Nutrient Cycling and Retention

1. Nutrient Cycling and Retention Chapter 19

2. 1. Describe the Nitrogen Cycle & processes Storage in atmosphere & oceans - N2 Not available to living things nitrogen fixing: lightening or bacteria *bacteria can use atmospheric supply directly. Energy-demanding process. N2 reduced to ammonia (NH3). Once N is fixed it is available to organisms. Upon death of an organism, N can be released by fungi and bacteria during decomposition.

3. 1. Processes con�t Volatilization - losses of ammonia from the soil surface to the atmosphere. Denitrification � return to N2 for storage Bacteria Runoff from natural sources & ag Breakdown of leaves, decaying plant & animal material Pollution � add to atmosphere burning fossil fuels esp. coal Other industrial processes

4. 1. Nitrogen Processes con�t Decomposition Decay of plant and animal material Precipitation Rain deposits N2 in soil Legumes w/ nitro fixing bacteria make it useful Leaching Loss of N Water seeps into ground, carrying N Settles below range of roots Microrhizae fungi can help but excess N kills Sewage Animals & humans http://muextension.missouri.edu/explore/envqual/wq0252.htm

5. 2. Why is nitrogen important to living things? DNA � dexoxyribonucleic acid RNA � ribonucleic acid Amino acids � protein (amino portion) Nitric Oxide (NO) � expands, contracts blood vessels

6. 3. What are the forms of nitrogen? Nitrogen gas (N2) - 78 per cent of atmosphere; not directly available for use by plants; used in nitrogen fixation and industrial fertilizer manufacture. Ammonia (NH3) � basic form of nitrogen fertilizer; unavailable to plants without nitrogen fixing bacteria. Nitrate (NO3-) - most common form available to plants; mobile, leachable form; usually the end product of mineralization.

7. 3. Nitrogen forms Con�t Ammonium (NH4+) - less-common plant-available form, but preferred nitrogen source; less energy required for uptake, many beneficial side effects and less likely to be lost than other forms. Nitrite (NO2-) - less-common plant-available form; an intermediate in the conversion of ammonium to nitrate; more toxic to plants and more prone to gaseous losses than nitrate. Nitrous Oxide (N2O) � greenhouse gas; form lost through denitrification. Nitric Oxide (NO) � form lost through denitrification; may be harmful to the ozone layer. Organic Nitrogen Compounds - complex; unavailable to plants; end products of immobilization.

8. 4. Draw the Nitrogen Cycle - word diagram.

9. 5. Describe the Carbon Cycle & processes Storage sites - Although some C cycles rapidly, some remains sequestered in unavailable forms for long periods of time. Atmosphere Bodies of living things, all organic molecules have a carbon backbone Carbonate rocks oceans photosynthesis n CO2 + 2n H2O + ATP + NADPH ? (CH2O)n + n H2O + n O2, n defined according to the structure of resulting carbohydrate Respiration � cell respiration in plants & animals releases CO2

10. 5. Con�t Combustion � burning organic material, wood, biomass, fossil fuels Rainforest destruction = 2X contribute to global warming Input to atmosphere by combustion Loss of CO2 removal from photosynthesis Decomposition Bacteria release CO2 Volcanic eruption input CO2 from land to air Transferred between trophic levels Consumption of plant & animal tissue In aquatic ecosystems, CO2 must first dissolve into water before being used by primary producers.

11. 6. Draw Carbon Cycle � word diagram

12. 7. What is mineralization? Why important? Rate at which nutrients are made available to primary producers is determined largely by rate of mineralization. Occurs primarily during decomposition. Rate in terrestrial systems is significantly influenced by temperature, moisture, and chemical compositions.

13. 8. Influence of living things on carbon and nitrogen cycles. EX 1. Leaf decomposition. Gessner and Chauvet found leaves with a higher lignin content decomposed at a slower rate. Higher lignin inhibits fungi colonization of leaves. Higher lignin deters herbivores Draw graph, which leaves decompose more quickly? Which do you think are preferred by herbivores?

14. Decomposition in Aquatic Ecosystems

15. 8. Ex 2: Stream Invertebrates Grimm showed aquatic invertebrates significantly increase rate of N cycling. Suggested rapid recycling of N by macroinvertebrates may increase primary production. Excreted and recycled 15-70% of nitrogen pool as ammonia. converted to useful form for plants

16. Stream Invertebrates con�t

17. 8. EX 3. Animals and Nutrient Cycling in Terrestrial Ecosystems Huntley and Inouye found pocket gophers altered N cycle by bringing N-poor subsoil to the surface. MacNaughton found a positive relationship between grazing intensity and rate of turnover in plant biomass in Serengeti Plain. Without grazing, nutrient cycling occurs more slowly through decomposition and feeding of small herbivores.

18. Animals and Nutrient Cycling in Terrestrial Ecosystems

19. Disturbance and Nutrient Loss From the Hubbard Brook Forest Vitousek studied effects of disturbance and environmental conditions on N loss. Trenching increased concentrations of nitrate in soil water up to 1,000 x. Nitrate losses are generally greatest at sites with rapid decomposition � due to leaching Uptake by vegetation is most important in ecosystems with fertile soils and warm, moist conditions. 1 reason tropical rainforest less fertile soils