Forest Health Final

Identify a pathway by which wind can cause increased susceptibility (as opposed to transmission) to infection by pathogens:

-Wind can dry out trees which leads to general stress. Makes trees canopy shy (which is when branches are hitting together and creating small wounds) You can get breakages, but also can lead to a lot of fine root damage. Main thing: if causes damages that open pathways for pathogens to enter. Breakage leads to areas that are exposed cambium and vascular areas and with higher winds, can cause migration of spores of pathogens to cause greater transmission Soil erosion through wind. Destroy fine root systems. Reduces water availability because of evaporation. Breakage on the tree.

Identify the mechanism by which plants shutdown secondary defensive chemical pathways and under the environmental conditions when this can occur.

Abscisic Acid: triggered by environmental stress such as drought.

What is the function of abscisic acid in protecting plants from environmental stress and why does activation of this hormonal pathway lead to increased plant susceptibility to biotic attack?

Abscisic acid is a general response to environmental stress which can shut down general pathways of secondary chemical production derived from salicylic and jasmonic acid Induced by temperature and moisture stress

Describe the patterns of insect decline in Europe in terms of what broad categories of insects have been impacted and the type of ecosystems which have recently shown insect population declines

All groups of flying insects have been impacted (that were quantified). The researches quantified declines by mass (weight). Relatively pristine areas showed these declines over a longer period of time. (areas of no herbicide or pesticide use).

How does Armillaria persist within stands following cutting?

Armillaria can persist as a saprotroph for a very long time It is a widespread root pathogen It can continue to survive on buried dead roots Buried dead roots can take hundreds of years to decompose

Contrast parasitoids with predators. Which is more effective for controlling insect outbreak?

Both can reduce populations or problematic insects · Parasitoids: include wasps and flies that have specialized body parts for attaching eggs to the surface within an insect host (ovipositor). Have adaptations for attacking a broad range of hosts; won't cause an immediate outbreak · Predation: employ a range of attack strategies such as active foraging to sit and wait. Mouth parts can be adapted to masticating insect bodies

what is the damage of emerald ash borer in its native range?

Buprestid beetle native to northeastern asia and do not have much of an effect in its native range unless the tree is almost dead already, then it might kill the tree.

Identify how forest managers can limit Eastern spruce budworm impacts silviculturally:

Can implement red and black spruce to help stop this insect Can also thin the density of the balsam and white.

American chestnut is a transformed species in eastern forests. In locations impacted by Cryphonectria parasitica (chestnut blight), describe the canopy position and average tree size for surviving individuals. Describe the effects on chestnut for piedmont forests invaded by Phytophthora cinnamomi:

Creates shorter, more shrub like trees. Breaks down the cambium and destroys the canopy. Overstory mortality, tree wilting, and epicormic and basal branching are linked to the pathogen. Kills bole cambium tissue and is only able to infect trees with a bole greater than 5-10cm.

Oaks respond to gypsy moth attack by increasing foliar phenolic concentrations (tannins) which are not particularly toxic. Identify how these compounds influence insect development times and susceptibility to nuclear polyhedrosis virus:

Defoliated oaks will regrow foliage with high concentrations of polyphenolic compounds which interfere with the protein absorption in the insects gut This ultimately quenches outbreaks Insect must consume foliage with NPV It decreases their ability to grow the polyphenolic compound interferes with protein absorption in the insect gut and limits nutrient availability. NPV transmission is done through eating the plants, and spreads through digestive cavities and bloodstream is tempered (COMBINED) by the polyphenolic compound. Combined reaction has a compounding effect.

Identify the three main genera of bark beetles in western conifer forests and rank them(1-3) according to their capacity to cause mortality of coniferous species:

Dendroctonus: they can attack and overcome the defenses of healthy trees, use pheromones to induce mass attack - Scolytus: mortality tied to drought, populations will increase progressively with local-to-regional changes in tree susceptibility, vector fungal pathogens - Ips: relatively weak bark beetles, driven by drought, can be controlled by stand density, not a major problem

What characteristic is essential to creating 'diseases of the site' and how does this influence the duration of disease in a particular location?

Diseases of the site examples: Armillaria, heterobasidian, phytopthera cinnamoni (creates hard shells around spores so they can live long in harsh conditions) as well as having a broad host range. They often exist in complex root systems that are hard to remove from the site and will likely persist forever and be characteristic of the land.

Bark beetle outbreaks can influence fire intensity but this effect has some important context. Describe when (either in terms of time or stand condition) outbreak is likely to cause hazardous fuel conditions:

Drought, high temperatures. Stands are more susceptible to bark beetle infestation when there i Stand density: competition is high, low resource availability, high competition = high susceptibility.

Draw a figure demonstrating the three principal classes including their strength of association

Ecological effect -Mutualists + + (Mycorhizae) -Parasites + - (Armallaria) -Saprotrophs neutral (Turkey Tail) Strength of association High Low High (drawn on figure with the top three in row on x axis, the strength is on Y, should look like upside down triangle)

How does environmental stress influence the capacity of plants to defend themselves? Justify your answer in terms of physical damage to plant tissues and defensive plant responses

Environmental stress influences whether or not a tree is going to spend its energy on defenses or for growth to try and outcompete nearby trees. (growth differentiation balance hypothesis) If there is a lot of environmental stress then the tree cannot waste its resources on defense. "To grow or to defend" Sometimes when resources are limited already it is beneficial to defend because regaining biomass is difficult anyways Other biotic effects = light, nutrients, water Need to overtop other plants Loss of tissue can be tolerated more at higher growth rates

What two factors tend to dampen or end gypsy moth outbreaks?

Female gypsy moths can't move. Female dispersal is limited. They do not fly. 2. BOOM BUST: Defoliated oaks will regrow foliage with relatively high concentrations of polyphenolic compounds which interfere with the protein absorption in the insect's gut. This slows nutrient absorption, insect development, and ultimately quench outbreaks. also causes insect crashes (BOOM HARD WITH UNDISTURBED TREES, BUST with low resources and high defense systems in tree)

Describe the mode of action by which swiss needle cast damages host tissue.

Foliar Disease, It grows within the inner stomatal space (it doesn't penetrate the leaf tissue). It can grow to a size that plugs the stomata and results in crown dieback. It doesn't kill the tissue directly.

What adaptations allow insects to survive low temperatures and high temperatures?

For cold temperatures, they have evolved enzymes that can function in a wide ranging set of temperatures. They experience behavioral and hormonal depression of physiological rates and can create antifreeze compounds. To warm up they will perch on a sunny side of a leave or rapidly vibrate wings to create heat. For extremely high temperatures, some insects have dorsal vents that pump water throughout the insect to provide cooling. Some insects will reside under a shady leaf. At too high temperatures, metabolic functions collapse and insect dies.

How does generalist vs specificity affect the ability of insects to control outbreak? Which characteristic would you select for a biocontrol program?

Generalists have a broad host range and would control outbreak easier. May be detrimental to natives

Define the following descriptions of host range and identify one example of generalist and specialist biotic agents:

Generalists: can infect a broad host range of many species of trees, shrubs, ferns: Example: Armillaria or P. ramorum Specialists: host range that is limited in a single host range or genera or type of tree. Example: Hemlock Wooly Adelgid

Describe the transmission dynamics for Heterobasidion root disease at the stand scale distinguishing between the two principal species or "types" (A and B) that affect California forests.

Heterobasidian in general: can survive as saprotrophs and survive in dead roots. Heterobasidian occidentale: the Fir type. It is native to north america. It does not need an open wound to infect the tree and it is harder to control than the pine type. Heterobasidian irregulare: the Pine type also native to north america. It kills trees more rapidly and creates disease centers. It requires a substantial wound to the tree for it to be successful and it is easier to control.

We are remarkably bad at detecting damaging insects and pathogens prior to their arrival in at risk forests. What characteristics do damaging invasive biotic agents tend to share in terms of their dynamics in their native range? Use these characteristics to describe and justify a research and management approach to limit their introduction and spread:

In their naive host range, most invasive biotic agents are not an effective pathogen ** or they have cyclical outbreaks** They have co-evolved to have a relationship with hosts in the area. In the invasive range, the plant defenses don't have a relationship built and fighting off the pathogen in plant defense can be difficult. The invasive pathogen also can spread quickly and easily among susceptible individuals. Weakness in individual trees and density among the stand lets the pathogen to spread quickly. Having a higher density decreases plant defense mechanisms because energy is allocated to competition. This allows for trees to be infected more easily. To manage this problem, doing something is often better than doing nothing. Once pathogens take hold of an area they are hard to eradicate. A study could be conducted to determine the ideal forest density to withhold pathogens from spreading, meanwhile an off hands approach would either evolutionarily take 100s of years to have mutated trees that are resistant to the pathogen or the host species would be wiped out as a whole which would detrimentally change forest structure as we know it.

Contrast induced and constitutive plant defenses to biotic attack:

Induced Can range from a minutes response to years Only occur when plant is being attacked Some chemicals that only present themselves during attack VOC's act as plant hormones info and can trigger chemical defense Plant thickness increasing Constitutive Maintained continuously Thorns, surface hairs, waxy leaf coatings, many chemicals (not as constant

When and where is Phellinus weirii most likely to be a management problem?

It is a major problem in dense closed canopy douglas fir production areas in the high moisture areas of the Pacific Northwest, such as Washington and Oregon. The problem can persist for long periods of time because inoculum builds up in the roots.

What characteristic of Phytophthora cinnamomi (the pathogen, not the disease) causes it to have a remarkably strong capacity to persist within a stand? How does this biological characteristic give managers a very simple solution for preventing spread

It is the fact that the pathogen has such long lived spores that are hard to kill. They can stay in the soil for many many years and the pathogen can also infect MANY different kinds of hosts. The only way to prevent the spread, because you can't kill it, is to WASH YER TRUCKS AND YER BOOTS anytime you think you have come across cinnamomi.

At what point during stand development in a second growth stand would you expect Armillaria inoculum will be at its greatest levels?

It's going to build up on dead roots. It'll build up in a time where there's large root acquisition. It's talking about timber and clear cuts. So when the dead roots start decomposing- to the new roots coming from trees. (10-15 years.). When you begin to reach the stem exclusion stage where canopy closure begins, thus root to root contact begins is when the inoculum will be at its greatest level, due to root to root contact being the way Armillaria spreads

For spruce budworm, what part of the insect's life stage is problematic?

Larval stage because this is when they attack Temperature affects these larval rates Increases larval development with balsam and white Increased with increased density also Decrease when black and red are introduced

Contrast resource acquisition between biotrophic (A) and necrotrophic (B) pathogens identifying the status of tissue where these pathogens will be found in an infected plant:

Necrotrophic- these pathogens kill tissue and then acquire resources from dead organic matter; biotrophic- these pathogens live within and feed off the products of living tissues; hemibiotrophic- pathogens live within living tissue, but feed off adjacent dead tissue

In considering the Ascomycota and Basidiomycota, is one group more important for forest health? Why?

Neither is more important/ it depends on what you're asking. Ascomycota: Sac like structure called ascus for spores Rarely form mushrooms Penicillin comes from here/ other antibiotics Fusarium (pitch canker disease) Cause diseases in wheat and veggies and other staples Greatest interest to plant pathologists Basidiomycota: Basidium spores Largest known organisms Mushrooms or smaller organisms Can decompose extensive amounts of organic matter Beneficial because they conduct nutrient cycling, fuel removal, and transfer of organic matter back to soil

Describe the impacts of hemlock woolly adelgid in its native range and contrast this with the impacts of the insect in western hemlock forests where it is exotic and was first described:

Not too harmful in native range No predators where it is exotic Minimum winter temps are how to slow down HWA outbreak They feed on ray parenchema cells endemic to asia. In invasive and exotic range (eastern US) it is a huge problem. The mortality of the eastern hemlock caused rapidly canopy thinning which means more light exposure and this creates a thick forest floor. Species that can germinate in thick forest floors and be shade intolerant were now selected for.

In general terms describe the relationship of the Oomycota to other fungi including the relative relationship to the other two principal groups of fungi (identify them as well):

Other two groups-Ascomycota and Basidiomycota. They both decompose OM, but oomycota persist in the environment off dead organic matter while Basidiomycota decompose large amounts of OM OOMYCOTA ARE NOT FUNGI they are similar but have a different cell-wall composition (no chitin)

Briefly describe where parasitoid insects complete development and identify how this could benefit forest management:

Parasitoids complete development inside host and consume them from the inside out and can reduce populations of problematic insects EX. wasps and flies

What are the three primary classes of plant-microbial interactions? How are these characteristics defined or structured?

Pathogen: acquire all nutrients from host plant, net cost to the host · Saprotroph: decomposer fungi that are critical for break down of plant products. Cellulose, hemicellulose, lignin · Mutualist: penetrate plants physical defense, and plants can provide water, protection, carbon

Describe the impacts of Phellinus weirii in Douglas fir forests of the Pacific Northwest including its impact on hosts, the timing or stand conditions conducive to transmission, and management responses to limit spread

Phellinus weirii is laminated root rot disease that is a problem in Pacific northwest Douglas fir timber stands (particularly Washington and Oregon). It is a basidiomycete fungus that spreads root to root due to close canopy closure. The disease is persistent through rotations and has intensified bc of an increase in timber production. It causes economic challenges and builds inoculum over time. It can change biogeochemical recycling rates.

How do volatile organic chemicals fit into the lifecycle or day-to-day lives of insects?

Pheromones: to track pheromone trails and find prey, to find susceptible plants, assembling large groups of insects that can overwhelm the chemical and physical defenses of individual plant Beetles; find susceptible trees, aggregate mass attack pheromone.

Identify the two principal groups of mistletoes (common names or genus is ok) and state their relative capacity to cause disease:

Phoradendron (leafy mistletoe): only a problem in a few forests and it relies on hosts for nutrients and water Dwarf Mistletoe: parasitize photosynthetic products as well as water, carbon, and other nutrients. It creates structures associated with wildfires.

Native biotic agents kill many trees despite a long evolutionary history with their hosts. Choose one example of a native pathogen or insect (does not need to be California-based) and describe its impacts, the host(s) it damages, and a management approach (can be preventative or restorative). Why does this agent continue to be so destructive despite the long evolutionary history?

Pine Bark Beetles, especially Dendroctonus and Ips have a long evolutionary history with their native plant region in the Sierra Mixed Coniferous forest. The outbreak we have been seeing has been from abiotic drives such as drought in the environment as well as a high density dependent mortality occurring in the forest that has caused such a significant outbreak for a native host. For the dendroctonus beetles they attack multiple pine species including, Pinus ponderosa, Pinus lambertiana, Pinus jeffreyi, and Pinus monticola, due to high density and low resource availability due to other environmental factors, such as drought, fire suppression and increased competition for resources. This continues to be an issue because of the climatic changes we are experiencing, with lower rates of snow accumulation in the Sierra Nevadas as well as progressively warmer and wetter winters not ceasing the cycling of the bark beetles life stages, thus continuing to accrue in population size. These beetles attack larger diameter trees, and according to the GDB hypothesis with low resource availability defense cannot stop the larger populations that attack. Turgor pressure is low in the trees and contributes to susceptibility to attack. A management approach to this would be first restorative with the amount of dead pine trees that are shown in the Sierra Nevada Mixed Coniferous forest, first salvage log, prescription burn the site, and wait for the rain. The next step would be a preventative measures, working towards promoting better stand heterogeneity, reducing tree density induced mortality by better spacing and management, and doing further research into climate induced defenses towards another outbreak, such as the range and shifts in ecological roles in tree ecosystems.

Describe the growth differentiation balance hypothesis drawing a figure showing the major factors and describing the differences in allocation to defense as a function of resource availability.

Plants must prioritize their energy allocation based on what the most important challenge at hand is. If resources are high, and competition is high, the plant must put a lot of energy into growth in order to outcompete other individuals, and induced defenses are suppressed. At high levels of growth, tissues can easily be replaced and therefore may be less well-defended. If resources are low, a plant may put more energy into constitutive defenses (like in a desert). "Allocation to defense is optimal at lower resource levels".

Draw the "disease triangle" labeling the figure for a specific problematic insect or Pathogen

Reference the triangle... do it

Mineral resources can limit many aspects of plant productivity, why then is the CN balance hypothesis so inadequate as an explanatory model?

The C:N balance theory posits that limitations on photosynthesis or mineral nutrients (particularly N) will have different impacts on plant defensive metabolic pathways However, many defensive responses are short lived The approach masks the turnover of secondary chemicals with short lifespans The theory may not yield predictions consistent with the shared evolutionary history of a host and biotic attacker.

How are declines in insect biomass different than extinctions? How are the impacts to ecosystems similar?

The decline in biomass is not leading to extinction however the lessened biomass is leading to lessened ecosystem services (functional extinction) The decline in these insects are leading to declines in other species that feed on the insects such as lizards birds and frogs They both cause a change in ecosystem services, bottom up trophic cascade

Contrast the two principle types of wood rot fungi in terms of the wood components they degrade. Identify the residual compounds for each:

White rot - attacks lignin, leaves cellulose (turns white) Brown rot - attacks cellulose, leaves lignin (oxidizes turns brown)

Insects and pathogens often kill trees in forests which are also frequently impacted by fire. Describe the impacts of biotic agents on fuel dynamics noting the distribution of fuels (and their changes) in the first two decades of outbreak or following mortality:

With an introduction of a biotic agent that kills trees, it's inevitable that fuel dynamics are going to change, more so, spike. Areas that are common for low-intensity fires already acquire fuel buildup. With the biotic agents, trees are dying at a faster rate adding to the susceptibility for high-intensity fires (canopy fires). Immediately after outbreak, you get a spike in canopy fuel, over time if falls and the canopy fuel decreases and ground fuels over time increase. Soils and regenerated plants are now more at risk because a ground fueld fire would take out the regenerations and sterilize the soil (removing microbes and natural decomposition.

Heart rot does not attack living tissue, by what mechanism can these tissues then be protected?

Wood composed of cellulose, hemi-cellulose, lignin They need to prevent the initial establishment of the heart rot because once established the plant can't do much A diverse community of fungal microbes (Including Penicillium and Trichoderma) which act as a defense to heart rot even though heart rot wood is dead and the tree itself can't necessarily defend itself against such fungi.

Insects are poikilothermic animals, what does this mean for their thermo regulation? Identify one adaptation or action insects use to limit excessively high and low temperatures:

body temperature varies with surroundings. Insects have evolved enzymes tolerant to a range of temperatures. Insect bodies are relatively small compared to most vertebrates which has both advantages and disadvantages in terms of thermoregulation. critically to escaping predators, finding prey or mates, and finding susceptible plants. 'the thermal warriors' Lower temperatures than optimum for many insects results in slower development or lower capacity to escape predators while excessive temperature can lead to physiological breakdown and death. They have vents to cool off inside body temps Anti-freeze compounds Bask in the sun or change posture to increase or decrease body temperature Generate heat by vibrating wings

How do concepts of value at the individual level differ among fields of health; what is the underlying reason for these differences?

dealing with forest health at the individual level is very costly

Swiss needle cast is an important foliar pathogen of conifers in wet environments. Describe what changes in the environment will cause an increase in disease severity. What land use or management factors will increase disease severity?

it grows within the inner stomatal space. It plugs stomata and results in a crown die-back. Wetter conditions lead to increased stomata count lead to increased susceptibility. They transmit via wind and water. Diversity stand structure: locate timber farms in areas with less rain.

How do beetles vector fungal pathogens? What morphological adaptations aid in Transmission?

many wood boring beetles have specialized structures called mycangium (pockets in their mouths to carry fungal spores or biomass between individual tree hosts.

Describe the growth differentiation balance hypothesis in the context of gypsy moth dynamics

the presence of gypsy moths slows ecosystem productivity on a long term scale. Decreasing foliar structures nutrient cycling slows and rate of decomposition slows. On a short term scale nitrogen can be kept in the soil so there wont be a loss of nutrients. Gypsy moths are generalists: no specific hosts: plant releases tanins as a defense mechanism. Defoliated oaks can reestablish canopy cover (energetic cost and loss of growth -defense) but it can survive the growing season) it takes three consecutive sessions to kill broad leafed species. during non outbreak years, phenolic defense is relatively low