Root Foraging for Apatite is
Influenced by N and P Availability
Shan Shan1, Hannah Devens1, Melany
Fisk1, Joel Blum2, Timothy Fahey3, Ruth
Yanai4
1Department of Biology, Miami University; 2Ecology and Evolutionary Biology,
University of Michigan; 3Department of Natural Resource, Cornell University;
4Forest and Natural Resource Management, SUNY ESF

Background
• Roots can respond to a limiting nutrient by
proliferating in localized patches of that nutrient,
defined as “foraging”.
control
core
non-limiting
nutrient
limiting
nutrient

• Aboveground productivity of BEF mature stands
increased in response to P addition.
• High P availability can decrease plant demand for P.
• High N availability can increase plant demand for P.
– P resorption (See et. al., 2015)
– Soil phosphatase activity (Ratliff et. al., 2016)
– Mycorrhizal association
Background

(a) Fine roots forage for P.
(b) High P availability reduces P foraging.
(c) High N availability increases P foraging.
Hypotheses

• 3 mature stands: C7, C8, C9
• Installed ingrowth cores in 2013
– Non-apatite cores: root-free soil
– Apatite cores: root-free soil + apatite
– Apatite: primary mineral P source, Joel Blum
measured apatite-derived P uptake (data not shown)
• 4 fertilization treatment plots, each with 8 pairs of non-
apatite and apatite cores
• Incubated in situ for 2 years
Methods

Control N
P NP

• Cores were extracted after 2 years of incubation.
• Roots were sorted into <2 mm (fine) and >2 mm (coarse), and
scanned.
Methods

• Cores were extracted after 2 years of incubation.
• Roots were sorted into <2 mm (fine) and >2 mm (coarse), and
scanned.
• Fine root length was measured with ImageJ.
Methods

Results
• Roots foraged for P in control plots.
• Roots did not forage for P where P was added.
• N increased fine root length.

• P limitation of aboveground productivity in
northern hardwood forests drives fine roots to
forage for P.
• Elevated P reduces apatite foraging.
• Elevated N increases total root growth, but not
foraging.
Conclusion
We gratefully acknowledge Shinjini Goswami, Jerome Barner,
Jenna Tiller, Bradley Wells and other crews for their help in
sample collection and process.