Lesson 32 Mineral Cycling - Alaska Geobotany Center

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Summary Aspects of nutrient cycling – Gaseous (e.g., Carbon and Nitrogen cycles) and sedimentary cycles (e.g., Potassium cycle). – Nutrients are compartmentalized into (a) rocks and soils, (b) soil solution, ( c) the atmosphere, and (d) biomass. – Transfer into or out of the system can be via meteorologic, geologic, or biologic events. – Time scales of cycles can require minutes, decades, or millennia to revolve. Biological cycling within systems is much more rapid than abiotic cycling. – Abiotic factors include fire, earth movement, and aspects of the hydrologic cycle (deposition, leaching, evapotranspiration, runoff, infiltration). – Biotic factors include litter production, organic matter accumulation, decomposition, ingestion and digestion, gas flux, root exudation, and retrieval of nutrients from deep soil layers through roots. – Stability of systems often depend on a variety of homeostatic mechanisms to retain nutrients in the sytem, including resorption (ability to withdraw nutrients from plant parts that senesce to avoid loss of nutrients in litterfall), high nutrient use efficiency (high rate of production per unit of nutrient), large storage pools within the system (such as large standing crop of trees), and immobilization of nutrients (e.g., in decomposer microorganisms, and plants to prevent leaching. – The carbon and nitrogen cycles are tightly linked because plant tissues have high demand for nitrogen. Production is often limited by the availability of nitrogen. – Acid rain affects mineral cycles through lower soil water pH, which leaches nutrients from the soil. Nitrogen saturation occurs from enhanced inputs of N in rain water and dry deposition and leads to stream eutrophication. – Increases in greenhouses gases including CO 2 , NH 4 ,N 2 O, and water vapor are of major concern because of possible effects on global climate.
Summary (cont ) Measurement of nutrient pools and fluxes – Measurement of nutrient pools and fluxes requires a great variety of tools including wiers to measure quantity and chemistry of stream waters, dry and wet deposition collectors to measure atmospheric inputs, lysimeters to measure chemistry of soil water, litter collectors to measure quantity of litter, litter bags and buried wooden dowels to measure decomposition rates, and harvest and mineral analysis of biomass to determine the nutrients in the vegetation. – Measurement of CO 2 , NH 4 , and N 2 O fluxes requires large coordinated efforts to simultaneously study climate, fluxes of trace gases at multiple scales, and monitor ground-surface changes through remote sensing studies. – The Hubbard Brook studies are an excellent example that has fully studied the biotic and abiotic aspects of nutrient cycling, focusing on potassium, calcium, and nitrogen cycles. – AmeriFlux and FIFE are examples of the large interdisciplinary efforts to study greenhouse gases.
Page 1 and 2: Lesson 32 Mineral Cycling • Essen
Page 3 and 4: Micronutrients
Page 5 and 6: A sedimentary cycle: the phosphorus
Page 7 and 8: Hubbard Brook LTER site: whole wate
Page 9 and 10: Atmospheric inputs of nutrients and
Page 11 and 12: Calcium addition experiment at Hubb
Page 13 and 14: Soil lysimeter to collect water for
Page 15 and 16: Essential plant nutrients • Nutri
Page 17 and 18: Nutrient supply in a coastal dune c
Page 19 and 20: Soil respiration for mixed hardwood
Page 21 and 22: Decomposition of litter material by
Page 23 and 24: Greenhouse Gases Total Greenhouse G
Page 25 and 26: Monitoring Greenhouse Gas Fluxes: F
Page 27 and 28: AmeriFlux Objectives Generally: •
Page 29 and 30: FLUXNET: Integrating worldwide CO 2
Page 31 and 32: Carbon and nitrogen cycling in terr
Page 33 and 34: Litter bags and dowels for measurin
Page 35: Summary of effects of nitrogen satu

Lesson 32 Mineral Cycling - Alaska Geobotany Center

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