regression to model tree mortality as a function of tree morphology (dbh) and bark thickness (BARK) and direct fire effects [percentage of the live crown scorched (PSCOR) and basal char measured as the percentage of the bole charred below 30 cm (CHAR)]. Models using dbh and BARK were modeled separately due to correlation between the variables. In all models, mortality decreased with increasing dbh and BARK and increased with increasing PSCOR and CHAR. Basal char contributed to the mortality of trees less than 40 cm but became less influential as dbh and BARK increased. Overall, probability of mortality modeled as a function of dbh, PSCOR, and CHAR correctly predicted the status of 78% of trees, whereas the model predicting mortality as a function of BARK, PSCOR, and CHAR had an increase in prediction accuracy of only 1%.

SELECTION OF DWARF MISTLETOE–INFECTED PONDEROSA PINES BY IPS SPECIES (COLEOPTERA: SCOLYTIDAE) IN NORTHERN ARIZONA

In 2002 a bark beetle epidemic severely impacted ponderosa pine (Pinus ponderosa Douglas ex C. Lawson.) forests in northern Arizona. Ponderosa pine mortality occurred over approximately 211,000 ha statewide (USDA 2002). Ips spp. (Ips pini Lecontei and I. lecontei Swaine, Coleoptera: Scolytidae) predominated within infestations and accounted for approximately 99% or about 208,000 infested hectares statewide (McMillin 2003, S.C. Kenaley personal communication). High rates of infestation and tree mortality occurred within the Coconino (24,400 ha), Prescott (30,600 ha), and Tonto National Forests (27,000 ha). In the Tonto National Forest alone, 47% of the ponderosa pine forest type was infested, and many stands had mortality rates of 80%‐90%. Western pine beetle (Dendroctonus brevicomis Leconte), roundheaded pine beetle (Dendroctonus adjunctunus Blandford), and mountain pine beetle (Dendroctonus ponderosae Hopkins) have also been detected within infested areas in northern Arizona, but these bark beetle populations have not yet reached epidemic levels. In many areas where bark beetle infestations occurred, ponderosa pine mortality was greatest in areas infested with southwestern dwarf mistletoe (Arceuthobium vaginatum

Prediction of delayed mortality of fire-damaged ponderosa pine following prescribed fires in eastern Oregon, USA

Prescribed burning is a management tool used to reduce fuel loads in western interior forests. Following a burn, managers need the ability to predict the mortality of individual trees based on easily observed characteristics. Astudy was established in six stands of mixed-age ponderosa pine (Pinus ponderosa Dougl. ex Laws.) with scattered western junipers at the south end of the Blue Mountains near Burns, Oregon, USA. Stands were thinned in either 1994 or 1995. Three treatments, a fall burn, a spring burn, and an unburned control, were randomly assigned to 12-ha experimental units within each stand. Prescribed burns occurred during mid-October of 1997 or mid-June of 1998 and were representative of operational burns, given weather and fuel conditions. Within each experimental unit, six 0.2-ha plots were established to evaluate responses to the burns. Ponderosa pine plot trees (n =3415) alive 1 month after the burns were evaluated and observed for four growing seasons. Nine fire damage and tree morphological variables were evaluated by logistic regression. A five-factor full model and a two-factor reduced model are presented for projecting probability of mortality. Significant variables in the full model included measures of crown, bole, and basal damage.

Ponderosa pine mortality following fire in northern Arizona

Sampling of 1367 trees was conducted in the Side wildfire (4 May 1996), Bridger-Knoll wildfire (20 June 1996) and Dauber prescribed fire (9 September 1995) in northern Arizona ponderosa pine forests (Pinus ponderosa). Tree mortality was assessed for 3 years after each fire. Three-year post-fire mortality was 32.4% in the Side wildfire, 18.0% in the Dauber prescribed fire, and 13.9% in the Bridger-Knoll wildfire. In the Dauber and Side fires, 95% and 94% of 3-year post-fire mortality occurred by year 2, versus 76% in the Bridger-Knoll wildfire. Compared with trees that lived for 3 years after fire, dead trees in all fires had more crown scorch, crown consumption, bole scorch, ground char, and bark beetle attacks. Logistic regression models were used to provide insight on factors associated with tree mortality after fire. A model using total crown damage by fire (scorch + consumption) and bole char severity as independent variables was the best two-variable model for predicting individual tree mortality for all fires. The amount of total crown damage associated with the onset of tree mortality decreased as bole char severity increased. Models using diameter at breast height (dbh) and crown volume damage suggested that tree mortality decreased as dbh increased in the Dauber prescribed fire where trees were smallest, and tree mortality increased as dbh increased in the Side and Bridger-Knoll wildfires where trees were largest. Moreover, a U-shaped dbh–mortality distribution for all fires suggested higher mortality for the smallest and largest trees compared with intermediate-size trees. We concluded that tree mortality is strongly influenced by interaction between crown damage and bole char severity, and differences in resistance to fire among different-sized trees can vary among sites.

Corrigendum to: Ponderosa pine mortality following fire in northern Arizona

Sampling of 1367 trees was conducted in the Side wildfire (4 May 1996), Bridger-Knoll wildfire (20 June 1996) and Dauber prescribed fire (9 September 1995) in northern Arizona ponderosa pine forests (Pinus ponderosa). Tree mortality was assessed for 3 years after each fire. Three-year post-fire mortality was 32.4% in the Side wildfire, 18.0% in the Dauber prescribed fire, and 13.9% in the Bridger-Knoll wildfire. In the Dauber and Side fires, 95% and 94% of 3-year post-fire mortality occurred by year 2, versus 76% in the Bridger-Knoll wildfire. Compared with trees that lived for 3 years after fire, dead trees in all fires had more crown scorch, crown consumption, bole scorch, ground char, and bark beetle attacks. Logistic regression models were used to provide insight on factors associated with tree mortality after fire. A model using total crown damage by fire (scorch + consumption) and bole char severity as independent variables was the best two-variable model for predicting individual tree mortality for all fires. The amount of total crown damage associated with the onset of tree mortality decreased as bole char severity increased. Models using diameter at breast height (dbh) and crown volume damage suggested that tree mortality decreased as dbh increased in the Dauber prescribed fire where trees were smallest, and tree mortality increased as dbh increased in the Side and Bridger-Knoll wildfires where trees were largest. Moreover, a U-shaped dbh–mortality distribution for all fires suggested higher mortality for the smallest and largest trees compared with intermediate-size trees. We concluded that tree mortality is strongly influenced by interaction between crown damage and bole char severity, and differences in resistance to fire among different-sized trees can vary among sites.

Susceptibility of Western Conifers to Laminated Root Rot (Phellinus weirii) in Oregon and British Columbia Field Tests

Abstract Several species of conifers were outplanted around infected stumps in Oregon and British Columbia to measure their susceptibility to laminated root rot caused by Phellinus weirii. Grand fir (Abies grandis) experienced nearly 30% mortality caused by P. weirii. Douglas-fir (Pseudotsuga menziesii) mortality exceeded 20%. Noble fir (A. procera), Sitka spruce (Picea sitchensis), giant sequoia (Sequoiadendron giganteum), western hemlock (Tsuga heterophylla), and ponderosa pine (Pinus ponderosa) mortality averaged less than 10%. Western white pine (P. monticola) and lodgepole pine (P. contorta) mortality was less than 1%. Phellinus weirii did not cause mortality of western redcedar (Thuja plicata) or redwood (Sequoia sempervirens). Apparent susceptibility, based on mortality over 17-20 growing seasons, was similar to that recorded in past field observations. West. J. Appl. For. 8(2):67-70.

A Signal Detection Framework to Evaluate Models of Tree Mortality Following Fire Damage

Abstract Signal detection theory provides an appropriate framework to evaluate the performance of various individual tree mortality models. Receiver operating characteristic (ROC) curves show the tradeoffs that are possible by varying the decision criteria, show predictive performance with respect to chance, and show the difference between various models. Two ROC curves were generated to predict ponderosa pine mortality following fall prescribed fires in northern Idaho. One ROC curve was developed from rules of thumb using percent crown scorch. A second ROC curve was developed from a logistic mortality model using diameter at breast height and scorch height. Overall, percent crown scorch is a better predictor of mortality than scorch height, and thus should be used to plan and conduct salvage operations in ponderosa pine following a fire. Because of the difficulties involved in predicting percent crown scorch before a fire, the logistic model based on scorch height can be used to plan understory prescribed fires. For. Sci. 36(1):66-76.

Ponderosa Pine Mortality from Spring, Summer, and Fall Crown Scorching

Abstract Mortality was compared among ponderosa pines (Pinus ponderosa) with various degrees of crown damage sustained during fall, spring, and summer prescribed burns. After 5 years, 12% of the trees scorched in the fall had died compared to 26% scorched in the spring, and 29% scorched in the summer. Eighty-five percent of this mortality occurred in trees less than 7 in. dbh. Scorch damage of up to 90% of the crown caused minimal mortality regardless of season. West. J. Appl. For. 2:14-16, Jan. 1987.

Fire Induced Tree Mortality in a Colorado Ponderosa Pine/Douglas-fir Stand

Abstract The impact of a fall season prescribed surface fire on Douglas-fir and ponderosa pine mortality during the first 22 months following fire was evaluated using discriminant function analysis. Crown scorch, expressed as a percentage of the prefire live crown length, was the single best determinant of tree mortality. Stem charting on the least impacted quadrant is also a relevant variable in mortality determinations. Larger diameter trees of both species withstood proportionally greater stem and crown damage than smaller trees. Crown consumption indicators added substantially to the discriminating power of the functions, but prefire live crown and maximum scorch height were not important variables. Within the same size range, there was little evidence of important differences between ponderosa pine and Douglas-fir in the levels of crown and stem damage that induce mortality. Forest Sci. 32:49-59.

Genetic stratigraphy of the Meteor Crater outer lip

Extensive ponderosa pine (Pinus ponderosa Dougl. ex Laws.) mortality associated with a widespread severe drought and increased bark beetle (Coleoptera: Curculionidae, Scolytinae) populations occurred in Arizona from 2001 to 2004. A complex of Ips beetles including: the Arizona fivespined ips, Ips lecontei Swaine, the pine engraver beetle, Ips pini (Say), Ips calligraphus (Germar), Ips latidens (LeConte), Ips knausi Swaine and Ips integer (Eichhoff) were the primary bark beetle species associated with ponderosa pine mortality. In this study we examine stand conditions and physiographic factors associated with bark beetle-caused tree mortality in ponderosa pine forests across five National Forests in Arizona. A total of 633 fixed-radius plots were established across five National Forests in Arizona: Apache-Sitgreaves, Coconino, Kaibab, Prescott, and Tonto. Prior to the bark beetle outbreak, plots with mortality had higher tree and stocking compared with plots without pine mortality. Logistic regression modeling found that probability of ponderosa pine mortality caused by bark beetles was positively correlated with tree density and inversely related with elevation and tree diameter. Given the large geographical extent of this study resulting logistic models to estimate the likelihood of bark beetle attack should have wide applicability across similar ponderosa pine forests across the Southwest. This is particularly true of a model driven by tree density and elevation constructed by combining all forests. Tree mortality resulted in significant reductions in basal area, tree density, stand density index, and mean tree diameter for ponderosa pine and for all species combined in these forests. Most of the observed pine mortality was in the 10–35 cm diameter class, which comprise much of the increase in tree density over the past century as a result of fire suppression and grazing practices. Ecological implications of tree mortality are discussed.