Ch. 55.4-5 Nutrient Cycling and Restoration

Rate of decompostions

Controlled by temperature, moisture, and nutrient availability

Rapid decomposition

results in relatively low levels of nutrients in the soil. Most nutrients tied up in trees/living organisms

Cold/wet ecosystems store large amounts of undecomposed organic matter (low decomposition rates)

Biogeochemical cycles

AKA nutrient cycles, involve both biotic and abiotic components

Less mobile elements

Phosphorus, potassium, calcium. Cycle locally in terrestrial systems but more in aquatic

Main reservoirs of elements defined by 2 characteristics:

1. whether they contain organic or inorganic matterial

2. whether these materials are directly available for use by organisms.

4 major factors to consider in the cycling of water, carbon, nitrogen, and phosphorus

1. Each chemical’s biological importance

2. forms in which each chemical is available or used by organisms

3. major reservoirs for each chemical

4. Key processes driving movement of each chemical through its cycle

Water cycle processes

moved by evaporation, transpiration, condensation, precipitation,  and movement through surface and ground water

Carbon cycle reservoirs

fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, the atm, and sedimentary rocks

Nitrogen cycle

Main reservoir is the atm. Must be converted by nitrogen-fixing bacteria to be used by plants

Ammonification

Organic nitrogen is converted to NH4+

Denitrification

when microbes convert NO3- back to N2

Phosphorus cycle

Reservoirs: sedimentary rocks or marine origin, soil, the oceans, and organisms. Weathering of rocks releases phosphate

Hubbard Brook Experimental Forest Case Study

Study for nutrient cycling. Constructed dam to monitor loss of water/minerals. Found that 60% of precipitation exits through streams and 40% lost by evapotranspiration. Most cycling of minerals conserved within watershed

Found that vegetation was very in conserving water and nutrients (they cut down all the trees in one section of the water shed).

Restoration ecology

seeks to initiate or speed up the recovery of degraded ecosystems.

two key strategies of restoration

1. bioremediation

2. biological augmentation

Bioremediation

use of organisms to detoxify ecosystems (fungi, plants, prokaryotes etc who take up these toxins and sometimes metabolize them). Ex: uranium spill: bacterium can metabolize it

Biological Augmentation

uses organisms to add essential materials to a degraded ecosystem (nitrogen-fixing plants, mycorrhizal fungi)