Week 5 - 24 Sep. 2013 Forest productivity

Homework due next week: Research paper outlines.

Altitude mimics latitude.  The farther you go from the equator, the colder it is.  The higher up you go on a mountain, the colder it is.  This is why we can find boreal forests and tundra on the tops of mountains that are located in the temperate zone.

Productivity – Creation of new organic matter.

Primary producers – Use sunlight to create their own organic matter from water, CO2, and nutrients, through the process called photosynthesis.

6CO2 + 6H2O + energy = C6H12O6 + 6O2

Primary production – the synthesis and storage of organic molecules during growth and reproduction of photosynthetic organisms.  This produces new chemical compounds and tissues.  Result – new biomass = amount of CO2 that is ‘fixed’

How to measure productivity?  Measure the mass (amount) of biological matter –

weight – weigh the fish, etc,

count – number of trees, etc.

size – diameter at breast height of trees

Secondary producers cannot make their own organic matter.  They must consume it. = organisms that consume the primary producers (cattle etc.)

Secondary production – creation of biomass in the consumers – such as an animal growing.

 

What does this mean for forests?  And for forests in Haiti?

Tropical forests – high productivity, double that of temperate forests.  (So then you might think soils are very fertile, but they are not!) 

Why are tropical forests twice as productive as temperate forests?

Geography and climate.

Remember – a biome is an environmental region define by plant community – as influence by geography & climate!

Let’s look at how geography influences productivity.

Maximum intensity of sun’s radiation is at the equator, and decreases as we move toward poles.

Therefore, the equator receives:

More sunlight

Constant sunlight throughout the year

Warm temperatures

Much rain

Which means photosynthesis can occur year round!

In drier and colder biomes, productivity is lower.

If you want to learn more, see

http://www.globalchange.umich.edu/globalchange1/current/lectures/kling/energyflow/energyflow.html

Paper outlines are due Oct. 1!

The forest chapter from A Community Guide to Environmental Health was provided to students as a reference source. 

Buy it here: http://store.hesperian.org/HB/prod/B160.html

Or download it here: http://hesperian.org/books-and-resources

Week 4 - 17 Sep. 2013 Disturbance and succession

We reviewed biomes and location of tropics  (between 23.5 N and 23.5 S)

Deciduous trees lose their leaves.

·         In the tropics this during the dry season.

·         In the temperate regions this is during winter.  Why?

o   Freezing temperatures would damage leaves.

o   Heavy snowfall would stick to leaves and break branches.

o   There is less light and less photosynthesis, the trees don’t need their leaves.

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

What causes disturbance in forests?

1.      Human

a.       Clearing – for agriculture

b.      Grazing – removes plants

c.       Burning – frequent fires will convert the tropical forest to a savannah.

                                                              i.      Edge of hot desserts, on the tropical side

                                                            ii.      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.

d.      Climate change

e.       Pollution – air and water

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

2.      Natural

a.       Storms: heavy rains, hurricanes, wind

b.      Tree fall – creates gaps  = openings created in the forest that allow sunlight to penetrate to the forest floor.
See this article for more information about tree fall and gaps http://scf.rncan.gc.ca/pages/215

Leads to Succession 

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

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

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

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

1.      Disturbance

2.      Fast growing plants colonize the area

3.      Slow growing plants take over and remain

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

Pioneer species in tropical forest – the first to colonize previously disrupted or damaged ecosystems.

·         heliconia (Heliconiaceae),

·         piper (Piperaceae),

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

·         cercopia (Urticaceae)

 

Research paper:

Be more specific with your topics!

Use google scholar to search for articles: http://scholar.google.com/

You do not need to see the entire article – just use the abstract.

Outlines due on Oct. 1.

Week 3 - 10 Sept. 2013 Geography and topography affects forests

We reviewed the 6 forest biomes and discussed the best one to live in.

Topography – shape and features of the earth, including elevation (relief)

Altitude = elevation as measured from sea level which is at 0 meters in elevation.

·         Temperature decreases as altitude increases.

·         Altitude affects the distribution of precipitation. 

·         Plant and animal species vary by altitude.

Sea level = 0 m

Pic Macaya = 2,347 m

RAIN SHADOW = a dry area on the LEEWARD sides of mountain ranges.  It is created due to an air mass rising up the windward side of a mountain.  As air rises and cools, water condenses and comes out as precipitation.  When this air mass passes over the mountain it descends but has no moisture. (and sometimes it also causes L'effet de foehn).

Windward – The side facing into the wind - directly receives the wind.  The upwind side.

Leeward – The side facing away from the wind.  The downwind side.

The mountain ranges on Hispaniola create a rain shadow over Haiti.  The DR receives more rain than Haiti.  The western valleys, along the Haitian border, remain relatively dry, with less than 760 mm (29.9 in) of annual precipitation, due to the rain shadow effect caused by the central and northern mountain ranges.

Altitude mimics latitude in temperature!

As an ecologist you need to understand these weather patterns because you will find different plants and animals at the top of a mountain than at sea level. 

Latitude and Longitude

Latitude lines are imaginary horizontal lines on the earth, like the equator.

Tropic of Cancer = 23.5˚ North and the Tropic of Capricorn = 23.5˚ South

Longitude lines are imaginary vertical lines on the earth, like the prime meridian.

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

Latitudinal diversity gradient – increasing biodiversity with decreasing latitude.

The tundra, at high latitude (80-90˚N), has fewer species than the tropical rain forest, near the equator (0˚)