Ch 22- Nutrient cycling

What is a nutrient? How are they acquired by different groups of organisms (detritovores, autotrophs, heterotrophs)

• nutrient= chemical elemnts for metabolism and growth

• detritivores→ breaking down organic decaying molecules

• auotrophs→ take up nutrients in simple soluble forms from the envt

• heterotrophs→ in food as large complex molecules

Explain how nutrients become available to organisms from their two major abiotic sources: rocks and the atmosphere.

Rocks

• minerals in rocks released by weathering

Atmosphere

• nutrients in atmosphere transformed/fixed by organisms

  • ex: carbon taken up as Co2 by autotrophs through photosynthesis and fixed into organic comps

Define the process of nitrogen fixation and explain why it is is only done by a few species of bacteria

• Nitrogen fixation=process of converting N2 into biologically useful form

• 78% nitrogen in atmopshere but this form cant be used by organisms bc lots of energy needed to break triple bond

  • nitrogenase enzyme in bacteria used to fix nitrogen (convert N2 into useful form)

• Legume plants have mutualistic relationship with N fixing bacteria

Define decomposition, including the roles of fragmentation and mineralization in the break down of detritus.

• the process by which detritivores break down detritus to obtain energy and nutrients

• fragmentation= physical breakdown of fresh detritus into smaller particles

  • increases SA, facilitates chem breakdown

• Mineralization: chem conversion of organic matter into inorganic nutrients

  • final step in decomposition

What impacts the rate of decomposition?

• climate

  • faster in warm, moist conditions

  • not too moist though or no O2 in soil, microorganisms get no O2

Explain the importance of chemical transformation of nutrients for their availability and cycling.

• Without these transformations, many essential elements would remain "locked" in unusable forms

  • ex: nitrogen fixation N2→ NH3→ NO3- (plants can absorb)

  • phosphorus locked inside rocks, weathering makes it available

Explain and interpret different factors that affect rates of nutrient cycling.

1. nutrients that limit primary production are cycled more rapidly than non-limiting nutrients

2. climate: temp and moisture affect metabolic rates of the organisms involved in nutrient transformations

3. chemical characteristics

Interpret examples showing how nutrient cycles can affect nutrient limitation in different types of ecosystems

• fast nutrient cycling (warm, wet envts)

  • nutrients move quickly but may not stay in soil

  • can lead to phosphorus limitation if P lost faster than replaced

• Slow nutrient cycling (cold/dry envts)

  • nutrients released slowly

  • often causes N limitation bc N mineralization slow

• LAKES

  • P (phosphorus) usually limiting nutrient bc sedimentation removes P from lakes nutrient cycle

  • nitrogen can cycle more easily through water column

Describe the processes affecting nutrient limitation and availability in oceans

• upwelling→ brings nutrient rich water to surface

• N often limiting bc Nitrogen fixation slow

• dead organisms sink and carry nutrients to deep water→ nutrients lost→ decreases availibilty

• Human impacts→ altered nutrient cycles

  • agricultural runoff can introduce excess nutrients

Identify the major pools of carbon in the caron cycle

• 99% is in sediments and rocks

• CO2/CH4 in atmosphere

• fossil fuels

  • coal, oil, natural gas

• Oceans

  • dissolved Co2

What are the main sources of anthropogenic release of carbon? How is this affecting global climate (note link to early chapters)

• 80% from burning fossil fuels

• 20% from land use change mainly deforestation

• causes ocean acidifcation→ more Co2 in atmosphere, more ocean takes up

• Changes in global temps

• change in freq of extreme events (droughts, storms, etc)

Discuss the ecological consequences of climate change, including:

a. Elevation and latitudinal shifts of species and ecosystems

• involves communities moving toward the poles

• but this isn’t simple bc most plants and animals can’t disperse due to barriers and habitat fragmentation constraints

• seattle to vancouver

Discuss the ecological consequences of climate change, including:

b. Rates of disturbance

• increases frequency, intensity, and duration of natural disturbances

  • more wildfires, hotter drier conditions

• more intense storms

• more droughts and heat waves→ plants die

Discuss the ecological consequences of climate change, including:

c. Pest and disease outbreaks

• Increased pest and pathogen outbreaks

  • bark beetles thrive more in warmer temps