LANDSCAPE ECOLOGY
SREM 3011
LECTURE 12
Dr Brendan Mackey
Department of Geography
The Australian National University
Conceptual framework,model response of ecological
‘criteria’/phenomena to the primary environmental regimes
At a meso scale,climatic variables based on long term,
mean monthly rainfall,maximum & minimum temperatures
provide fundamental inputs to light,heat,moisture regimes
Nutrient regime Discuss next week
Next few lectures:
- role of topography in defining PERs at a topo scale
moisture regime
radiation regime
- climate (meso) vs topo-scaled topographic effects
Next 2?weeks lectures:
A,Topo-scaled modelling of PERs
B,Other statistical models for analyzing site data
C,Ecological classification & regionalization
If species distributions are a function of the moisture,
radiation,thermal and nutrient regimes,then the more
accurately we ‘track’ them (ie,the PERs),the better
we can ‘track’ plant and animal response
Moisture regime is only coarsely approximated by
precipitation
- precipitation is a useful index of moisture regime at
regional scales,but limited/problematic at both
continental and smaller scales
Problem,estimate moisture regime across entire
landscape,factoring in
(1) evaporation
(2) topography and
(3) soil profile
,how to generate gridded estimates in an
analogous manner to our climate models?
Mean annual precipitation (mm)
within a region,evapo ~ ‘constant’
P- E& available moisture (AM)
As E>,P must > to have same amt
of AM
Therefore important for continent-
wide analysis
Average evaporation from Australian Standard Tanks,in units of mm/year
Potential evaporation is
a function of,
1,Solar radiation4
2,Temperature (surface)
3,Atmospheric moisture
4,Turbulence/aerodynamic
roughness
US Weather Bureau Class A evaporation pans
with screen in the foreground and without screen
in the background.
ANUSPLIN surfaces have been fitted to Australian
network of ‘class A’ pan data thereby enabling
gridded estimates of potential evaporation to be
generated,Therefore,can calculate (P-E) or (P:E)
But PE? actual evaporation (AE)
AE is limited by soil moisture
Therefore need to factor in soil water availability
and calculate a moisture index as a function of
1,Precipitation
2,P.E.
3,Soil water status
So-called water-balance can be calculated on a daily,
weekly or monthly time step:
Available water capacity = f (soil depth,soil texture)
in this example,AWC = 100mm
Moisture index = 1 if ‘bucket’ is full
= 0 if ‘bucket’ empty
25mm 50mm 25mm 50mm 25mm 50mm
1.0
0.75
0.0
0.75
0.5
0.25
JAN FEB MAR
Can generate prediction of MI at any location at which
you know:
1,XYZ?Precipitation,potential evaporation
2,Soil depth + texture?AWC
Ultimately,what’s important for a plant is not how much
rain falls,but how much water is in the soil where its
roots are!
But how to generate gridded MI values across entire
landscapes?
- need ‘micro’ scaled soil maps
- most soil maps do not map profile depth
- depth more important to AWC calculation than texture
Influence of field texture and structure on water retained between -10 and
-1500kPa for a range of Australian soils (Williams 1983)
mm water retained per 10cm soil
calculate average at sites using this table
if we had more time,could calculate MI on a gridded basis assuming
soil depth constant or f (slope)
Structure and evaporative capacity of major Australian plant formations
(which may be regarded as climatic climax formations).
Relationships between
(a) mean monthly Moisture Index (Ea/Eo)
(b) the evaporation coefficient k (and
Foliage Projective Cover) and the per-
centage of annual precipitation which
is retained in the soil within the rooting
zone of the plant community.
Below the 100% value of annual precipitation,
water may be lost by runoff or internal drain-
age; above 100% water may be gained by run-
on or subsoil seepage from adjacent areas.
SREM 3011
LECTURE 12
Dr Brendan Mackey
Department of Geography
The Australian National University
Conceptual framework,model response of ecological
‘criteria’/phenomena to the primary environmental regimes
At a meso scale,climatic variables based on long term,
mean monthly rainfall,maximum & minimum temperatures
provide fundamental inputs to light,heat,moisture regimes
Nutrient regime Discuss next week
Next few lectures:
- role of topography in defining PERs at a topo scale
moisture regime
radiation regime
- climate (meso) vs topo-scaled topographic effects
Next 2?weeks lectures:
A,Topo-scaled modelling of PERs
B,Other statistical models for analyzing site data
C,Ecological classification & regionalization
If species distributions are a function of the moisture,
radiation,thermal and nutrient regimes,then the more
accurately we ‘track’ them (ie,the PERs),the better
we can ‘track’ plant and animal response
Moisture regime is only coarsely approximated by
precipitation
- precipitation is a useful index of moisture regime at
regional scales,but limited/problematic at both
continental and smaller scales
Problem,estimate moisture regime across entire
landscape,factoring in
(1) evaporation
(2) topography and
(3) soil profile
,how to generate gridded estimates in an
analogous manner to our climate models?
Mean annual precipitation (mm)
within a region,evapo ~ ‘constant’
P- E& available moisture (AM)
As E>,P must > to have same amt
of AM
Therefore important for continent-
wide analysis
Average evaporation from Australian Standard Tanks,in units of mm/year
Potential evaporation is
a function of,
1,Solar radiation4
2,Temperature (surface)
3,Atmospheric moisture
4,Turbulence/aerodynamic
roughness
US Weather Bureau Class A evaporation pans
with screen in the foreground and without screen
in the background.
ANUSPLIN surfaces have been fitted to Australian
network of ‘class A’ pan data thereby enabling
gridded estimates of potential evaporation to be
generated,Therefore,can calculate (P-E) or (P:E)
But PE? actual evaporation (AE)
AE is limited by soil moisture
Therefore need to factor in soil water availability
and calculate a moisture index as a function of
1,Precipitation
2,P.E.
3,Soil water status
So-called water-balance can be calculated on a daily,
weekly or monthly time step:
Available water capacity = f (soil depth,soil texture)
in this example,AWC = 100mm
Moisture index = 1 if ‘bucket’ is full
= 0 if ‘bucket’ empty
25mm 50mm 25mm 50mm 25mm 50mm
1.0
0.75
0.0
0.75
0.5
0.25
JAN FEB MAR
Can generate prediction of MI at any location at which
you know:
1,XYZ?Precipitation,potential evaporation
2,Soil depth + texture?AWC
Ultimately,what’s important for a plant is not how much
rain falls,but how much water is in the soil where its
roots are!
But how to generate gridded MI values across entire
landscapes?
- need ‘micro’ scaled soil maps
- most soil maps do not map profile depth
- depth more important to AWC calculation than texture
Influence of field texture and structure on water retained between -10 and
-1500kPa for a range of Australian soils (Williams 1983)
mm water retained per 10cm soil
calculate average at sites using this table
if we had more time,could calculate MI on a gridded basis assuming
soil depth constant or f (slope)
Structure and evaporative capacity of major Australian plant formations
(which may be regarded as climatic climax formations).
Relationships between
(a) mean monthly Moisture Index (Ea/Eo)
(b) the evaporation coefficient k (and
Foliage Projective Cover) and the per-
centage of annual precipitation which
is retained in the soil within the rooting
zone of the plant community.
Below the 100% value of annual precipitation,
water may be lost by runoff or internal drain-
age; above 100% water may be gained by run-
on or subsoil seepage from adjacent areas.
