Lecture 31 NutrientCycling2009 forweb

Lecture 31 NutrientCycling2009 forweb - Nutrient Cycling:...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Nutrient Cycling: Inputs, Outputs, and Cycles N N P Chp. 21, continued 2 Today’s Outline • Nutrient inputs to ecosystems • Internal nutrient cycling – N cycle – P cycle • Nutrient losses from ecosystems • Alterations to nutrient cycles: 2 examples 3 Essential nutrients N : Proteins, esp. photosynthetic enzymes P : Nucleic acids, phospholipids Ca Ca: Plant cell walls, wood Mg : Central to chlorophyll K : Osmotic regulation (stomates) Mo Mo: N fixation enzymes Si: Diatom cell walls Fe Fe: Micronutrient in enzyme synthesis (including N fixation) 4 Generic Nutrient Cycling: Inputs, Outputs, and Cycles Plants Dead Organic Dead Organic Matter Matter Deposition, N Fixation Soluble Nutrients Nutrients U p t a k e M o r l i y , L f Immobilization Mineralization Leaching, Erosion Weathering Microbes Gas Loss 5 New Inputs: Supplied from Atmosphere Atmospheric Deposition: – Precipitation e.g., dissolved HNO 3 , H 2 SO 4 – Fog / “Cloud” e.g., dissolved HNO 3 , H 2 SO 4 – Gases e.g., NH 3 , HNO 3 , SO 2 – Particles / dust e.g., (NH 4 ) 2 SO 4 aerosols • Dominant input route for N , S •D u s t inputs of Ca , P , Fe can be significant in some ecosystems “Wet” “Dry” 6 N deposition to temperate forests has increased 5- to 50-fold over pre-industrial conditions. 1860 1993 50 20 10 7.5 5.0 2.5 1.0 0.5 2.5 0.5 Galloway and Cowling, 2002; Galloway et al., 2002b Modeled N Deposition Rate (kg N ha -1 y -1 )
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
7 New Inputs: Supplied from Weathering • Rock-derived nutrients supplied by weathering • Dominant input route for: Ca , Mg Mg , K, , P, Na Na Interesting exceptions: pyrite as S source; shale, N ! • Rate of input depends on: Composition of initial parent material (Limestone? Granite?) Extent of past weathering (intensity, duration) • Base cations leached away? • Phosphorus leached away and/or bound? 8 Supplies of P decrease over time – and are low in very old soils Boreal & temperate (post-glacial) Volcanic soils Old, highly weathered tropical soils (not all tropics) 10 6 years 10 3 years 9 New Inputs: N Fixation 78% of the atmosphere is N 2 gas (N N, inert); must be transformed to be used by plants An aerobic process: Nitrogenase enzyme poisoned by O 2 Energy-demanding process – Carbon supplied from photosynthate produced elsewhere
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 6

Lecture 31 NutrientCycling2009 forweb - Nutrient Cycling:...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online