Lecture Seven - Biogeochemical cycles I

Question 1

What is biogeochemistry?

Answer 1

Science deals with “controls on the concentration and cycling of chemical elements in and above the Earth’s crust by the synthesis, death and decomposistion of organisms, most of which capture their energy from the sun” (Gorhan, 1991).

OR

The cycling of chemical element sbetween biotic and abiotic environments.

Question 2

What are some of the major processes on Earth which are dependent on biogeochemical cycles?

Answer 2

Climate change.

Eutrophication - too many nutrients.

Land surface transformation - loss of forests or habitat.

Agricultrue.

Biodiversity.

Question 3

Define:

Macro and micro nutrients, Pools, Resivoirs, Input, Sources, Output, Sinks, Fluxes and Residence time.

Answer 3

Macronutrients - chemical elements required in alrge amounts for growth. E.g. C, N, S and P.

Micronutrients - chemical elements required in small amounts for growth. E.g. Zn, Ca, Na, Mo.

Pools - ecosystem pools are reservoirs (sources of a resource). E.g. plant biomass pool, soil organic C pool, soil mineral C pool, microbial biomass pool etc.

Input/sources, output/sinks - where the resources come in and out of a system.

Fluxes - Rate of element transfer between pools. Can be measured directly or calculated indirectly.

Question 4

What is a general model of nutrient cycling?

Answer 4

Question 5

Define libile and recalcitrant.

Answer 5

Labile = readily undergoing change or breakdown.

Recalcitrant = does not readily undergo change or breakdown.

Question 6

Draw the carbon cycle.

Answer 6

Question 7

Show which processes in the carbon cycle are fast and which are slow.

Answer 7

Question 8

What role do decomposers have in the carbon cycle?

Answer 8

Cellulose and toher components of plant cell walls resist decomposition. Organisms that can degrade these products are important in the C cycle.

Coprophilous dung fungi and specialized decomposers.

Complex succession.