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Today’s Outline
Ecology (BIOL 250)
Lecture 9: Decomposition and Nutrient Recyclin g
Announcements
Nutrient Cycling
Nutrient Decom position
Decomposition in terrestrial
ecosystems
Decomposition in aquatic
ecosystems
Nutrient Recycling within an Ecosystem
Nutrient Recycling within a Plant
!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
Nutrient Recycling within a Plant
Rates of Decomposition
!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.
Decomposition in Temperate Forest
Ecosystems
!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.
•Higher environmental temperatures may have also
played a role.
