Effect of season and interval of prescribed burns in a ponderosa pine ecosystem on tree growth and understory vegetation.

After decades of fire exclusion many stands now have historically unprecedented (high) levels of fuels and overstocking. As a result these stands have developed a variety of health issues. In response to these problems land managers are using prescribed fire to restore fuel loads and stand stocking to pre-fire exclusion levels. The impacts of season of prescribed burn as well as burn interval are not well understood. Managers need the ability to better predict these impacts on such things as tree mortality from fire, associated insect attack and disease development, tree growth, and plant communities. The “Season of Burn” study complex was established in 1997 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. Three treatments, a fall burn, spring burn, and unburned control, were randomly assigned to 12-ha experimental units within each stand. Within each experimental unit, six 0.2 ha-plots were established to evaluate responses to the burns. Prescribed burns occurred during mid-October of 1997 or mid-June of 1998. In summer 2002 the objectives of the original study were expanded to include an examination of the impact of interval of burn and cattle grazing on the trees and understory vegetation. Each of the burn units was split and units were randomly assigned to either a 5-year or 15-year burn interval. Within each of the controls and the 5 year interval treatment units 0.2 ha cattle exclosures were randomly located to study the effects of the interaction of cattle grazing and season of burn on the understory vegetation. The 5 year interval units were prescribed burned for a second time in fall 2002 and spring 2003. The JFSP project reported here continued the expanded Season of Burn study. The five year interval of burn treatment units were successfully burned for the third time in fall 2007 and spring 2008 and previous protocols for monitoring were continued. Our results indicate that Ponderosa Pine growth rates are not negatively impacted and the incidence of insect attack or disease does not increase as a response to repeated prescribed burns. With each burn iteration further reducing the fuel load accumulated during the period of fire exclusion, repeated prescribed burns may be needed to significantly reduce fuel loads after prolonged fire exclusion. We found that removing cattle after prescribed fire reburns significantly enhanced the native plant community. Five years of grazing exclusion increased: (1) total vegetative cover, (1) native perennial forb cover, (3) shrub cover (4) grass stature and, (5) grass reproductive success. Remarkably, total cover increased by more than one-third. Neither spring nor fall reburning increased perennial native species cover or richness, and reburning reduced sedge cover. Fall reburning increased cover of native colonizers and exotic species cover and richness. We demonstrate that removing a novel disturbance process such as grazing significantly benefits the native plant community, but we document few benefits associated with adding the historic disturbance of fire, even in the absence of grazing

Red turpentine beetle primary attraction to (-)-β-pinene+ethanol in US Pacific Northwest ponderosa pine forests.

Red turpentine beetle, Dendroctonus valens (Coleoptera: Curculionidae: Scolytinae) is a non-aggressive pine bark beetle native to North America, and more aggressive invader in China. Dispersing pioneer beetles are attracted to potential host trees by oleoresin monoterpene kairomones, but respond more strongly to those combined with ethanol, a mixture often released from stressed, dying, or recently dead trees. (+)-3-Carene, usually the dominant or co-dominant monoterpene in ponderosa pine, Pinus ponderosa, is a stronger attractant than α-pinene or β-pinene where tested over a large portion of the D. valens range, while (+)-3-carene+ethanol was shown previously to attract twice the beetles of (+)-3-carene. A field test comparing D. valens attraction among the three monoterpenes when all are released with ethanol has never been reported, and was our objective. In three US Pacific Northwestern pine forests, (-)-β-pinene+ethanol lures attracted 1.4 to 1.9 times more beetles than (+)-3-carene+ethanol. (+)- or (±)-α-pinene+ethanol lures were least attractive. A 1:1:1 monoterpene mixture+ethanol lure attracted more beetles than the 1:1:1 lure, but it was not statistically higher. Monoterpenes were dispensed from low density polyethylene bottles and their release rates monitored in laboratory and field tests. Under laboratory conditions (+)-3-carene was released much more rapidly than (+)-α-pinene or (-)-β-pinene when dispensed separately, or in a 1:1:1 mixture. (+)-3-Carene in the 1:1:1 mixture increased the release of both pinenes over their rates when dispensed separately. (-)-β-Pinene+ethanol is currently the strongest kairomone lure for D. valens attraction in US northwest pine forests, and has value for beetle detection, monitoring, research, and management

The Fire and Tree Mortality Database, for empirical modeling of individual tree mortality after fire.

Wildland fires have a multitude of ecological effects in forests, woodlands, and savannas across the globe. A major focus of past research has been on tree mortality from fire, as trees provide a vast range of biological services. We assembled a database of individual-tree records from prescribed fires and wildfires in the United States. The Fire and Tree Mortality (FTM) database includes records from 164,293 individual trees with records of fire injury (crown scorch, bole char, etc.), tree diameter, and either mortality or top-kill up to ten years post-fire. Data span 142 species and 62 genera, from 409 fires occurring from 1981-2016. Additional variables such as insect attack are included when available. The FTM database can be used to evaluate individual fire-caused mortality models for pre-fire planning and post-fire decision support, to develop improved models, and to explore general patterns of individual fire-induced tree death. The database can also be used to identify knowledge gaps that could be addressed in future research