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Plant Ecology - Chapter 14

Plant Ecology - Chapter 14. Ecosystem Processes. Ecosystem Ecology. Focus on what regulates pools (quantities stored) and fluxes (flows) of materials and energy in abiotic and biotic components. Ecosystem Ecology. Turnover time - how rapidly does it move through the system

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Plant Ecology - Chapter 14

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  1. Plant Ecology - Chapter 14 Ecosystem Processes

  2. Ecosystem Ecology • Focus on what regulates pools (quantities stored) and fluxes (flows) of materials and energy in abiotic and biotic components

  3. Ecosystem Ecology • Turnover time - how rapidly does it move through the system • Retention time - how long does it reside in a component

  4. Ecosystem Ecology • Pools, fluxes connected together into biogeochemical cycles • Biology, geology, chemistry interconnected

  5. Ecosystem Ecology • Plants under the influence of some cycles, influence others • Water, oxygen, carbon, nitrogen, phosphorus, sulfur, potassium

  6. Water Cycle

  7. Water Cycle • Terrestrial plants are only living things to have significant effect on water cycle • Evapotranspiration from plants can provide huge proportion of moisture in atmosphere - affect rainfall patterns

  8. Water Cycle • Cutting rainforests can result in decreased evapotranspiration, decreased rainfall, increased air temperatures at ground surface

  9. Water Cycle • Since plants intercept rainfall, reduce its impact on ground, removing vegetation can alter infiltration/runoff relations

  10. Water Cycle • Even removing vegetation in semi-arid regions can reduce rainfall, increase soil temperatures, induce onset of desertification

  11. Water Cycle Flux differences among, within biomes

  12. Water Cycle • Potential evapotranspiration (PET) - water lost via this process if water is freely available and plant cover is 100% • Actual evapotranspiration (AET) - precipitation minus runoff and infiltration • PET>AET in dry climates • PET=AET in intact tropical rain forests • AET linked to productivity, decomposition

  13. Primary productivity - rate of transfer of inorganic C from atmosphere into organic C in plants via photosynthesis Carbon Cycle

  14. NPP - dry metric tons/ha/yr Carbon Cycle

  15. Productivity Different forests - latitude, climate, elevation Different ecosystems - related to leaf biomass

  16. Productivity

  17. Estimating Productivity • Standing biomass after a growing season • Drawbacks: destructive, and ignores belowground productivity (can be majority in some plants)

  18. Estimating Productivity • Indirect measures: develop formulae for relating plant size changes to biomass changes • Allometric relationships used by timber companies, forest ecologists • Drawback: formula needed for each species

  19. Estimating Productivity • Indirect measures: use relation between productivity and AET • Fairly good estimates of productivity over broad range of climates • Drawback: poor predictor of productivity where precipitation and temperature are both high

  20. Estimating Productivity • Remote sensing - use reflectance of light wavelengths by chlorophyll to estimate productivity • Normalized difference vegetation index (NDVI) - good correlation between NDVI and NPP ground measurements NDVI = NIR-VIS NIR+VIS

  21. Decomposition Dead stuff becomes soil organic matter, then via mineralization becomes inorganic nutrients, CO2, water, and energy

  22. Decomposition - Saprophytic fungi are the major decomposers of dead leaves, plant litter - Bacteria also essential, but only in latter stages

  23. Decomposition Root decomposition of soft and hardwoods • Decomposition largely an aerobic process - very slow in waterlogged, cold soils • Physical, chemical characteristics also affect rate of decomposition

  24. Net Ecosystem Production • NEP is net accumulation of carbon per year by ecosystem • Positive during growing season, negative during non-growing season

  25. Net Ecosystem Production • Undisturbed ecosystems usually show small, positive accumulations of C each year • Accumulation of woody tissue in long-lived plants

  26. Soil Carbon: Pools and Fluxes

  27. Nitrogen & Productivity

  28. Nitrogen Cycle • Rapid flux through living organisms • Large global pool with slow turnover

  29. Phosphorus Cycle • Does not have major atmospheric • pool like other cycles • Mostly recycled in organic form • through other living organisms

  30. Calcium Cycle • Sedimentary cycle • Needed by plants for chemical (growth, stress regulation), structural (support) roles • Largely lost in leaf fall - must be replaced each year

  31. Calcium Cycle • Calcium depletion occurring in many forests today • Acid deposition displaces soil calcium, logging removes it • Decreased growth, higher mortality (more susceptible to pathogens)

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