Official 29 - lecture 1

Listen to part of lecture in a plant ecology class.

so far we've cover biodiversity in hard wooden forest here in the Upper Peninsular of Michigan from a number of angles.

we looked everything from how biodiversity relates species stability, to competition for forest resources, and more.

but now I wanted to discuss what's called pedodiversity.

Pedodiversity is the variation of soil properties (usually characterized by soil classes within an area.

pedodiversity is basically soil diversity.

when we analyze pedodiversity within an area, we're measuring how much variability there is in soil properties, and how many different types of soil there are in a particular area.

so we look at soil chemistry, for example, how much nitrogen or magnesium there is in the soil in one spot, and we compare it with the chemistry of the soil a short distance away.

Nitrogen 氮

Magnesium 镁

Hydrogen 氢

Oxygen 氧气

Potassium 钾元素

Carbon dioxide, Oxide, Hydroxide, Trioxygen.

Until recently there hasn't been a whole lot of attention paid to pedodiversity.

but that's changing rapidly.

more and more studies have been done in this field.

this is a link between biodiversity and pedodiversity, and obvious relationship between soil and flora and fauna.

flora is all plant life present in a particular region or time, generally the naturally occurring native plants.

fauna is all of the animal life present in a particular region or time.

which is why pedodiversity really should be considered in forest management.

a high degree of soil variability in a small area is common, particularly in the forest.

if you compare soils from a forest with soil that don't come from a forest, the amount of variability will most likely be greater in the forest soil.

It generally has more diversity.

there are three main causes of pedodiversity within old-growth forests here in our region of Michigan.

One is tree species, different species have different influence on soil formation and soil properties.

for example, pine trees drop pine needles, and those needles add a lot of acid to the soil.

pine tree:

The organic litter of another tree species might add less acid but more of something else.

organic littler

A lot of different types of trees in an area might mean more pedodiversity.

another cause? gaps created when trees fall.

you see, where there are gaps, open areas, in the forest, the soil there changes.

for instance, without a tree absorb radiation from the sun, to offer shade, the full intensity of that radiation reaches the ground.

the soil where the tree used to be heats up.

And without a tree to soak up moisture from the ground,the soil remains wetter than in the surrounding forest.

soak up: to make something very wet, or to be absorbed in large amounts.

with higher temperature and more moist conditions, the process of organic matter decomposition speeds up.

organic matter decomposition

in other words, organic matter gets broking down, and added into the soil more quickly in these gaps than in the surrounding forest.

OK,and the third cause: trees being uprooted.

when a tree is uprooted, it might fall into other trees on its way down, thus failing only part way over, or it might crash all the way down to the forest floor.

either way, if its roots are pulled up from out of the ground as the tree topples over, then there's usually a big hole -- a pit-- left in the ground where the roots used to be.

topple: to cause lose balance and fall down.

pit:

and there is still a lot of soil attached to the roots, clinging to the roots.

clinging to:

As that soil is eventually shed from the roots by rain and wind and the movement of squirrels climbing around, things like that, as the soil is shed, it drops down and forms a little hill of dirt, a mound.

shed: to lose a covering, such as leaves, hair, or skin.

squirrel:

mound: heap entry, pile a mound of dirty laundry.

pits and mound have significantly different soil properties than other area for the forest.

you get a redistribution and mixing of soil as deep roots are ripped up from the ground.

rip: to pull apart, to tear or be torn violently and quickly.

rock fragments can be pulled up too, if they've gotten entangle with the roots over the years.

entangle: to cause something to become caught in something such as a net or ropes.

so rock fragments from the subsoil can be end up concentrated on the surface.

there are forest management implications I wanna point it out.

implication: an occasion when you seem to suggest something without saying it directly.

forest management impacts soil quality.

And when we better understand pedodiversity,we will be better able to predict the impact of forest management on soil.

But in general, for positive impacts, forest management practices should mimic natural forest processes.

mimic: imitate 模仿

And the goal should be to promote pedodiversity,and through this,biodiversity in general.

I have a handout, an article on pedodiversity in a section of a forest near here.

handout: 讲义

I want you to read it, because it makes the points I've only touch on.

From what I've been saying about the causes of pedodiversity,you might assume that the relationship between forest dynamics--what happens to the trees--and pedodiversity is a one-way street.

As the article explains,forest dynamics affects pedodiversity,but pedodiversity also affects forest dynamics. It's worth bearing in mind.

bear: 1. to accept, tolerate or endure something. 2. to have or continue to have something. 3. to carry and move something to a place. 4. to give birth to young or of a tree or pant to give or produce fruit or flowers.