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Ch. 2
Changes in Honckenya and Glaucium populations
on Racing Beach, Cape Cod
Marilyn Del Donno
May 16-24, 2013
2013 Ch. 2
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Ch. 2
Changes in Honckenya and Glaucium populations on Racing Beach
We have been monitoring the presence of Honckenya peploides because of our
concern about its disappearance from our beach. This year’s data showed that
Galucium had bounced back from 2012 levels, but Honckenya declined. This could
relate to the strongly cobbled appearance of the beach this year.
Introduction
Racing Beach is characterized by a wider and steeper boulder and cobble covered
northern end which slowly gives way to a narrower, more sandy and more gently sloping
southern end. Current, water table and soil studies over the years have indicated a long
shore current to the north and the buildup of detritus at that end, resulting in an upper
intertidal fauna of terrestrial, salt tolerant plants. There are about 20 species of plants
covering an area of about 250 m along the upper beach. This area has been dominated by
Ammophilia, and by Rosa rugosa, which is restricted to the northern end. The southern
end of the transect, which has always seemed to be much more cobble covered, contains
a more diverse community of plant species that tend to be smaller and sparser. Though
we had been concerned about the disappearance of Honckenya peploides in previous
years, we had noticed an increase over the last two years. This lovely, salt tolerant plant
which is listed as endangered or of special concern in R.I., N.H., Ct. and Md (US Plants
Database). Though present along the shoreline communities of Massachusetts, most of
the research on its physiology is by Canadian and Scandinavian researchers with few
citations from our geographical area.
In general, the upper beach is a harsh environment characterized by low water and
nutrient availability, increased salinity due to both soil and, more importantly, salt spray
(Rozema, 1985), and the potential for both sand burial and major erosion events.
Surprisingly, Honckenya is not particularly tolerant to burial and high salinity as are some
other plants in this area, but its subvertical rhizomes and ability to form deeply rooted
clones allow rapid recovery after erosion events. (Gagne & Houle, 2002) Its seeds
tolerate submergence in sea water, and its deep root system is an advantage when water is
scarce (Sigurdsson, 2009). A study by Sanchez-Vilas and Retuerto (2009) noted a spatial
segregation of the sexes, possibly due to their different strategies for coping with water
stress. The importance of Honckenya in the coastal ecosystem has been studied by Gagne
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and Houle (2001), who suggest that Honckenya facilitates the recruitment of L. mollis
seedlings by forming embryo dunes, indicating that this species could have a key role in
the development of beach plant communities. The Honckenya mounds reduce wind speed
at the air-substrate interface, causing sand and seed sedimentation and so seed burial and
retention. Studies also indicate that the distribution of Honckenya and Glaucium might be
related to sediment size (Walmsley&Davy, 1997).
The 2012 CSW study showed a dramatic decrease in the levels of Glaucium with
a corresponding increase in Honckenya. The Honckenya plants were usually found
protected in the rock wall at the narrow, southern end of the beach, and growing in
detritus or rocks in the north. The Glaucium was strictly at the northern end where the
beach is wider. We will repeat the study and hope to see a greater number of Honckenya.
In addition, we expect to see a continued increase in Glaucium, which is of concern as an
invasive species.
Materials
Ruler
GPS
Procedure
1. Walk down the first stair and turn south to the very end of the beach. Walk
slowly and look in the upper intertidal region for patches of Honckenya and
Glaucium. Be careful to look within the rock wall as well as in cobble grass, and
detrital layers.
2. Note the location with the GPS, as well as the substrate it is found in (cobble, rock
wall, detritus).
3. Note approximate size of the patch in centimeters.
4. Repeat 1-3 with Glaucium, but estimate patch area only and not patch number
because of the high density of the species.
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Results
Map 1, Figure 1: Honckenya Comparison: The patch area of Honckenya declined, and the amount was
stable over the course of the week.
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Map 2, Figure 2: Glaucium Comparison: There was a significant increase in Glaucium in the northern end
of the beach, and there was little change over the course of the week.
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Map 3, Figure 3: Honkenya and Glaucium Comparison: Plants are most common on the wider northern
and southern ends of the beach. Glaucium has increased once again, while Honckenya has decreased.
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Conclusion
The decreased patch area of Honckenya is disappointing but not surprising given the
strongly cobbled nature of the beach this year, which presumably is covering the small
Honckenya plants. The dramatic weekly changes shown in earlier years was not
apparent this year, perhaps because of the relatively calm weather and neap tides and the
lack of removal of the cobble shelf. Glaucium once again increased after last year’s drop,
and but was still not present in the southern end. We suggest that a tracking study of all
three species be continued along with a greater examination of plant root structure in
various areas, and that a study of the relationship between particle size and distribution of
these species be started.
Bibliography
CSW Botany Studies: Jenn Kessler (2010), Rustino & DelDonno (2010)
Gagne & Houle (2001), Can. J. Botany, 79(11): 1327-1331 “ Facilitation of Leymus
mollis by Honckenya peploides on coastal dunes in subarctic Quebec Canada.”
Gagne & Houle (2002), American J. Botany, 89: 479-485 “Factors responsible for
Leymus mollis and Honckenya peploides spatial segregation on arctic subcoastal dunes”
Rozema, Bijwaard, Prast, Broekman (1985), Vegetatio,62: 499-521 “Ecophysiological
adaptations of coastal halphytes from foredunes and salt marshes.”
Sanchez-Vilas & Retuerto (2009), Plant Biol(Stuttg), 11(2):243-54 “Sex-specific
physiological, allocation and growth responses to water availability in the subdioecious
plant Honckenya peploides.”
Sigurdsson (2009), Surtsey Research, 12:77-80 “Ecosystem Carbon fluxes of
L.arenarius and H.peploides in Surtsey in relation to water availability”
Walmsley & Davy (1997), J. Applied Ecology, 34: 154-165 “The restoration of coastal
shingle vegetation: effects of substrate composition on the establishment of container
grown plants.”
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