Cycling can be studied at different scales

Watersheds of northeastern South Island, New Zealand

Arial view of research plots for examining nutrient movement -- North Island, New Zealand

Biogeochemical Cycling: movement of elements within or between ecosystems caused by organisms, by geological, hydrological, and atmospheric forces, and by chemical reactions Elements within a cycle can move as: Solids, Liquids, or Gases The chemical form of an element can vary among physical states or within a physical state (e.g., Nitrogen as NH 4 +, NH 3, N 2 ) Elements involved in cycling can also have different chemical forms (e.g., Carbon as CO 2 (carbon dioxide) or CO (carbon monoxide)

There are two basic terms used in cycling: Pools: the amount of an element within a physical location or component of a cycle (sinks) e.g.: tree, ocean, atmosphere, soil Fluxes: the rate of movement of an element between pools e.g.: evaporation, burning, dissolution of a rock, river carrying materials from land to the ocean

Residence Time The length of time that an atom or molecule of a particular element spends in a particular location or component of a cycle Mean Residence Time Altering cycling rates can alter mean residence times and have the potential to lead to either depletion or pollution Recycle Time

We’ll consider four biogeochemical cycles of elements required by organisms for life Carbon Nitrogen Phosphorus Sulfur

The Carbon Cycle Carbon Forms: CO 2, CO, CH 4, H 2 CO 3, organic matter, CaCO 3

Major pools of the carbon cycle in billions of tons of carbon. The oceans contain the largest pool of carbon.

Recycling rate of H 2 O, O 2 and CO 2 among the atmosphere, hydrosphere, biosphere and lithosphere McKinney and Schoch 2003

Why do we care about carbon cycling?

How many trees are needed to remove the same amount of carbon you release to the atmosphere in one year? My house: need to plant 37 trees and let them grow for 40 years Go to: to find your carbon debt!

The Nitrogen Cycle

Nitrogen Fixation The nodules on the roots of this bean plant contain bacteria called Rhizobium that help convert nitrogen in the soil to a form the plant can utilize.

The Nitrogen Cycle

What’s so important about Nitrogen cycling? essential nutrient (fertilizers, growing legumes as crops) – changes in native species composition of ecosystem atmospheric pollutent (burning fuels) groundwater pollutent

The Phosphorus Cycle The phosphorus cycle is much slower than that of C or N

The Sulfur Cycle

Dimethylsulfide (DMS) is released by phytoplankton, is then oxidized to sulfur dioxide and ultimately sulfate in the atmosphere. Sulfate can cause clouds to form by having water droplets condense on it.

Some key points: Elements move! Among spheres, spatially and temporally Cycling occurs at local to global scales Biogeochemical cycles have 2 basic parts: pools and fluxes Elements are recycled among the biosphere, atmosphere, lithosphere and hydrosphere Cycles of each element differ (chemistry, rates, pools, fluxes, interactions); each cycle can influence other cycles Cycling is important because it can affect many other aspects of the environment and the quality of our lives