Transcript Lecture Notes 2

Human Resource Use
Human Values & Attitudes
(Socio-political)
Human Land Use Practices
1) Agriculture
2) Suburban Development
Let’s pick on Indiana:
•
•
97% of land in state = privatelyowned
In central Indiana,
• 70+% of land in row crop
• <10% in forest
• Urban sprawl intensifying
Human Impacts
Ecosystem simplification: elimination of
species from food webs via human
alterations to land
Example: vertebrate communities in ag.
landscapes
Intensive Agriculture
&
Clean Farming
Timber Extraction
&
Fragmentation
Formation of
Terrestrial “Islands”
Oceanic Island = Terrestrial Island ?????
Species-Area Relationship
S = cAz
S = # of species
A = island area
• Positive correlation between island size
& number of species
• Applies to terrestrial “islands” also
Island Biogeography
• equilibrium model suggesting that the
number of species occurring on an
island represents a balance between
immigration (in) and extinction (out)
• Robert MacArthur & E.O. Wilson
Habitat Fragmentation
• Process of breaking contiguous unit into
smaller pieces; area & distance
components
• Leads to:
< remnant patch size
> edge:interior ratios
> patch isolation
< connectivity
• Community & Ecosystem processes
altered
Formation of
Terrestrial “Islands”
#patches
Patch isolation
Patch size
Edge
What about
aquatic systems?
What about
aquatic systems?
Con.Bio 12(6)
Increased Edge Habitat
Increased Edge Habitat
Habitat Fragmentation
• First-Order Effects: fragmentation leads
to change in a species’ abundance and/or
distribution
• Higher-Order Effects: fragmentation
indirectly leads to change in a species
abundance and/or distribution via altered
species interactions
Habitat Fragmentation
• area-sensitive species: species that
require minimum patch size for daily
life requirements
• Edge effects: influence of factors from
outside of a patch
Edge Effects
• Habitat surrounding a patch can:
- change abiotic conditions; e.g., temp.
- change biotic interactions, e.g.,
predation
Example of nest predation = edge effect of
approximately 50 m into forest patch
But can extend 100’s of meters….maybe
km’s
Edge Effects
• How does patch size (in a landscape) &
shape affect amount of edge?
• Groups – give me a mathematical
example with forested landscapes that
have timber extraction via clearcutting
Exponential vs. Logistic
dN
 N
 rN 1  
dt
 K
dN
 rN
dt
No DD
All populations same
DD
All populations same
No Spatial component
Incorporating Space
Metapopulation: a population of
subpopulations linked by dispersal of
organisms
• subpopulations separated by unsuitable
habitat
• subpopulations differ in population size
& distance between
Metapopulation Model
dp
 cp 1  p   ep
dt
p = habitat patch (subpopulation)
c = colonization
e = extinction
Another Population Model
Source-sink Dynamics: grouping of
multiple subpopulations, some are sinks
& some are sources
Source Population = births > deaths = net
exporter
Sink Population = births < deaths
Source-sink Dynamics
>1
<1
<1
Source-sink Dynamics
Corridors
Who Cares?
Why bother discussing these models?
Metapopulations & Source-sink Populatons
highlight the importance of:
• habitat & landscape fragmentation
• connectivity between isolated
populations
• genetic diversity
Vancouver Island marmot
(Marmota vancouverensis)
~100 left
Isolated from hoary and
Olympic marmots
Vancouver Island marmot
(Marmota vancouverensis)
Natural tree succession
Vancouver Island marmot
(Marmota vancouverensis)
• Logging – disjunct patches
- max. dispersal = 7 km
• Climate
• Prey-Predator Dynamics
Differential Sensitivities to
Habitat Alteration
• Niche breadth (diet & habitat) – inverse
relation
• Range periphery = more sensitive (W & N)
• Body size = mobility (allometric relation)
• Social and territorial behavior (limited K)
Swihart et al. 2003
Ways to Manage
1) Featured Species Mgt
– single species
– particular purpose
– e.g., white-tailed deer
– could also include “umbrella species” and
“flagship species” or “sensitive species”
Ways to Manage
2) Species Richness Mgt
– maintain diversity and certain # of each
species (follow MVP concept)
3) Indicator Species Mgt
– use a species (or group of species) to
monitor environmental conditions
– not necessarily managing for these spp.
– bioindicators, biosentinels, “canary in
coal mine”
Ways to Manage
4) Guild Mgt or Life-Form Mgt
– grouping of species based on use of same
type of resources (e.g., foraging guilds)