frst 201 midterm forest ecology & nutrient cycling

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nanajun
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240938
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frst 201 midterm forest ecology & nutrient cycling
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2013-10-16 14:18:29
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nutrient cycling
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  1. factors that determine the nature of the ecosystem that develops on a given site
    • - climate
    • - topograhy
    • - soils
  2. temperature and precipitation regimes determined by
    • - latitude
    • - elevation
    • - maritime influence
    • - relief - orgraphic precipitation
  3. what affects climate
    • - elevation
    • - aspect
  4. what factors affect topography
    • - slope position
    • - aspect
  5. what factor does slope position influences, and how?
    • moisture
    • higher position of the slope more rapid drainage
  6. what is disturbance
    any relatively discrete event in time that disrupts ecosystem, community or population structure, and changes resources, substrate availability or the physical environment
  7. examples of forest disturbances
    • fire
    • logging
    • land slide
    • pathogens
    • flooding
    • wind
    • etc.
  8. what is stand
    spatially contiguous group of trees and associated vegetation having similar structures and growing under similar soil and climatic conditions
  9. spatially contiguous group of trees and associated vegetation having similar structures and growing under similar soil and climatic conditions
    stand
  10. what is forest?
    a heterogeneous mosaic of forest stands
  11. a heterogeneous mosaic of forest stands
    forest
  12. what is landscape
    a heterogeneous mosaic of forest stands and non-forest ecosystems
  13. a heterogeneous mosaic of forest stands and non-forest ecosystems
    lanscape
  14. what is cohort
    a group of trees regenerating after a single disturbance until growing space is filled
  15. what are the stages of stand development
    • 1. stand initiation
    • 2. stem exclusion
    • 3. understory re-initiation
    • 4. old growth
  16. what happen in stand initiation stage
    • Re-colonizing the site 
    • •Available growing space and resources 
    • •Open growth 
    • •Single cohort 

    • • Many species invade 
    • • Competition with non-tree species 
    • • Foliage to the ground
  17. what happen in stem exclusion stage
    • – no available growing space 
    • – increasing competition among trees 
    • – above ground (light) 
    • – below ground (water, nutrients) 
    • •crown closure 
    • •mortality of smaller trees 
    • •self-thinning 
    • •no regeneration
  18. what happen in understory re-initiation stage?
    • •Canopy begins to open 
    • –some overstory trees die 
    • –crowns thin as trees get older 
    • –branches die, ripped off by wind 
    • •more light reaches the understory 
    • •understory trees often different species 
    • •advanced regeneration 
    • •at least two cohorts
  19. what happen in old-growth stage
    • •trees of all ages and sizes 
    • •diversity of tree and non-tree species 
    • •gaps, clumps
  20. what are the different types of crown classes?
    • •Dominant 
    • •Co-dominant 
    • •Intermediate 
    • •Suppressed
  21. why there are different crown classes?
    • •age 
    • •micro-sites 
    • •competition 
    • •genetically superior
  22. what happens in gaps in forest?
    • •openings of any size in the overstory 
    • •death of one or several trees 
    • •late-successional species perpetuate themselves 
    • •usually little disturbance of forest floor
  23. what happen when there is a stand-replacing disturbance?
    stem exclusion, understory re-initiation and old-growth stages will return to stand initiation stage.
  24. macronutrients
    N  P  S  Ca  Mg  K
  25. Micronutrients
    Mn  Zn  Bo  Fe  Cu  Mo
  26. Nutrient Availability

    Concentration of nutrients accessible to roots
    • dissolved in soil solution

    In forms that can be taken up by roots
    • ionic forms
        • nitrate NO3-, ammonium NH4+, phosphate PO42-
    • or simple organic forms e.g. amino acids

    Small proportion of total soil nutrient pool

    Can limit primary productivity
  27. how are nutrients available to plants?
    • - dissolved in soil solution
    • - in ionic forms or simple organic forms
  28. inputs to ecosystem (nutrient cycling)
    • - fixation of gaseous N2, CO2
    • - dry deposition
    • - wet deposition
    • - weathering
  29. outputs to ecosystem (nutrient cycling)
    • - leaching, erosion
    • - volatilization
    • - denitrification, respiration
  30. soil -> tree (nutrient cycling within ecosystem)
    uptake:absorbed by plant roots and associated mycorrhizae
  31. within tree (nutrient cycling within ecosystem)
    • *Assimilated
    • – incorporation into organic forms
    • - used as needed for metabolism and growth

    *Remobilized – converted back into mobile forms

    *Redistributed – moved throughout plant as needed

    *Reassimilated – converted into new forms

    *Resorbed – remobilized and removed from tissue prior to tissue death
  32. Resorption within-tree cycling
    remobilized and removed from tissue prior to tissue senescence and abscision
  33. Senescence
    aging and death
  34. Abscision
    separation from tree
  35. tree -> soil (nutrient cycling within ecosystem)
    • - litterfall
    • - consumption
    • - throughfall and stemflow
    • - root exudates
  36. within soil (nutrient cycling within ecosystem)
    • - litter decomposition
    • - mineralization
  37. site nutrient supply depends on:
    • nutrient capital
    • nutrient availability
  38. decomposition measured as:
    • - mass loss in litterbags
    • - CO2 release
    • - residence time
  39. Decomposition
    primarily a consequence of extracellular enzyme activity of soil microorganisms (fungi and bacteria)
  40. rate and completeness of decomposition is influenced by
    • - any factors that affects microbial activity
    • - leaching of water
    • - soil fauna
    • - sunlight
  41. Amount of nutrient mineralized depends on ...
    rate of decomposition and concentration of the nutrient in the material

    Rates of net N mineralization are positively correlated with rates of net primary production in forests
  42. Site nutrient management entails
    • • minimizing losses of nutrients or disruptions of nutrient cycling
    • • ameliorating low nutrient supply to increase productivity

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