Biogeochemistry 2 Flashcards
What are the basic ingredients for building an ecosystem?In particular, after C, H, and O, which are the most predominant elemental constituents of organic matter, what are the next two common elements needed for plants? For each of the 5 elements, what is their ultimate source (where do plants/ecosystems get these elements)?
carbon - from the atmosphere (photosynthesis)
hydrogen - from the atmosphere, water
oxygen - from the atmosphere
nitrogen - from the atmosphere and soil (biological fixation)
Phosphorous - from chemical rock weatherng
Describe the simple conceptual model of soil/ecosystem development presented in class and in the Chadwick et al. reading. What nutrients are expected to be limiting early in ecosystem development, and which ones later?
young soils should be rich in rock-derived elements (P, Ca, cations) and poor in atmospherically derived elements and those from prganic degredation. Limited by Nitrogen.
old soils should be poor in rock derived elements due to leaching and richer in elements from atmospheric deposition and organic matter degredation. Limited by Phosphorous.
Hawaiian islands are a great example of this.
Applying the above simple conceptual model of soil/ecosystem development, which nutrients do you expect to be limiting in northern temperate zones, and which in tropical zones? Why?
Tropical zones are probably richer in decomposed organic material because of year round growth.
What is stoichiometry?
Stoichiometry is the balance of elements necessary for a particular ecosystem, it is the constraint on growth.
What general difference is observed between the C:N:P stoichiometry of marine organisms (called the Redfield Ratio) and that of terrestrial plants? What is the reason for the difference?
What general difference is observed globally between the C:N:P stoichiometry of terrestrial plant litter and that of the comparable foliage from which it derives? What is the reason for the difference?
What are the reasons why N is an essential nutrient for plants?
Nitrogen is necessary to make amino acids, which build proteins. Plants also need nitrogen because it determines photosynthetic capacity.
In what forms do plants typically take up N?
N2 -> NH4
What is N-fixation? What is N mineralization? What is denitrification? (Be able to draw the N cycle)
N fixation is the conversion of atmospheric N2 to NH4. It requires abundant energy and P and is inhibited by oxygen because the bacteria performing the task are anaerobic. N mineralization
What are some of the requirements of biological nitrogen fixation?
What are three activities engaged in by humans that alter the amount of Nitrogen that is fixed globally?
addition of fertilizers, burning of fossil fuels, and production of nitrogen fixing legume crops
What are some ecosystem impacts Nitrogen cycle alterations caused by human activities.
algae blooms, acid rain, smog (NO). acid rain will cause Al to be released from clay, which is toxic. Eutriphication reduces diversity and uses up available oxygen in aquativ environments
