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Dynamics of the Northern Hardwood Ecosystem

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

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Dynamics of the Northern Hardwood Ecosystem

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  1. Dynamics of the Northern Hardwood Ecosystem Yuqiong Hu, Jeff Plakke, Sharon Shattuck, Erin Wiley

  2. 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.

  3. Results: Physical Properties • Average texture, based on Textural Triangle= Sand • AWC= 0.14 cm^3 H2O/cm^3 soil

  4. 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%

  5. Results: Biological PropertiesMicrobial Biomass and N-Mineralization

  6. Results: Biological PropertiesBiomass and Nitrogen Pools

  7. 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

  8. 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.

  9. 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

  10. 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

  11. 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).

  12. 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?”

  13. DISCUSSION & SYNTHESIS: Climate evapotranspiration snowpack moisture Rate of microbial activity Nutrient pool Litter quality Plant community Litter Quantity

  14. DISCUSSION & SYNTHESIS: Topography Disturbance Regime Plant community Nutrient Pool Litter quantity pH Litter quality Rate of Microbial Activity

  15. Questions?

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