Dynamics of the Northern Hardwood Ecosystem

Yuqiong Hu, Jeff Plakke,

Sharon Shattuck, Erin Wiley

Introduction: Field Review-Moraine deposits composed of old outwash plains-Abrupt, hilly topography-higher latitude and elevation

cooler temperatures

-Sandy soil-Well-developed profile-Bh horizon

-Overstory dominated by Acer saccharum-Many mesic indicators

Conclusion: Most important factors influencing this site are topography and climate.Topography leads to fire suppression and climate influences soil moisture.

Results: Physical Properties

• Average texture, based on Textural Triangle= Sand

• AWC= 0.14 cm^3 H2O/cm^3 soil

Northern Hardwood Forest Soil Texture Breakdown

87%

8%5%

% sand

% silt

% clay

Results: Chemical Properties

• pH– Water pH: 5.31– CaCl2 pH: 4.66

• Organic Matter: – Organic Matter: 3.26%– Organic Carbon: 1.63%

• CEC and Base Saturation– CEC: 3.87 cmol charge per kilogram– Base Saturation: 96.4%

Results: Biological PropertiesMicrobial Biomass and N-

Mineralization

Northern Hardwoods

Aeolian Ant

Farm ξPed Zeplin Average

Microbial Biomass g C/M² 6.94 18.92 10.65 12.17

Specific Microbial Respiration Rate mg/g/d 395.55 129.38 264.85 263.26

Net Nitrogen Mineralization g N/m²/d 0.175 0.09 0.344 0.203

Net Nitrification g N/m²/d 0.079 0.004 0.182 0.088

Ratio of C respired to N mineralized ug C/ug N 15.73 25.54 8.209 16.493

Results: Biological PropertiesBiomass and Nitrogen Pools

Northern Hardw oods Nitrogen Pools

794

165

2509

0

500

1000

1500

2000

2500

3000

Aboveground Forest Floor Below ground

Nitr

ogen

Con

tent

(kg

N/h

a)

Northern Hardw oods Biom ass Pools

314

13.4 32.3

0

50

100

150

200

250

300

350

Aboveground Forest Floor Below ground

Bio

mas

s (M

g C

/ha)

Discussion: Physical PropertiesTexture

• Sandy texture (87% sand)– Cannot hold moisture well

• low surface area: volume ratio

– Because parent material and texture are similar to Northern Oak site, there must be another driver for ecosystem development

Discussion: Physical Properties Available Water Content (AWC)

• AWC Relatively low, but higher than site on similar parent material. Why?– Physiography and Climate

• Parent material= sand• Higher elevation, higher latitude influences snowmelt

– Lower Solar Penetration due to high Basal Area– Organic Matter

• Field evidence: – Presence of Bh horizon in soil profile indicates organic matter

breakdown.

Discussion: Chemical PropertiespH and Organic Matter

• pH: What controls it? – Litter quality– Microbial activity (because pH is acidic, fungi are

primary decomposers in this ecosystem)– Parent Material (soil buffering capacity)

• Organic Matter– Low in soil compared to O.M. pool in overstory;

indicates high rate of decomposition– Increases water-holding capacity– Field evidence: Bh horizon indicates high amount of

O.M. in system

Discussion: Chemical PropertiesCEC and Base Saturation

• CEC and Base Saturation– CEC somewhat low due to parent material

• Sand= low CEC• Higher than site on similar parent material due to

higher O.M. content

– Base Saturation: Indication of large nutrient pool

• Lack of Fire• Young, relatively unweathered Parent Material

Discussion: Biological Properties

Microbial Activity and Nitrogen Cycling– Litter Production high + litter accumulation low = high

Microbial Biomass -“look up, look down”– Litter Quality is high = high C:N ratio

– N mineralization = NH4+ lots of “Goodies”

– Nitrification is high • Nitrobacter spp. NH4

+ NO3-

• Potential for nutrient loss through leaching NO3- (highly

mobile, sandy soils, water movement) after a disturbance (decreased plant uptake).

Discussion: Biological Properties

Biomass and Nutrient Pools• Aboveground Biomass is highest “look up…”

– drives N mineralization and Nitrification through litter decompostion

• Belowground Nitrogen Pool is Highest

• Forest floor is lowest for both “…look down.” = high rate of decomposition.

“what about the roots?”

Climate

snowpackevapotranspiration

moisture

Rate of microbial activity

Litter quality Plant community

Nutrient pool

Litter Quantity

DISCUSSION

& SYNTHESIS:

Topography

Disturbance Regime

Nutrient Pool Plant community

Litter qualityRate of Microbial Activity

pH

DISCUSSION

& SYNTHESIS:

Litter quantity

Questions?