PDS AP Environmental Science 8th Period 2010-11

Soil Formation and Structure

“The Nation that Destroys Its Soil Destroys Itself” -FDR

Agriculture is the single most damaging thing we, humans, do to the environment. While “damaging” and “environment” are both very vague terms for a very complex problem, agriculture is responsible for loss of habitat, biodiversity, and the cause of dead zones. But agriculture is also responsible for the feeding of  billions of people. Currently, 38% of land surface is used for agriculture, with the bulk of that land used for crops (the rest is for livestock rangeland). Temperate grasslands and forests are the best farmland for agriculture use. A balance must be struck between the usefulness of agriculture and its environmental consequences, and the answer lies within soil. Soil is a complex mixture of inorganic materials (sand, silt, and clay) that makes up 50% of the soil composition. Water and gases make up 45% of soil, and organic materials, such as detritivores, decomposers, and decaying matter, make up the remaining 5% of soil composition.

Soil is a renewable resource, as it is able to make ‘new’ soil, though this can take 100s to 1000s of years to make 1 inch of good topsoil. Agriculture, if unchecked, can exhaust this topsoil. Soil is made up of layers, horizons, which are as follows: Horizon O-Horizon O doesn’t really count, because it is made up of biome specific material, like leaves and twigs. Horizon A-Horizon A is made up of topsoil, preferably made up dark, organically rich soil called humus (like the dark potting soil). Horizon E-Not all samples have Horizon E. Horizon E is the layer where minerals have been leached out, leaving the soil light colored. The leached out nutrients may collect further down in the sample, in lower horizons. The farther you go down the soil horizons, the more rock you get in each sample. Soil builds upward from rock layers.

The macronutrients in soil are Nitrogen, Potassium, and Phosphorus. Detritivores and decomposers, which are organic, ‘feed’on organic material. They break down the organic material (Ex. by using nitrogen fixation) and release nutrients into the soil. In the central case study in our book, Guatemalan farmers leave a layer of organic material on top of the soil, and as that material is broken down nutrients are realized into the soil.

SOIL FORMATION

Soil has to be formed somehow, and the most important process by which soil is formed is weathering (physical, chemical, biological). Physical weathering can come in the form of ice wedging and tectonic movement, which breaks down rock into smaller pieces. Chemical weathering uses H2O + CO2–> H2CO3 (Carbonic Acid) to break down rock, whereas biological weathering uses lichen and roots as the ‘break down force’. Erosion, a transportation mechanism, cannot occur without weathering. Erosion does not break down rock to eventually make soil, but rather transports it (the most common transportation mechanisms are wind and water).

(https://www.bestcourseforgolf.org/images/soilComposition.gif is where I got the soil composition diagram. Many gardening sites/golf course management sites, like this one, include diagrams of soil composition and instructions on how to enrich soil nutrient content).

(http://www.uvm.edu/place/images/soil_horizons.gif is where the Soil Horizon diagram is from.)

http://www.npr.org/blogs/pictureshow/2011/02/08/133573667/dobrowner?sc=fb&cc=fp

Thought the artistic interpretation of Urban Sprawl was fascinating. Enjoy! (even though there are only 2 pictures)

Hello! We discussed more in depth today the concept of foundation and keystone species, and I understand examples wherein, for example, kelp is the foundation species. Without it the biotic aspects of the ecosystem crumble…the kelp is like an anchor for the foodchain. However, I’m a little fuzzy on keystone species. I get that once you take out a top predator, everything crumbles in like a keystone in an arch…is it because the predator is gone and thus the prey population explodes, exhausting resources, so everything stops functioning, or is it more specific than that? if thats the case then why isnt every situation in which a predator leaves in whatever capacity a keystone situation/any predator is a keystone? is isle royal a keystone situation when the wolves leave and the elk overshoot carrying capacity?

thanks, Miriam

(is it too early to do a reflection post? I’m afraid I’ll forget to ask tomorrow.)

I understand the carbon cycle from: atmospheric CO2, traveling through the biome (producers, consumers, detritivores, respiration) through diffusion INTO the ocean, and the formation of coral reefs/calcium carbonate, but I don’t understand what the last step in the cycle is. The CO2 has to return to the atmosphere, right? How does the CO2 exit the coral that’s been formed/deep ocean, and return to the atmosphere? Or is the step where calcium carbonate is formed a ‘branch’ off the cycle, and the real place where CO2 is returned is through respiration of surface aquatic organisms on the ocean-top?

Thanks, miriam.

On October 1st, our APES Class took a field trip to Davidson College to participate in an experimental design lab in the field. The day went as follows: we arrived at Davidson College, and attended a lecture by Dr. Mike Dorcas, a leading herpetologist. The lecture was interesting, and frightening, because it was about….giant Burmese pythons! Dr. Dorcas showed us a powerpoint concerning the history of how Burmese pythons were introduced to the Florida Everglades, how the python populations have grown, and what is being done to try and curtail the rapid growth of the python populations. For those of us in AP Stat, many of the statistical tools we learn in class were presented in Dr. Dorcas’ data, and the overall presentation was an excellent example of how precise field work can really make a difference. We also heard a presentation about Barn Swallow nesting habits, another example of a lab designed for the field.

Here is a link to a website talking all about Burmese pythons, and a video in which Dr. Dorcas is interviewed. (it’s the first one) http://www.nps.gov/ever/photosmultimedia/invasives.htm

Second, we actually went out into the ecological preserve. We split into groups, and walked around the forest area, looking for organisms (mainly frogs, snakes, and the occasional spider) in the drift fences on the ground. Drift fences are small tarps that are put up and 5 gallon buckets line the edge of the fence. The aim is to get organisms who walk towards the fence, and can’t get passed it, to walk along the edge of the tarp until they fall into a bucket and can be examined. We found small bullfrogs, spiders, and a dead mouse, but our group found no snakes. Along the drift fence were several traps for larger animals, such as larger snakes, that were lined with bait. Next, we went to a more clear area, and checked under coverboards (large boards made of wood or tin that can serve as resting places for ectothermic animals who need external temperature to regulate their own temperature). Snakes and small critters such as insects use these coverboards, and can be a useful place to look for organisms.

Checking Coverboards

We then went back to the buildings themselves to eat lunch and attend student presentations. (and hold a black snake!) The presentations were helpful in learning how to set up an experimental design. Some things we learned: 1) funding and man power can make a lab tricky. The result is to adapt to get the results you need. One of the students designed a lab to count types of frogs, yet didn’t have the funding to go out and search for hours for frogs. Instead, she listened to frog calls at dusk with other students (cost-friendly) and gathered her research that way. 2) labs that are done outside can take a lot longer than those done inside. We are accustomed to labs that can occur in one class period, or at most over the weekend, whereas some experimental design labs outdoors can last years. One of the student presentations was of a lab that lasted all summer, and will continue next summer. 3) It is important to get good and accurate data for many reasons; to prove your model (or disprove your model), make yourself understood, get published, and get more funding for research.

Finally, we headed back out to the field to start our detritivore lab. We split into boys and girls, and the boys went to the oak dominated forest, girls to the pine dominated forest. We learned how to use transects (measuring tape that is extended a certain number of feet, depending on the size of the area under study), a random number generator (numbers that are chosen off of a piece of paper to decided how far (in ft.) to travel to the left or the right of the transect) and a quadrat (a piece of tubing, square shaped, that can be any size. A quadrat is used to keep a constant amount of ground under research. We used our quadrat to collect the same amount of leaf litter from each area). Transects and quadrats are ways to take control of a situation when doing experiments outdoors: the transect and random number generator ensure that you take samples from all different areas of the space you are examining, and the quadrat helps to ensure you take the same amount of samples from the different areas.

After collecting our samples, and bagging and labeling them, we went to an open field with what looked like corn plants. (I have no idea if that is actually true, probably not.). The purpose of this exercise was to use a transect-like set up, where we used two measuring tapes stretched up and down and side to side. We then used larger quadrats, 1m by 1m I believe, and counted the number of stalks to each side of the transect like device. Our group leader, a spider lover and expert, then used sweep nets (they look like big butterfly nets made of canvas) to swish over the plants 20 times (10 to each side) and collected insects from off of the plants. We put the insects he caught in pharmacy bottles and examined them, looking at the biodiversity in the area of insects (note* they were not all insects, there were some spiders in there as well)

From our Davidson field trip, we learned some techniques of how to take samples in the field for experimental design labs. It was very helpful, and Mr. Willard recommends we discuss actual METHODS of how to collect data in our AP essays, as that is a more clear idea of what you are trying to convey.

I think the biggest environmental problem is the amount of fresh water available world wide. As Americans, we use a lot of water excessively, but the distribution of clean water is uneven through out the world. I don’t know too much about water pollution, but I think water tables are affected by pesticide use and things like that. Also (and again, we’ll learn this I don’t know that much right now) glaciers are melting at a fast rate because of the greenhouse effect, thus messing up the usual system of how fresh water is available. Areas where there used to be a lot of water are drying up (like in Israel the dead sea has shrunk to almost half its size in only 15 years), and landscapes are changing accordingly.