Week 5 Lecture Notes - Sept. 27

A quiz was given and mangrove papers returned.

Parallel between diversity in an ecosystem and diversity in agriculture

Monoculture – Growing one type of crop – for example, all corn.

            Susceptible to disease, drought, the entire crop being destroyed.

            For example, there was a drought in the US this year and farmers lost 80% of their corn.

Polyculture – Growing many species in the same plot.

            More disease resistant.

            If one crop dies you still have the remainder.

You can mimic succession with the crops – see fig. 6-9 pg 214. – The land can then be productive for > 50 yrs.

Fig. 6-9 Tropical forest succession and crop polyculture that mimics it. (Kricher Tropical Ecology)

 

What interrupts succession?

1. Invasive plants = Exotic = Non-native

Plants that don’t normally grow in an area.

Example - A grass that is native to Africa, that takes over a field in Haiti.

They disrupt the natural ecosystem and change it.

They tend to be able to grow where the land is disturbed, and do better than the native plants, thus out-compete them.

(There are also invasive animals, madan sara, etc. and they compete with other animals for resources.)

2. Frequent fire 

3. Grazing 

Both kill the new plants coming in.  Disturbs the soil.

Combining the two can further arrest succession.

 

From Kricher Tropical Ecology.

Seeds exhibit

1. Negative density dependence  =  Seeds cannot grow near the parent trees (see Fig 5-5 = The probability of successful germination and development into a tree increases with distance from parent tree.)

Because - Competition for resources
If a seed falls next to the parent, the parent is a stronger competitor.
Successful germination and growth increases farther the seed falls from the parent.

**Something to keep in mind when you are reforesting.

2. Seed shadow effect  - More seeds land closer to the parent (see Fig 7-5 = seed density (#/m2) vs. distance from parent.)

From Kricher Tropical Ecology.

Dispersal of seeds = movement or transport of seeds away from the parent plant.

Wind   vs  animal dispersal
1. Seed size:     

Wind -     Small because need wings (heavier the item, larger the wing, like an airplane)

Animal -   Large – animals carry it.

2. Distance dispersed.     

Wind - Not as far.    

Animal – Farther

Long distance dispersal > 60 m is rare for any type of seed.

Fruit production varies by biome:

Tropics – Has a constant temperature and day length, therefore can produce fruit year round.

Temperate regions – Fruit is produced only during mid-summer (June) – autumn (October).

Frugivore – an animal whose diet is greater than 50% fruit.

Many frugivores in tropics, none in temperate regions.

SLIDES - frugivore birds from Chapter 7.

Reviewed outline format in class.   

An outline is a numbered list summarizing a paper.  Subheadings are lettered.

You MUST turn in your outline in the format I gave in class.

Google Scholar is a good place to find articles.

You can use just the abstract if you cannot download the article.

Literature cited:

Journal articles – Give the author, year, title, journal, volume, and dates.

Books – Give the author, year, title, publisher.