Colorado Statewide Forest Resource Assessment

Recently, foresters, the public and the media also have focused signifi cantattention on a condition dubbed sudden aspen decline (SAD). 30 Early thiscentury, older aspen stands in many areas of Colorado began dying ratherquickly. In 2008, aerial surveys conducted by the USFS and CSFS found atleast 500,000 acres of aspen with some level of mortality. 31 Ungulate grazing,fi re exclusion and perhaps drought are factors in the lack of regeneration thatis evident around the edge of many established groves. Stands of vigorousyoung trees that regenerated, both naturally and through forest management,prior to the drought in the early years of this century may have remainedhealthy because the root systems were able to sustain a lower volume ofwoody biomass. Many insects and fungi have been associated with SAD, butto date, they appear to be indicators rather than direct causal agents.Insect and Disease Analysis: The most effective actions to reduce insectand disease damage involve alleviating stress or competition and restoring aforest’s resilience prior to attack. Once infestation has begun, managementoptions to mitigate intensity and spread are limited. The assessment teamworked with the USFS Forest Health Technology Enterprise Team (FHTET)and the CSFS to develop a data layer showing areas across Colorado wherepro-active forest management could reduce the potential for unwantedimpacts from insects and disease. The key components of this analysis arepast insect and disease activity and future risk of infestation based on basalarea.For the fi rst component of the analysis, the FHTET used 6 years of aerialsurvey data to identify where insect and disease activity has occurred, aswell as where it has occurred repeatedly in the same location. The secondcomponent was developed using current basal area to identify forests that aresusceptible to insect and disease infestation. These two components werecombined to reveal landscapes that are at high risk for insect and diseaseoutbreaks in the future, but have not been so signifi cantly impacted by pastactivity levels that mitigation efforts would be ineffective. Areas with extremelyhigh insect and disease activity over the past 6 years were excluded from thisfi nal layer because they were deemed to be too signifi cantly damaged forforest management to be helpful.The fi nal layer showing potential for mitigation of unwanted insect and diseaseimpacts reveals that 5.5 million acres of forest land in Colorado have highto very high potential for the proactive use of forest management. Theseopportunities exist in all forest types but are greatest in spruce-fi r, piñonjuniperand aspen forests. The USFS manages the majority of these lands,followed by the BLM and private landowners. It is important to note that someforest types, such as spruce-fi r, have a naturally high basal area. Managerswill need to examine conditions on the ground in these forests to determinewhether management to reduce basal area or address insect and diseaserisks is warranted.30This paragraph is adapted from the CSFS 2008 Report: The Health of Colorado’s Forests.31For more information, please see the 2008 Aerial Survey Highlights at http://www.fs.fed.us/r2/news/press-kits/2009/colo-aerial-survey/colo-survey-higlights.pdf.33