C Nutrient Cycling Begin Climate Discussion. Day 29 December 2, Take-Home Test Due Dec 11 5 pm No Final Exam

Transcription

1 NREM 301 Forest Ecology & Soils C Nutrient Cycling Begin Climate Discussion Day 29 December 2, 2008 Take-Home Test Due Dec 11 5 pm No Final Exam Our discussions for the semester have centered on Clipsrot

2 No N from Weathering/All from Atmosphere Fertilization Free Living Bacteria Symbiotic N-fixers Rhizobium Frankia Nitrogen Cycle Geochemical = 16% Biogeochemical = 45% Surface Runoff Biochemical = 39% Anaerobic Uptake Nitrobacter Bacteria Leaching & tiles Nitrosomonas Bacteria Mineralization

3 Very Little Atmosphere Addition The P cycle 60% Loss from animal & plant harvest Fertilizer & Manure Addition No Gaseous Loss Erosion P Sorbed To Soil Weathering Addition Plant Uptake Soil Solution P Organic P Decomposition Mineralization Minor Leaching P Sorbed To Soil

4 Group Activity What are the major differences in the N & P sub-cycles in these two ecosystems? N geochemical fertilization, leaching, surface runoff, N-fixers Biogeochemical less annual litterfall, more rapid decomp., higher ph, more nitrification Biochemical no internal reallocation P geochemical surface runoff, fertilization with animal manure Biogeochemical - less annual litterfall, more rapid decomp., higher ph, more available P Biochemical no internal reallocation

5 CO 2 Most Atmosphere Input PS O 2 & CO 2 RS Carbon Cycle RS C Movement As Sugar Stored as Starch Loss from animal & human eating harvest of plants (lumber, corn, ethanol etc.) C Storage Eating Dying Tree/Plants Major C Storage Sequestration OM ~ 45%C Litter RS Manure Addition Erosion Soil Excreation No Plant Carbon Uptake Humus Carbon Sequestration OM ~ 55%C Organic C Storage & Decomposition Very Minor Leaching No Weathering Addition

6 Atmosphere Carbon Cycle What are the major: Inputs/Cycling? Sinks? Outputs? Pg. 505 text

7 Carbon Cycle & Photosynthesis Leaf tissue 42% C, 42% O, 8% H; 8% Ash (1-2% N) C comes from atmosphere & gets into the plant by Ps C functions as an energy source & structural material Photosynthesis & Respiration sort of opposing processes using C GP = gross photosynthesis RS = respiration NP = net photosynthesis NP = GP - RS NP is equal to Plant Growth It is what we see

8 P 492 text Response of NP = GP RS to temperature

9 P 498 text How does seasonal C allocation vary why? Carbon Allocation to Different Parts of the Plant Low numbers high priority What is its role in the survival strategy of the tree?

10 Plant Community (no animals) NPP = GPP RA (respiration of plants - autotrophs) (NPP = net primary production of all plants; GPP = gross primary production of all plants) Ecosystem (plants & animals) NEP = GPP (RA + RH) where RH = respiration of animals (heterotrophs) NEP = Net ecosystem production or Ecosystem Biomass (plants & animals) NEP ~ 45% sequestered C

11 Atmosphere Carbon Cycle What are the major: Inputs? Sinks? Outputs? Sequestered C Pg. 505 text

12 Five major biomass pools in an ecosystem? 1. Above/below-ground biomass 2. Woody debris 3. Forest floor 4. Mineral soil (6 types of OM in soil) 5. Tissues of heterotrophs (animals)

13 What are the largest biomass sinks in different forests? P 504 text What are the major differences in total biomass production between forests? How much biomass is there in the animal component of the ecosystem?

14 What has happened to the C that was sequestered on these sites? Consider: Above-ground biomass Below-ground biomass Soil carbon How do we increase C sequestration in these landscapes?

15 A What major nutrient(s) are most likely moving via the geochemical subcycle (out of the ecosystem)? B C D

16 Nutrient cycles that are open The geochemical sub-cycle in action How can we close these cycles some & continue farming? Iowa s Polluted Surface Waters

17 What role does this buffer system play in the nutrient cycle of the landscape?

18 What is the role of Terraces, Contour Field Buffers, Grass Waterways, Detention Ponds in the nutrient cycle of the landscape?

19 How do no- till & cover crops influence the nutrient cycle?

20 How do livestock exclusion or controlled access influence the nutrient cycle?

21 What is the impact of logging a disturbance of succession on the nutrient cycle, sediment movement & hydrologic cycle? Hubbard Brook Experiment New Hampshire Clear-cut, no product removal, no roads or skid trails, herbicide killed all sprouts 3 growing seasons

22 Time of Cut & No Vegetation Clearcut Forest Undisturbed Forest Group Activity Why the differences in Streamflow & Evapotranspiration

23 Group Activity Explain nutrient & sediment movement following the clearcut How does the forest response differ from the row-crop response? Cut Watershed

24 Model of Changes Use this figure to explain increases in streamflow, erosion and nutrient loss following clear cutting

25 What is the impact of logging on the nutrient cycle?

26 Nutrient response To different harvesting Strategies. Row-crop Agriculture