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Determining How Soil Amendments Enhance the Recovery
of Ammophila breviligulata Following Dune Die-Off Events in
Coastal New England
Gregg E. Moore,*David M. Burdick, and Andrew R. Payne
Jackson Estuarine Laboratory
School of Marine Sciences and Ocean Engineering
University of New Hampshire
Durham, NH 03824, U.S.A.
ABSTRACT
Moore, G.E.; Burdick, D.M., and Payne, A.R., 2020. Determining how soil amendments enhance the recovery of
Ammophila breviligulata following dune die-off events in coastal New England. Journal of Coastal Research, 36(1), 88–
93. Coconut Creek (Florida), ISSN 0749-0208.
Coastal dunes are valued for habitat provision and flood protection. The dominant dune plant in New England, American
beachgrass (Ammophila breviligulata) stabilizes dunes by trapping sand and slowing erosion. The system’s natural
mechanism to stabilize sediment and protect coasts from erosion may be threatened by die-off, a rapidly spreading blight
affecting coastal dunes from Maine to Virginia. To determine whether soil amendments could help mitigate die-off and
aid recovery, fertilizer and lime were applied to dunes at three sites that had recently been defoliated by die-off and
subsequently replanted. The limeþfertilizer treatment resulted in a significantly greater percentage of live plants and
percentage of cover of A. breviligulata, as well as greater total plant cover. The combined application of lime and fertilizer
may hasten recovery from die-off and improve restoration success in the region.
ADDITIONAL INDEX WORDS: Nutrient addition, coastal resilience, lime, soil pH, restoration, beachgrass.
INTRODUCTION
Sand dunes are increasingly important to coastal resilience
as sea levels rise and powerful storms become more frequent
because of global warming (Del Genio, Mao-Sung, and Jonas,
2007). Low-lying coastal zones are some of the most heavily
populated areas worldwide (McGranahan, Balk, and Anderson,
2007), and projected sea-level rise of up to 1.9 m by 2100
(Vermeer and Rahmstorf, 2009) may cause significant dis-
placement and property damage. Although dunes are associ-
ated with many ecosystem services such as habitat provision,
water regulation, and aesthetics (Everard, Jones, and Watts,
2010), their ability to attenuate flooding and reduce storm
damage is arguably the most important to coastal property
owners (Sigren et al., 2018). Native plants help maintain this
service by stabilizing dunes through root and rhizome growth
(Sigren, Figlus, and Armitage, 2014; Silva et al., 2016). Plant
shoots also help to trap sand blown by wind and were found to
play the key role in controlling maximum dune height (Dura
´n
and Moore, 2013). In New England, Ammophila breviligulata
(American beachgrass) is the most common dune plant (Dunlop
and Crow, 1985; Godfrey, 1977), but extensive die-off of A.
breviligulata along the New Hampshire seacoast and North
Shore of Massachusetts has raised concerns over the potential
loss of productivity and dune stability.
Die-off of A. breviligulata and other dune plants has been
well documented (Bourdreau and Houle, 2001; Seliskar and
Huettel, 1993). In Delaware, Seliskar and Huettel (1993)
showed large areas of dunes that were nearly devoid of
vegetation and identified parasitic nematodes as the cause.
However, a more recent genomic study suggests die-off in some
New England dunes results from a combination of nematode
and fungal infection (G. Moore, unpublished data). Because
dunes are generally nutrient-deficient systems, fertilizer
application may increase productivity of A. breviligulata
(Boudreau and Houle, 2001; Day et al., 2004; Seliskar, 1995)
and make it more resistant to infection. While A. breviligulata
may benefit from fertilization in terms of total stem density and
number (Day et al., 2004), overall plant diversity may decline
as a result of chronic fertilization treatments (Day et al., 2018).
A study in Delaware also found that dune soil was acidic in die-
off areas and that the application of lime to increase pH
resulted in greater A. breviligulata survival (Seliskar, 1995).
Seliskar’s (1995) work in the mid-Atlantic warranted an
examination of whether fertilizer and lime addition or their
combination would have similar benefits to A. breviligulata and
other dune plants in New England. A field experiment was
conducted to determine whether these soil amendments could
enhance recovery of A. breviligulata in replanted areas
following a die-off event.
METHODS
The effects of fertilizer and lime were examined on dune
plant communities at three sites on the northern end of Plum
Island, Massachusetts: Reservation Terrace (42848051.900 N,
70848047.800 W), Penny Lane (42848036.000 N, 70848034.200 W),
and Temple Blvd (42847028.500 N, 70848028.000 W) (Figure 1). The
three sites were selected because of recent evidence of die-off
(e.g., extensive areas of rapid defoliation spreading in a radial
DOI: 10.2112/JCOASTRES-D-19-00026.1 received 8 March 2019;
accepted in revision 12 June 2019; corrected proofs received
4 September 2019; published pre-print online 23 September 2019.
*Corresponding author: gregg.moore@unh.edu
Ó
Coastal Education and Research Foundation, Inc. 2020
Coconut Creek, Florida January 2020Journal of Coastal Research 36 1 88–93
pattern outward across the dune over one growing season).
Each of these recently barren areas were hand-planted with A.
breviligulata at 30 cm centers in spring 2017 with peat moss
and fertilizer. As documented by others in the region (Dunlop
and Crow, 1985), surrounding vegetated areas of the dune
contained typical native dune vegetation, primarily comprising
A. breviligulata with scattered seaside goldenrod (Solidago
sempervirens), beach pea (Lathyrus japonicus), seabeach
knotweed (Lechea maritima), jointweed (Polygonella articula-
ta), sea rocket (Cakile edentula), and beach clotbur (Xanthium
echinatum), whereas beach heather (Hudsonia tomentosa)was
present at only the Temple Blvd site (see supplemental
material for percentage of cover of all species present).
Experimental Design
A randomized block design was used for the experiment with
three sites (blocks) comprising four treatments: (1) control (no
amendments), (2) lime, (3) fertilizer, and (4) limeþfertilizer
(Figure 2). The plot size was 16 m
2
, with four treatment
replicates per site. A commercially available slow release
fertilizer (OsmocoteeN14-P14-K14) was applied by hand in
June 2017 at the rate of 720 mL or ’765 g per plot (67 kg N/ha,
29 kg P/ha); pulverized Dolomitic Limestone (21.6% Ca, 10.0%
Mg), hereafter referred to as lime, was spread using a sieve at a
rate of 1.79 kg per plot (1120 kg/ha) (Seliskar, 1995). Fertilizer
and lime were partially mixed into the sand after application to
limit transport by wind or rain.
Soil pH
A 5-cm soil core was taken from the center of each plot about
3 weeks after soil amendments were applied to assess the effect
of lime on soil pH. A 20-mL subsample of the core was mixed
with 10-mL deionized water. The mixture was allowed to sit for
1 hour before pH was analyzed using a Thermo Scientific 5-Star
pH meter outfitted with a temperature-compensated Ross
sureflow triode probe calibrated prior to use.
Plant Assessment
Plants were assessed for percentage of cover, percentage of
live plants, plant height, and number of reproductive shoots in
late summer/fall 2017 and 2018 at Penny Lane and Temple
Blvd. The entire experimental plot at Reservation Terrace was
lost during the winter because of an extreme erosion event and
therefore was assessed only in 2017. To use data from all three
study areas over the full period of the study, the average of the
2017–18 data from Penny Lane and Temple Blvd was
compared with the 2017 data from Reservation Terrace. Yearly
data for each of the three sites are provided in the online
supplemental material. To assess plant responses, subsamples
of each plot were selected haphazardly by tossing a weighted
flag a total of three times per treatment plot. The weighted flag
served as the center of the vegetation sampling quadrat, which
was consistently oriented parallel to the plot boundaries. If the
quadrat was within 0.5 m of the plot edge once centered on the
weighted flag, it was flipped over once toward the center of the
plot to limit edge effects. If the quadrat overlapped with
another quadrat, a new sampling location was determined
using the same haphazard method (i.e. tossing a weighted flag).
Within each 0.5-m
2
quadrat, the percentage of cover of each
species was determined using visual estimation, and the
number of live and dead A. breviligulata plants were counted.
Among the live A. breviligulata, plant height was determined
by measuring the longest leaves of the tallest three individuals
(excluding reproductive shoots), and the number of reproduc-
tive shoots was recorded.
Data Analysis
Species richness was determined as the total number of
species present in each plot. The Shannon-Weiner index was
used to determine species diversity from the percentage of
cover data (proportion of plant area intercepting light). The
percentage of live plants was calculated by dividing the number
of live plants by the total number of plants3100. All data were
analyzed using two-way ANOVA in JMPePro 14 Statistical
Analysis Software. Differences between treatments were
tested using Fisher’s Protected LSD Test. The Shapiro-Wilk
test was used to determine whether residuals met the
assumption of normal distribution. When assumptions were
not met, data were arcsine transformed (Ammophila percent-
age of cover and percentage of live Ammophila)orlog
transformed (total percentage of cover).
Figure 1. Map of the study sites on the northern end of Plum Island,
spanning the coastal municipalities of Newbury and Newburyport, Massa-
chusetts.
Figure 2. Grids showing randomized experimental treatments at each site.
C¼control, L¼lime, F¼fertilizer, LþF¼lime and fertilizer.
Journal of Coastal Research, Vol. 36, No. 1, 2020
Recovery of Ammophila breviligulata 89
RESULTS
Lime application resulted in higher soil pH, which ranged
from 5.2 to 7.2 in controls. Plots treated with lime had a soil
pH approximately 0.5 units higher than controls and
fertilizer-only plots (Figure 3). The effect of lime on soil pH
was statistically significant (p,0.001) as well as the effect of
site (p,0.0001), with the highest pH measured at Penny
Lane. The interaction between treatment and site was not
significant; the buffering effect of the lime was similar across
all three sites.
Overall, plants appear to have benefited from fertilizer and
lime application. Total plant cover was low (10–40%) but
improved significantly as a result of soil amendments. Total
plant cover was 72% higher in limeþfertilizer plots than in
controls (p,0.05; Figure 4), and cover was higher at
Reservation Terrace than at Temple Blvd (p,0.01). The
percentage of cover of A. breviligulata showed a similar
pattern, where the average was highest in the limeþfertilizer
plots and lowest for controls and lime plots (Figure 5). The
effect of soil amendments on A. breviligulata percentage of
cover was significant (p,0.05), and cover was higher at
Reservation Terrace than the other sites (p,0.0001).
Diversity ranged from 0.55–0.62, and species richness ranged
from 5.2–5.9 (Table 1). Neither metrics were affected by soil
amendments. Although the percentage of live A. breviligula-
ta plants differed between sites (p,0.0001), there was no
effect of soil amendments when data were averaged from
2017 and 2018 (p¼0.120; Figure 6a). However, when only
2018 data from the remaining two sites were analyzed, the
effect was significant (p,0.01), and the percentage of live
plants was higher in limeþfertilizer plots by nearly 20%
(Figure 6b). Means for each site and year are provided in the
online supplemental material. The tallest A. breviligulata
plants were found in limeþfertilizer plots (Figure 7), but the
effect was not significant (p¼0.073). Fertilizer and lime-
fertilizer plots contained the highest number of reproductive
shoots, but differences were not significant because of high
variability (Figure 8).
DISCUSSION
The results suggest that a combination of lime and
fertilizer helped replanted dune communities recover from
die-off events, as shown by the greater percentage of live
plants and cover of A. breviligulata.Inasimilarstudyin
Delaware, Seliskar (1995) found that nutrient addition
resulted in greater plant height, culm bunch circumference,
number of shoots per bunch, and percentage of cover of A.
breviligulata. While Seliskar (1995) did not show the
combined effect of fertilizer and lime, lime-only treatments
increased A. breviligulata survival in dunes where initial pH
had ranged from 4.0 to 5.5. Because the control pH in the
present study sites ranged from 5.2 to 7.2, dune soils may not
have been acidic enough for the lime-only treatment to
Figure 3. The effect of soil amendments on pH three weeks after
amendment application. Error bars represent standard error (SE). Different
lowercase letters denote significant differences among treatments when
blocked by site. Uppercase letters denote significant differences among sites.
Figure 4. Total percentage of cover 6standard error (SE) of all plant species
for Penny Lane and Temple Blvd (2017–18 averaged) and Reservation
Terrace (2017 only because of loss of site in 2018). Different lowercase letters
denote significant differences among treatments when blocked by site, and
uppercase letters denote significant differences among sites.
Figure 5. Percentage of cover of Ammophila breviligulata 6standard error
(SE). Averages from 2017–18 are shown for Penny Lane and Temple Blvd,
whereas only 2017 data were available for Reservation Terrace.
Table 1. Species richness (
6
standard error [SE]) and Shannon-Weiner
diversity index calculated using percentage of cover. Data from all sites and
years were averaged (n¼12 plots). No significant differences among
treatments were found.
Control Lime Fert. LimeþFert.
Richness 5.2 60.53 5.3 60.33 5.6 60.54 5.9 60.61
H00.58 60.08 0.62 60.06 0.60 60.07 0.55 60.08
Journal of Coastal Research, Vol. 36, No. 1, 2020
90 Moore, Burdick, and Payne
significantly benefit plants; however, the combination of lime
and fertilizer amendments resulted in a greater percentage of
live plants in 2018, after plants had been exposed to a winter.
In another field experiment in Quebec, Boudreau and Houle
(2001) found that shoot biomass and density of A. breviligu-
lata were higher in fertilized dune areas than in controls.
Similarly, Day et al. (2004) showed total stem density and
Ammophila-specific stem density increased during a 10-year
fertilization period in a coastal barrier island in Virginia;
however, Day et al. (2018) later noted that fertilizer in these
plots had a negative effect on dune plant diversity. Soil
amendments in the present study did not appear to decrease
species diversity, nor was there a significant effect on species
richness over the course of the study. The lack of effect on
these parameters may be a result of low overall plant cover
following die-off, the lower rate of fertilizer application, or the
shorter study period. The beachgrass native to Europe,
Ammophila arenaria, was also found to benefit from
fertilizer, with one study showing greater productivity in
fertilized areas (Van Der Putten, 1990) and another showing
greater plant height and shoot density (Willis, 1965).
A series of Nor’easters resulted in the loss of Reservation
Terrace over the winter of 2017–18. This site was located just
north of a jetty extending from the mouth of the Merrimack
River. The jetty was restored by the Army Corps of
Engineers in 2014, resulting in increased water velocity
that may influence beach scouring and rates of beach and
dune erosion witnessed at the site. Quarterly dune profile
surveys have documented extensive erosion resulting in loss
of the beach front and dune crest at Reservation Terrace (G.
Moore, unpublished data). Changes to water flow and
sediment dynamics, combined with effects of more frequent
severe storms likely contributed to the dune loss at
Reservation Terrace. At Penny Lane and Temple Blvd, the
effect of limeþfertilizer on all growth metrics increased
between 2017 and 2018, suggesting additional supporting
results if Reservation Terrace had not been destroyed in
2018.
By improving the health of dune plant communities
through soil amendments, coastal resource managers may
increase resilience to storm flooding. Studies have shown
that belowground plant growth helps to stabilize dunes and
prevent erosion (Sigren, Figlus, and Armitage, 2014; Silva et
al., 2016). Although belowground growth was not measured
in this study, the finding that fertilizer and lime increased
thepercentageofcoverandpercentageofliveplantsofA.
breviligulata suggests there will be more plants in soil
amendment areas and therefore more roots stabilizing the
Figure 6. Percentage of total A. breviligulata plants that were alive: (a) the
average of both years; (b) 2018 only. Lowercase letters denote significant
differences among treatments when blocked by site, and uppercase letters
denote significant differences among sites. Error bars show standard error
(SE).
Figure 7. Plant height of A. breviligulata 6standard error (SE) measured
as the average height of the tallest three plants for each treatment. Penny
Lane and Reservation Terrace data from 2017–18 were averaged, but
Reservation Terrace data were available from 2017 only.
Figure 8. The density of inflorescences 6standard error (SE) for Penny
Lane and Temple Blvd (2017–18 averaged) and Reservation Terrace (2017
only).
Journal of Coastal Research, Vol. 36, No. 1, 2020
Recovery of Ammophila breviligulata 91
dunes. Tiller density and leaves per tiller of A. breviligulata
have been shown to correlate positively with sand accumu-
lation (Emery, Bell-Dereske, and Rudgers, 2015), suggesting
that the higher plant cover found in amended dune soils will
trap more sand and increase dune height. Because burial
results in greater biomass of A. breviligulata (Disraeli, 1984;
Harris, Zinnert, and Young, 2017) and other dune plants
(Perumal and Maun, 2006), an enhanced sediment-trapping
effect could improve plant growth while also building a taller
dune barrier against wind-driven waves and storm surges as
sea levels rise. Healthier plant communities will also
improve habitat for small mammals, insects, and birds such
as the threatened piping plover (Charadrius melodus),
which has been shown to preferentially nest in areas with
higher A. breviligulata shoot density at some sites (Flem-
ming, Chiasson, and Austin-Smith, 1992). Although excess
nutrients from fertilizer can contribute to eutrophication in
nearby water bodies, this is more of a concern in enclosed
areas such as estuaries and coastal lagoons (Bricker et al.,
1999; Taylor et al., 1995) rather than open coasts. Whether
planting because of die-off, blow outs, or following sand
additions (i.e. nourishment) to beaches and foredunes, the
addition of fertilizer and lime treatments at levels used
herein is expected to stimulate growth of common native
dune species and may be an effective approach to increase
dune resilience.
CONCLUSIONS
The application of fertilizer and lime to coastal dunes appears
to be a cost-effective way to promote regrowth following die-off
and to build dune resilience to climate change. More long-term
studies should be done to determine the optimal application
frequency for dune plants in New England and potential
impacts to water quality in sheltered areas. Dunes are dynamic
environments that are constantly changing in size, shape, and
position because of the forces of wind and water. No amount of
soil amendments or vegetation can prevent erosion entirely,
but healthier plant communities will benefit both the natural
ecosystem and the property owners that depend on dunes for
protection from storms and sea-level rise.
ACKNOWLEDGEMENTS
We thank Doug Packer and Julia Godtfredsen of the
municipalities of Newbury and Newburyport, respectively,
and Darryl Forgione of the Massachusetts Department of
Conservation and Recreation for their partnerships and
cooperation. We recognize the support of Plum Island
landowners who encouraged the research and provided access
to their properties. We are indebted to Alyson Eberhardt of
UNH Cooperative Extension/NH Sea Grant for engaging
student volunteers from Triton Academy and Bagnall and
High Plain Elementary Schools who assisted in dune
restoration planting. Field assistance was provided by
Christopher Peter, Robert Lafrenierre, and Grant Moore.
This work was supported by the U.S. Department of the
Interior in partnership with National Fish and Wildlife
Foundation Hurricane Sandy Resiliency Competitive Grant
Program (Award #41766) and NH Sea Grant (Award #
111D80). Published as Scientific Contribution Number 571
from the Jackson Estuarine Laboratory and School of Marine
Science and Ocean Engineering at the University of New
Hampshire.
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