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

Belowground Carbon Aboveground Carbon Soil Organic Matter Soil Microbial Activity Forest Floor Carbon N pools CO 2 pH Water Availability Quantity and Quality Temperature Quantity and Quality Quantity & Quality Vegetation Topography Parent Material

The differences in soil parameters observed at our four sites can be chiefly explained as influence of: Parent Material Parent Material Chemistry – Calcareous, high nutrient (cation) availability Chemistry – Calcareous, high nutrient (cation) availability  acts as a pH buffer Texture – Sandy to Loam Texture – Sandy to Loam  Influence low to moderate water holding capacity for plant use Topography – Ice-Contact Kettles and Kames Topography – Ice-Contact Kettles and Kames Temperature – Slope, N/S Aspects, Position on slope Temperature – Slope, N/S Aspects, Position on slope  Solar energy input Water Availability – Slope position, N/S Aspects Water Availability – Slope position, N/S Aspects  loss/gain H 2 O, litter accumulation (OM)

The differences in soil parameters observed at our four sites can be chiefly explained as influence of (continued): Temperature Temperature  Vegetation – Global trends driven by growing season length Vegetation Vegetation Temperature – More vegetation insulates soil from sun (& evapotranspiration) Temperature – More vegetation insulates soil from sun (& evapotranspiration) Water– More vegetation  increased transpiration Water– More vegetation  increased transpiration

Belowground Carbon Aboveground Carbon Soil Organic Matter Soil Microbial Activity Forest Floor Carbon N pools CO 2 pH Water Availability Quantity and Quality Temperature Quantity and Quality Quantity & Quality Vegetation Topography Parent Material

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 cm 3 H 2 O/cm 3 to 0.37 cm 3 H 2 O/cm 3 (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 % 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.

Belowground Carbon Aboveground Carbon Soil Organic Matter Soil Microbial Activity Forest Floor Carbon N pools CO 2 pH Water Availability Quantity and Quality Temperature Quantity and Quality Quantity & Quality Vegetation Topography Parent Material

Influences on Microbial Data Neutral pH: Good Ample moisture: Moderate Warmer temperatures: Good Ample carbon (food) Good? What do these communities prefer, and how do these main influences play out at Stinchfield?

Microbial Data NW top: major outlier, discounted from analysis NW top: major outlier, discounted from analysis Predictions: Predictions: High efficiency correlated with high C:N ratio High efficiency correlated with high C:N ratio pH/AWC/temp correlated with respiration rates pH/AWC/temp correlated with respiration rates Low OM correlated with high respiration rates or low C inputs (aboveground C) Low OM correlated with high respiration rates or low C inputs (aboveground C) Recall: OM=Input-Microbial Activity (Respiration)

Microbial Data: Trends A few notes… Specific Respiration: well correlated with C:N N Availability: well correlated with pH C:N ratio: variable across site

How did our predictions fare? High efficiency correlated with high C:N ratio? High efficiency correlated with high C:N ratio? No! The opposite of expected! No! The opposite of expected! pH/AWC/temp correlated with respiration rates? pH/AWC/temp correlated with respiration rates? Complex interaction of these factors; AWC might be a driver Complex interaction of these factors; AWC might be a driver Low OM correlated with high respiration rates OR low C inputs (aboveground C)? 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. OM and respiration rates do not necessarily correlate… so let’s see if the story is complete with biomass analysis. C/N Specific Respiration

Correlations and Hypotheses Does Microbial Biomass correlate with: Does Microbial Biomass correlate with: Depth of A: not really (r of 0.6 with slope of 0) Depth of A: not really (r of 0.6 with slope of 0) OM%: No (r of 0.5 with slope 0) OM%: No (r of 0.5 with slope 0) AWC: 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! pH: Yes (r of >0.7) BUT NEGATIVELY! But Remember: We only have 3 data points!! But Remember: We only have 3 data points!!

Belowground Carbon Aboveground Carbon Soil Organic Matter Soil Microbial Activity Forest Floor Carbon N pools CO 2 pH Water Availability Quantity and Quality Temperature Quantity and Quality Quantity & Quality Vegetation Topography Parent Material

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 CO 2 Account for the difference? Does the microbial respiration of C to CO 2 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 Above Grnd C - Forest Floor C… Where did all the C go?

Oak-Hickory Summary AWC increases as texture becomes loamy and OM content increases AWC increases as texture becomes loamy and OM content increases Vegetation suggests OH a drier site Vegetation suggests OH a drier site Calcareous Parent Material leads to high base saturation Calcareous Parent Material leads to high base saturation Specific Respiration correlates with C:N ratio Specific Respiration correlates with C:N ratio Mildly acidic & well-drained encourages microbial activity Mildly acidic & well-drained encourages microbial activity BA not a good measure of AG Carbon BA not a good measure of AG Carbon FF Carbon not correlated with AG Carbon across our 4 sites – good indicator of microbial respiration FF Carbon not correlated with AG Carbon across our 4 sites – good indicator of microbial respiration

Unknowns What drives respiration rates? What drives respiration rates? What is the main driver for site productivity? What is the main driver for site productivity? Why is efficient respiration related to higher quality sites? Why is efficient respiration related to higher quality sites?