Georgian Court University

Our original proposal for the Carex study
(Proposal received funding from the New Jersey Marine Science Consortium)

Read about the results of this study

Learn more about the Biology Department at Georgian Court University

 Introduction

Carex kobomugi is a sand-dune sedge that is a native of Asia.  It was accidentally introduced to the North East Coast of North America early in the twentieth century, and later was deliberately planted in many areas to stabilize coastal sand dunes (USDA 1983). The species grows well in back-dune areas where native species, such as American beach grass (Ammophila breviligulata), tend not to thrive (summarized in Shisler et al. 1987).  Its naturally spiky nature was also seen as an advantage in that it naturally discouraged foot traffic away from established trails, without the longer-term negative effects of native species such as poison ivy that often thrive in this habitat in the absence of C. kobomugi (Shisler pers. Comm).  As a result, the known populations on both Island Beach State Park and Sandy Hook National Recreation Area have expanded to between 25,000-30,000m2 in each Park over the last century. 

Recently Carex kobomugi has begun to be perceived as an “invasive exotic” species and management practices have changed from introduction to elimination (Virginia Department of Conservation and Recreation and Virginia Native Plant Society, date unknown; Chris Lea, Assateague Island National Seashore pers. comm.)   However the rationale for this change in policy is unclear.  A fact-sheet currently being prepared about this species by Chris Lea characterizes the species as being “capable of quickly forming extensive colonies through rhizomes”.  It also suggests that “Asiatic sand sedge can effectively outcompete native dune-binding grasses, such as American beach grass and sea oats (Uniola paniculata)” and that “dunes dominated by the sedge are more vulnerable to wind blowouts and storm erosion”.   However it is not clear upon what evidence these statements are based.  For example, while there is agreement that C. kobomugi dunes tend to be lower than those formed in association with A. breviligulata or U. paniculata, it is not clear that C. kobomugi dunes are intrinsically less stable than those formed in association with other dune grasses.  Indeed there is some anecdotal evidence that the dunes stabilized by C. kobomugi in front of the Governor’s house at Island Beach State Park actually survived several serious storms in the early 1990s better than those stabilized by A. breviligulata (Chris Miller pers. comm).  It is also unclear to what degree the species warrants serious concern or treatment as an invasive species.

Efforts to propagate this species by the scientists at the Cape May Plant Materials Center during the time when the plant was being deliberately introduced to the dunes were plagued by failure.  Even careful transplanting of vegetative tissues often failed to result in successful establishment of the species (Shisler et al. 1987; USDA 1983), and propagation from seed has been found to be extremely difficult (Belcher et al. 1984; Small 1954).  Such observations would tend to call into question the degree to which this plant is likely to be an aggressive invasive.  Similarly, the expansion rate of this species has not been particularly rapid compared to that of other species generally termed “invasive”.  A population on Island Beach State Park that is believed to be that originally described by Townsend in 1929 as “a much battered pocket population” was mapped at 2000m2 in 1939 and had expanded to 3000m2 by 1951.   Moreover there was no single stand larger than this present in the Park in 1986 (Shisler et al. 1987), although the number of stands surveyed in this study had increased (or perhaps more stands had been located by this time), resulting in a total cover of 25,116m2 in Island Beach State Park in the 1986 survey.   At Sandy Hook, stand sizes were reported at about 4500m2 (a little more than 1 acre) in 1979 (Stalter 1980) and to be similar in 1986 (Shisler et al. 1987) but to have increased to about 28,000m2 (7 acres) by 2000, mostly in the back dunes areas of North and Gunnison beaches.

In keeping with recent trends toward removal of non-native species from National and State Parks, Carex kobomugi stands have recently been slated for removal from both Island Beach State Park and Sandy Hook National Park.  This removal is already underway in Island Beach State Park, where Dr. Greg McLaughlin has been using “Roundup” to remove C. kobomugi stands, and using students from the MATES program to plant American Beach Grass in its place (Greg McLaughlin, pers. comm.).  In Sandy Hook the National Park Service had, until recently, proposed to use a small bulldozer to remove sand containing C. kobomugi and a “Surf Rake” to remove the plant material from the collected sand.  Again the proposal was for the area to be replanted with American beach grass.  In both cases, many of the stands of C. kobomugi that are being removed or are slated for removal are in back-dune areas where beach grass grows poorly, if at all.  Moreover, given that the roots of this species are usually found to extend more than a meter into the sand (Shisler et al. 1987) the likely effectiveness of using a bulldozer to scrape away C. kobomugi stands is unclear, and the effects of using such an intrusive mechanism of removal in the well-traveled areas of the park in which the stands are found is unknown.    In addition, elimination of Carex kobomugi stands may not be prudent in some dune habitats where removal of this species may increase the risk of dune erosion and over-wash. 

The alternative to removal is to manage the existing patches, while working to thwart further expansion of this species into areas currently occupied by native grasses.  However such management would be hindered because it is currently unclear by what mechanisms this plant is dispersing into new habitats.  The species has proven difficult to propagate from seed, and mature transplanted plants often fail to thrive (Shisler et al. 1987).  We have observed that Carex kobomugi forms long vegetative runners that run at fairly shallow depths below the dune surfaces, by which it propagates into new habitats.  We have also observed this species to produce abundant seeds within certain stands, while producing absolutely no seed within others (probably because this plant is dioecious, and some stands appear to be made up almost entirely of either male or female flowering individuals).   Without this knowledge it is hard to assess the risk of spread from existing patches, should they be allowed to remain.

The planned study will assess the tolerance of the axial buds (centers of vegetative growth) of these runners to salt water and to drying.  The purpose of these experiments is to simulate the potential for vegetative materials eroded from dunes during over-wash, and that eroded by wind or motorized vehicles moving in the pathways along the dunes to transport C. kobomugi into new habitats into which it could then become established.  An understanding of the tolerance of C. kobomugi to these potential vectors should be helpful in assessing the risks of allowing existing stands of this species to remain within park grounds.

 Study Sites:

Mapping efforts will focus upon the areas in which stands of C. kobomugi were found and mapped by Environmental Concerns  (Shisler et al. 1987).  These areas include Island Beach State Park, Sandy Hook New Jersey, Barnegat Light, Avalon and Wildwood Crest NJ.  However, we will attempt to contact botanists in the area to determine whether any other stands of this plant are present in this area.

 Project Objectives:

1.      Locate and map the stands that were mapped by Environmental Concerns 1986 (Shisler et al. 1987) and compare the sizes, species composition (diversity) and plant densities of each in order to determine the rate of spread of this species.   Document the location of each stand using a GPS system so that direction and rates of expansion can be assessed in the future. 

2.      Collect information on any new stands found since the 1986 study.   Again map size, specie composition, plant densities and position of each stand.

3.      Document any losses of stands since the 1986 survey, including the ones already treated with Roundup in Island Beach State Park by Greg McLaughlin.

3.      Assess the rates and extents of invasion of C. kobomugi in dune systems of Ocean and Monmouth Counties. 

4.      Assess the species composition of plants within the C. kobomugi stand and in the adjacent areas so that future studies can assess whether some species are more strongly impacted by spread of C. kobomugi stands, if occurring, than others

5.      Monitor the success of the removal projects already underway at Island Beach State Park, including assessing degree to which C. kobomugi returns in treated areas and the degree to which the transplanted beach grasses appear to thrive as well as the degree and nature of any natural re-establishment of other species within these plots.  These data would presumably be part of an on-going monitoring project that would extend beyond the time frame of the present proposal and potentially may form the basis of a future proposal for continued research.

6.      Collect seed from plants in various stands and look at germination success under various environmental conditions (light, moisture conditions, soil salt content, and duration of immersion in seawater before planting).  This would allow some evaluation of the risk of this plant spreading via sexual rather than vegetative mechanisms (vegetative propagation having been the focus of most of the efforts by the Cape May Plant Materials Center (USDA 1983, Shisler et al. 1987)).

7.      Make recommendations about management strategies for C. kobomugi within the New Jersey Park systems.  Does the evidence support the need for removal of these species or not?  Moreover, whether or not there is strong evidence supporting removal, if there is still a political will to remove this species, to make recommendations as to preferred methods of removal and appropriate species to be used to replant exfoliated regions (species likely to succeed in those areas on the longer term, as well as to have dune-binding and other desirable characteristics).

 

Methods

Objectives 1-4:  Areas covered by stands of Carex kobomugi will be mapped using the same methods used by Shisler et al 1987).  Specifically:  Length of each stand will be measured along the longshore axis.  Widths across each stand will be measured at 5-meter intervals (2-meter intervals for small stands) along the length of the stand.  After the stand is measured, the dune zone in which the stand is growing will be identified.  Again following Shisler et al. (1987), dune zone will be partitioned into five categories: primary foredune, primary topdune, primary backdune, secondary dune and other (any area which does not fit into any of the other four categories).  A portable GPS unit will be used to pin-point the location of the center and extreme edges of the stand.  GPS data will also be used to map stand dimensions onto topographical maps using the “3-D Topoquads” (Delorme) software package. These data will be used to calculate the area covered by each stand and these areas will be compared to those reported by Shisler et al.1987 to determine the rates of change in stand area since that time.

Objective 5:   Again following Shisler et al. 1987, circular, 1 m2 plots will be randomly selected within the stand and the position marked with a center pole.  Enough plots will be establish to sample between 1 and 5% of the stand area, depending on stand size and homogeneity (relatively more replicates will be used for smaller stands and for those with higher levels of heterogeneity in cover or species composition).    Species composition will be determined in each plot by rotating a 0.56 meter stick around the center point and counting and identifying all plants which intersect this radius.  Shoot density will be measured by clipping and counting stem densities in 0.1m2 quadrats and approximate areal coverage for the various species present within each quadrat will be estimated visually for each 1m2 quadrat.    Similar plots will be established in the areas of dune between 1-5m outside the Carex kobomugi stand. These plots will be positioned seaward, landward and at both ends of the stand and the position of each will be documented with GPS.  Species composition and number of plants within each plot will be assessed as for those within the Carex kobomugi stand.

Objective 6:  The sites in which Roundup has been sprayed on C. kobomugi will be visited every 3-6 months for a year.   Evidence of re-emergence of C. kobomugi shoots will be documented qualitatively, and  establishment of Ammophila breviligulata and regrowth of C. kobomugi   as well as the presence of any other species will be monitored by counting shoot densities in 1m2 plots within each stand.   Enough plots will be establish to sample between 1 and 5% of the stand area, depending on stand size and homogeneity (relatively more replicates will be used for smaller stands and for those with higher levels of heterogeneity in cover or species composition).   If establishment is successful enough that shoot densities rise above numbers that can practically be monitored within a full meter square quadrat, a subplot of either 0.1 or 0.25m2 will be randomly selected within the original quadrat, and shoot density within that quadrat will be measured and counts extrapolated to the full m2.

Objective 7:  Seed will be collected from C. kobomugi from as many stands as possible in Island Beach State Park and Sandy Hook and elsewhere (at least 3 different stands), keeping careful note of which seed originated from what stand.  The seed will then be taken back to the lab where known numbers of seeds will be sown in sand collected from the dune systems and incubated in existing incubator and greenhouse facilities using a variety of light, temperature and watering regimes to assess germination success.  In addition, paired samples of seeds will first be soaked in seawater for 1, 2, 3 and 7 days to simulate transport from one site to another in the ocean and germination success of these seeds will be compared with that of seeds not exposed to seawater.

Objective 8: A literature review will be carried out, and interviews with park rangers involved with management of C. kobomugi in other areas of the US will be conducted in order to assess the state of knowledge about the growth and control of C. kobomugi.  This information will be combined with the information gathered here to build recommendations about appropriate management strategies for this species.

 

Expected Results

Current plans to remove C. kobomugi stands in both Island Beach State and Sandy Hook National Parks are based on little scientific data.  This is of particular concern for the stands at Sandy Hook where the proposed mechanism of removal (scraping via bulldozer) is particularly intrusive, and, given the extreme depth of the root system of this plant (>1m), is perhaps less likely to succeed than the herbicide-based removal project underway at Island Beach State Park.  This study will provide a rigorous scientific basis for evaluation of the intrusiveness of C. kobomugi by mapping the sizes of current stands of this species and comparing them with those documented by Environmental Concerns in 1986 (Shisler et al. 1987).  It will also allow use of the already on-going C. kobomugi removal project at Island Beach State Park as a type of “experimental treatment” whose effectiveness and results can be evaluated against the “control” of remaining stands at Island Beach and Sandy Hook.  The results of this study will provide a powerful tool to allow park officials to make informed decisions as to the appropriate management strategies for this species.

 

Schedule of Activities

Research will commence  with the collection and planting of vegetative propagules as soon as permits are obtained. Mapping is expected to commence in mid-May 2002 with the mapping of all remaining stands of C. kobomugi, and will continue into the fall and winter if necessary.  Seed will be collected in late September or early October and germination experiments will be conducted during the fall and spring semesters.  Monitoring of Roundup treated sites will be carried out every 3-4 months starting in May 2002 for at least a year.

Literature Cited

Belcher CR, Webb FH, Duell RW, Sharp WC. 1984.  Registration of the Sea Isle Japanese Sedge.  Crop Science 24: 1214.

Lea, Chris. U.S. National Park Service, Assateague Island National Seashore, Berlin, MD

McLaughlin, Greg.  Office of Natural Lands Management.  Trenton, New Jersey.

Miller, Chris.  USDA. Natural Resources Conservation Service. Somerset NJ.

Small JA. 1954.  Carex kobomugi at Island Beach, New Jersey.  Ecology 35:289-91.

Shisler JK, Wargo RN, Jordan RA.  1987.  Evaluation of Japanese sedge, Carex kobomugi, for use in coastal dune planting and stabilization.  New Jersey Agriculture Experiment Station Publication number P-40502-03-87

Stalter, R. 1980.  Carex kobomugi Ohwi at Sandy Hook, New Jersey.  Bulletin of the Torrey Botanical Club 107:431-2.

USDA (United States Department of Agriculture), Soil Conservation Service and New Jersey Agriculture Experiment Station.  1983.  Proposed Release of Carex kobomugi.  64pp.

Virginia Department of Conservation and Recreation and Virginia Native Plant Society.  Date unknown.  Invasive alien plant species of Virginia.  Asiatic sand sedge (Carex kobomugi Ohwi)

 

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