Shared Flashcard Set


Forest Ecosystems
Cusack- UCLA
Undergraduate 4

Additional Geography Flashcards




Define disturbance
-Discrete event that causes:
-death of vegetation,
-loss of biomass both below and above ground
-removal of soil
Short and long term results from disturbances
-short term: Change in structure
-change in soil fertility(nutrient cycling)
-change in growing spaces(increase & light
-Change in water availability

-either short term sustain, a return to prior ecosystem, or an entirely new ecosystem develops
-Resistance vs. Resilience in disturbances
Resistance: Capacity to withstand disturbance; characteristics include- wood strength & density, bark thickness(fire), anti-herbivore compounds.

Resilience: Ability to recover after disturbance; has a lot to do with reproductive strategies(regeneration)
-Germination:based on SEED BANK- (inital floristics), fire-resistant seeds, and SEED SOURCE(relay floristics)- seeds coming in from remaining forest around; Lower/slower rate of success to develop from seeds but highest genetic diversity.
-SPROUTING: Grow from stump or roots of dead parent material or RHIZOMES(underground stems that can resprout- Ginger); HIGHER success dependent on time of season, but no genetic diversity, clone of parent.
-ADRANCE REGENERATION: shade tolerant plants under canopy that grow slowly until disturbance opens up more light availability, grow fast, quickly reiniitiate canopy! They are products of seed so HIGH genetic diversity, grow fast when exposed to sun, High survival rates.
Types of disturbance severity?
Punctuated vs. chronic?
-How to characterize your disturbance
-Stand replacement: Complete loss of ecosystem, no resistance/all resilience; kills of seed bank, dependent on "relay floristic" of surrounding trees. Ex- volcano, clear cuts, land slides, wildfires, tsunami; TOTAL LOSS OF CANOPY/SEVERE SOIL DISTURBANCE

-MAJOR DISTURBANCE: not complete stand replacement, still some seedbank. BOTH resistance/resilience IMPORTANT. Ex. wildfires, hurricanes, landslides, LOSS MAJORITY OF OVERSTORY

MINOR DISTURBANCE: Spatially discrete, doesn't effect entire canopy, fastest recovery, help maintain biodiversity! CREATES A MOSIACE OF SUCCESIONAL STAGES SPATIALLY; Ex. Tree falls, small landslides, lightning, erosion, silviculture(thinning/controlled burns), COMPLEX- requires mechanistic understanding

CHRONIC DISTURBANCE: occur slowly over time, forcing ecosystem into new state, ex.warming, beetle infestation, acid rains!
How does distance change growing space?
-increase total growing space(temporarily)
-Nitrogen-fixing places come in, increase # of plants able to grow
-Pioneer species come in- capture water from fog, "FOG DRIP"
-Roots-aerate soil, reduce compaction
-Tanspiration-> aerates soil.
Explain the 4 phases of stand development after a major disturbance: Initiation, Exclusion, Reininitiation, Old Growth
For each phase, think about characteristics/changes in the following: IMPORTANT TERMINOLGY IN DIFFERENT PHASES FROM ABOVE.
Microsites- ex. Most important in stand initiation, important for seedlings
Density dependent mortality (in what phase is this most important?), ex. As seedlings get established they compete with each other, competition leading cause of death important for what phase, Stem exclusion?
Density independent mortality (in what phase is this most important?), ex. Pests, outbreaks, not competition- Old Growth phase.
Gap dynamics- small scale, chronic disturbance, good for old growth
Autogenic versus Allogenic changes in stand structure- Other words for density dependant and independent, Autogenic is independent, Allogenic is usually dependent on density(Not always

-STAND INITIATION: new individuals establish until they fill growing space; dependent on multitude of facots for species composition(see other card)

STEM EXCLUSION: biggest growth phase, "Pipe-stem model of tree growth"- grows straight up like pipe stem.
-high shade/lowest light availability for understory(no new individuals after initial cohort developed), cooling of forest & increased humidity(ameliorating climate)
-Crown differentiation: depends on species diversity, can have complex canopy structure w/in singe cohort forest. Differentiation will cause deaths of some canopy with leads into...understory reinitiation

-death of individuals from 1st cohort
-emergence of crown shyness(middle aged-forest)
-more spotty second cohort depending on light openings
-adding more CWD(dead wood) from falling trees & snages, more herbaceous plants
-INCREASED Biodiversity of non-woody plants and animals but also of woody species richness.

OLD GROWTH- complete daeth of 1st cohort, dominated by more shade tolerant species that come in later.
-steady state: death= new growth, carbon in=carbon out(photosynthesis=respiration)
-Dominated by large mature trees
-Minor disturbances are integral to this stage.
Units of measurement for Forests:
-Volume per tree
-Tree growth efficiency
-yield: standing volum or mass of wood per area(acre/board foot)
-Growth: change in yield over time
-GPP, Gross primary productivity- gross primary productivity= biomass increment + mortality.
-NPP: New growth, biomass increment
-VOlume per tree- How big is each individual tree and how does it change over time; site conditions impact time to crown closure, spacing impacts growth after crown closure.
-Tree growth efficiency: highest sustained growth/area(objective for forestry)
Stand density index & -3/2 slope
-spcies and regionally specific
-# of trees/area(spacing) over avg. diameter on graph of a linear curve of -3/2 slope results in change in density from competition, more trees, less they can grow, give you best yield to five a shorthand of maximum diameter.
Tools to find methods of research: tree basal area for stand volume, Boring, Cookies, wedges, alimeter, allometry, DBH, Densitometer,PAR sensor mini-rhizotrons
-tree basal area: measure DBH, or height by angles or laser range finder
-Cookies:slice of trunk, taken as low on tree as possible, kills tree, shows entire ring
-Wedges: doesn't kill tree but misses whats happening to other side of tree, i.e. fire
-Tree core: good for tree age, find cohorts age differences, water/nitrogen resources they were tapping, pull out little insert of full tree core, can't see scars/ branches
-altimeter: an instrument used to measure the altitude of an object above a fixed level.
-allometry:study of the relationship of body size to shape
-densitometer:Concave mirror that measures a sites light to leaves.
-PAR sensor: photosynthetically active radiation to determine which wave lenghts of light are coming through.
-root coring: takes core of roots to separate and count individually in lab or there is mini-rhizotrons which are - tube in soil w/ light source & mirrors and camera at top that observes root growth, need tons to get an idea of how entire root system is growing.
Ways of measureing Ecosystem function:
-microbial biomass:how many grams of microbes/1gram of soil- fumigate sample which release carbon/nitrogen, extract lipids, decomposition litter bags-see how much mass disappears over time to indentify rate of decomposition.
-infrared gas analyzer- use infrared light and absorption into gases to observe gases. Can measure instantaneous infrared rates from "clamping leaves" - only works for CO2
-Gas chromatograph- detects different gases, if you're measuring for ecosystem functions.
-Canopy openness: can tell what restrictions if any are there.
-fisheye pictures: can see sun flecks
-Eddy flux towers: towar above canopy w/ measuring station that records water vapor, CO2 concentration, and other GHG, give total input/output of canopy.
-Sap flow measures water
-Elemental analysis of C N
Alpha(Shannon/simpson) and beta diversity(Sorensen/Whittakers)
i. Shannon Index: Increases w/ greater species number and evenness. Most widely used(But only uses 2 factors of biodiversity); Shannon index= Sum of all species(evenness of 1 species/all species (natural log) one species/all species)- means abundance of one species relative to all species.
ii. Simpson Index: Also takes into account species number and evenness. Homogenous population will have a score of 0, perfectly heterogeneous population will have a score of 1; Simpson index= sum of all species(evenness of one species/ all species) square.
-Shannon= Richness
-Simpson= evenness

i. Sorensen’s Similarity Index: Takes into account total # of species in community 1 and 2, and # of common species between the sites;
ii. Whittaker’s measure: Takes into account the total number of species in both communities, and the avg number found within the communities. Total for entire area divided by avg.

-Sorenson: take species from community 1 and 2 and divide by common shared

Whittakers- Total # found in both divided by avg # found within communities.
evidence for global warming
i. Global average temperatures have risen by 0.75 degree celcius over last century
ii. 11 of last 13 years were warmest ever recorded
iii. World Temp. could rise between 1.6 and 6.4 degrees or more during 21st century- Like having a fever, if normal temp(98.6) goes up you feel like crap.
Source pool and mixed pools of isotopes
k. For H20:
i. Source pool= rain, stream, ground water
ii. Heavy or Light: Main factor is evaporation- For groundwater no evaporoation loss of isotopes(intermediate- LIGHT), streams have lots of evaporation(bias towards HEAVY), rain (coastal distance, topography, VARIABLE-specific to site)
iii. Mixed pool= Tree, heaviness of water shows where tree is getting water from. Tree ring is 2nd measure- can tell if it’s a good/bad year.
l. For Nitrogen:
i. Mixed pools= Trees,
ii. Heavy or Light: for fixation- favor LIGHT, for decomposition- off-gases leaving HEAVY behind, atmosphere is VARIABLE- have to figure out for specific site)
iii. sources= atmospheric smogs/acid rain, N fixation, decomposition (mineral/organic cycle)
m. For Carbon:
i. Mixed pool: Soil- see in layers of soil decomposition to determine if grass or trees.
ii. Source pool: Tree & Grass
iii. Heavy & Light: Trees= light, Grass=Heavy
How will global warming effect forests and how can forests mitigate climage changes w/ proper management and preservation?
i. Fertilization & Irrigation of Forests
1. Carbon costs of production, transport, pumping…Must look at full picture.
ii. Forestry adaptation:
1. Hardwood, long-lived species vs. Fast growing species, longer plantation rotations
2. Time span of carbon sink in trees?
iii. Maintain Forest lands
1. need to show additionally
how much carbon are we adding to the atmosphere every year?
How are natural processes helping us with global warming problems?
-6 gigatons; 3-4 after uptake
-oceans take up more as t gets warmer, photosynthesis increases w/ increase CO2
Know how CO2 concentrations in the atmosphere have changed over hundreds of thousands of years (inter-glacial cycles), and in the past 100 years.

-how much has temperature increased in past 100 year?
-temperate has increased 0.74 celcius or 1.33 farenheit,determined by ICPP.
What is CA asembly bill 32?
-What are some C sequestration strategies in the bill?
-What is target of bill in 10, 50 years
-what are we hoping to accomplish?
-What are forest strategies of bill
-Do you think it'll work? how can it be improved? Which parts are unfeasible and should be dropped?
Carbon market for companies(rights to pollution) can be traded, total # goes down every year
1. Increasing Forest volumes, harvest later(increase rotation lengths)
2. clear cut to selective cuts
3. Fire thinning for electricity fuel
4. Changing agricultural practices: Conservation tillage, cover cropping.- 3 to 4 times as much carbon in soil than above ground biomass,
5. Rangeland afforestation- letting grasslands go back to forests naturally, not through planting. There has always been grazing even in wild so grasslands that have never been forests will change. 23 million hectares of rangelands, 50% available for rangeland afforestation.
1. Emissions at 2000 levels by 2010, 11% below business as usual. Reduction of 60 million tons.
2. 2020 emissions at 1990 levels
2050: Emissions at 80% below 1990 levels (ultimate goal based on climate change science)
What is the IPCC and what does it do?
-Intergovernmental Panel on Climate Change
-a scientific intergovernmental body[1][2] tasked with reviewing and assessing the most recent scientific, technical and socio-economic information produced worldwide relevant to the understanding of climate change. It provides the world with a clear scientific view on the current state of climate change and its potential environmental and socio-economic consequences, notably the risk of climate change caused by human activity
What are the 3 types of species interactions and which are most important for which phase of stand development?
a. Competition
b. Predation- Primary producer (plants)primary consumers (herbivores-Grazers(grass)/Browsers(Leaf) & Detritivores/Decomposers(Dead material)Secondary consumers (rodents, etc.)  Tertiary consumers.(carnivores/scavengers)
i. In relation to isotopes- The higher the trophic level, the more concentration of heavy isotopes due to greater respiration of lighter isotopes.
c. Symbiosis- Just means two organisms living in close relationship, can be obligate(species evolved so long, can’t be found separated) or facultative(can live together, but can break relationship as well)
i. Mutualism- Both Species benefit; ex. Acacia plant(nitrogen-fixers) provides shelter and amino acids in floral nectaries, ants protect plant from lianas, herbivores; Tree & nitrogen fixing bacteria in mutualism relationship as well.
ii. Commensalism: Only one-sided beneficial; External Seed dispersal, attaches to fur, no cost to animal.
iii. Parasitism: Mistletoe, parasites usually don’t kill hosts just take nutrients/water to extent that is detrimental but doesn’t kill it; Mycorrhizol- if tree can’t photosynthesize as well, the mycorrhizol attached takes more than tree can provide and becomes parasitic.
What are some reciprocal adaptations of plants and animals?
d. Co-evolution: Animal regulation of plant natural History
i. Herbivory and plant defense-
1. Focus on fast growth to tolerate herbivore disturbances
2. Focus on Defense to avoid herbivore disturbance(physical-Thorns, hairs, unpalatable; and chemical-toxins, reduced nutrient content, change pH)
a. Counter for herbivores is- timed to come out early in growing season before defense is up, which will shift plant growth, and constant re-adaptation on both sides.
- iii. Large animal grazing and adaptation to chronic disturbance.
1. Ungulates constantly grazing on plants, plants become highly adapted to sprouting.
How to characterize your disturbance
-frequency/return interval
-spatial distribution
-shape(edge effect-more= easier to recover)
What are the factors that species composition is dependent on during a stand initiation?
-disturbance type
-timing of disturbance
-seed bank and/or seed rain
-duration: depends on disturbance severity, size/shape, site quality, compeition from non-woody, herbaceous species.
-Cohorts- Everything established at same time.
What are the 4 classes of crown dominance in Old Growth forests?
-Dominant: emergent are dominant
Define structural development and processed development
-Processed: physical development, stage in competition, disturbances, history of forest and trajectory, WHERE HAS IT BEEN & WHERE IS IT GOING?
-Structural: Elements/function
Spatial and temporal variability in tree invasion and stand development during stand initiation phase.
-Stand initiation: Micro-site characteristics(for seedlings)- either uniform(low diversity) or variable(more diversity); Ex. nutrient availability, moisture, litter & debris, light. In addition to micro-site, SPECIECS CHARACTERISICS- relative competitiveness.

-STAND Initiation to Exclusion: move from clumped tree to random distribution- Clumping caused of density dependency mortality in exclusion, Where as in initiation phase most of mortality caused by site conditions; Based on 1-on-1 competition, randomization of distribution.

-Understory reinitation:
Factors:stand density(light, overstory competition over water/nutirents, space variability, light interceptions(species related characterisic- more strata=less light to understory), vertical spatial variability; shift from initiation to density independent mortality, trees established past stand excluson, DIE FROM disturbance/age; dependent on disturbances type- fire(climate/humans), windthrows*forest edges/emergent trees/ridges), insects(insect behavior); LOW CWD- less snags(standing dead trees) compared to first two phases.
Spatial and temporal variability in tree invasion and stand development during understory re initiation phase.
Factors:stand density(light, overstory competition over water/nutirents, space variability, light interceptions(species related characterisic- more strata=less light to understory), vertical spatial variability, light variability

-shift from initiation to density independent mortality, trees established past stand excluson, DIE FROM disturbance/age; dependent on disturbances type- fire(climate/humans), windthrows*forest edges/emergent trees/ridges), insects(insect behavior); LOW CWD- less snags(standing dead trees) compared to first two phases.
Factors of light variability during stand development
-Crown shyness
-sun flecks(upt 50% of light in understory)
-Decreased stand density/gaps
-light must be within bandwidth of photosynthetic active radiation(400-700)
-Depends on size of gaps, stand height, overstory species(# of strata) and spatial variabilit horizontally, latitude of forest.
-UMBRAL SHADE: light directly shaded under canopy, "umbrella" effect, darkest shade/full light harvest.
-Penumbral shade- partial light harvesting, shade can still allow utilizable light.
Spatial and temporal variability in tree invasion and stand development during the old growth phase
-Transition from understor reinitiation:
-lots of CWD & snags
-good animal habitats
-NURSE LOGS- other trees germinate on them, good source of nutrients, last upto 500 yrs.
allogenic vs. autogenic
-allogenic= dying because of disturbance factors outside of tree; minor disturbances
-Autogenic= dying due to tree-driven causes; age, sucked up all nutrients
Tree growth measurements at stem, foliar biomass, branches, coarse/fine roots
-Stem growth: easiest to measure(diameter & height);
-Diameter at breast height(1.3 meters)
-height altimeters: find distance to tree and angle to tip.
-Allometry(above ground): Use basic measures of shape to calculate volume or mass; based on species features.



ROOTS- shoot ratios & site characterisicsl usually 50% above and 50% below ground biomass.
Selective logging
-thinning for lumber, way to maintain forested land and still get economic value from it
-mimics old growth "minor disturbances"
-drawbacks: no snags(CWD), removes nutrients, soil compaction, high grading
Multiple-Cohort logging vs. single cohort
-Single: more volume each cute, completely removed and start over
-Multiple: frows less height(some shading) and can select older ones and leave younger to select later(which grow sooner than single cohort regrowth)
-spacing w/ age graph
-Volume w/ age
-Constant yield
-# of tres/area(spacing) over Stand age; j-shaped showing lots of saplings in beginning but density reduces and stabilizes species #

-Volume w/ age: Volume/area over tree #/area(spacing), j-shaped curve, more trees equals less volume

-constant yield: initial spacing doesnt matter, baed on volume/area & stand age. Narrow spacing will reach crown closure(max growth rate) faster than wide spacing AS A ENTIRE STAND but both will obtain max yield at some point, based on Crossover effect; constant yield better for carbon sequestration.
Isotopes as tracers
-Stable isotopes: C12 & C13, last forever
-Radio isotopes: C14, any phase change will discriminate against heavier isotopes, evaporate for example favors lighter isotopes, as does biological activity/decomposition
-Lighter isotopes always more abundant
-light isotopes: C12, N14, H1, O16
-Heavy isotopes: C14, N15, H2, O17/18
Change in nitrogen source seen through isotopes
You have a site w/ natives and invasive, invasive fix nitrogen so you think that’s how invasive have advantage. Microbes can take N2 and make into mineral N, a usable form, no bias for 15N(heavy), atmosphere is mostly 14N and few 15N, so mineral nitrogen will look just like atmospheric nitrogen ratio. Leaves have no bias as well, so they contain the atmospheric ratio as well. THE Native trees get nitrogen from processing leaf litter, etc(recycling nitrogen), when decomposers are processing the biomass, some bacteria turn some nitrogen to gas(your lighter nitrogen) and the mineral nitrogen left behind will be a higher ratio of heavy nitrogen. SO native trees are taking up more heavy nitrogen, and leaves are going to show bias of the soil. If invasives are a lot lighter in leaf tissue they are relying heavily on biological fixation, but they can also take up nitrogen from soil if there is adequate amount.
-e. Nitrogen deposition also occurs as the nitric acids(smog, acid rain) based on what formed it like fossil fuel(Light nitrogen- no bias), fertilizer(ultra light, man-made no heavy nitrogen in it). To find if deposition is effecting your forest you collect rainwater and measure ratio of N15 in rainwater to determine source of nitrogen.
-f. NITROGEN FIXATION Trees= Lighter N
g. NITROGEN DECOMPOSITION= Heavy N in soil, Ultralight in gases.
Changes in Carbon Isotopes for land use study based on photosynthetic pathways
C3- trees
C4- Grasses(especially tropical)
iii. Most carbon in atmosphere is CO2(12) and some CO2(13)
iv. Trees are bias in photosynthesis- mostly C12 uptake
v. Grasses adapted to hot temperatures, minimizing water loss, not as free exchange of gas in and out, so they lack bias in carbon, turn everything into photosynthate, C12 & C13, heavier carbon in leaves.
vi. Example of using Carbon isotopes for land change- Hawaii had lots of grasses put in when colonizers came, if you observe top layer of grasses they will be heavy w/ no bias, as you dig deeper into soil you will get lighter and lighter of more bias older trees that indicates there were trees on site prior to grass invasion.
Change in Oxygen isotopes for change in H20 source
i. You can look at oxygen isotopes in tree rings to see what water may have been hundreds of years ago.
ii. Different sources of water: Groundwater- trapped so light isotopes retained, no evaporation; Stream/lake- evaporation out of open system loses light isotopes and leaves the heavier isotopes. You can go back in tree rings to see when trees were using ground water (during dry periods) or stream water(wet periods). Rainwater- Isotopic composition varies, how many times droplets has evaporated an re-condensed (depends on distance to ocean, topography-mtns, and latitude)
source pool/Mixed pools
-Source: where elements are coming from; rain, stream, ground water(for H20), atmospheric smogs/acid rain, N niation, decomposition(for nitrogen); tree/grass(for carbon)
-Mixed pools: tree leaves or soil
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