NREM 301
Reading Guide
Chapters 3
Please be prepared to discuss the material in Chapter 3 byThursday, September 3, 2009.
Chapter 3 Forests as Part of the Global Ecosystem
The following is a list of terms from this chapter that you should be able to use in discussions.
Janus-like character
Ecosystem services
Gaia hypothesis
Biogeochemistry
Gaseous cycle
Sedimentary cycle
Carbon, Nitrogen, Sulfur cycles
Net primary productivity (NPP)
Net ecosystem productivity (NEP)
Sink vs Source
Flux
Dryfall vs wetfall
Nucleating agents
Hydrologic cycle
Evapotranspiration
Climatic modes
Global ecology
Stochastic factors
State factors
Albedo
Eutrophicationj
Cover Type
Phenotype/Genotype
Site
Physiography
Silviculture
Section 3.1, the distinct signatures of life, presents a very important concept associated
with why life exists on the planet and how that is related to global climate change. The
Carbon Cycle is powered by plants and has dramatically modified the atmosphere of planet
earth to allow life as we know it to exist. Discussions on global climate change are trying to
forecast what the impact of climate changes might have on the structure, function and
distribution of life on the planet. Please be sure the you can describe the concepts that are
presented and be prepared to relate the concentrations of carbon dioxide, nitrogen and oxygen
in the earth atmosphere with that on Mars.
Section 3.1.2 – please be prepared to reflect on the quotation by Leslie, 2005 in terms of native
ecosystems like forests and prairies but also in terms of the agricultural plant community that
dominates most of Iowa – what environmental services do or do they not provide in comparison
to those of native ecosystems. Can our management of those annual plant communities
provide or allow those communities to provide some of the ecosystem services that have been
lost by conversions of native to annual plant communities?
Section 3.1.3 – please be prepared to describe the concept of the Gaia hypothesis in the
context of complex positive and negative feedbacks that allow life to influence the abiotic
environment that it exists in and allows it, in turn, to respond to the changes in the abiotic
environment that result from the changes that living organisms have triggered.
Section 3.1.4 – be prepared to describe the difference between the gaseous and sedimentary
nutrient cycles and be able to identify the major elements that are found in the two.
Section 3.1.4.1 – Carbon - be prepared to describe the general movement of carbon between
the three major reservoirs or sinks on the planet. Which is the largest sink? How does
temperature influence the flux of carbon movement into and out of this sink? What are the
major pathways for carbon movement between the atmosphere and land? I would expect you
could provide a general diagram for the movement of carbon between the various sinks (show
sinks and labeled arrows). I would not expect you, at this point, to know the quantities
associated with these sinks, etc. This is true for the other cycles presented in this Chapter. We
will spend more time on each cycle later in the semester. For the carbon cycle be prepared to
have a general discussion on it role in global climate change.
Section 3.1.4.2 – Nitrogen – I do not expect you to be able to reproduce the nitrogen cycle as
presented in Figure 3.3 – we will prepare different diagrams later in the semester. For N we
again would like you to be able to describe the major sinks and the pathways that N takes in
moving between them. Pay attention to how N gets from the atmosphere into the soil and
plants and how it is returned to the atmosphere including the important role of forest fires. Also
be prepared to discuss the impacts that humans have had on the cycle – what conditions have
been created that result in increased movement of N between various sinks. This is especially
applicable to Iowa.
Section 3.1.4.3. – Sulfur – How does sulfur move between its major sinks – what is the role of
humans in that movement? What are dry and wetfall – note the box on page 27 refers to
development of raindrops which wash the air of particulate matter which then is deposited as
wetfall on the surface.
Section 3.1.5 – Hydrologic Cycle – What you need from this short section is the location of
most of the water on the planet, and how it moves between the earth surface and the
atmosphere – please be aware of the relative percentages of precipitation that ends up as
evapotranspiration and as stream flow.
Setction 3.1.6 – Linkages among land, sea, and air – several major points I would like you to
get from this section – 1) the importance of wildlife in moving materials between local and
global ecosystems; 2) the interactions between terrestrial and aquatic ecosystems both for
streams & lakes and oceans. The importance of climate modes on regulating climate (I do not
expect you to remember the three or four major locations of these climatic modes at this point).
What is the importance of global ecology and the discussion of global climate change – what is
the argument you always hear by those who do not subscribe to global warming?
Section 3.2.1 – Forest use of solar energy to drive processes – Figure 3.7 summarizes this
section and is a critically important figure that will shape our discussions throughout the
semester. Note that we have already provided you with an acronym for state factors.
Therefore be prepared to discuss and even diagram or list the important state and stochastic
factors and ecosystem functions and services. Note that this diagram is not limited to forests
but to all ecosystems.
Section 3.2.2 – Global leaf area – this is another key concept to get under your belt. Leaves
are the machines that capture energy and produce the carbon compounds that all life depends
on. I will expect that you have an idea of the percent of the planet that is covered by forests,
savanna, grasslands, tundra, deserts and cultivated lands & wetlands. So Table 3.2 is
important. I also want you to know how much of the leaf area on the planet is found in forests
compared to grasslands and deserts (know those percentage differences) and also be familiar
with the relative ranking of leaf area by different plant communities as shown in Figure 3.8.
Section 3.2.3 – Global heat balance – first understand the importance of reflection to the heat
balance of the surface, what influences albedo and how different land areas compare in terms
of albedo. Then be prepared to explain what happens to most of the energy that is absorbed
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by forests and other plant communities, how much is used in photosynthesis and how is the
heat balance linked to the hydrologic cycle – good stuff. What are the implications of changing
land-uses, forests and grasslands to row crop agriculture or urban areas, etc.
Section 3.2.4 – Carbon storage – note the importance of forests as sinks for carbon storage –
note that the carbon is stored both in the plants and the soil. What are the implications of
reforestation and global warming? Why to corporations pay to have trees planted in the tropics
to offset carbon emissions?
Section 3.2.4 – Water cycling – be prepared to discuss the six ways in which plants influence
the water cycle – at this point you do not have to be able to list the six ways but if I present you
with one or more of them you should be able to explain them. In the US how much water runoff
(stream flow) is generated from forests? In the west that number increases to almost 90%.
Section 3.2.4.1 – Forests and rainfall – be prepared to describe why forests are so important
to rainfall production and why even though there is such a large ocean surface, much of the
rainfall over land does not come from water evaporated over the oceans.
Section 3.2.4.2 – Forests and stream hydrology - note that there are two major issues in this
story: 1) water yield from forests, and 2) timing of that water yield of flow. For those of you who
have taken NREM 407/507 or another hydrology class, the equation on page 35 can also be
written as Q = P – ET – delta S where Q is stream flow (water yield) and P includes both the P
and CW in the formula on page 35. What generally happens to stream flow when forests are
cut? How does that relate to what has happened when prairie was converted to cropland in
Iowa? What happens to flow as the forest regrows? How does this relate to flows associated
with keeping Iowa from regrowing native prairie?
What is the impact of forests on controlling floods? Note that the general consensus is that
deforestation tends to increase flood peaks and volumes which are reduced as the forest
regrows – relate that to flooding conditions here in Iowa. But note that the extent to those
increases depends on a number of factors including: rate of logging, how it is done, road
network, rate of regrowth, weather patterns, weed control, etc. Be prepared to discuss the
impacts of these different factors.
Carefully read the indented paragraph on page 38, column 1 and the 5 bulleted points in the
same column and be prepared to explain them.
Section 3.2.5 – Soil stabilization – note that the authors state the mouths of most of the world’s
rivers appear to be eutrophying. Be prepared to explain the reasons for that discussed in the
text and think about similar situations here in Iowa with most of our rivers and their contributions
to the hypoxia issue in the Gulf of Mexico. Don’t worry about Figure 3.11 at this point.
Section 3.3 – Forests and human health – note the discussion about the severity of
Hurricane Katrina on New Orleans – would this level of destruction have happened with the
same size storm 200 years ago? Think about the flooding in Iowa City and Cedar Rapids last
year – would that have been as severe a problem to the area 200 years ago? Briefly review
Figure 3.12 to get a sense of the relationship between forests and general human health.
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