The effect of nitrogen on
mycorrhizal colonization associated
with Populus grandidentata
Megan McLin
Bartlett Experimental Forest
MELNHE Project

Bartlett, NH

The MELHNE project
-studying N and P acquisition and limitation through a
series of nutrient manipulations in northern hardwood
forests

Mycorrhizal Fungi

Background: Mycorrhiza the root
fungus
• Symbiotic Fungi
• Crucial link between root system and
soil
• Creates surface area
• Releases enzymes in soil to
to break down nutrients
Egli, S.; Brunner, I. (2011): Mykorrhiza. Eine faszinierende
Lebensgemeinschaft im Wald. 3. Aufl. Merkbl. Prax. 35 8 S

Nitrogen Deposition

Nitrogen Deposition: Questions?
• Will nitrogen exceed the nutritional needs of the
ecosystem causing a decrease in mycorrhizal
abundance?
• Studies have shown that ecosystems have been
susceptible to decline in response to nitrogen
deposition. (Bevege, 102)

Arbuscular vs Ecto Mycorrhizae

Arbuscular vs Ecto Mycorrhizae
• Ecto can be seen within the naked eye or
dissecting microscope 10x-50x magnification
• Arbuscular can be seen with high
magnification 200x magnification
• In spite of their profound morphological and
taxonomic differences,some of the effects of
AM fungi and ECM fungi on host physiology
are similar (Tinker, Jones & Durall,1992).

Bigtooth Aspen

Methods
• Mycorrhizal colonization will be measured by directly
collecting Populus grandidentata roots. Both AM and
EM mycorrhizal colonization will be quantified on each
root with a microscope and staining techniques.

Field Methods
• The collection of the roots came from
nitrogen plot.
• Three treatment trees and three control trees
were sampled
• Control trees were sampled outside buffer
and also on same slope
• Organic horizon depth was used to root
trace

Field Methods cont.
• Tree DBH was taken for trees as well as
nearby neighbors
• Four Cardinal directions for root tracing
• Tree roots were placed in corresponding test
tubes

Lab Methods: Ectomycorrhizal
• Roots were separated from soil.
• Cut into 5 mm sections
• Examined under dissecting microscope
• The portion of ectomycorrhizal root tips were
calculated

Lab Methods: Ectomycorrhizal
Gridline intersect method
(Figure 4.5A in Brundrett et al. 1996).

Lab Methods: Arbuscular

Figure 4.4B in Brundrett et al. 1996).
Figure 4.4B in Brundrett et al. 1996).

Results

Data
Control Ecto
Quantifying
Treatment Ecto
Quantifying

Data cont.

Conclusion
• Nitrogen decreases mycorrhizal colonization
• Control showed more mycorrhizal activity
• Treatment trees showed more DSE hyphae
• Different staining technique

Future Work
• Continue work with senior thesis
• Molecular work
• Trying different staining techniques

Cited sources
Bevege DI. 1968. A rapid technique for
clearing tannins and staining intact roots
for detection of mycorrhizas caused by
Endogone spp. and some records of
infection in Australasian plants.
Transactions of the British Mycological
Society 51: 808- 810.
Cripps, C. L. 2001. Mycorrhizae of Aspen
Forests: ecology and potential
application. In: Sustaining Aspen in
Western Landscapes: Proceedings of the
Symposium on Western Aspen Forests,
Grand Junction, CO, June 2000. pp. 285-
298.

Acknowledgments
The Shoestring crew
Ruth Yanai
Craig See
Adam Wild
Franklin Diggs
Tougaloo College