PDS AP Environmental Science 8th Period 2010-11

I’m not sure we covered these in class, but what are the differences/ main points about El Niño, La Niña, and thermohaline circulation… basically, what do you think we need to know?

I was just wondering if anyone knew exactly which pieces of legislation we need to know for the test, and how much we need to know about them?

Many common problems affect soil around the world on a daily basis. The ones we covered in class are: desertification, salinization, water logging, and reduced fertility.

DESERTIFICATION-

Desertification is mainly due to drought, but human activity can also speed up the process. Whenever humans plow, overgraze, deplete water sources, and so on, they run the risk of desertification of marginal lands, or grasslands close to a desert. The desert expands into the marginal lands because human activities remove the plants that hold the soil and keep the water in place, and the wind blows the soil away, leaving desert conditions.

Above: a farmer examines his once fertile soil–now cracked and unusable.

Desertification affects 250 million people worldwide. How can we stop it? We can use different planting techniques such as low till, no till, or greenbelts (also known as agroforestry).

Watch this video about desertification and its role in the world right now

SALINIZATION

Salinization–as we learned in our first lab this year–occurs when there is too much salt in the soil for plants to live. Salinization is caused from over-irrigation, and is a problem for 20% of our farmlands worldwide. When soil is over-watered, the water evaporates more quickly from the soil. As the water rises through the soil, it carries salt, and as it evaporates, it leaves the salt deposited on the surface.

The white spot on the field is an aerial view of a salt covered field

Since it’s too expensive for most farmers to filter their water of salt, other preventions are reducing the amount of irrigation or switching to drought tolerant crops so not as much irrigation is needed. As far as cleanup, farmers can attempt to flush their soil, stop growing, or create an underground draining system if salinization is already a problem.

WATERLOGGING

1/10 if all cropland is affected by waterlogging, which occurs when farmers attempt to flush their soil and leach salt deeper. Instead of getting rid of the salt, they accidentally raise their water tables so that extra water sits in the soil, drowning the roots of their crops. This lack of oxygen can cause root rot–a fungal disease.

Left: Waterlogging has caused excess water to sit on the surface and drown the plants

REDUCED FERTILITY

(The other three soil problems are physical, but reduced fertility is a chemical problem.) Reduced fertility , or not enough nutrients in the soil, can be fixed by either organic or inorganic fertilizers.

Organic fertilizers help build soil structure and organic matter (humus), but do so very slowly because they depend on bacterial decomposition.There are three types: compost (plant matter), animal manure, and green manure (legumes ground into the soil to increase nitrogen levels due to the nitrogen fixing bacteria in their roots).

Inorganic dissolve quickly and are precise doses of certain chemicals, but they don’t help build soil composition, and they create pollution problems when they leach through the soil and contaminate groundwater or evaporate into the air and cause air pollution.

Check out this website for the advantages and disadvantages of inorganic fertilizer (as shown in pic)

Since we didn’t discuss the handout in depth, what do you think are the main points we should take away from it?

Hey guys- I’m still a little confused about climate.. I understand that uneven heating and water distribution were the two things we listed as “factors” to establish climate, but I thought that climate was more about precipitation. I know this sounds simple but I guess my real question is are climates and biomes the same? Or can one biome have multiple climates?

Hey guys-

so the book website defined a logistic growth curve as most likely to happen when there’s a small population with unlimited resources. Doesn’t it seem like unlimited resources would lead to an exponential growth curve because there are no limiting factors? I’m confused on the difference and exactly which types of populations lead to which curves. thanks!

I’m confused about what happens when plates diverge. I know lava pushed them apart, but how is that not a volcano? Does it slowly seep up? If so, wouldn’t the lava get pushed back down by the first layer of crust that cooled?

Today in class we focused on the phosphorus cycle, which is concentrated mostly in the lithosphere and oceans. Phosphorus is a very important element because it builds part of vital molecules such as ATP, ADP, DNA, and RNA–all molecules we recognize as part of the building blocks of life. Despite the fact that Phosphorus is such a critical part of organisms, there is surprisingly little Phosphorus in the biosphere compared to the lithosphere and hydrosphere. Another unique feature of the phosphorus cycle is that there is virtually no phosphorus in the atmosphere. Because of this, the phosphorus cycle is relatively slow because it takes a long time for phosphorus to move through systems without being diffused into the atmosphere.

The top 4 reservoirs for Phosphorus are:

1. sediment (lithosphere)   2. soil (lithosphere)   3. oceans   4. mineable rock (lithosphere)

Here’s a  link to a good animation of the pathway: http://www.wadsworthmedia.com/biology/starr_udl11_tour/phos_anim.html

As you can see, most of the world’s phosphorus is “locked up” in rocks–it can only be released by weathering. A lot of the phosphorus that runs off into the ocean also gets “buried” into the ocean floor  because it precipitates into solid form and settles to the bottom as sediment. Only the occasional upwellings in the ocean can recycle phosphorus back to the top of the ocean. **Note that birds are one of the few manners of carrying phosphorus back to land because they eat fish (that eat phosphorus-rich phytoplankton) and then poop the phosphorus back onto land (bird poop = guano.)

The most important thing for us to notice here is that phosphorus is only available to organisms in small quantities. For this reason, phosphorus is a limiting factor for plant growth. If there isn’t enough phosphorus in the soil for the plants’ roots to take up, they die and cannot pass phosphorus onto consumers.

Here’s the link to image source

There are two main human impacts on the phosphorus cycle:

1. Concentrated Animal Waste. In “feedlots”, where we pack animals in to raise them for food, there is a huge amount of phosphorus-filled waste in one space– what we call “waste lagoons”. The excess phosphorus runs off into bodies of water when it rains.

2. Mining. We mine phosphorus to produce both inorganic fertilizers and detergents. The extra phosphorus in fertilizers runs off into bodies of water when it rains.

The main problem with phosphorus run off is illustrated through the Ch. 7 Case Study: Here’s the basics:

phosphorus heavy run-off empties into bodies of water (Gulf of Mexico) … the excess phosphorus causes tons of phytoplankton and algae to bloom (limiting factor, remember?) … population EXPLOSION so they run out of food … they die and decomposers go crazy decomposing their bodies … but, they need lots of oxygen to do all this decomposing, so they use all the oxygen available … the amount of dissolved oxygen in the water isn’t enough to keep organisms alive so it because a dead zone because of hypoxia (low DO)

Link to image source

Here’s the Gulf’s Dead Zone- the red is where there’s little to no dissolved oxygen.

Hey guys, this isn’t a question, but its something I asked Mr. Willard that I thought you guys may want to know too:

Dry vs. Rainy seasons only apply to deserts, grasslands, and chaparrals. This is why these 3 biomes can’t support big trees-they would die during a dry season.

All the other seasons have relatively constant precipitation so they can support big producers year round.

Also, in general,

any pole biome usually has two seasons, temperate biomes have four, and tropical biomes have one.. they vary because of the amount of solar radiation they receive.

Hey guys! I understand the basic lineage of where environmentalism came from, but I’m confused as to the very starting point from where the first basic philosophy came. Was it the romantics or the preservationists that really started the movement? I know the romantics were responsible for the first feelings of respect toward nature, but are they considered the founders of environmentalism as well?