Oak Hickory on Coarse
Textured Kamic Soils
Stinchfield Woods, MI
Jennifer Austin
Joshua Berk Knox
Erin Uloth
Jennifer Dowdell
Presentation for Soil Properties and Processes
Parent
Material
Topography
Temperature
Water
Availability
pH
Vegetation
Aboveground
Carbon
N pools
Quantity and Quality
Forest Floor
Carbon
Soil Microbial
Activity
CO2
Quantity and Quality
Quantity & Quality
Soil Organic
Matter
Belowground
Carbon
The differences in soil parameters observed at our four sites can
be chiefly explained as influence of:

Parent Material

Chemistry – Calcareous, high nutrient (cation) availability
 acts as a pH buffer

Texture – Sandy to Loam
 Influence low to moderate water holding capacity for plant use

Topography – Ice-Contact Kettles and Kames

Temperature – Slope, N/S Aspects, Position on slope
 Solar energy input

Water Availability – Slope position, N/S Aspects
 loss/gain H2O, litter accumulation (OM)
The differences in soil parameters observed at
our four sites can be chiefly explained as
influence of (continued):

Temperature
 Vegetation – Global trends driven by growing season
length

Vegetation


Temperature – More vegetation insulates soil from sun
(& evapotranspiration)
Water– More vegetationincreased transpiration
Parent
Material
Topography
Temperature
Water
Availability
pH
Vegetation
Aboveground
Carbon
N pools
Quantity and Quality
Forest Floor
Carbon
Soil Microbial
Activity
CO2
Quantity and Quality
Quantity & Quality
Soil Organic
Matter
Belowground
Carbon
Soil Diagnostics
Texture
Field Results:
Loam and loamy sand
Lab results:
Silt loam to loamy sand
The surface area created by texture and structure contributes to available
water content and base saturation. ORGANIC MATTER will also play
a pivotal role in these characteristics.
Relationship with other sites… particularly Mixed Oak.
Available Water Content
OM contributes to aggregate formation.
OM was 3-4% by weight.
AWC ranged from 0.18 cm3 H2O/cm3 to 0.37 cm3 H2O/cm3 (mid-range
compared to other sites).
Vegetation confirms this:
Quercus velutina
Quercus alba
Carya glabra and ovata
Carex pensylvanica
Contrasts with the Mixed Oak site…
Cation Exchange Capacity/ Base Saturation
CEC is determined in part by clay minerology, OM content, and cation concentration from
parent material. OM contributes 30-90% of total CEC.
Oak Hickory:
Stinchfield parent material is calcareous and our results confirm that it has
a high base saturation. 95-99 %
CEC ranges from 3.83 cmol/kg to 8.94 cmol/kg. The site that has the
highest CEC, NW slope, also has the highest OM and is significantly
different in texture: Loam. Higher clay content leads to a higher
potential to attract and absorb cations.
Contrasted with Mixed Oak ecosystem… same base saturation but different CEC.
Parent
Material
Topography
Temperature
Water
Availability
pH
Vegetation
Aboveground
Carbon
N pools
Quantity and Quality
Forest Floor
Carbon
Soil Microbial
Activity
CO2
Quantity and Quality
Quantity & Quality
Soil Organic
Matter
Belowground
Carbon
Influences on Microbial Data
What do these communities prefer, and how do
these main influences play out at Stinchfield?
Neutral pH: Good
Ample moisture: Moderate
Warmer temperatures: Good
Ample carbon (food) Good?
Microbial Data


NW top: major outlier, discounted from analysis
Predictions:



High efficiency correlated with high C:N ratio
pH/AWC/temp correlated with respiration rates
Low OM correlated with high respiration rates or
low C inputs (aboveground C)
Recall: OM=Input-Microbial Activity (Respiration)
Microbial Data: Trends
Microbial Microbial Specific
Biomass
Resp
Resp
Site # (gC/m2)
(µg/g/d)
(µg/g/d)
NE Mid
4
6.620
23.000
264.540
NW Bottom
3
5.185
40.631
916.000
NW Top
2
0.932
37.000
5319.800
SW Top
1
5.400
26.400
530.660
N Min (g
N/m2/d)
1.480
1.102
0.317
0.873
N Nit (g
N/m2/d)
0.044
0.016
0.008
0.001
Ratio C
Resp/N
Min
22.520
36.879
15.630
30.240
pH (H20)
6.42
5.84
5.74
5.53
AWC (cm3
H2O/cm3)
0.28
0.37
0.32
0.18
A few notes…
•Specific Respiration: well correlated with C:N
•N Availability: well correlated with pH
•C:N ratio: variable across site
OM (%)
4.03%
4.90%
4.40%
3.03%
How did our predictions fare?

High efficiency correlated with
high C:N ratio?


pH/AWC/temp correlated with
respiration rates?


No! The opposite of expected!
Complex interaction of these
factors; AWC might be a driver
Low OM correlated with high
respiration rates OR low C inputs
(aboveground C)?

OM and respiration rates do not
necessarily correlate… so let’s
see if the story is complete with
biomass analysis.
C/N
40
38
36
34
32
30
28
26
24
22
20
0
200
400
600
800
Specific Respiration
1000
Correlations and Hypotheses

Does Microbial Biomass correlate with:





Depth of A: not really (r of 0.6 with slope of 0)
OM%: No (r of 0.5 with slope 0)
AWC: No (r of 0.5 with slope 0)
pH: Yes (r of >0.7) BUT NEGATIVELY!
But Remember: We only have 3 data points!!
Parent
Material
Topography
Temperature
Water
Availability
pH
Vegetation
Aboveground
Carbon
N pools
Quantity and Quality
Forest Floor
Carbon
Soil Microbial
Activity
CO2
Quantity and Quality
Quantity & Quality
Soil Organic
Matter
Belowground
Carbon
Site
#
NE Mid
NW Mid
NW Top
SW Top
Tues Mean
Mon. Mean
4
3
2
1
Aboveground
Carbon
Mg* ha-1
102
246.4
83.4
80
127.9
141.6
Forest
Aboveground Forest Floor
Floor
Nitrogen
Carbon
Nitrogen
kg N* ha-1
Mg* ha-1
kg N*ha-1
207.1
536.8
167.3
150
265.3
302.2
13
7.7
7.3
9.5
9.4
8.7
86.4
50
47.6
0.06
46
56.7
Microbial
Soil
Soil
Biomass
Carbon Nitrogen Basal
Mg*ha-1 Mg*ha-1 kg N*ha-1 Area
0.0007
0.0005
0.0009
0.0005
0.0007
45.5
57.3
59
30.1
48
54.5
1356
1404
1609.2
1193
1390.6
1362.6
20
38.6
50
18
31.7
We learned that:
• BA not a good measure of AG carbon:
• Site #2: highest BA, but 2nd lowest Aboveground (AG) C & N.
(difference due to DBH distribution)
• The AG Carbon is 2.6 times what is in the soil.
• F.Floor C NOT correlated with AG C across the 4 sites.
It varied from 3 to 12 % of AG C. .. So …
Why Not?
Above Grnd C - Forest Floor C…
Where did all the C go?
Microbial BM does NOT account for the “missing” C:

and:
Soil carbon accounts for only 40% on average of the “missing” C.


Flux vs Pools: OM accumulation :10kg/ha*yr -> 5780 years to accumulate
wow!
Does the microbial respiration of C to CO2 Account for the difference?

YES!! r=.903!!
As Resp declines, the ratio of FF to AG (controling for %OM) increases.



With less microbial respiration,
more FF C builds up per unit AG C
Oak-Hickory Summary




AWC increases as texture becomes loamy and OM
content increases
Vegetation suggests OH a drier site
Calcareous Parent Material leads to high base
saturation
Specific Respiration correlates with C:N ratio



Mildly acidic & well-drained encourages microbial activity
BA not a good measure of AG Carbon
FF Carbon not correlated with AG Carbon across our
4 sites – good indicator of microbial respiration
Unknowns



What drives respiration rates?
What is the main driver for site productivity?
Why is efficient respiration related to higher
quality sites?