Plant Ecology - Chapter 14
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Transcript of Plant Ecology - Chapter 14
![Page 1: Plant Ecology - Chapter 14](https://reader035.fdocuments.in/reader035/viewer/2022081504/56812c67550346895d90fb54/html5/thumbnails/1.jpg)
Plant Ecology - Chapter 14
Ecosystem Processes
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Ecosystem Ecology
Focus on what regulates pools (quantities stored) and fluxes (flows) of materials and energy in abiotic and biotic components
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Ecosystem Ecology
Turnover time - how rapidly does it move through the systemRetention time - how long does it reside in a component
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Ecosystem Ecology
Pools, fluxes connected together into biogeochemical cyclesBiology, geology, chemistry interconnected
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Ecosystem Ecology
Plants under the influence of some cycles, influence othersWater, oxygen, carbon, nitrogen, phosphorus, sulfur, potassium
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Water Cycle
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Water Cycle
Terrestrial plants are only living things to have significant effect on water cycleEvapotranspiration from plants can provide huge proportion of moisture in atmosphere - affect rainfall patterns
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Water Cycle
Cutting rainforests can result in decreased evapotranspiration, decreased rainfall, increased air temperatures at ground surface
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Water Cycle
Since plants intercept rainfall, reduce its impact on ground, removing vegetation can alter infiltration/runoff relations
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Water Cycle
Even removing vegetation in semi-arid regions can reduce rainfall, increase soil temperatures, induce onset of desertification
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Water CycleFlux differencesamong, within biomes
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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 infiltrationPET>AET in dry climatesPET=AET in intact tropical rain forestsAET linked to productivity, decomposition
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Carbon CyclePrimary productivity - rate oftransfer of inorganic C fromatmosphere into organic Cin plants via photosynthesis
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Carbon Cycle
NPP -dry metric tons/ha/yr
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ProductivityDifferent ecosystems -related to leaf biomass
Different forests - latitude,climate, elevation
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Productivity
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Estimating Productivity
Standing biomass after a growing seasonDrawbacks: destructive, and ignores belowground productivity (can be majority in some plants)
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Estimating Productivity
Indirect measures: develop formulae for relating plant size changes to biomass changesAllometric relationships used by timber companies, forest ecologistsDrawback: formula needed for each species
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Estimating Productivity
Indirect measures: use relation between productivity and AETFairly good estimates of productivity over broad range of climatesDrawback: poor predictor of productivity where precipitation and temperature are both high
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Estimating Productivity
Remote sensing - use reflectance of light wavelengths by chlorophyll to estimate productivityNormalized difference vegetation index (NDVI) - good correlation between NDVI and NPP ground measurements
NDVI = NIR-VIS NIR+VIS
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DecompositionDead stuff becomes soil organic matter, then viamineralization becomes inorganic nutrients, CO2,water, and energy
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Decomposition- Saprophytic fungi are the major decomposers of dead leaves, plant litter- Bacteria also essential, but only in latter stages
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Decomposition
Decomposition largely an aerobic process - very slow in waterlogged, cold soilsPhysical, chemical characteristics also affect rate of decomposition
Root decomposition ofsoft and hardwoods
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Net Ecosystem Production
NEP is net accumulation of carbon per year by ecosystemPositive during growing season, negative during non-growing season
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Net Ecosystem Production
Undisturbed ecosystems usually show small, positive accumulations of C each yearAccumulation of woody tissue in long-lived plants
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Soil Carbon: Pools and Fluxes
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Nitrogen & Productivity
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Nitrogen Cycle- Rapid flux through living organisms- Large global pool with slow turnover
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Phosphorus Cycle- Does not have major atmospheric pool like other cycles- Mostly recycled in organic form through other living organisms
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Calcium Cycle
Sedimentary cycleNeeded by plants for chemical (growth, stress regulation), structural (support) rolesLargely lost in leaf fall - must be replaced each year
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Calcium Cycle
Calcium depletion occurring in many forests todayAcid deposition displaces soil calcium, logging removes itDecreased growth, higher mortality (more susceptible to pathogens)