This document summarizes a study that examined how the physical, chemical, and metabolic characteristics of sugar maple leaves vary with their depth in the tree crown and with the addition of nutrients. The study found that foliar nitrogen and chlorophyll increased deeper in the crown and with nitrogen addition, while foliar phosphorus increased with phosphorus addition. The study concludes that most leaves are shaded rather than just "sun" or "shade" leaves, and that examining the vertical gradient in a tree crown can help reveal relationships between leaf characteristics and nutrients.

1. Sugar maple leaf characteristics
vary with depth in the crown and
nutrient addition
Alex Young, Rakesh Minocha, Ruth Yanai

2. Does it matter where you get
your leaf samples?

3. Leaves are amazing.
Most leaves are shaded.
“sun” leaves
“shade” leaves

4. 12 sugar maples
3 mature stands
~5 branches per tree

5. Physical characteristics
● Leaf area, leaf mass, twig length, twig mass
Chemical characteristics
● N, P, Ca, Mg, Al, Mn, B
Metabolic characteristics
● Chlorophyll: A, B, carotenoids
● Amino acids: GABA, Glu, Arg, Ala, Val
● Polyamines: Putrescine, Spermidine, Spermine
Crown depth
N response
P response

6. Foliar N increased with depth, and with N addition
Per unit mass Per unit area

7. Foliar P increased with P addition
Per unit mass Per unit area

8. Chlorophyll was higher throughout crown with N
Per unit mass Per unit area

9. Take-away messages
The majority of the leaves in the world are shaded,
Not just “sun” and “shade” leaves, but gradient
N is important for leaves
Examining the vertical gradient can help reveal novel relationships
Acknowledgements
•P.I.’s Ruth Yanai, Melany Fisk, Tim
Fahey
•Drs. Rakesh Minocha, Stephanie Long
•Drs. John Drake, Danilo Fernando
•Yanai B9 Forest ecology lab
•Summer 2017 and 2018 crew
•NSF-REU “Canopy Herbivory and
Tardigrades”