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

Abstract

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.

Predicting postfire Douglas-fir beetle attacks and tree mortality in the northern Rocky Mountains

“…Bark-char codes, or some measure of char height, have often been used as a surrogate for cambium injury in modeling postfire tree mortality, to avoid direct sampling of the cambium (Wyant et al 1986;Peterson and Arbaugh 1989;Thies et al 2006). However, our comparison of ocular estimates of bark char with direct measurement of cambium condition suggests that a great deal of uncertainty would be introduced into a model that uses the extent of bark char rather than a direct measurement of cambium status.…”

“…Lindl.) (van Mantgem and Stephenson 2004). Although the trees were unburned in this study, the results provide evidence that coring trees to assess cambium status does not contribute to tree mortality.…”

“…Many studies have shown that larger trees have a lower P m than smaller trees, given the same level of fire injury (Bevins 1980;Wyant et al 1986;Harrington 1993;Mutch and Parsons 1998;Stephens and Finney 2002;Hood et al 2007). However, the opposite has also been found (Ryan 1990;Ryan and Frandsen 1991;Hood et al 2007), and a few studies have reported that DBH was not a significant variable in explaining tree mortality (Stephens and Finney 2002;Thies et al 2006;Hood et al 2007). The inclusion of an interaction term for DBH and beetle-attack level in our Douglas-fir mortality model accounts for the relative importance of tree size, fire injury, and Douglas-fir beetle attacks (Weatherby et al 2001).…”

Delayed conifer mortality after fuel reduction treatments: interactive effects of fuel, fire intensity, and bark beetles

“…Large ponderosa pine, however, may become more susceptible to direct mortality from fire as size (diameter) increases, because interactions among previous injuries allow fire to kill a greater portion of the live cambium, fuels accumulate near the base of the tree and lead to higher fire intensity near roots and cambium, and carbohydrate levels decline because of preexisting stress . Research on ponderosa pine in drier portions of northeastern Oregon suggests that the probability of mortality increases logarithmically with needle loss after fire, but increases linearly with bole char (Thies et al 2006).…”

Evaluation of a post-fire tree mortality model for western USA conifers

“…size, bark thickness). Most models have been developed for western United States (USA) conifers (Peterson and Arbaugh 1989;Harrington 1993;Regelbrugge and Conard 1993;Mutch and Parsons 1998;Stephens and Finney 2002;Keyser et al 2006;Sieg et al 2006;Thies et al 2006;Hood and Bentz 2007). Logistic regression mortality models have also been developed for some species in Canadian (Beverly and Martell 2003;Hély et al 2003), European (Rigolot 2004), and South American (Barlow et al 2003) forests.…”