Evaluation of Light Intensity under a Salt Marsh ...
Evaluation of Light Intensity under a Salt Marsh Boardwalk Utilizing Two Different Materials Kari St.Laurent, Ph.D.1 Michael G. Mensinger1 Delaware Estuary Science & Environmental Summit January 25th, 2017
1Delaware
National Estuarine Research Reserve
Delaware National Estuarine Research Reserve “…serves to preserve and manage the natural resources within the Reserve as a place for research, provide education and outreach programs that promote better understanding of Delaware’s estuarine and coastal areas, and promote informed coastal decision-making.”
Increase access to nature! St. Jones Boardwalk • Trail ~ 2 miles • Boardwalk ~0.25 miles
Increase access to nature! St. Jones Boardwalk • Built ~1996 • Major redo 2011
Access to nature explained ~8% of the variance in community cohesion, which was directly and indirectly related to reduced crime (Weinstein et al., 2015 BioScience)
Boardwalks reduce foot traffic, increase access, BUT Installation
causes disturbance Pressure-treated wood (pre-2004) Chromated-copper
arsenic treated wood Maximum Cu and As after 5 years, decline by 11 years Affected area ~1 ft of structure (Lebow and Foster, 2010) Reduce
sunlight to underlying vegetation Bethany Beach, Wikimedia
Research Question Problem: Boardwalks can locally limit light to the underlying vegetation.
Ho: Implementing light penetrating panels will allow more light. Logan et al., 2015
Light Penetrating Panels Open-Space ThruFlow uv-resistent Non-mircobial No treatment needed ~12%
~38%
Light Penetrating Panels Open-Space
Wooden
Plastic
Open space area
11.8%
38.8%
Cost per section
$95
$485
5X more expensive… Long-term maintenance still an on-going test!
~12%
~38%
SJ MET Station
Light intensity data logger
Site 4
Site 3
Site 2
Site 1
Which one of these are not the same?
Probability Density Functions >0 to removed night Mann‐Whitney‐Wilcoxon, Kolmogorov‐Smirnov, Anderson‐Darling, Pearson Chi‐Square, Student’s T Control
Obviously different Wait a second…. Also different!
Site.2
Control Site.2
Reject
Site.3
Site.3
Reject
Reject
Site.4
Reject
Accept
Site.4 Reject
Site 2 and 4 are the same But site 3 is different….
Not Conclusive…. If panel openness controls light penetration, all should be the same
Not Conclusive…. If panel openness controls light penetration, all should be the same
Sunlight is a function of angle and penetration
4
3
Control has a different angle to the sun 10:00 AM
3:00 PM
10‐Aug‐16
ΔA
ΔB
ΔA
ΔB
Control
92
‐111
‐40
‐185
Site 2
‐5
158
‐97
80
Site 3
‐9
154
‐92
75
Site 4
5
172
‐88
92
Control has a different angle to the sun 10:00 AM
Higher PAR under N-S oriented docks compared to E-W (Alexander, 2012)
3:00 PM
10‐Aug‐16
ΔA
ΔB
ΔA
ΔB
Control
92
‐111
‐40
‐185
Site 2
‐5
158
‐97
80
Site 3
‐9
154
‐92
75
Site 4
5
172
‐88
92
Let’s take a closer look…
Cannot tell if material or position Through panels Under boardwalk Under boardwalk
Redefine the Growing Season Length lumens/ft2 In June, the plastic panels received 3.5 to 5.8X more light intensity than the control. In January, the plastic panels received 2.1 to 2.8X more light intensity.
Redefine the Growing Season Length lumens/ft2 In June, the plastic panels received 3.5 to 5.8X more light intensity than the control. In January, the plastic panels received 2.1 to 2.8X more light intensity.
Summer light season length (as % of calendar year) Control
10.8 ± 1.4%
Site 2
18.3 ± 2.4%
Site 3
19.1 ± 3.7%
Site 4
19.4 ± 2.4%
# days exceeding summer mean /365 days *2011-2015
Next steps: New Control Control Background Site 4 Site 3
Site 2
Control
Maryland boardwalk study Spartina alterniflora replaced Spartina patens, suggesting S.alt more shade tolerant (Vasilas et al., 2011)
Conclusions…To Be Continued!
Goal: decrease marsh impact Light-penetrating: decrease localized light limitations? Panels had more light intensity, especially during fall and spring On-going monitoring to determine: material or sun angle
Acknowledgments and Questions
Michael G. Mensinger, DNERR Jennifer Holmes, Calvary Christian High School Charlie Bishop, DNERR
National Estuarine Research Reserve System
Not a question of intensity…but exposure How does the light intensity under the boardwalk compare to: Desk Light
Direct Daylight
Control
70.2%
0.2%
Site.2
82.6%
8.4%
Site.3
78.3%
4.8%
Site.4
83.6%
8.3%
Probability Density Functions >0 to removed night Obviously different
Mann‐Whitney‐Wilcoxon, Kolmogorov‐Smirnov, Anderson‐Darling, Pearson Chi‐Square
Wait a second…. Also different!
Control Control
Site.2
Site.2
Reject
Site.3
Site.3
Reject
Reject
Site.4
Reject
Reject*
Site.4 Reject
*Different via Student’s T-test
Season: Winter
Site 2 and 4 are the same
Winter: Mann‐Whitney‐Wilcoxon Control Control
Site.2
Site.2
Reject
Site.3
Reject
Reject
Site.4
Reject
Accept
But site 3 is different….
Site.3 Site.4 Reject
“peak light” varied in time, shape, and size
11:45 am
11:30 am
12:15 pm
10:45am
Redefine the Growing Season Length Summer light season length (as % of calendar year) Control
10.8 ± 1.4%
7.6 to 8.7% of a calendar year longer Site 2
18.3 ± 2.4%
Site 3
19.1 ± 3.7%
Site 4
19.4 ± 2.4%
# days exceeding summer mean /365 days *2011-2015
1Delaware
National Estuarine Research Reserve
Delaware National Estuarine Research Reserve “…serves to preserve and manage the natural resources within the Reserve as a place for research, provide education and outreach programs that promote better understanding of Delaware’s estuarine and coastal areas, and promote informed coastal decision-making.”
Increase access to nature! St. Jones Boardwalk • Trail ~ 2 miles • Boardwalk ~0.25 miles
Increase access to nature! St. Jones Boardwalk • Built ~1996 • Major redo 2011
Access to nature explained ~8% of the variance in community cohesion, which was directly and indirectly related to reduced crime (Weinstein et al., 2015 BioScience)
Boardwalks reduce foot traffic, increase access, BUT Installation
causes disturbance Pressure-treated wood (pre-2004) Chromated-copper
arsenic treated wood Maximum Cu and As after 5 years, decline by 11 years Affected area ~1 ft of structure (Lebow and Foster, 2010) Reduce
sunlight to underlying vegetation Bethany Beach, Wikimedia
Research Question Problem: Boardwalks can locally limit light to the underlying vegetation.
Ho: Implementing light penetrating panels will allow more light. Logan et al., 2015
Light Penetrating Panels Open-Space ThruFlow uv-resistent Non-mircobial No treatment needed ~12%
~38%
Light Penetrating Panels Open-Space
Wooden
Plastic
Open space area
11.8%
38.8%
Cost per section
$95
$485
5X more expensive… Long-term maintenance still an on-going test!
~12%
~38%
SJ MET Station
Light intensity data logger
Site 4
Site 3
Site 2
Site 1
Which one of these are not the same?
Probability Density Functions >0 to removed night Mann‐Whitney‐Wilcoxon, Kolmogorov‐Smirnov, Anderson‐Darling, Pearson Chi‐Square, Student’s T Control
Obviously different Wait a second…. Also different!
Site.2
Control Site.2
Reject
Site.3
Site.3
Reject
Reject
Site.4
Reject
Accept
Site.4 Reject
Site 2 and 4 are the same But site 3 is different….
Not Conclusive…. If panel openness controls light penetration, all should be the same
Not Conclusive…. If panel openness controls light penetration, all should be the same
Sunlight is a function of angle and penetration
4
3
Control has a different angle to the sun 10:00 AM
3:00 PM
10‐Aug‐16
ΔA
ΔB
ΔA
ΔB
Control
92
‐111
‐40
‐185
Site 2
‐5
158
‐97
80
Site 3
‐9
154
‐92
75
Site 4
5
172
‐88
92
Control has a different angle to the sun 10:00 AM
Higher PAR under N-S oriented docks compared to E-W (Alexander, 2012)
3:00 PM
10‐Aug‐16
ΔA
ΔB
ΔA
ΔB
Control
92
‐111
‐40
‐185
Site 2
‐5
158
‐97
80
Site 3
‐9
154
‐92
75
Site 4
5
172
‐88
92
Let’s take a closer look…
Cannot tell if material or position Through panels Under boardwalk Under boardwalk
Redefine the Growing Season Length lumens/ft2 In June, the plastic panels received 3.5 to 5.8X more light intensity than the control. In January, the plastic panels received 2.1 to 2.8X more light intensity.
Redefine the Growing Season Length lumens/ft2 In June, the plastic panels received 3.5 to 5.8X more light intensity than the control. In January, the plastic panels received 2.1 to 2.8X more light intensity.
Summer light season length (as % of calendar year) Control
10.8 ± 1.4%
Site 2
18.3 ± 2.4%
Site 3
19.1 ± 3.7%
Site 4
19.4 ± 2.4%
# days exceeding summer mean /365 days *2011-2015
Next steps: New Control Control Background Site 4 Site 3
Site 2
Control
Maryland boardwalk study Spartina alterniflora replaced Spartina patens, suggesting S.alt more shade tolerant (Vasilas et al., 2011)
Conclusions…To Be Continued!
Goal: decrease marsh impact Light-penetrating: decrease localized light limitations? Panels had more light intensity, especially during fall and spring On-going monitoring to determine: material or sun angle
Acknowledgments and Questions
Michael G. Mensinger, DNERR Jennifer Holmes, Calvary Christian High School Charlie Bishop, DNERR
National Estuarine Research Reserve System
Not a question of intensity…but exposure How does the light intensity under the boardwalk compare to: Desk Light
Direct Daylight
Control
70.2%
0.2%
Site.2
82.6%
8.4%
Site.3
78.3%
4.8%
Site.4
83.6%
8.3%
Probability Density Functions >0 to removed night Obviously different
Mann‐Whitney‐Wilcoxon, Kolmogorov‐Smirnov, Anderson‐Darling, Pearson Chi‐Square
Wait a second…. Also different!
Control Control
Site.2
Site.2
Reject
Site.3
Site.3
Reject
Reject
Site.4
Reject
Reject*
Site.4 Reject
*Different via Student’s T-test
Season: Winter
Site 2 and 4 are the same
Winter: Mann‐Whitney‐Wilcoxon Control Control
Site.2
Site.2
Reject
Site.3
Reject
Reject
Site.4
Reject
Accept
But site 3 is different….
Site.3 Site.4 Reject
“peak light” varied in time, shape, and size
11:45 am
11:30 am
12:15 pm
10:45am
Redefine the Growing Season Length Summer light season length (as % of calendar year) Control
10.8 ± 1.4%
7.6 to 8.7% of a calendar year longer Site 2
18.3 ± 2.4%
Site 3
19.1 ± 3.7%
Site 4
19.4 ± 2.4%
# days exceeding summer mean /365 days *2011-2015
