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An outline for a lecture on ecology, specifically focusing on decomposition and nutrient recycling. Topics covered include nutrient cycling, decomposition in terrestrial and aquatic ecosystems, nutrient recycling within a plant, rates of decomposition, and decomposition in temperate forests. The document also discusses the impact of temperature, moisture, and chemical compositions on decomposition rates.
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Today’s Outline Ecology (BIOL 250 ) Lecture 9 : Decomposition and Nutrient Recycling Announcements Nutrient Cycling Nutrient Decomposition Decomposition in terrestrial ecosystems Decomposition in aquatic ecosystems
!As a plant tissue senesces (dies) nutrients are returned to the soil as dead organic matter. !But, plants reabsorb a portion of their nutrients (and water) from senescing tissue, which is stored and reused. "In fall carotinoids and Xanthophylls (yellow and orange) begin to show in tree leaves. "Some plants produce anthocyanins (red and purple) "Some plants contain large quantity of tanins (browns) such as the oaks. !As much as 70 % of nitrogen can be recovered from green leaves as they senesce. "However, dependant on species
!Rate at which nutrients are made available to primary producers is determined largely by rate of mineralization. "Occurs primarily during decomposition. !Rate in terrestrial systems is significantly influenced by temperature, moisture, and chemical compositions.
! Melillo et.al. used litter bags to study decomposition in temperate forests. "Found leaves with higher lignin:nitrogen ratios lost less mass. !Suggested higher N availability in soil might have contributed to higher decomposition rates.
!Nutrient quality of dead organic matter varies widely. "Dead organic matter is between about .5 - 1.5% nitrogen. "The higher the % the higher the nutrient value is for bacteria and fungi.
! Rate at which nutrients are made available to primary producers is determined largely by rate of mineralization. " The transformation of nitrogen (and other nutrients) contained in organic compounds into inorganic (or mineral) forms. !Rate in terrestrial systems is significantly influenced by temperature, moisture, and chemical compositions. ! But, these same decomposers require nitrogen for their growth and reproduction. " Thus when mineralization occurs immobilization also occurs. This is the uptake or assimilation of nitrogen by decomposers.
!Net mineralization rate - difference between the rates of mineralization and immobilization ! This rate will vary over time. "Initially N will decline as soluble compounds are leached out of the plant matter "Immobilization follows as bacteria and fungi obtain outside nitrogen to carry out decomposition. "As carbon quality declines (greater lignin content) mineralization will be greater than decomposition