Impacts of black stain root disease in recently formed mortality centers in the piñon-juniper woodlands of southwestern Colorado

Abstract

Thirty discrete black stain root disease (BSRD) mortality centers, caused by Leptographium wageneri (Kendr.) Wingf. var. wageneri, were examined in 1999 to determine the effects of BSRD on the composition and structure of piñon–juniper woodlands at the tree, shrub, and herbaceous plant levels and on tree-seedling regeneration. In these recently formed mortality centers, the majority (68%) of all piñon (Pinus edulis Engelm.) was dead, 76% of piñon were affected by BSRD, and 70% had evidence of piñon ips bark beetle (Ips confusus Leconte) attack. BSRD mortality centers had a mean area of 0.28 ha (range 0.07 to 0.63 ha). There were no statistically significant (p > 0.05) differences in shrub composition, cover, or diversity between mortality centers and the unaffected surrounding woodlands. Herbaceous plant cover was significantly greater (p < 0.001) within mortality centers and frequency responses were species specific. There were no significant (p = 0.629) differences in the density of piñon regeneration inside mortality centers compared with outside mortality centers. The pathogen was regularly isolated from piñon roots dead for 5–8 years and once from a root dead for 16 years. The rate of radial expansion of mortality centers averaged 1.1 m/year (0.07 SE). The rate of mortality center expansion was not significantly (p > 0.05) related to available water-holding capacity, percent organic matter, pH of soils, piñon density, or any other site data recorded.

Relationship of stand characteristics to drought‐induced mortality in three Southwestern piñon–juniper woodlands

“…In southwestern Colorado, including the Mesa Verde location), black stain root disease (Ophiostoma wageneri Goheen and Cobb) has been an important mortality agent during the last century; while present in the Mesa Verde study area, all dead trees in the plots also had evidence of pinyon ips. Other insects and fungi may weaken trees, predisposing them to pinyon ips infestation (Kearns and Jacobi 2005). Although we searched diligently for evidence of all of these agents in three southwestern study areas, pinyon ips was present on nearly all of the dead pinons (except seedlings) in this study, and although other agents (such as black stain root disease) are present in the area, their effects were masked by the widespread beetle kill.…”

“…While twig beetles (Pityophthorus sp. Other insects and fungi may weaken trees, predisposing them to pinyon ips infestation (Kearns and Jacobi 2005). ), pin˜on needle scale (Matsococcus acalyptus Herbert), and pinyon blister rust are also common agents of stress and mortality in pin˜on populations in all three locations (for others, see Leatherman and Kondratieff 2003), the current regional die-off of pin˜on has been attributed primarily to explosion of pinyon ips bark beetles (Negron and Wilson 2003, Mueller et al 2005, Shaw et al 2005.…”

Historical and Modern Disturbance Regimes, Stand Structures, and Landscape Dynamics in Piñon–Juniper Vegetation of the Western United States

“…Wingf.) on P. edulis in southwestern Colorado (Kearns and Jacobi 2005). Stand dynamics are also punctuated more dramatically by episodic mortality or by recruitment events that occur in response to extreme weather patterns and insect outbreaks (Betancourt et al 1993;Swetnam and Betancourt 1998;Knapp and Soule´1999;Soule´and Knapp 2007).…”

Persistence of Pinyon Pine Snags and Logs in Southwestern Colorado

“…In another California study, snag persistence was related to species, diameter, height, and mortality agent (Morrison and Raphael 1993). As snag and log retention and durability in pinyon pine is not well understood, this study was undertaken as part of a larger study of the impacts of insects and disease on pinyon pine (Kearns and Jacobi 2005).…”