Proceedings of the Third International Conference on Invasive ...

<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive SpartinaChapter 4: Spartina Control and ManagementFig 5. November 2003 GPS locations <strong>of</strong> main S. anglica infestations recordedduring hovercraft survey.Fig. 4. Comparison <strong>of</strong> S. anglica distribution on Roberts Bank in 2003 and2004.S. anglica Distribution on Roberts Bank and BoundaryBayIn 2003, S. anglica was present on Roberts Bank inthree 3-m diameter clones and approximately 50 scatteredseedlings and tussocks up to 1 m in diameter. The totalmudflat area affected was 60 ha (148 ac), but <strong>the</strong> actual totalarea covered by S. anglica was only about 0.1 ha (0.2 ac).The average plant density and height in <strong>the</strong> main clone(n=4) was 217 ± 42 shoots/0.25 m 2 and 108 ± 6 cm,respectively). Individual seedlings were much smaller,ranging from 0.1–0.3 m (4–12 in.) in height.In 2004, new seedling growth was found on RobertsBank, despite previous clearing in 2003 (Fig. 4). Seedlingdistribution, mapped in June and October, showed that <strong>the</strong>distribution <strong>of</strong> <strong>the</strong> plants continued to expand through <strong>the</strong>summer. Above-average temperatures experienced in <strong>the</strong>summer <strong>of</strong> 2004 appeared to increase <strong>the</strong> spread <strong>of</strong> S.anglica.In 2003, S. anglica in Boundary Bay was concentratedin two nodes near Beach Grove, in <strong>the</strong> west and between 96 thand 112 th Streets in <strong>the</strong> central portion (Fig.5). Most <strong>of</strong> <strong>the</strong>observed S. anglica was present as seedlings or smalltussocks, with occasional clones ranging from 1–3mdiameter. Total area impacted was about 135 ha (330 ac),but total coverage was estimated at 1% or 1.35 ha (3 ac).Similar to Roberts Bank, Boundary Bay seedlingabundance increased in 2004, and new areas weredocumented in Surrey and Mud Bay in <strong>the</strong> eastern section <strong>of</strong>Boundary Bay. The most densely infested area was locatedwest <strong>of</strong> 112 th Street, outside <strong>the</strong> FOC mapped area. Thecomposite map <strong>of</strong> Spartina anglica locations is shown inFig. 6.Spartina RemovalIn 2003, <strong>the</strong> one-day removal effort (total <strong>of</strong> 21 persondays)was successful in removing all S. anglica plants fromRoberts Bank, except for those in <strong>the</strong> three 3-meter diameterclones. Roberts Bank sediments were quite s<strong>of</strong>t which madewalking and digging more difficult. Manual removal <strong>of</strong> <strong>the</strong>dense growth in <strong>the</strong> clones was slow, and only half <strong>of</strong> one <strong>of</strong><strong>the</strong> 3-m diameter clone was removed by six volunteersworking a full day (Fig. 7). The sediments were washedfrom <strong>the</strong> plants to reduce <strong>the</strong> weight <strong>of</strong> collection bags. InBoundary Bay, <strong>the</strong> sediments were firmer (i.e. sand) whichfacilitated removal. The use <strong>of</strong> an all-terrain vehicle toremove <strong>the</strong> bags greatly reduced <strong>the</strong> labour. The 140 persondays<strong>of</strong> removal effort in 2004 was not sufficient to removeall <strong>the</strong> S. anglica.The excavator and in situ burial used in 2004 proved toFig. 6. Distribution <strong>of</strong> S. anglica on Roberts Bank and Boundary Bay.- 239 -