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Resorption Trees retranslocate elements from senescing
leaves Helps establish nutrient balance in trees Nutrient conservation and recycling
Questions What can green leaf concentrations tell us about
limitation?
Can we see N and P interactions in resorption?
ARE WE THERE YET?!
What do we see? N resorption
efficiency correlated with green leaf P o NOT with
green leaf N! P resorption
efficiency correlated with green leaf N o NOT with
green leaf P!
2014 data in C2
Field Methods
Green leaves in August Leaf litter in October Eight stands
o Bartlett • C4, C6, C8, C9
o Hubbard Brook • HBM, HBO
o Jeffers Brook• JBM, JBO
Three species o Beech (all stands) o Red maple (mid-aged) o Sugar maple (old)
Resorption efficiency The percent difference between green leaf and
litter concentrations of an element
Summary Green leaves
o Green leaf N lower when P added o Green leaf P not affected by N treatment o N:P ratios indicate that trees in control plots are P-limited or
co-limited; adding a nutrient shifts limitation Leaf litter
o Litter N higher with nitrogen fertilization, with or without P o Litter P higher with phosphorus added, with or without N
Resorption efficiency o Nitrogen – no effect of treatment! o Phosphorus accumulation = negative resorption efficiency!