Exam 3 study questions Flashcards
(64 cards)
What is community physiognomy? How do plant functional traits affect it?
Community physiognomy: form, structure, external appearance of a plant community
(includes dominant spp growth/life form; life span; size; degree of woodiness; morphology; phenology; etc)
How would you characterize a plant community using a bisect?
Use plant functional traits to describe communities (ex: types of leaves, shape/form, size, whether woody or herbaceous, etc)
What is a vertical profile of a plant community? How would you expect
vertical profiles of a boreal and temperate deciduous forest to differ?
-takes height & canopy coverage of each layer
–boreal forests are almost entirely canopy trees with few shrubs—understory has up to 75% forbs and graminoids
–temperate deciduous forests have slightly taller canopy trees with some more understory trees (10-15% area), and have some shorter shrubs—typically <= 10% herbaceous cover
When do you think would the Raunkaier classification be useful/not useful
for describing plant communities?
since looks at distribution of growth forms (trees, shrubs, forbs, etc) would be helpful to get understanding of overall “look” of ecosystem—not so much for specific species or understanding of ecosystem niches/functioning
What are the different ways we use to characterize community diversity?
-spp richness (# of spp in the community)
-evenness (extent to which spp in community are equally abundant)
-dominance (most abundant spp in community <evenness/diversity)
What are the two reasons that make plot size, or area sampled, important in
estimating plant species richness?
1) environmental heterogeneity increases with area sampled (additional niches + new spp in larger area)
2) chance of encountering a new species increases with number of spp sampled
What is a species-area curve? Why is it important?
-describes the increase in the number of species found as the area sampled increases
-Uses one of many proposed mathematical functions and nested quadrats to try and calculate spp richness/ community diversity
What field measurements are needed to describe community composition?
–spp presence; spp frequency; spp cover; density; spp importance value; spp biomass
How would one use Euclidean distance & Pythagorean theorem to measure
how similar are simple communities composed of two species?
–using geometric formulas and multivariate statistics to compare spp composition similarities between different communities
What does Jaccard index do? What information do you need to calculate it?
-measures similarity between 2 sites using presence/absence of a spp in both
-uses # of spp in both sites / (sum of spp in both + spp in 1st site + spp in 2nd site)
What is community percent similarity? How would you calculate it?
-how similar two different communities are to each other in terms of species composition. You can use one of several formulas, including Jaccard index.
What are the differences between primary and secondary succession?
-primary succession (like old growth)—initial colonization after disturbance (clean slate—no propagules from previous plants)
-secondary succession– occurs on substrate that has been previously vegetated (propagules are likely already present in soil seed bank)
Describe succession drivers & patterns after the eruption of Mt. St. Helens.
-volcanic eruption in 1980
-before eruption (primary succession occurs on substrate w/o previous vegetation, starts with little to no soil and builds over time
-after eruption, large amount of mountain was gone, seed banks/soil deposits greatly disappeared—vegetation vastly decreased due to lava flows, ash deposits, etc
-a few years later, water runoff streams start to gather some vegetation, by 1994, much more vegetation (including trees)
-del Moral et al (2005)—study plots around volcanic substrates—over time, spp richness generally increased, took about 20 yrs for smaller colonizers to start getting outcompeted by larger spp; all of the plots seem to converge around same value around this time
What is a chronosequence approach to study of succession? What is it used for and
what are its strong and weak points? Use examples to illustrate.
-compares communities established at different times since disturbance.
-Better for studies looking at long-term trends that cannot be monitored by humans (> than a human lifespan)—can look at ecosystems at different life/successional stages at the same time or even at historical states.
-Weak points: assumes successional processes are highly predictable; that species pool remains the same throughout entire time period; and that communities in same region are similar enough to be considered in same successional sequence
Describe how succession may have occurred on the dunes of lake Michigan.
Lichter (1998): looked at 72 shore-parallel dune ridges along Lake Michigan. Used radiocarbon dating, tree cores, & land surveys
-found that 1 dune is formed about every 33 years
-dune succession- large compositional changes across dunes of different ages (early dunes are colonized by beachgrass; middle age had more shrubs; older dunes had much more shrubs/conifers, oldest also had increases in hardwood cover)
-oldest dunes had basically 100% similarity in spp composition, young dunes had 0% similarity
-structural changes across dunes of different ages
-once trees were dominant, plant density would level off
-changes in abiotic environment amongst dunes
-amount of sunlight decreased with age until flattening with tree dominance; soil moisture increases with shading from trees; biomass flattens out over time as well
What were the hypothesized successional stages after glacial retreat in Glacier bay,
Alaska? What roles did the main species play in each stage?
-late 1700s, entire bay was covered by glacier that retreated over time
-by 1900s, glacier was almost completely out of bay
-5-10 yrs: pioneer community (cyanobacteria, horsetails, lichens, liverworts)
-35-45 yrs: mountain avens (Dryas drummondii), some willow, cottonwoods, alders, spruces
-60-70 yrs: alder dominated (Alnus sinuata)
-200-225 yrs: spruce dominated (Picea sitchensis)
-bulk soil density declined over time (leaf litter/woody debris/other less dense materials); organic soil carbon increased; soil pH declines (conifer needles, etc); total soil nitrogen had intermediate increase before decreasing some/leveling out (compositional change from N-rich litter into less N-rich litter with spruce)
What is old-field succession and its role in eastern United States? How would you
think it’s rate my potentially respond to climate warming? Why?
-old agricultural fields that have been abandoned and allowed to regenerate. Seed banks might still be there, but climate change can impact survivability of spp, invasives/pioneers might be present and complicate things
How did plant communities at Andrews Forest responded to disturbance over time?
–2nd succession after intensive forestry—Andrews Experimental Forest (PNW)-2 watershed were logged & burned in 1960s
-looked at effects of this treatment immediately after and 20 years after
-at 20 yrs—well forested with younger trees
-at 40 yrs—much larger trees—but still nowhere close to old-growth size
-different groups of colonizing spp and forest residual spp had different compositional changes & trends over time
–gradual compositional recovery of community types over time
Contrast facilitation, inhibition, and tolerance models of Connell & Slatyer.
-Facilitation (relay Floristics theory—Clementsian) early successional species might facilitate the colonization and growth of later successional species
-Inhibition -some spp prevent others from establishing by monopolizing resources such as light, water, or nutrients
-Tolerance (initial floristics theory) - species neither help nor hinder colonization by other species
What is a disturbance regime? How would you characterize it?
An important natural structural element of plant communities that often brings about significant changes to an ecosystem.
Important factors: duration & timing; intensity; frequency; and disturbance size
* disturbance type determines how these 4 components affect plant communities
Contrast in detail the disturbance regimes for volcanic eruptions vs. flooding.
Use examples.
-Volcanic eruptions are typically very infrequent and intense events that often affect large areas
ex: Mount St. Helens caused drastic changes to the surrounding environment (large portion of mountain suddenly gone, lava flows and ash deposits removed vegetation and propagules in seed bank of areas, much of the soil was gone. Took a number of years before nearby plants could start to colonize the area (creates primary succession conditions)
-Flooding can happen due to different means with different levels of frequency and severity depending on ecosystem type/location.
Ex: flooding caused by a rain event vs flooding caused by a tropical storm such as hurricane Katrina. Depending on severity and event duration, can alter riparian habitats and the species composition within them
How does importance of fire as a disturbance agent vary across the globe
and across North American plant communities? For example, what are the
differences in fire regime between prairie, eastern deciduous forest, and pine
forests of the US Great Lakes?
Fire disturbance regimes vary in frequency and intensity depending on ecosystem type and area of the world.
In North America, prairies have surface fires at least every few decades if not every decade. Eastern deciduous forests depend on whether mesic or xeric forest type, mesic have very little propensity for fire whereas xeric typically have low-intensity surface fires every 25 years. Pine forests around the Great Lakes have very infrequent intense surface and/or crown fires every few centuries.
Discuss the history and roles of fire suppression & prescribed fire in the US.
Fire suppression leads to a build-up of fuel loads—subsequently causes catastrophic fires. Prescribed burns are frequent low-intensity surface fires used to reduce these fuel loads and thereby reduce risk of severe wildfires
Contrast the annual sediment discharges by the Amazon vs. the Mississippi.
What does it tell us about the disturbance regimes in the two watersheds?
both release decent amounts of sediment—but Amazon releases >10X the amount. This shows that the Amazon river has a much more severe disturbance regime
