Systems Group Goal:
                        Our team mission is to gain an understanding of mathematical modeling of biological systems as well as an understanding of actual ecological processes occuring in the Rainforest.  We will apply this knowledge, along with useful information from other groups, to create two models of specific examples of interactions in the Rainforest.  We will use these models to make recommendations on some vital parameters necessary to maintain ecological equilibrium.

My Role:
        10-28-02: Our group has recently, through the help of Dr. Bras and others, begun to learn more on modeling software that currently exists which should make our jobs easier immensely. The software we may use are Vensim for a flow diagram of the many systems involved and a spatial distribution analysis using ArcView. Along with becoming more familiar with the downloadable Vensim software, I have been looking into the various components we will include in the Vensim model. I have many books on biogeochemical cycles, from which we can select existing cycles and try to integrate them into our Vensim model. I also have a book on how to evaluate ecosystem health; from this we should be able to learn how to evaluate the results of our models and make our recommendations/set our limits for parameters.
        10-14-02: I am assigned the job of understanding the interactions btw Soil and Water as a means of integrating two of the groups the Mission class has been split up into. Others in Systems have been assigned other relationships, and as a team we will try to put all of it together. I am continuing my reading on community ecology - the Putman book is a great resource in understanding the interactions of a community as a whole.

Current Research:
10-28-02:
- Info on species and interspecies interaction (from Stiling) (more info gathered but not yet entered)
    - Extinction
- Major threats to rainforest (from Markham)
    - threats include: drying trends, change in rainfall and seasonalilty- leads to significant change in species distribution and composition- leads to extinction
    - Fragmentation is the worst factor- makes it impossible for the rainforest to repair itself
        - reducing fragmentation can lead to keeping the biodiversity and ecosystems service and the ability to withstand climate change
        ***therefore, one of our recommendations as Systems for the preservation of the Amazon should be to halt the current projects (Avanca Brazil, etc) which would lead to further fragmentation***
- Species composition and community assembly- what species will occur where- (from Putman)
    - determined by availability (biogeographic distribution) and dispersal ability
    - a tolerance curve of species shows only the what species will not occur in an an area - shows limits of tolerance to environmental conditions
    - Dispersal- first a species must reach the area
        - depends on size and type of species- must be considered for each individual species
    - Establishment
        - failure if: abiotic conditions wrong, no food organisms, better competition exists, better predators
        - challenges continue once species is established
    - "Community subject to continuous flux of colonizations and extinctions" ie. there is a constant turnover of species in a community
        ***what does this mean for Mission??*** - how can we determine which species are necessary to preserve for the rainforest if they are constantly changing anyway?

10-15-02: (from Putman)
- Info on stability of food webs
    - a single species population expresses damped oscillation around a stable point - termed "stochastic fluctuations"
        - this is amplified in models of 2-3 species
        - higher orders in a food web express more dramatic fluctuations
        - this is a better reason for the limited number of levels in a food web NOT the commonly thought 10% rule for energy flow through trophic levels
- Complex communities can develop under conditions of environmental constancy
    - as complexity of the system increases, the stability will likewise increase up to a critical level of connectance, at which point the system suddenly goes unstable
        - connectance is the number of links species can form with each other, and is inversely related to the number of species in a system

10-11-02:
- Information regarding quantitative and qualitative modeling of interactions btw species: (from Putman)
    - Types of Models- both with benefits
        - Quantitative: beneficial in numerical understanding; restricted to population dynamics of 1-2 species
        - Qualitative: holistic approach through simplification; can understand relationships and interactions of many ecological factors
    - have a table of relative effects of simple interactions of 2 species on population health (uses +, 0, -)
    - other complex interactions exist
        - direct and indirect interactions
        - include effects of 3rd species
- From Woods Hole site:
    - info on "arc of deforestation", increased risk of forest fires, GIS data

10-01-02: In our group meetings during class, we have been updating each other on our current research and have decided on better paths to follow.
    See the Systems team website for our current plans.

9-26-02: Basic Ecology (impt pieces in red) (from Stiling)
- 4 types of ecology
        - Behavioral- indiv. organism
        - Population- pop. of species and how limited by food, competition, natural enemies
        - Community- biodiversity, influences on # species in area
        - Ecosystem- energy flow
- Alternate hypotheses for relationship btw # species and ecosystem stability
        - diversity-stability hypothesis: # species proportional to stability (increase together)
        - rivet hypothesis (w/ plane analogy): each species has small role; some we can afford to lose
        - redundancy hypothesis: some species critical for ecosystem; some unimportant
        - idiosyncratic model: no relationship at all btw community richness and ecosystem fxn
    redundancy hypothesis has much empirical support

9-23-02: I have been researching basic information on tropical rainforests, as our group has decided to know more about the basics of ecological systems in the rainforest before specializing further.
Characteristics of Rain Forests: (fromWhitmore)
- Climate     - constant high temperatures, rainfall of >100 mm/month
                        - forest have internal microclimates different from outside canopy
                                floor: cool, dark, humid to opposite at canopy
                        - "tropical moist forest" sometimes used as blanket term for rain and monsoon/seasonal forests -- but impt. differences
- Occurrence
                - S. America, Eastern tropics, Africa
                        -American (neotropical)- 1/2 of global total
                                  - Amazon/Orinoco basins, across Andes, Brazilian
- Variations produce Forest Formations:
                - based on climate, soil water, soils, elevation
                - in Amazon area:
                        - tropical lowland everfreen rainforest- rich in life and species, everwet- W. Amazonia
                        - semi-evergreen rain forest- strong dry season - E and S Amazon
                        - heath forest- everwet, acidic soil - only 6% of Amazon
                        - freshwater swamp forest- flooded, high pH - extensive in Amazon
- Growth cycle
                - canopy has gaps due to dying trees; filled in by seedlings
                - cycle: gap phase, building phase, mature phase, possible degenerative phase
                - 2 things can occur:
                        - succession: climax (present) species give way to pioneer species - when canopy gap large enough
                        - climax species self-perpetuate - gap regrowth in cyclic replacement
- canopy layers stratified
- large variety of plant species requires that they be species of very limited range
- variations btw formations caused by biogeography, disturbance, habitat
- variations w/in formations caused by topography (rivers), soils, presence of seedlings (gap-phase replacement)
 

Bibliography:
Markham, Adam (ed). Potential Impacts of Climate Change on Tropical Rainforest Ecosystems. Dordrecht: Kluwer Academic Publishers, 1998.
Putman, R.J. Community Ecology. London: Chapman & Hall, 1994.
Stiling, Peter. Ecology: Theories and Applications. Upper Saddle River, NJ: Prentice Hall, 2002.
Whitmore, T.C. An Introduction to Tropical Rain Forests. New York: Oxford University Press, 1998.
Online. Woods Hole Research Center: The Future of Amazonia. Accessed 10-11-02. http://whrc.org/science/tropfor/setLBA.htm
 

Site last updated 10-28-02

This website is for the Mission 2006 class offered by MIT