Fire 123 Final
Discuss the three modes of asexual reproduction
Discuss the three modes of asexual reproduction The first mode of asexual reproduction is known as suckering. Suckering asexually is when the Vegetative formation of a new stem and root system from an adventitious bud of a stem or root, either naturally or by human action. The second asexual reproduction mode is known as basal sprouts. Basal sprouts typically appear near the base but there are also dormant buds on branches and on the bole and the sprouts from these buds are known as epicormic sprouts, epicormic sprouts assist in rebuilding a predominantly burnt crown. The third mode of asexual reproduction is known as layering. Layering is when a branch will "think" it is a root and start making smaller roots and root hairs.It starts producing cytokinins; stops making as muchauxins.Local apical dominance for the branch is lost and the branch tip starts to grow upward.
What is an epicormic bud?
An epicormic bud is a bud that sprouts from dormant buds and they are known to greatly influence tree quality and reduce stem value.
Why do asexual stems grow faster than sexual stems?
Asexual stems tend to grow faster than sexual stems because when a plant is asexually reproducing, they begin with an intact root system that is locked with starch proving to be a strong advantage in becoming a canopy and shading out the trees below them, and resulting in any sexual reproducing plant in "losing the game".
Redding burns way more than we do in Arcata. Why?
Due to the low relative humidity, high fuel aridity and lack of precipitation and latent wood in redding makes it ideal for fire to sweep through. This is mostly due to Arcatas close proximity to the ocean which brings in cold, humid air. Which makes Arcata practically unburnable.
Arson is a big deal in the Santa Monica Mountains. It contributes little to the number of ignitions but a lot of the area burned. Why?
Because arsonists know how to make it a bad fire, often waiting for the high winds during the dry season causing a large fire usually starting far away from any nearby fire stations. The environment usually consists of grasslands or trees that are not adapted for fire causing lots of fuel.
Discuss the annual area burned as a function of fuel aridity
Chatgpt:"fuel aridity measures the extent to which dryness turns trees into tinder(dry flammable material) fuel aridity directly affects the rate at which fires can spread. Dry fuels ignite more easily and burn more rapidly, leading to faster-moving and more intense wildfires.The moisture content of fuels is influenced by climate, weather conditions, and the overall hydrological cycle of the region. Extended periods of drought can lead to drier fuels and increase the likelihood of wildfires."
Contrast evaporation and condensation
Evaporation differs from condensation in that it chases phases as "Liquid to Gas", moving heat into liquid as it undergoes vaporization(similar to melting). Condensation differs from evaporation in that it changes phases as gasses to liquids, where the heat leaves the gas as it condenses(similar to freezing).
Contrast conduction, radiation and convection as methods of heat transfer
Conduction differs from radiation and convection in that it transfers heat through direct contact conducting heat from one particle to another through direct contact. Radiation differs from convection and conduction in that it transfers heat in a straight line through a GAS that tends to heat up any intervening spaces. Convection differs from radiation and conduction in that it transfers heat not only as a gas but also a LIQUID, in which two types of convection may occur, laminar or turbulent.
Why is the fire number for a region a poor guide to the area burned?
Fire size variation, ignition sources, fuel types and availability, fire management practices, weather conditions, land use, spatial distribution, and fire severity.
Why is flame duration so important for cambial death?
Flame duration is important for cambial death because Heat needs to penetrate bark and reach >60 deg C Tree dies from heat getting into cambium and bubbles forming in xylem cells Kills the cambial cells. Without them the tree cannot make new phloem or xylem. The cambial death need not kill ALL the cambium; just most of it at one level on the bole. I.e. It can be analogous to girdling the tree with a knife at one height on the trunk.
For those species that can generate reliably asexually, fire does not change the species composition very much. Explain.
For the species that can reliably generate asexually, fire will not change the species composition very much because there is a 100% gene transfer to progeny making the process for asexual reproduction very simple.
Why are easterly winds so often associated with big fires and smoke/health issues in CA?
In CA the prevailing winds are western. This means that eastern winds in CA come from dry, warm deserts with warm dry winds. A fire with eastern winds in california also means that the smoke will travel from more rural areas into dense cities such as the bay area and orange county, causing health concerns. Once the dry warm eastern air hits the windward side it mixes with the cold air it sinks causing the wind to speed up. This fast warm wind is perfect for an intense fire
Which places in CA have always been completely crown fire regimes?
In CA, crown fire regimes are primarily in chaparral/ serotinous trees and subalpine forests.
In Ca, south aspects are drier than north aspects. Why?
In california the prevailing winds are western as well as a north east wind pattern, meaning that the Majority of north east aspects are windward while south west aspects are leeward. Mountains make a rain shadow on the lee side with a rainy area on the windward side. On the windward side of the mountain range, air is forced to rise. As it rises, it cools. As it cools, it loses its ability to hold water and precipitation occurs on the windward side. As the air travels up and over the leeward side, it no longer contains as much moisture and it warms as it descends.
Discuss the role of cytokinins and auxins in determining whether a bud breaks dormancy.
In damp/dark environments, branches will start to produce cytokinins because they begin to believe that they are roots, which means that it stops producing auxins and tends to grow root hairs as well as much smaller roots. When determining whether a bud breaks, auxin and cytokinin act antagonistically to regulate the growth pattern of strawberry axillary buds, by which auxin keeps the dormancy of axillary bud and cytokinin changes the cell fate of the dormant axillary meristem, and overall regulating the buds growth as well as development.
Why is tree death directly from a lightning stroke exceedingly rare outside Florida?
In the US, lightning is most common in the SE corner of the continent. I.e. nearest the sources of very warm tropical water. (Remember the oceanic circulation. . . Water is way warmer in Florida than in Baja; much warmer near Virginia than SF. These warm waters make for a high relative humidity. And RH and lighting are well correlated. Also the warm waters are on both sides due to Florida's shape
Why does damp fuel prevent the chain reaction of a sustained fire?
Latent heat is the reason that damp wood will not burn because pyrolysis begins,immediately a lot of that heat goes into the water vapor molecule as it transitions from a liquid water molecule. That is, evaporation robs the local area of heat. If the fuel is too damp, you do not have enough heat to liberate enough flammable gasses to get the chain reaction you need. You cannot even get a flame, only a bit of smoldering, and the smoldering soon stops.
Why is the windward side of a mountain range wetter than the leeward side?
On the windward side of the mountain range, air is forced to Rise. As it rises, it cools. and, it loses its ability to hold as much water vapor, the vapor condenses, and so droplets form on the windward side (visually expressed as clouds). As the drop gets heavier (more water molecules added), it starts falling faster (gravity). Eventually, we have precipitation falling to the Surface. As the air travels up and over to the leeward side, it no longer contains as much moisture as before AND it warms as it descends. So the air is much drier on the lee side of mountains, and precipitation there is far less abundant than on the windward side
Following fire, what are two methods for determining the direction the fire was moving Locally?
One way could be finding the origin by studying which way the grass/groundcover fell as it burned as it will fall in the direction the fire was burning. One can then follow the burn direction back to the origin of the fire. Another way could be measuring/forecasting the wind direction at the time of the fire, wind is major Factor in the success of a fire and it will push the fire in any direction it blows.
Why is lightning associated with thunderstorms?
Particles in a thunderstorm cloud are constantly jostling with one another because of strong vertical winds. It is guessed that falling ice particles generate a negative charge as they collide with one another.
Introduce you to the traits of plants that allow them to (a) resist fire or
Plants are able to resist fire due to a few factors, in the case of a wildfire the leading factors to plants resisting fires is due to a layer of thermal insulation provided by a thick bark, the leaves of the plants containing a higher moisture content, and the presence of dead material on or around the plant. (b) "embrace" it, seorinty or, in most cases, (c) simply get hammered by it. Fire reducing photosynthesis diminishes plant vigor disrupting the ability for plants to absorb nutrients. Causing the demise of the species in the area.
Discuss the basics of prescribed fire and wildland fire suppression
Prescribed fire has been used by humans for thousands of years. Prescribed fire is the act of burning Smaller fuels and ladder fuels to stop the build up fuels. So in the event of fire it will have a much Harder time traveling as well as being far less intense.
Discuss the episodic nature of fire spread in a burn that lasted a month.
Quizlet: a. Wind can affect how long the fire goes on so it can be slow for a bit, but then pick back up as soon as the wind gets strong again b. Other fires may just continue burning for days or weeks after they've reached their maximum size
Which types have ONLY species employing strictly sexual reproduction.
Species that ONLY employ sexual reproduction are annual grasses, douglas fir and lower forested slopes, mixed conifer forests(mid elevations), and subalpine forests.
Why is there so little lightning in the west compared to the east in North America?
The SE corner of the US is close to sources of very warm tropical water. Lightning requires warm, moist air, so it will occur where those conditions are.. the oceans are much warmer on the east
Learn about what happens after fire in relation to plant regeneration, as well as look at the response of animals.
The burnt forest turns into a highly fertile place for trees and plants to grow back at a fast rate. Although animals die during these fires, many seem prepared and unbothered staying a safe distance Away, some even hunting near the fires edge. Many animals such as rodents come back to the burn site after the fire to take advantage of new food opportunities.
Why can serotinous species not persist in a stand-replacing regime with an RT of 4 years?
The earliest that serotinous trees reproduce is at 8 years old, which is the breaking point where the tree is least able to replace itself. With a RT of 4 years, the fire will occur before the tree has a chance to produce cones, preventing it from being able to exist on that landscape.
Why is the summer RH much higher in Arcata than in Nevada?
The temperature is a lot colder in Arcata because we're close to the ocean and get strong winds keeping the temperature low.
Why do chaparral and grasslands not have surface fires?
There is not enough clearance between the top of the flame heights and the low heights of chaparral and grasses. They will always only experience crown fires.
Discuss ways in which trees can protect themselves from surface fire.
Thick bark to protect cambium from heat of frequent surface fires Self-pruning of branches to eliminate ladder fuels to prevent surface fire from reaching canopy No serotiny indicates adaptation to high frequency low intensity surface fires No serotiny, with traits a. and b. are indicative of c.
What is the difference between weather and climate?
Weather= day to day occurrence in measures such as precipitation, temperature, relative humidity, etc. Climate=mean values of these measures over a long time
Why is the net air movement in an intense (strong wind) fire at about a 45 degree angle?
When an intense fire burns at about a 45 degree angle, the net air movement increases in speed due to the fresh air pushing downwards onto the slope igniting the fire and spreading it faster, and further preheating the fire on an upslope.
Define combustion
When the decomposition of a materials molecules so that gas is produced, when the gas is produced liberates causing pyrolysis, and finally when oxygen is added to the gasses caused by pyrolysis, combustion is created.
What are the three main kinds of abiotic mortality for canopy trees in North America. Discuss their geographic segregation and the climatic causes.
Wind : eastern hardwood forest and tropics Ice : northern part of eastern hardwood forest Fire : everywhere else This is most likely due to how cold and warm fronts affect east and west differently but idrk.
What is dry lightning? Why is it more common in the west than the east of this continent?
major source of wildfire ignition in central and northern California Lightning occurring with less than 2.5 mm of rainfall typically referred to as 'dry lightning'—is a Across the state, nearly half (∼46%) of all cloud-to-ground lightning flashes occurred as dry Lightning The normal situation: Lightning emitted from a thunderstorm at 4000 feet; lots of rain at the surface. Effect: ignition but no flames, no smoldering. Even better for us, that now-hydrated vegetation will not burn for several weeks. Dry lightning: the thunderstorm is much higher up(over 10,000 feet) from the bottom of the storm cloud. And the air below the storm is so dry the rain evaporates before it hits the ground Effect: The stroke causes smoldering or flames without sufficient rain to put it out.
Discuss the role of bark thickness and crown consumption in determining whether a tree dies during a fire
A tree with thick bark is attempting to resist a low intensity fire, whereas a tree with thin bark is not attempting to resist a fire whatsoever. Degree of crown scorch, foliage consumption, bud mortality, and stem damage to the bark and cambium layer (just under the bark) determine whether trees will survive. While complete crown scorch causes rapid tree death, many trees with partially scorched crowns survive. Buds may not be killed in a tree that has been moderately scorched, in which case the tree would probably recover.
Why is the ocean near DC swimmable, while we, at the same latitude, need wetsuits?
Air in Arcata is westerly, and so it is cold because it has moved across cold water. The water is so cold due as it comes from swells caused by storms far in the upper pacific northwest. •In the summer air in Washington DC has moved across the hot central US. In the winter that westerly flow will be much colder. As well as north traveling ocean currents coming from southern waters which are warmed by the equator
Discuss weather impacts on fire intensity
From slides: Elevation(Elevation can impact variations in temperature and relative humidity), Topography(how water reacts with mountains), Cloud Cover(Lower v.s. higher average surface temps), Wind(Day: Lowers air temperature, Raises humidity, Night: Keeps air temperatures warmer, Lowers humidity) Proximity to bodies of water(prevailing winds) Me:Wind speed is a major concern the more oxygen a fire can get the more intense the fire will be. High winds can make a fire unfightable as it causes the fire to spread at a rapid rate. Wind direction is also a factor as depending on location(California has northwest prevailing winds that are cold and humid) the difference between cold humid air v.s. Warm arid air is very extreme. Precipitation is the most important factor as an area with low precipitation and/or drought are at extreme risk of wildfire as where a forest with lots of precipitation and/or humidity year round are practically unburnable. Chatgpt:"The moisture content of fuels is influenced by climate, weather conditions, and the overall hydrological cycle of the region. Extended periods of drought can lead to drier fuels and increase the likelihood of wildfires.
Learn about the role of fuels and weather in determining ignition, combustion, and fire spread
Fuel and weather are the two most important components in determining as the weather during and Leading up to a fire are often the cause of the fire (ie dry conditions+dry lightning), while the fuel Usually paints a picture of where the fire came from, as the fuel will fall lying in the direction the fire came from
Learn what fire is; what is required to get combustion
Heat+oxygen+fuel What do you need to make a forest fire? Two things. 1.Ignition- humans or lightning 2.Dried fuels (i.e. there has been a preceding drought) What do you need to make a LARGE forest fire? Three things. 1.Ignition- humans or lightning 2.Dried fuels (a preceding drought. 3. Strong winds
Compare human ignitions with lightning: where on this continent is lightning a more important fire ignition source during the summer? Why?
Human ignitions are more common than lightning in summer pretty much everywhere but especially in the west. Most common near roadways, near cities, agricultural areas b. Where human density is very low i.e., Alaska, oregon/rural areas of northern california, (dry)lightning predominates
A burnt forest has 25% of its trees standing. Roughly: estimate how many years ago the fire took place.
If a burnt forest has 25% of its trees standing, the fire took place roughly 80 years ago.
Contrast stable and unstable air
If it falls rapidly with height, the atmosphere is said to be unstable; if it falls more slowly (or even temporarily increases with height), a stable atmosphere is present. Unstable is caused by air with a different temperature than the air around it, it will then rise or fall rapidly to find a similar temperature
Discuss the minimum and maximum return times the 4 types (grass, chaparral, serotinous trees, and non-serotinous trees) can tolerate.
RT < 30 years should be grassland. 30 < RT < 75 should be chaparral. 75 < RT > 170 should be serotinous tree species RT > 170 should be non-serotinous tree species Serotinous Trees: Start producing cones at 8 years old The minimum RT that allows serotinous trees to persist is 75 years; will persist if RT is greater than 75 years Nonserotinous species: Will start producing cones at a later age (over twice as long as minimum reproduction age of serotinous species) Minimum RT for Nonserotinous species to persist is 170 years Chaparral: Fast growing shrubs can produce their first fruits within about 3 years Minimum RT is 30 years to persist A RT between 30-75 years is ideal; if RT is greater than 75 the serotinous trees will begin to shade out the shrubs Grasses: Annual grasses produce their first seeds in a single growing season Critical minimum RT can be a few months, but nowhere in the world burns that rapidly because there is not enough fuel to burn and so grasses do not really have a minimum RT, they only a maximum
Discuss convection, conduction and radiation in relation to the drying and death of plant parts
Radiation plays a key role in all aspects of the drying and death of plant parts, radiation causes the tree trunks to preheat, tree branches to preheat, brush to preheat, fallen logs to preheat, and all litter and duff to preheat. Within the radiation of branches preheating convection also plays a part in this by causing the area surrounding the branches to heat up and produce heat. Conduction assists radiation primarily through the preheating of logs and litter/duff by spreading through direct contact with any combustible material it touches.
Rank these veg types in order of RT: oak woodland, mixed conifer forest, subalpine forest.
Ranking from 1(being highest in RT) and 3(being lowest in RT): 1.subalpine forests(150-500) 2.mixed conifer(125-500) 3. Oak woodland(50-150)
What is meant by return time?
Return time = how long do you have to wait to burn 100 square miles in total?
Where are serotinous species found. Why there?
Serotinous species are found prevalently in CA.This is because most of the serotinous species used to have an extensive range in CA but due to climate changes like fire restrictions have reduced their range to be quite rare but there is a large amount of species diversity.
A short duration fire is usually elliptical in shape. A long duration fire is more squared off. Why?
Short Duration Fires (Elliptical Shape):In short duration fires, the wind may change direction and intensity relatively quickly. As the wind shifts, it influences the fire's direction of spread.The fire responds to these variations in wind by elongating in the direction of the prevailing wind. This elongation results in an elliptical shape, with the longer axis aligned with the predominant wind direction.The fire front is more sensitive to the immediate wind conditions, and as a result, the shape of the burned area reflects these variations. Long Duration Fires (Squared Off Shape): In contrast, long duration fires experience more sustained and consistent wind patterns over an extended period.When the wind persists in a relatively constant direction, the fire is less responsive to short-term changes in wind speed or direction.The fire front becomes more "squared off" or boxy because the continuous wind drives the fire in a consistent direction, minimizing the elliptical elongation seen in short duration fires.
Discuss the role of (a) wind and (b) spotting in fire spread
Wind is a massive factor in the success of a fire for many reasons. Wind speed is a major concern the more oxygen a fire can get the more intense the fire will be. High winds can make a fire unfightable as it causes the fire to spread at a rapid rate. Wind direction is also a factor as depending on location(California has northwest prevailing winds that are cold and humid) the difference between cold humid air v.s. Warm arid air is very extreme. Spotting in when due to the highwinds embers from the crown or higher up in the tree, gets picked up by a draft of wind and moves to another location creating another source of ignition. These embers can travel miles before creating another ignition source. Burn-out time = how long before the flame on the ember lasts Quizlet: a. Wind can spread the fire far - can be make or break for how big a fire ends up being b. Spotting - embers can travel far, makes fire breaks useless; controlled by uplift in heated plume, horizontal wind speed, and terminal velocity of embers
Why does western Mexico have its drought in the winter while Arcata has its drought in the summer?
a. During the summer, the High (descending air in the Hadley cell) is centered at the latitude of northern Baja, so CA gets no rain. b. During the winter, the subtropical High is centered at the latitude of central Mexico. The jet stream moves south, so CA gets a lot of rain and the west coast of Mexico has its dry season.
Discuss RH, fuel size (s/v ratio; time-lag categories) and the equilibrium moisture content
a. RH: A measure of how close we are to the condensation point (where the air can't hold anymore water and it will condense into liquid form). It varies with temperature and absolute amount of moisture in the air. b. Fuel Size: most flammable fuels have small diameter (twigs, leaves, small branches) i. Water only evaporates from the surface, so high s/v ratio means faster burning ii. Time-lag intervals: time required to lose 63% of difference between original moisture content and equilibrium moisture content at a constant temp and RH. This refers to 1-hr, 10-hr, 100-hr, 1000-hour fuels c. Equilibrium moisture content: moisture level where wood neither gains nor loses water (at equilibrium with surrounding relative humidity). Has a positive relationship with relative humidity(11%-13%) Dry Bulb Temperature = 95 °F Wet Bulb Temperature = 56 °F
