<str<strong>on</strong>g>Proceedings</str<strong>on</strong>g> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> <str<strong>on</strong>g>Third</str<strong>on</strong>g> <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Invasive</strong> SpartinaChapter 2: Spartina Distributi<strong>on</strong> and SpreadTable 4. Change in Area <str<strong>on</strong>g>of</str<strong>on</strong>g> N<strong>on</strong>-native Spartina at Pre- and Post-treatment Sites M<strong>on</strong>itored in 2003.Site namePiper Park(entire treatment areaincluding east stripmarsh)Piper Park(primary treatment areaw/out east strip marsh)PRNS-Drakes/LimantourEsteroTreatmentYear(s)2002 Post 0.03/ 123.02002 PostArea2001 Ac/m 2 2002Ac/m 2 2003Ac/m 20.03/122.172002 Post n/a0.02/97.120.02/85.920.06/233.53PRNS-Drakes Estero 2003 Pre n/a n/aBolinas Lago<strong>on</strong> North 2002 Post n/a0.002/7.07% Change2002-2003% Change2001-20030.01/ 50.47 -48.0% -59.0%0.01/ 23.00 -73.2% -81.2%0.00005/0.200.005/19.630.00001/0.03-99.9% n/aTreatment & CommentDig Winter 2003;2002-3 treatment, volunteers did not finish<str<strong>on</strong>g>the</str<strong>on</strong>g> entire treatment area. Nor did <str<strong>on</strong>g>the</str<strong>on</strong>g>y digevery plant in <str<strong>on</strong>g>the</str<strong>on</strong>g> primary treatment areathus not 100% kill.Dig Winter 2003;2002-3 treatment, primary treatment area,however volunteers did not dig every plantthus not 100% kill.Trample & Cover Summer 2002; Onecl<strong>on</strong>e at Creamery Bay had a patch thatgrew out from under <str<strong>on</strong>g>the</str<strong>on</strong>g> tarp.n/a n/a Trample & Cover Fall 2003.-99.6% n/aBolinas Lago<strong>on</strong> South 2003 Pre n/a n/a 38.47/ 0.01 n/a n/a*Emeryville CrescentEmeryville Crescent –Mowed Porti<strong>on</strong>Emeryville Crescent –Mowed & CoveredPorti<strong>on</strong>Richm<strong>on</strong>d Inner Harbor– Steege MarshAlameda Island – NorthElsie Roemer200220032002200320022003Pre &PostPre &PostPre &Post0.05/215.680.05/205.2775n/an/a0.00/ 3.53 n/a2003 Pre 0.01/ 32.19 n/a2003Pre &PostPier 94 2003 Pre0.53/2143.970.04/171.72n/a* Pre-treatment data <strong>on</strong>ly. No percent change results.n/an/a0.63/2547.520.38/1539.580.08/306.150.02/100.460.53/2125.050.08/318.94n/a 1081.2%n/a 650.0% Mow 2003.n/a 8566.7%n/an/a*n/a -0.88n/an/a*Dig Winter 2002; Return visits foundoccasi<strong>on</strong>al new sprouts.Trample & CoverSummer 2003.Mow & CoverSummer 2003; Small scale 2002 mowingtreatment had no effect thus mostly seeingspread.Mow & CoverSummer 2003.Trample & CoverFall 2003.Mow/Mow & Spray2002/Fall 2003; GIS based area calc 2003.Area calculati<strong>on</strong>s may be "imperfect".Dig, Trample & CoverSummer 2003.Washingt<strong>on</strong> from 800 ha (1977 ac) to 1,000 ha (2471 ac)between 1988 and 1999 (Daehler and Str<strong>on</strong>g 1996). Theformati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> hybrids between S. alterniflora and S. foliosamay have greatly increased <str<strong>on</strong>g>the</str<strong>on</strong>g> spread <str<strong>on</strong>g>of</str<strong>on</strong>g> hybrid Spartinarelative to S. alterniflora; e.g., hybrids expanded 150% inCogswell Marsh, Hayward, California between 1999 and2000, including some individual hybrid cl<strong>on</strong>es that increased300% (Zaremba, 2001). Ayres and Str<strong>on</strong>g (2000) reported aremarkable 740% increase <str<strong>on</strong>g>of</str<strong>on</strong>g> S. alterniflora-hybrids from5% to 42% at San Lorenzo Marsh between 1997 and 2000. Ithas been proposed that <str<strong>on</strong>g>the</str<strong>on</strong>g> formati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> hybrids expains <str<strong>on</strong>g>the</str<strong>on</strong>g>rapid rate <str<strong>on</strong>g>of</str<strong>on</strong>g> expansi<strong>on</strong> in <str<strong>on</strong>g>the</str<strong>on</strong>g> San Francisco Estuary relativeto o<str<strong>on</strong>g>the</str<strong>on</strong>g>r estuaries where hybridizati<strong>on</strong> does not occur. Ayreset al. (2004) speculated that <str<strong>on</strong>g>the</str<strong>on</strong>g> recent rapid spread <str<strong>on</strong>g>of</str<strong>on</strong>g>hybrids in <str<strong>on</strong>g>the</str<strong>on</strong>g> Estuary may be a result <str<strong>on</strong>g>of</str<strong>on</strong>g> selecti<strong>on</strong> forhybrids with exp<strong>on</strong>ential cl<strong>on</strong>al growth and seed producti<strong>on</strong>.Theoretical models found greater-than-exp<strong>on</strong>ential spreadrates can occur when cl<strong>on</strong>al growth and seed producti<strong>on</strong> areunder selecti<strong>on</strong> (Hall et al. this vol.; Hall et al. 2006).Cover by n<strong>on</strong>-native Spartina increased at all site typesfrom 2001 to 2003, however, site types differed in <str<strong>on</strong>g>the</str<strong>on</strong>g> rate atwhich cover increased. The large variati<strong>on</strong>s in spread ratesam<strong>on</strong>g site types likely reflects <str<strong>on</strong>g>the</str<strong>on</strong>g> proximity <str<strong>on</strong>g>of</str<strong>on</strong>g> individualssites to seed source in additi<strong>on</strong> to habitat suitability.Fringing tidal marshes, mudflats, and estuarine beaches(Site Type II) experienced <str<strong>on</strong>g>the</str<strong>on</strong>g> greatest increase in cover(504% increase). Tidal and microtidal marshes, formerlydiked baylands, and back barrier marshes (Site Type I ) andurbanized shorelines (Site Type IV) increased by about170%. Cover in tidal sloughs, creeks, and flood c<strong>on</strong>trolchannels (Site Type III) increased by 108%. The differencesam<strong>on</strong>g site types may be related to successi<strong>on</strong>al processesPre-PostTreatment-79-
Chapter 2: Spartina Distributi<strong>on</strong> and Spread<str<strong>on</strong>g>Proceedings</str<strong>on</strong>g> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> <str<strong>on</strong>g>Third</str<strong>on</strong>g> <str<strong>on</strong>g>Internati<strong>on</strong>al</str<strong>on</strong>g> <str<strong>on</strong>g>C<strong>on</strong>ference</str<strong>on</strong>g> <strong>on</strong> <strong>Invasive</strong> Spartinalinked to sedimentati<strong>on</strong> c<strong>on</strong>sistent with S. alterniflora and S.townsendii invasi<strong>on</strong>s in New Zealand and S. anglica inEngland (Daehler and Str<strong>on</strong>g 1996), and predicti<strong>on</strong>s byCallaway and Josselyn (1992).One interpretati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> spread rate differences am<strong>on</strong>gsites is that invasi<strong>on</strong> rates <str<strong>on</strong>g>of</str<strong>on</strong>g> susceptible habitat are initiallyhigh and <str<strong>on</strong>g>the</str<strong>on</strong>g>n slow until more susceptible habitat is createdby sediment accreti<strong>on</strong>. Fringing marshes, mudflats andbeach habitat (Site Type II) experienced <str<strong>on</strong>g>the</str<strong>on</strong>g> highest rate <str<strong>on</strong>g>of</str<strong>on</strong>g>spread from 2001 to 2003, suggesting a new invasi<strong>on</strong> fr<strong>on</strong>twas being exploited by hybrids. Presumably, after <str<strong>on</strong>g>the</str<strong>on</strong>g> initialrapid col<strong>on</strong>izati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> suitable “empty-niche” habitat, <str<strong>on</strong>g>the</str<strong>on</strong>g> rate<str<strong>on</strong>g>of</str<strong>on</strong>g> spread would slow to match <str<strong>on</strong>g>the</str<strong>on</strong>g> rate at which <str<strong>on</strong>g>the</str<strong>on</strong>g> Spartinaaugments sedimentati<strong>on</strong> and creates additi<strong>on</strong>al habitat toinvade.Established S. foliosa marshes and open mudflats <str<strong>on</strong>g>of</str<strong>on</strong>g> anewly opened restorati<strong>on</strong> sites (Site Type I) are initiallyhighly susceptible to invasi<strong>on</strong> by pollen and by seed,respectively. The formerly diked bayland Citati<strong>on</strong> Marshexperienced a 900% increase in hybrid cover in three years.Then, <str<strong>on</strong>g>the</str<strong>on</strong>g> rate <str<strong>on</strong>g>of</str<strong>on</strong>g> cover increase slowed as suitable habitatwas filled in.Site Type IIIs may be initially slower to col<strong>on</strong>izebecause <str<strong>on</strong>g>the</str<strong>on</strong>g>y include deep channels and creeks, wheresediment must accrete before <str<strong>on</strong>g>the</str<strong>on</strong>g>y are at suitable elevati<strong>on</strong>for more extensive col<strong>on</strong>izati<strong>on</strong>. Once <str<strong>on</strong>g>the</str<strong>on</strong>g> channel beds havesufficiently accreted, col<strong>on</strong>izati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> remaining channelbanks and bottoms is rapid, with cl<strong>on</strong>al col<strong>on</strong>ies quicklycoalescing into meadows. Rate <str<strong>on</strong>g>of</str<strong>on</strong>g> spread in urbanizedshoreline (site type IV) may likewise be relatively low dueto poor or little sediment availability.Am<strong>on</strong>g <str<strong>on</strong>g>the</str<strong>on</strong>g> three n<strong>on</strong>-native Spartina taxa, hybridsspread <str<strong>on</strong>g>the</str<strong>on</strong>g> most rapidly (317% in three years). Hybrids havehigh rates <str<strong>on</strong>g>of</str<strong>on</strong>g> vegetative spread, produce large quantities <str<strong>on</strong>g>of</str<strong>on</strong>g>pollen, have successful seed set, and readily backcross to <str<strong>on</strong>g>the</str<strong>on</strong>g>native S. foliosa. Spartina foliosa exposed to pollen <str<strong>on</strong>g>of</str<strong>on</strong>g>hybrids produces hybrid seeds, fur<str<strong>on</strong>g>the</str<strong>on</strong>g>r accelerating <str<strong>on</strong>g>the</str<strong>on</strong>g>hybrid invasi<strong>on</strong>. The rate <str<strong>on</strong>g>of</str<strong>on</strong>g> col<strong>on</strong>izati<strong>on</strong> is particularly rapidin <str<strong>on</strong>g>the</str<strong>on</strong>g> early stages <str<strong>on</strong>g>of</str<strong>on</strong>g> invasi<strong>on</strong>. For example, EmeryvilleWest showed an increase in cover <str<strong>on</strong>g>of</str<strong>on</strong>g> 2,175%, between 2001and 2003. All habitats in <str<strong>on</strong>g>the</str<strong>on</strong>g> Bay appear to be susceptible toinvasi<strong>on</strong> by this S. alterniflora hybrid.S. densiflora, which has a cespitose growth form andinvests more reproductive effort in seed producti<strong>on</strong> thanvegetative spread, didn’t spread to <str<strong>on</strong>g>the</str<strong>on</strong>g> same degree as didhybrids: 52% averaged over all site types. Site Type Iexperienced <str<strong>on</strong>g>the</str<strong>on</strong>g> greatest increase in cover <str<strong>on</strong>g>of</str<strong>on</strong>g> S. densiflora(68%).S. patens apparently decreased in cover by 84%, but it isfound <strong>on</strong>ly at Southampt<strong>on</strong> Marsh where <str<strong>on</strong>g>the</str<strong>on</strong>g>re is less thanan acre <str<strong>on</strong>g>of</str<strong>on</strong>g> total cover. The apparent decrease is likely due tomapping error not a true decrease in cover.Of <str<strong>on</strong>g>the</str<strong>on</strong>g> three Bay regi<strong>on</strong>s, <str<strong>on</strong>g>the</str<strong>on</strong>g> Central Bay, nearest to <str<strong>on</strong>g>the</str<strong>on</strong>g>original introducti<strong>on</strong> sites in <str<strong>on</strong>g>the</str<strong>on</strong>g> Frem<strong>on</strong>t and San Brunomarshes, had <str<strong>on</strong>g>the</str<strong>on</strong>g> largest increase in cover, 292%. Hybrids,<str<strong>on</strong>g>the</str<strong>on</strong>g> fastest spreading species (392%), dominate this regi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g><str<strong>on</strong>g>the</str<strong>on</strong>g> Bay. Clearly, <str<strong>on</strong>g>the</str<strong>on</strong>g> hybrids are <str<strong>on</strong>g>the</str<strong>on</strong>g> dominant invasiveSpartina taxa and are well established, and both <str<strong>on</strong>g>the</str<strong>on</strong>g>iracreage and rate <str<strong>on</strong>g>of</str<strong>on</strong>g> spread is greatest in <str<strong>on</strong>g>the</str<strong>on</strong>g> heart <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> Bay.Some new n<strong>on</strong>-native Spartina populati<strong>on</strong>s were foundin <str<strong>on</strong>g>the</str<strong>on</strong>g> sites surveyed at <str<strong>on</strong>g>the</str<strong>on</strong>g> request <str<strong>on</strong>g>of</str<strong>on</strong>g> land owners,managers, and stakeholders. In <str<strong>on</strong>g>the</str<strong>on</strong>g> South Bay, a survey <str<strong>on</strong>g>of</str<strong>on</strong>g><str<strong>on</strong>g>the</str<strong>on</strong>g> Plummer Creek Mitigati<strong>on</strong> Site found <strong>on</strong>ly nativeSpartina. However, 19% <str<strong>on</strong>g>of</str<strong>on</strong>g> seedlings from a Spartina spp.populati<strong>on</strong> at <str<strong>on</strong>g>the</str<strong>on</strong>g> Cooley Landing/Ravenswood PreserveRestorati<strong>on</strong> Project were genetically tested and determinedto be hybrids. Both <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g>se sites are near extensive hybridpopulati<strong>on</strong>s, and c<strong>on</strong>sidered to be at risk. Genetic surveyswere performed at a few small sites in <str<strong>on</strong>g>the</str<strong>on</strong>g> Central Bay(Crissy Field, Steege Marsh and Beach Drive) as part <str<strong>on</strong>g>of</str<strong>on</strong>g> amanagement regime to identify and remove newlyestablished n<strong>on</strong>-natives.GISThree difficulties emerged during <str<strong>on</strong>g>the</str<strong>on</strong>g> 2003 m<strong>on</strong>itoring:imprecisi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> measuring small cl<strong>on</strong>al patches or small areasdue to <str<strong>on</strong>g>the</str<strong>on</strong>g> limits <str<strong>on</strong>g>of</str<strong>on</strong>g> precisi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> GPS units, differencesbetween aerial photo interpretati<strong>on</strong> estimates and groundtruthdata, and low power to detect small changes in areacoverage because <str<strong>on</strong>g>of</str<strong>on</strong>g> broad cover class intervals (Zaremba etal. 2004). Field mapping with three-meter- resoluti<strong>on</strong> GPSunits is imprecise for small areas such as new invasi<strong>on</strong> sites,which necessarily c<strong>on</strong>tain small populati<strong>on</strong>s, and <str<strong>on</strong>g>the</str<strong>on</strong>g>physically smaller Spartina species, S. densiflora and S.patens. These possible sources <str<strong>on</strong>g>of</str<strong>on</strong>g> error could account for <str<strong>on</strong>g>the</str<strong>on</strong>g>apparent decrease in cover <str<strong>on</strong>g>of</str<strong>on</strong>g> S. patens at Southhampt<strong>on</strong>Marsh or S. densiflora at Pickleweed Park or Blackie’sPasture and Creek.Remote sensing using aerial infra-red photography haspotential for synoptic mapping <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> spread <str<strong>on</strong>g>of</str<strong>on</strong>g> invasiveSpartina compared with labor-intensive field mapping.However, am<strong>on</strong>g <str<strong>on</strong>g>the</str<strong>on</strong>g> five sites where we compared <str<strong>on</strong>g>the</str<strong>on</strong>g>semethods in 2003 <str<strong>on</strong>g>the</str<strong>on</strong>g>re were two sites where aerial estimateswere 8-33% less than field estimates and three sites whereaerial estimates were 9-661% greater than field estimates.Averaged over all five sites, <str<strong>on</strong>g>the</str<strong>on</strong>g> field measurements were170% greater than <str<strong>on</strong>g>the</str<strong>on</strong>g> aerial photo measurements. Aerialphoto interpretati<strong>on</strong> methods may prove useful to m<strong>on</strong>itor<str<strong>on</strong>g>the</str<strong>on</strong>g> spread <str<strong>on</strong>g>of</str<strong>on</strong>g> n<strong>on</strong>-native Spartina in grossly invaded areas,but it is not currently precise enough to map without fieldtruthing. The examples <str<strong>on</strong>g>of</str<strong>on</strong>g> both higher and lower aerial photointerpretati<strong>on</strong> cover estimates indicate that <str<strong>on</strong>g>the</str<strong>on</strong>g> currentmethod <str<strong>on</strong>g>of</str<strong>on</strong>g> digitizing polyg<strong>on</strong>s around <str<strong>on</strong>g>the</str<strong>on</strong>g> marsh or Spartinapatch with a cover class may be too coarse to estimate coverprecisely.-80-
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