Changes in transpiration and foliage growth in lodgepole pine trees following mountain pine beetle attack and mechanical girdling

Ecosystem CO2/H2O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

“…We suggest it is because spruce-fir is a very slow response ecosystem [Aplet et al, 1988] where the reallocation of resources and release of surviving trees after disturbance happen slowly, on the order of 5-15 years [Veblen et al, 1991]. Thus, even though Engelmann spruce die much more slowly from spruce beetle [Mast and Veblen, 1994] than, for example, lodgepole pine from mountain pine beetle [Hubbard et al, 2013], the entire mortality event still occurs much faster than any of the feedbacks in the spruce-fir ecosystem.…”

“…This commonly results in tree mortality and a reduction of the assimilation of carbon within the disturbed ecosystem [Brown et al, 2012]. For pine trees affected by mountain pine beetle, the cascade of hydraulic failure to reduced photosynthesis [Katul et al, 2003] and ultimately tree mortality [Edburg et al, 2012] can happen within months [Hubbard et al, 2013;Knight et al, 1991;Yamaoka et al, 1995]. Yet this can take much longer in spruce forests [Mast and Veblen, 1994], possibly because spruce are among the few plants that survive without tightly regulating stomatal conductance to plant hydraulics [Ewers et al, 2005].…”

“…Blue-stain fungi play a vital role in bark beetle infestations by helping overcome tree defenses with fungal penetration and sapwood occlusion [Paine et al, 1997] and can do so quickly over a few weeks as observed with mountain pine beetle [Hubbard et al, 2013;Yamaoka et al, 1990]. Leptographium abietinum is the most common mycelial fungus isolated from spruce beetle [Six and Bentz, 2003] though Ceratocystis rufipenni is often found in infested Engelmann spruce [Wingfield et al, 1997].…”

“…The ability of Engelmann spruce to survive for several years after catastrophic hydraulic failure is remarkable. Experiments in the Rocky Mountains found that lodgepole pine die within 1 year when xylem is occluded by blue-stain fungi [Hubbard et al, 2013;Knight et al, 1991]. Engelmann spruce appears more resilient.…”

Implementation of a Marauding Insect Module (MIM, version 1.0) in the Integrated BIosphere Simulator (IBIS, version 2.6b4) dynamic vegetation–land surface model

“…Similarly, the linear unfolding of insect activity (i.e., equal day-to-day damage over the entire duration; see Eq. 1) is a simplification that could be refined in future implementations of MIM; yet, it provides a reasonable approximation of the intra-annual progression of damage caused by the IFTs considered (Régnière and You, 1991;Cook et al, 2008;Hubbard et al, 2013). For example, although the individual feeding rate for the fifth and sixth larval instars of the eastern spruce budworm is much higher than for younger instars, the decreasing population density throughout summer leads to an approximately linear progression of total defoliation (Régnière and You, 1991).…”