Transcript Document

Project groups and topics due next Wednesday
Also remember to sign up for a field trip!
We will be adding one more field trip soon
More copies of the textbook available in the library
soon
Reading: Chapter 2
Remember that all lecture slides excluding photos
are on the website; the final summary slides from
Monday’s lecture are on the web
http://soilslab.cfr.washington.edu/esc110/
lecturewtr04/
Biogeochemical Cycling
Cycling can be studied at different scales
Watersheds of northeastern South Island, New Zealand
Arial view of research
plots for examining
nutrient movement -North Island, New
Zealand
Biogeochemical Cycling: movement of elements within or
between ecosystems caused by organisms, by geological,
hydrological, and atmospheric forces, and by chemical reactions
Elements within a cycle can move as:
Solids, Liquids, or Gases
Elements involved in cycling can also have different
chemical forms (e.g., Carbon as CO2 (carbon dioxide)
or CO (carbon monoxide)
The chemical form of an element can vary among physical
states or within a physical state
(e.g., Nitrogen as NH4+, NH3, N2)
There are two basic terms used in cycling:
Pools: the amount of an element within a physical
location or component of a cycle (sinks)
e.g.: tree, ocean, atmosphere, soil
Fluxes: the rate of movement of an element
between pools
e.g.: evaporation, burning, dissolution of a
rock, river carrying materials from land to the
ocean
Residence Time
The length of time that an atom or molecule of a
particular element spends in a particular location or
component of a cycle
Mean Residence Time
Recycle Time
Altering cycling rates can alter mean residence times and
have the potential to lead to either depletion or pollution
We’ll consider four biogeochemical cycles
of elements required by organisms for life
Carbon
Nitrogen
Phosphorus
Sulfur
The Carbon Cycle
Carbon Forms: CO2, CO, CH4, H2CO3, organic matter, CaCO3
Major pools of the carbon
cycle in billions of tons of
carbon.
The oceans contain the
largest pool of carbon.
McKinney and Schoch 2003
Recycling rate of H2O, O2 and CO2 among the atmosphere,
hydrosphere, biosphere and lithosphere
Why do we care about carbon cycling?
What’s your carbon debt?
How many trees are needed to remove
the same amount of carbon you release
to the atmosphere in one year?
My house: need to plant 37 trees and let them grow for 40 years
Go to: www.lpb.org/programs/forest/calculator.html
to find your carbon debt!
The Nitrogen
NitrogenCycle
Cycle
The
Nitrogen Fixation
The nodules on the roots
of this bean plant contain
bacteria called
Rhizobium that help
convert nitrogen in the
soil to a form the plant
can utilize.
The Nitrogen
NitrogenCycle
Cycle
The
What’s so important about Nitrogen cycling?
essential nutrient (fertilizers, growing legumes as crops) –
changes in native species composition of ecosystem
atmospheric pollutant (burning fuels)
groundwater pollutant
TheThe
Phosphorus
Cycle
Phosphorus
Cycle
The phosphorus cycle is much slower than that of C or N
The Sulfur Cycle
Dimethylsulfide (DMS)
is released by
phytoplankton, is then
oxidized to sulfur
dioxide and ultimately
sulfate in the
atmosphere.
Sulfate can cause
clouds to form by having
water droplets condense
on it.
Some key points:
• Elements move! Among spheres, spatially and temporally
• Cycling occurs at local to global scales
• Biogeochemical cycles have 2 basic parts: pools and
fluxes
• Elements are recycled among the biosphere, atmosphere,
lithosphere and hydrosphere
• Cycles of each element differ (chemistry, rates, pools, fluxes,
interactions)
• Cycling is important because it can affect many other
aspects of the environment and the quality of our lives