SOE 306 Outline 1 What s a healthy forest 2 Concepts and Characteristics 3 Causes and Symptoms 4 Disease and Outbreak 5 Bark Beetles 6 Diana Six TED Talk Is this a healthy forest Snags in a silver fir forest Is this a healthy forest Lodgepole pine recruiting after wildfire Is this a healthy forest Patch clearcuts with regeneration Is this a healthy forest Variable retention harvesting Is this a healthy forest Clearcuts with Erosion Is this a healthy forest Radiata pine Pinus radiata plantation in Australia Is this a healthy forest Invasive conifers in New Zealand alpine heath Is this a healthy forest Spruce bark beetle outbreak Mesa Mtn Colorado Forest Health 1 What s a healthy forest 2 Concepts and Characteristics 3 Causes and Symptoms 4 Disease and Outbreak 5 Bark Beetles 6 Diana Six TED Talk Forest Health Ability of a forest to provide sustained ecosystem services that meet human needs providing stable and sustainable services Forest Health is an anthropogenic concept Only from a human perspective could the abundance of a native species bark beetle be considered a problem Disturbance is natural and integral to ecosystems 8 Indicators of a Healthy Forest 1 Trees and understory plant health stand density growth and mortality in historical range of variability 2 Diverse vegetation appropriate for light water nutrients space 3 Capable of tolerating and recovering from known disturbances 4 Minimal soil erosion stable stream banks with riparian veg 5 Aquatic species diversity indicator species present 6 Wildlife diversity and population appropriate 7 8 Ecological processes in natural range of variability Insect disease fire frequency in historical range of variability Challenged by global change Historical Range of Variability HRV Convincing managers to use HRV is was an improvement over earlier guidelines and practices But climate change will likely invalidate use of HRV New Focus Resistance Resilience Sustained Ecosystem Services Ecosystems Services Millennium Ecosystem Assessment 2005 Resistance Resilience Resistance Ability to resist change Resilience Ability to recover Trumbore et al 2015 How to manage for maximum resistance and resilience Manage for Resistance and Resilience Millar et al 2015 How to Assess Forest Health Trumbore et al 2015 USFS Forest Health Protection Forest Health 1 What s a healthy forest 2 Concepts and Characteristics 3 Causes and Symptoms 4 Disease and Outbreak 5 Bark Beetles 6 Diana Six TED Talk Causes of Poor Forest Health 1 Large area disturbances logging overgrazing that result in uniform even aged highly dense forests 2 Aggressive exotic invasive species 3 Change in the environment pollution global change including nutrient deposition and climate change 4 Quantity of live and dead fuels that increase risk of wildfire more severe than typical of ecosystem Uniform even aged dense forests Pathways to Structural Change Empty forests importance of wildlife in forest health Lewis et al 2015 Exotic Invasive Species x Pinus albicaulis Whitebark pine Cronartium ribicola White pine blister rust Exotic Invasive Species Pine woodwasp Bronze bug Pine pitch canker Eucalypt leaf pathogen Wingfield et al 2015 Climate Change x Hotter Drought AKA Global Change Type Drought High stand density also a factor in high mortality rate At one site 2002 2004 undid 75 years of stand density increase Dense forests at risk of atypical fire Northern Arizona Pinus ponderosa Eastern Washington Threats to Forest Health Windthrow Ozone damage Trumbore et al 2015 Timescales of Forest Stress Normalized Difference Vegetation Index Greenness from space x Forest Drought Stress Index Millar Stephenson 2015 Adapted from Williams et al 2013 Forest Health 1 What s a healthy forest 2 Concepts and Characteristics 3 Causes and Symptoms 4 Disease and Outbreak 5 Bark Beetles 6 Diana Six TED Talk Disease in Forests Plant and forest diseases are an interaction the disease triangle The Disease Triangle Disease in Forests Hennon et al 2020 Koch s Postulates Koch s Postulates Koch s Postulates Koch s Postulates Limitations Some pathogens cannot be cultured Some plant pathogens can be present without causing disease Molecular techniques DNA RNA enable different approach Decline Diseases Complex set of interactions leads to poor tree health and death The Disease Triangle Manion 1991 Sudden Oak Death Invasive pathogen on west coast Phytopthora ramorum Big Sur California Healthy forests have tree mortality Diseases and outbreaks may have negative positive or no impact on forest health Tree mortality is an inherent component of forest stand dynamics Many trees must die to produce a patch of old growth forest Manion and Griffin 2001 Factors influencing outbreaks Dendroctonus rufipennis Factors influencing outbreaks are related to population growth Density independent factors Do not depend on population size in an area density Abiotic weather storms wildfire etc Density dependent factors Depend on population size in an area density Disease competition availability of prey or food predation Negative density dependent feedbacks Positive density dependent feedbacks Density Dependent Feedbacks Negative Equilibrium point E when births b deaths d Population density below or above E moves towards E Specifics depletion of food resources increase in death rate with density Density Dependent Feedbacks Outbreak Threshold T when births b deaths d Population density below or above T moves away from T Specifics advantage in numbers increase in birth rate with density Positive Density Dependent Feedbacks Negative Positive Outbreak Characterization Favorable environment Abiotic disturbance Delayed density dependence Host defenses Natural enemies predators parasitoids disease Hemlock Woolly Adelgid Forest Health 1 What s a healthy forest 2 Concepts and Characteristics 3 Causes and Symptoms 4 Disease and Outbreak 5 Bark Beetles 6 Diana Six TED Talk Subfamily Scolytinae In Curculionidae family Formerly the Scotylidae family Bark Beetles Some ambrosia beetles attack healthy hosts Bark beetles typically only attack weakened trees But that can shift In North America Dendroctonus sp are often considered more aggressive than Ips sp Host selection Dendroctonus brevicomis Western pine beetle Lindgren Funnel Trap Bark Beetle Life History 1 Dispersal phase initial host selection 2 Aggregation pheromone 3 Concentration phase mass attack 4 Anti aggregation pheromone Verbenone packet Dendroctonus brevicomis Western pine beetle Bark Beetle