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.

Week 4 Lecture Notes - Sept. 20

Paper topics and mangrove report were due.  There will be a quiz next week!

Review WHY is there a latitudinal diversity gradient? 

Environmental stress and Complex Physiognomy

Other things that add to the complexity (Ch 6 trop eco, ch 3 neotrop)

Disturbance = means just what it sounds like – the ecosystem is disturbed by something.

I. Human Disturbance

1. Clearing – for agriculture

2. Grazing – removes plants

3. Burning – frequent fires will convert the tropical forest to a savannah, one of the biomes we mentioned the 1st day of class.

        (Savannahs : 

• Edge of hot desserts, on the tropical side. Spiny shrubs, small trees loose leave during dry winter.   
• Where it is grazed by large animals we have savanna – grasses with scattered trees.  – 
• AFRICA with giraffes, antelope, etc.)

4. All of causes of deforestation.

5. Conclusion – humans have a huge impact on nature – enough to change it into a different biome.

II. Natural Disturbance

1. Gaps  = openings created in the forest that allow sunlight to penetrate to the forest floor.

      A. Size

           1.  Small – leaf fall, branch fall

           2. Large – hurricanes, landslides in wet season

      B. Creates complexity both horizontally and vertically

            1. Reduces the biodiversity at 1st

            2. Then biodiversity increases as new plants move in

      C. Shade tolerance plays a large role

            1. Shade tolerant sp are slow growing

            2. Shade-intolerant (sun-loving) will grow quickly if there is a disturbance that allows sun onto the forest floor.

            3. Vines and non-woody herbaceous plants grow quickly

       D. Conclusion – not as severe as the disturbance created by humans, thus the ecosystem can recover.

2. Fire  (p 210 tropical ecology textbook)

      A. Lightning strikes

      B. Scientists can tell when a forest burned by looking at charcoal deposits.

Leads to Succession = old-growth - - - >  disturbance - - - >   2nd growth

Succession = an ecological process in which fast growing plants colonize and area that has been disturbed, to eventually be replaced by slower-growing species that remain indefinitely (until the next disturbance)

Secondary succession – what we see in tropical forest.  There is already a plant community, then it is disturbed and a 2nd community comes along.

Primary succession – occurs where there are no plants – the rock breaks down into soil and slowly plants move in.  Requires 100s of year.

What we are talking about in this class is secondary succession.

General steps

1. Disturbance opens up the forest floor

2.Rapid colonization by fast growing species (pioneer species = vines, herbaceous, non-woody) 1 to 3 years

3. Fast growing, light-loving trees form a canopy 10 – 30 yrs

4. Shade-tolerant plants begin to grow 75-100 yrs, eventually they…

5. Shade-tolerant plants become the canopy – now looks like an undisturbed forest.  Lasts until the next disturbance.

This also illustrates how long it takes for a forest to recover from human activities.

pioneer species – the first to colonize previously disrupted or damaged ecosystems.

     heliconia (Heliconiaceae),

     piper (Piperaceae),

     legumes (Fabaceae) – trees, shrubs, vines, herbs,

     cercopia (Urticaceae)

Canopy – the uppermost layer of vegetation in a forest.

Succession differences due to natural vs human disturbance –

1. Disturbance is usually more severe and in a larger area.

2. Natural disturbance, unless it’s a hurricane or wind storm, destroys individual trees.

3. There may not be seeds left to recolonize the area.

Seed bank = seeds laying dormant in the soil.

Amazon has 500 – 1000 seeds/m2

Seedling bank – seedlings that need light to continue growth

Plate 9-1 - A large gap created by a landslide.

Fig. 6-9 - Succession in a tropical rain forest.

Homework due Sept. 27 - outline

Please complete this for the Sept. 27 class.  I will then help you during class, and it will be due Oct. 4.

Number and label each part (or else it is not an outline, and I will deduct points).

Late outlines will not receive credit.

1. Title of your paper
2. Your name
3. Affiliation and contact info – your email
4. List 5 key words
5. Introduction – basic background information about the subject. 
1. What is the subject
2. Geographical region
3. Who is involved – country, group, etc.
6. The problem, concern, main point of the paper.
1.  Why is this important?
2. Why do you want to write about the subject?
7. Literature Cited – list 4 sources of information you will use

Homework due 20 Sept. 2012

Read Aubé, M. and L. Caron. 2001. The mangroves of the north coast of Haiti - A preliminary assessment. Wetlands Ecology and Management 9:271–278. 

In a 1 – 2 page paper, answer how the article addresses the following 6 steps of the scientific method (write a short paragraph per step).  Turn this paper in on Thursday.

Scientific method 

1. Make observations. List the observations made by the authors. 
2. Ask questions. What questions did the authors ask? 
3. Form a hypothesis (tentative answer to the question). What hypothesis did the authors make? 
4. Make predictions based on the hypothesis. What predictions did the authors make? 
5. Test the predictions through observation or experiments. How did the authors test the predictions? (This is usually in the methods section) 
6. Make conclusions based on the predictions. What conclusions did the authors make? (This is usually in the last paragraph)

Week 3 Lecture Notes - 13 Sept. 2012

We reviewed the AUC academic policy and the grading policy for this class.

Review –        

• Earth’s biomes           
• Latitude defines the location of the tropics – closer to the equator higher precipitation and temperature.
• Remember – There are many tropical ecosystems.  The tropical forest ecosystem (or biome) occupies 7% of earth’s surface, but includes 50% of the world’s biodiversity!

(see Neotropical Companion Chapter 4 pg 86; Tropical Ecology Ch 4 pg 120)

Latitudinal diversity gradient – the reduction in diversity with increasing latitude.

Breeding birds

Greenland 56 species

New York 195 species

Guatemala 469 species

Panama 1,100 species

Columbia 1,395 species

How many breeding bird species are on Hispaniola?  You would have to go through the Birds of the DR and Haiti book of 309 species and count which ones breed here (good paper subject!).

WHY is there a latitudinal diversity gradient? 

Environmental stress and Complex Physiognomy

1. Environmental stress

Lower in the tropics, higher in temperate and higher latitudes.

Polar and temperate climates impose physical stresses.

Remember the temperature ranges of each biome:

• Tundra temperature = -25C to 5C    (-13F to 41F)
• Temperate forest = Wide flux in temperature winter to summer  -5C to 30C (23F to 86F)
• Grasslands have even higher temps in summer
• THUS animals and species need to survive very cold winters and very hot summers

And less precipitation 

• Tundra 23 cm precipitation
• Temperate forest 81 cm
• Grassland 31 cm

Tropics – consistent rain and temperature!  Less environmental stress.

Mammals – 950 species of bats in world.

• 39% of all neotropical mammal species are BATS!  (they are in 75 genera)
• In higher latitudes (temperate regions), bats represent a lower percentage of mammals

• US has 423 mammal species, of which 40 species are bats, 9% are bats (with 2 feeding habits – insects and fruit)
• Belize has 84 species of bats
• Costa Rica has 103 species of bats
• Bats in neotropics have 7 different feeding habits – insects, fruit, nectar, carnivores, fish, blood, generalists

Majority of native mammals in Haiti are bats - 16 species

We watched videos about - reefs, bats, and hummingbirds.

2. Complex Physiognomy – Physical structure of an ecosystem.    

Plate 3-29 The complex physiognamy of a tropical forest (Tropical Ecology, Kricher)

Tropical forests have elaborate structure - trees, palms, ferns, vines, epiphytes, etc.  (see Plate 3.29 Tropical Eco.)

Thus more niches with less competition for any one niche, thus can support more species.

Ecological niche = place that an organism occupies in an ecosystem; both the ecological role and physical habitat that an organism occupies.

But how do we measure diversity?

Biodiversity = we had defined it as the number of species in an area, but it actually can be described by 2 concepts.

1. Species richness = Number of species within a given area.  Macaya report found 37 species of birds = species richness of 37.

But are there the same number of individuals of each species?  No, they found from 1 to 55 individuals of each species.

2. Evenness = how richness is distributed relative to population size. 

• Rated on a scale of 0 to 1.
• If there are the same number of individuals per species, evenness = 1.  This is high evenness, typical of tropics.
• If there are highly different numbers per species, evenness = 0.  This is low evenness, typical of temperate regions.
• Evenness is expressed as decimal number is in between.  0.15 is a lower evenness than 0.85.

Example: 100 doves, 1 parrot, 1 woodpecker.

Species richness = 3.  But is this really diverse?  Not very diverse since most of the animals are doves.

To evaluate diversity, we need to also consider 2 things: area sampled, and sampling effort.

Area

100 species are found in 10-square mile Park A, and 10 species are found in a 1-square mile Park B.  Can we say that Park A has a higher species richness?  No, we need to look at richness per unit area.  So:

• Park A  100 sp / 10 mi2 = 10 species per mi2.
• Park B  10 sp / 1 mi2 = 10 species per mi2.

Conclusion, they have the same species richness per unit area.

Sampling effort – Amount of time spent surveying (searching, sampling, etc.).

The more time you spend searching, the more species you will find (up to a certain point).

Spend 2 days searching in Macaya, but 4 days searching in Foret de Pines, you will probably find more birds in Foret.  But that doesn’t mean there are more birds.  Just that you spent more time looking.

So for research, you need to spend the same amount of time in both places so you know you are comparing them the same way.  That is why the Macaya paper went into so much detail about how long they spent searching in both sites.  To prove they spent the same sampling effort at both sites, thus could compare data and with confidence say that one site did have more birds than the other.

• 1 day surveying birds at AUC yields 10 species.
• 10 days surveying birds at the Botanical Garden yields 100 species.
• Which place had higher species richness?

You first need to put these into the same units of sampling effort:

• AUC  10 sp / 1 day = richness of 10 per day
• Garden 100 species / 10 days = richness of 10 per day

They are the same!

 

You will reach a point where you don’t find any more new species.  You see this on the graph where it levels out (the asymptote).

Figure 4-1 Tropical Ecology (Kricher)