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BIOGEOGRAPHY
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GEOG 3B
Land, Water & Life
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Biogeography: the study of the distribution of species
over space and time; also includes biogeochemical
cycling
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Summer 2008
Ecosystems
Distribution of species and community dynamics
Biomes
Biogeochemical cycling
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ECOSYSTEM
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GEOG 3B
Land, Water & Life
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What is an ecosystem?
Eco  logy : the study of the house
[oikos  logos]
Maintenance of human life
Summer 2008
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ECOSYSTEM
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GEOG 3B
Land, Water & Life
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What is an ecosystem?
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Summer 2008
It is a natural system made up of abiotic factors (air, water, rocks,
energy) and biotic factors (plants, animals, and microorganisms).
Characteristic functional units (e.g. vegetation, soils, wildlife
communities)
Terrestrial, wetland, or marine
Open systems
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ECOSYSTEM MODEL
Inputs
•Energy
•Nutrients
•H2O
Plants
Consumers
Soils
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ENERGY INPUTS
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GEOG 3B
Land, Water & Life
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Energy sources:
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Sun
Kinetic and thermal energy (e.g. wind, waves, flooding; fire)
Biochemical energy (e.g. proteins/carbohydrates, organic chemicals)
Sulfur & geothermal energy
Energy is the main currency of the ecosystem,
Energy can also affect ecosystems through disturbance, such as landslides,
flooding and windthrow.
Summer 2008
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PRIMARY PRODUCERS
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GEOG 3B
Land, Water & Life
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Primary producers
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Summer 2008
Photosynthesis & Transpiration (02 – CO2 cycle)
Primary productivity & biomass production
Soil stabilization
Vegetative [ecosystem] structure & composition & biodiversity habitat
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VEGETATIVE STRUCTURE &
COMPOSITION
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Vegetative structure:
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GEOG 3B
Land, Water & Life
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Vegetation type
Dominant growth forms
Measured Parameters
Spatial distribution
Vegetative composition
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Summer 2008
Species composition
Biodiversity indices
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Sample data from Lake Elsinore, CA - 2007
Table 5.1: Reference canopy structure for the willow-cottonwood woodland (N=19).
Species
Trees ( 5” dbh)
Salix gooddingii
Salix lasiolepis
Populus fremontii
Total
Saplings
Salix gooddingii
Salix lasiolepis
Total
Shrubs
Tamarix ramosissima
Baccharis salicifolia
Total
Density
(Stems/acre)
Basal area
(ft2/acre)
Frequency
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9
4
137
53.2
3.8
10.1
67.1
0.79
0.11
0.21
360
10
370
---
0.79
0.11
329
223
552
---
0.26
0.32
Table 5.2: Understory species composition (Top 20 species) for the willow-cottonwood woodland.
Species
Heliotropium curravasicum
Distichlis spicata
Ambrosia psilostachya
Scirpus spp.
Urtica dioica
Carex praegracilis
Typha latifolia
Portulaca oleracea
Plantago major
Chenopodium rubrum
Eleocharis sp.
Apium graveolens
Juncus mexicanus
Juncus xiphioides
Melilotus officinalis
Cressa truxillensis
Anemopsis californica
Elymus glauca
Leymus condensatus
Sonchus asper
% cover
5.1  15.5
4.5  15.1
2.5  8.2
2.0  2.8
1.7  5.9
1.1  2.7
1.1  4.6
0.7  2.0
0.7  2.9
0.5  2.3
0.5  2.3
0.3  1.2
0.3  1.1
0.3  1.1
0.3  1.1
0.2  0.6
0.1  0.6
0.1  0.6
0.1  0.6
0.1  0.6
Frequency
0.82
0.79
0.43
0.15
0.31
0.14
0.24
0.11
0.15
0.12
0.12
0.06
0.06
0.06
0.06
0.03
0.03
0.03
0.03
0.03
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Figure 4: Stem size-class distribution for the willow-cottonwood woodland.
Figure 5: Stem size-class distribution for a degraded site.
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CONSUMERS
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GEOG 3B
Land, Water & Life
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Consumers:
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1 and 2  consumption (respiration & nutrient cycling)
Grazing & biomass removal
Competition, predator – prey relationships
Seed dispersal & ecosystem maintenance
Biodiversity
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Summer 2008
Decomposers (biomass reduction & nutrient cycling)
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SOIL AND WATER RESOURCES
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GEOG 3B
Land, Water & Life
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Soil and water resources:
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Summer 2008
Provides substrate for ecosystem development
Nutrient supply, biogeochemical cycling
Decomposers
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ECOSYSTEM SERVICES
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GEOG 3B
Land, Water & Life
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Ecosystem services:
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Summer 2008
Food & fiber production (Agriculture, rangeland, fisheries, forest
resources)
Soil stabilization & flood control
Water quality treatment and sediment trapping (wetlands)
Climate regulation & biogeochemical cycling
Biodiversity (medicines, industrial products, foods)
Aesthetics & recreation
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BIOMES
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Biomes
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GEOG 3B
Land, Water & Life
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Describes the largest spatial scale at which vegetation types can
be classified based on climate
Classification systems
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Summer 2008
Formations [units based on similar vegetation structure]
Ecological equivalents [similarity of life forms, growth forms &
vegetation structure even in geographically distinct areas]
Life zones [based on TC, rainfall & ET]
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HOLDRIDGE LIFE ZONES
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THE DISTRIBUTION OF SPECIES
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GEOG 3B
Land, Water & Life
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The abundance & distribution of life on the planet is
determined several factors, including:
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Summer 2008
Climate (TC, rainfall, ET)
Soils (edaphic factors), topography
Island biogeography
Biological interactions (predation, competition, pathogens)
Disturbance (e.g. fire, windthrow, landslides, flooding)
Time (e.g. migration & dispersal, extinction, succession)
Humans (ecosystem degradation, climate change)
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TEMPERATURE
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PRECIPITATION
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ISLAND BIOGEOGRAPHY
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SPECIES INTERACTIONS
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Disturbance - fire
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BIOGEOCHEMICAL CYCLING
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Nutrient Cycling
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GEOG 3B
Land, Water & Life
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Includes the circuits or pathways by which chemical elements and
compounds move though the biotic ("bio-") and abiotic ("geo-")
compartments of an ecosystem;
Biogeochemical Cycling
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Is concerned with the chemical processes that operate in and through
the biosphere, lithosphere, atmosphere, and hydrosphere.
Can be thought of as nutrient cycling on a global scale
Summer 2008
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BIOGEOCHEMICAL CYCLING
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Primary cycles of interest:
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GEOG 3B
Land, Water & Life
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CO2, O2 (Climate change; photosynthesis/respiration)
H2O (Hydrologic cycle)
N (Nitrogen fixation, Protein synthesis)
P, K, S, Mg (Essential plant nutrients, Mineral cycles)
Similar to the Hydrologic cycle, we can represent
biogeochemical cycles as:
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Each component of a biogeochemical contains:
Reservoirs [ ΔS ]
Flows [ Inputs & outputs ]
Change in state
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Summer 2008
We can write Mass Balance Equations to represent the flows of
elements and compounds through the system.
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CO2 & CLIMATE CHANGE
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