Light Characteristics of an Urban Forest Canopy
Gabriel DeJong, Calvin College
Species-Specific Comparisons
Objectives
Restoration Project
• Characterize the quantities of photosynthetically active
LAI Decrease in Restoration Plots
radiation (PAR) penetrating a mature urban forest canopy
LAI
• Compare physical attributes of native and invasive plant
species in an urban forest to inform a restoration plan
• Compare LAI’s (leaf area indices) and light intensities in
several plant communities
• Initiate a restoration study and start documenting changes
in the light regime of a forest canopy that is undergoing
restoration
Species
Sugar Maple
Glossy Buckthorn
Common Buckthorn
Highbush Cranberry
Redbud
Bladdernut
Ash
Light Profile
LAIc
1.18
1.16
1.11
0.94
0.8
0.75
0.59
Leaf Area
(cm2)
15684
8476
17108
5832
7190
12949
4090
Volume
(m3)
1.3
3.6
41
1.2
0.7
2.2
0.8
Leaf Area
per Acre
6517
11059
12188
5146
4092
8765
5407
No significant differences were found among plant species in
the Fieldhouse woodlot for either effective LAI and actual
leaf area
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Before
After
1
2
3
4
Plot
Before
After
Buckthorn removal decreased LAI’s significantly in all four
plots, despite the initial differences in forest structure between
the sites
Plant Canopy Comparisons
Average Daily Light
Penetration
Average Daily LAI
Distance from Edge
(m)
AM-PM
Late PM
Below Above LAIB-A
PARB
PARA
PARA -B
0
2.7
2.4
0.3
40.1
57.4
17.3
1
4
2.1
1.9
14
85.2
71.2
6
3.3
2.7
0.6
14.3
67.1
52.8
11
2.4
2.6
-0.2
35.9
65.3
29.4
0
2.7
2.1
0.6
589.9
556.6
33.3
1
3.3
2.2
1.1
25.1
401.3
-376.2
6
2.9
2.9
0
30.5
42.2
-11.7
11
2.9
2.9
0
20.7
16.7
4
• Rhamnus cathartica (Common Buckthorn) and Rhamnus
frangula (Glossy Buckthorn) absorb significant quantities
of PAR on the forest edge (1-6 m in from the drip-line)
• R. cathartica and R. frangula add significantly to the LAI
of the forest edge, but not to the forest interior
• By asserting itself on the western edge, buckthorn seems
to take advantage of the high PAR levels in late afternoon
and evening, transmitting little PAR to under story plant
species
Species or
Community
Gray Dogwood
Sugar Maple
Hawthorn
Common Buckthorn
Glossy Buckthorn
Fieldhouse Woodlot
Young Growth Forest
Preserve
Old Growth Forest
Preserve
LSD0.05
LAI
4
4.6
3.2
2.9
LAI
5
3.7
2.8
2.4
Canopy
Openness
5.9
8.6
11.7
Light
7.04
6.65
30.8
2.4
2.1
15.5
35.9
2.3
2.0
16.0
7.81
2.2
1.9
17.1
6.97
0.6
0.5
3.8
--
• Plant communities exhibited significant
differences among their LAI’s
• Buckthorn was only present underneath
the hawthorn stand, yet sites with lower
LAI’s seemed to restrain buckthorn
establishment
Conclusions
• LAI is a valuable measure of the dynamic light regime in
a plant community, characterizing the quantity of light
(PAR) available for photosynthesis
• While buckthorn seems to thrive in areas with low LAI,
presumably by growing rapidly in response to high levels of
available PAR, it does not completely explain why
buckthorn may become established in one plant community
and not another
•When established, buckthorn stands quench much of the
available PAR, producing a high LAI that could inhibit the
health and survival of under story plant species
• Future studies could consider the effect of light quality on
the establishment of buckthorn in mid- and under-stories of
a forest, or whether buckthorn changes light quality to gain
competitive advantage
T itle:
(Cal vin/Seal /T agline.eps)
Creator:
Adobe Il lustrator(TM ) 7.0
Previ ew:
T his EPS pi cture was not sav ed
with a preview i ncluded i n i t.
Comment:
T his EPS pi cture wil l pri nt to a
PostScript pri nter, but not to