EARTHSS 164 Lecture Notes - Lecture 16: Redfield Ratio, Crich, Biomolecule

• School: UC-Irvine
• Department: Earth System Science
• Course: EARTHSS 164
• Professor: Professor Allison

Document Summary

The ratios of chemical elements in ecological systems or processes. Ratios of available nutrients in seawater matched plankton ratio. Suggests organisms manipulate nutrient supplies to match demand. Can nitrogen fixate if limited by nitrogen. Differs from element ratios in earth"s crust and atmosphere. Leaf c:n ~ 50, wood c:n >100. P content depends on the presence of bone. May have cell walls with n-rich peptidoglycans. When nutrient demand exceeds supply = nutrient limitation. Nutrient limited plants have higher nutrient efficiency (nue) [b]/[n] = biomass/ nutrient concentration in annual litterfall. The scarcest element (relative to organismal demand) limits growth. Degree of limitation depends on stoichiometric flexibility. Sometimes two or more resources are equally limiting. At ecosystem scale, different plant may be limited by different resources. Strategy is to hold on to scarce resources. Plants can resorb (rcapture) nutrients before it dies. More time to fix c with a given amount of nutrients. Nutrient demand and limitation depend on organism stoichiometry.