Review for Ecology Test in AP ENVS  07

We have focused on terrestrial ecosystems, specifically the forest at Maury where we collected point-quarter data, soil samples, leaf litter=> macroinvertebrates, and temperature data.  The basic concepts apply to all ecosystems, but I like to tie them to a local system.   

We have addressed in class
Energy or trophic pyramids  (I did not focus on food webs-that is a different type of data)
Primary productivity and factors that affect productivity
          NPP net primary productivity is sort of like free energy-it is what is left to grow on
Ecosystems are all different  primary productivity depends on nutrient availability (here we addressed autochthonous and allochthonous sources of nutrients and we pointed out that usually N and P are limiting nutrients but in our ecosystem, allocthonous sources are possible

Precipitation is tied to climate (weather is what is happening now; climate is weather over decades) when, how much, and in what form greatly affects primary productivity

We talked about which ecosystems are most productive ( Chesapeake Bay WAS one of the most productive ecosystems in the world-bar none!)

Obviously, climate change greatly affects what ecosystem function will be like and what the structure will be like.

Here is where our discussion of succession, especially in our area, secondary succession, applies.  Primary succession is when the plants begin to colonize from rock.  Secondary means there was an ecosystem there, but it has been left to recolonize.   If we clear an area for agriculture, then allow it to fill back in on its own, that is secondary succession.  Clearing a forest for a road and then allowing the sides of the road to recolonize is secondary succession.  Maury was a forest and there were springs, natural springs that formed more like watering holes and less like a pond.  After the area was dammed, then the pond formed.  It was fed by those springs.  The forest that used to be there may or may not be the forest that is there now.  That is your job-to discover what kind of forest looks like the current occupant and if you think it was always that way or if there has been a change or is changing now. 

The two opposing points of view are Clements (Clementsian succession) and Gleason (Gleasonian succession.)  Clements says it always follows the same order, no matter what, and concludes in a predictable climax community.  If there is a storm or wind and there are wind throws (trees that fall to the ground), that succession will revert a couple of stages and then it will go back to its original progression and end up at the same climax community. 

Gleason does not believe that succession is orderly or predictable.  There is no set climax community.  The community that best fits the nutrients available, hydrology, and has the seeds etc to grow, that will be the community you find.  If there is a storm or another devastating event, like a fire, then the community that becomes established following that perturbation may or may not be like the community that was there before the event occurred.  It would depend on current nutrients, hydrology, ….and so on. 

I had hoped to spend some time on niche versus habitat and the relationships that result from these concepts. 

Niche is your role in the community.  We can’t all be center striker on the soccer team.  We can’t all be sixth graders!  Usually when roles overlap, the species evolve to occupy a more specific niche or there is competition and a species has to find somewhere else to succeed.  If you become highly specific, then if conditions change, your role may no longer exist.  If you are general in function, then if conditions change, you may be able to survive, but you may have to compete for your place in the ecosystem. 

Habitat is where you live-do you prefer to have wet feet, but you can stand it if it is dry for long periods of time?  Then you are FACW-facultative, wetland.  Do you absolutely have to have dry feet all of the time?  Then you are obligate upland.  Can you stand to be inundated with water two times a day?  Then you live in the littoral zone at the beach.  Can you fly from branch to branch and eat bugs that live in bark of trees?  Then your habitat is the tree canopy. 

I won’t get any more specific than this on this first test.

What happens if your population is stressed?  My env sci pop is stressed, or I wouldn’t be writing this.  I don’t want my population to exceed their limits of tolerance and all end up with nervous breakdowns.  So, I am ameliorating one of the factors that could stress you.  If the population is stressed beyond it’s limit of tolerance by any one factor (test seems to be it), then that population will cease to exist.  When everyone is perfectly happy, and everyone has 100% on every test, then the population is said to be at biotic potential.  Could any population be at biotic potential?  If they are utilizing resources (nutrients or space or any one of a number of possibilities), could they truly be at biotic potential?  What about environmental resistance?

For example, many of you noticed that the bark on the pine trees had holes in it and was falling off.  Pine trees can’t be at biotic potential if only because the pine bark beetle population is growing.  Pine bark beetles are a form of environmental resistance – in this instance a parasite.  Even if you eliminated pine bark beetles, could the pine tree population every reach biotic potential? 

We will investigate storms some time.  Not now.  But in chapter 6, on page 115, the author addresses climate. That is helpful as is page 120 and ozone.  On page 122, I don’t want you to worry about all the biomes now.  That will come later.  But, I would like you to know that precipitation and temperature drive biomes.   

You will need to know basic definitions from population to NPP.   

I like to have an environmental law on every test, but we won’t have one this run.  

What can I possibly get 12 points about in an essay?  We have spent most of our time hugging trees and playing in leaf litter.  How could that become an essay?