Nutrient cycling & Ecosystem Health READINGS for this lecture series: KREBS chap 27. Ecosystem Metabolism III: Nutrient Cycles KREBS chap 28. Ecosystem Health: Human Impacts; Pp 590 – 600 WEB Downloads

NUTRIENT CYCLING Energy – 1-way flow - eventually gets “lost” Nutrients – cycle Organic (living organisms) Inorganic (rocks, air, water) assimilation mineralization

Human activity

1. Biochemical cycles: Redistribution within an individual organism This really is r- and K-selection from first term 2. Biogeochemical cycles: Exchange within an ecosystem N, P - rapid exchange Ca - long if stored in long-lived tree tissue 3. Geochemical cycles: Exchange of chemicals between ecosystems Nutrients and dust CO 2, SO 2, NO x Three main types of cycles:

1. Biochemical cycles: Redistribution within an individual organism This really is r- and K-selection from first term 2. Biogeochemical cycles: Exchange within an ecosystem N, P - rapid exchange Ca - long if stored in long-lived tree tissue 3. Geochemical cycles: Exchange of chemicals between ecosystems Nutrients and dust CO 2, SO 2, NO x Three main types of cycles:

1. Biochemical cycles: Redistribution within an individual organism This really is r- and K-selection from first term 2. Biogeochemical cycles: Exchange within an ecosystem N, P - rapid exchange Ca - long if stored in long-lived tree tissue 3. Geochemical cycles: Exchange of chemicals between ecosystems Nutrients and dust CO 2, SO 2, NO x Three main types of cycles:

Krebs Fig ; p573 SULPHUR CYCLE

Krebs Fig. 28.8; p591 CARBON CYCLE respiration photosynthesis

Krebs Fig ; p579 NITROGEN CYCLE

78% of air is N 2

These figures have: All sorts of rates of transfer We can compare between systems More interesting: What influences the rates? What are the impacts of altering the rates?

These figures have: All sorts of rates of transfer We can compare between systems More interesting: What influences the rates? e.g. forms of nutrients, types of organisms What are the impacts of altering the rates? e.g. disturbance, pollution, etc.

Compartment Models Quantitative descriptions of storage and movement of nutrients among different compartments of an ecosystem “Coarse” – few broad compartments e.g. plants, herbivores “Fine” – many detailed compartments e.g. separate species

Compartment Models POOL – “the quantity of a particular nutrient in a compartment” FLUX – “the quantity moving from one pool to another per unit time” TURNOVER TIME – “the time required for movement of an amount of nutrient equal to the quantity in the pool” (POOL/FLUX)

Krebs Fig p562 Phosphorus cycle in a lake (simplified) Turnover time (water): 9.5 (pool) /152 (flux) = 0.06 day

NUTRIENT PUMP Any biotic or abiotic mechanism responsible for continuous flux of nutrients through an ecosystem Biotic – tree roots, sea birds, Pacific salmon Abiotic – lake overturn, ocean upwelling

Nutrient pump (Terrestrial) Mycorrhizae

Soil micelles “CEC” Cation Exchange Capacity

Marine ecosystem

Nutrient pumps (Marine) Microbial loop Upwelling