Does soil nitrogen control phosphorus resorption in a co-limited system?

Craig See

SUNY-ESF

Photo: USFS

Before the leaves fall. . .

•Nutrients move from leaves to stem tissues

•Resorption Efficiency = percent of leaf nutrients resorbed before abscission

•Resorption efficiencies vary

•Critical for plant nutrient conservation

Ryan and Bormann 1982

NITROGEN PHOSPHORUS

Single element hypothesis:

The resorption of a nutrient should be higher when that nutrient is in low supply

Soil phosphorus

ph

osp

ho

rus

reso

rpti

on

ph

osp

ho

rus

reso

rpti

on

ph

osp

ho

rus

reso

rpti

on

Soil phosphorus

Soil phosphorus

Multiple element hypothesis:

In a co-limited system, the resorption of an element should depend on the relative availability

of all limiting elements.

Soil Nitrogen

ph

osp

ho

rus

reso

rpti

on

METHODS• 18 30x30m plots in 6

stands at BEF• 1 quantitative soil pit

per plot• 5 litter baskets• Resorption data for up

to 5 trees/species/plot

Bartlett Experimental Forest

Methods

• Stands Sampled 2009, 2010

• Fresh leaves sampled August, litter sampled in October

RE=(G-L)/G

RE=Resorption EfficiencyG=Green leaf nutrient concentrationL=Litter nutrient concentration

Soil Phosphorus (mg/m2)

0 10 20 30 40 50 60

Ph

osp

ho

rus R

eso

rptio

n E

ffic

ien

cy

0.0

0.2

0.4

0.6

0.8

1.0

No detectable correlation between soil P and P resorption for any of the species studied.

Total soil N was positively correlated with P resorption efficiency in 4 of 6 species:

American beech (p<0.01)yellow birch(p=0.04)white birch (p=0.05)sugar maple (p=0.07)

Soil Nitrogen (mg/m2)

)

100 200 300 400 500 600

Ph

os

po

ru

s R

es

orp

tio

n E

ffic

ien

cy

0.3

0.4

0.5

0.6

0.7

0.8

0.9

BEFC1

BEFC2

BEFC4

BEFC6

BEFC8

BEFC9

Soil N (mg/m2)

200 250 300 350 400 450 500

Ph

osp

ho

rus R

eso

rpti

on

Eff

ecie

ncy

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

R2= 0.89P<0.01

Possible mechanism

Phospholipases, nucleases cost N (and C) to produce…

Conclusions

• P resorption correlates positively with soil N, but not with P.

• Relationship is stronger at the community level, when weighted by the species composition of litterfall.

Future research: Post-fertilization resampling

Thank you!

Ruth Yanai

Melany Fisk

Matt Vadebonceour

Shoestring Crew