Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Ch. 2 Changes in Honckenya and Glaucium populations on Racing Beach, Cape Cod Marilyn Del Donno May 16-24, 2013 2013 Ch. 2 p.1 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 2013 Ch. 2 p.2 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. 2013 Ch. 2 p.3 Results Map 1, Figure 1: Honckenya Comparison: The patch area of Honckenya declined, and the amount was stable over the course of the week. 2013 Ch. 2 p.4 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. 2013 Ch. 2 p.5 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. 2013 Ch. 2 p.6 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.” 2013 Ch. 2 p.7