* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download I. What is it? I. What is it? II. Who does it?
Survey
Document related concepts
Nitrogen cycle wikipedia , lookup
Surface runoff wikipedia , lookup
Soil erosion wikipedia , lookup
Arbuscular mycorrhiza wikipedia , lookup
Soil horizon wikipedia , lookup
Soil salinity control wikipedia , lookup
Soil compaction (agriculture) wikipedia , lookup
Agroecology wikipedia , lookup
Crop rotation wikipedia , lookup
Soil respiration wikipedia , lookup
Plant nutrition wikipedia , lookup
Canadian system of soil classification wikipedia , lookup
Soil food web wikipedia , lookup
No-till farming wikipedia , lookup
Terra preta wikipedia , lookup
Soil contamination wikipedia , lookup
Transcript
Decomposition The Global Carbon Cycle - 1990s Units Gt C and Gt C y-1 Atmosphere (Ch. 19: 424-429 ) I. II. III. IV. What is it? Who does it? What controls it? How does it fit into the big picture? 3.2 …are leading to a build up of CO2 in the atmosphere. 750 63 500 Plants 60 Soil 2000 6.3 Fossil Deposits About 16,000 1.6 Fossil emissions ... 91.7 90 …and land clearing in the tropics... Oceans 39,000 Fate of tundra and boreal soil C? I. What is it? Respiration of dead organic matter: litter & SOM http://www.actagro.com/art/maincontentpix/soildiagram.jpg I. What is it? • Consumption of dead organic matter • Mass loss Æ release of CO2 • Release of organically bound nutrients • Link between C and N cycles II. Who does it? • Primary decomposers: bacteria & fungi – Extracellular enzymes for degrading complex organic molecules • Conditioners – Mechanical: increased surface area – Biological: gut passage 19.5 1 Primary decomposers: Bacteria and Fungi • • • • Conditioners Get carbon and energy from organic sources Release enzymes Enzymatic breakdown of substrate Products diffuse back into hyphae or bacterial cells CO2 Products diffuse back and are used in respiration and to build biomass Worms: conditioners III. What controls it? A. Climate - precipitation 19.5 Same MAT ~16.5 oC III. What controls it? A. Climate - temperature 19.9 2 III. What controls it? A. Climate 19.8 B. Organism controls – litter quality 19.7 IV. In the big picture Brief Nitrogen Cycle A. Nutrient regeneration – feedback to production • Emphasize: inputs, recycling, outputs • Inputs: lots in atmosphere, but little available. – N-fixation, importance in early succession • Recycling - Mineralization: N regeneration in plant available form Æ plant uptake • Losses: – denitrification (Fertilizer inputs Æ N2O (greenhouse gas)) – Leaching Æ eutrophication IV. In the big picture B. Source of CO2 to atmosphere, component of NEP - on average, in balance with production - except early successional ecosystems. C. Balance of Prod and Decomp leads to large diffs in C pools among ecosystems • Implications – – C feedback in tundra – C loss with ag in grasslands – Soil fertility in tropics Schlesinger 2001 3 Soil Organic Matter Content Source: W. W. Hargrove and R. J. Luxmoore http://www.unl.edu/nac/atlas/Map_Html/Stable_and_Productive_Soils/National/Soil_Organic_Matter_Content/Soil_Organic_Matter_Content.htm Loss of SOM with tillage http://www.ipm.iastate.edu/ipm/icm/2002/3-18-2002/croprotationgraph.gif Low soil organic matter in tropical soils Andy Rogers / P-I 1/22/08 John Aeschliman shows a spot where rain has washed soil from a neighboring farmer's property onto the road. Aeschliman says his method of farming, in which plants are seeded directly into the remains of the previous crop without tilling, gives stability to the soil, enabling it to retain water and preserve the organic matter within it. http://www.seattlepi.com/local/348200_dirt22.html Tropical forest in Panama http://www.lancs.ac.uk/staff/bardgett/Research.html END 4