03035nas a2200181 4500008004100000245014500041210006900186260001200255490000700267520240200274653002302676653002002699653002502719100002702744700001802771700002402789856004002813 1996 eng d00aEffects of environmental manipulations on Triglochin palustris: implications for the role of goose herbivory in controlling its distribution0 aEffects of environmental manipulations on Triglochin palustris i c267-2780 v843 a

1 Arrowgrass (Triglochin palustris) is a preferred forage species of geese in the Yukon-Kuskokwim Delta (south-western Alaska) where it is found primarily on slough levees in coastal areas. Geese may affect nutrient availability, interspecific light competition, and salinity. These variables were manipulated in order to identify interactive effects of interspecific competition and abiotic factors on arrowgrass size, biomass allocation and distribution, which are likely to be significant in relation to the effects of herbivory on arrowgrass abundance and distribution.

2 Arrowgrass individuals were transplanted from two slough levee communities to the same two communities and to the adjacent slough margin and wet Carex meadow communities. Geese were excluded and nutrient availability, light competition and salinity levels were manipulated.

3 When light levels were not manipulated, fertilization had a negative effect on plant biomass and allocation to bulbs. Under decreased competition for light, plant biomass of fertilized plants was not significantly different from that of control plants. Fertilization appears to have a negative effect on arrowgrass as a result of increased competition for light.

4 Plants in the slough margin habitat were smallest, had the lowest allocation to leaves and stolons, and the lowest N concentrations and total N mass. Results from the fertilization treatment suggest plants in this community are limited primarily by physical factors.

5 Plants in the Carex wet meadow had higher allocation to leaves than in other communities under unfertilized conditions, but decreased allocation to leaves under fertilization. Plants in this community appear light- and nutrient-limited under unfertilized conditions, and primarily light-limited under fertilization.

6 Our results suggest that the presence of geese may control arrowgrass distribution because (a) faeces deposition has a negative effect on arrowgrass, (b) this negative effect is ameliorated by consumption of neighbours, and (c) the combination of high light competition and highly selective foraging for arrowgrass limit expansion of arrowgrass into the Carex meadow community. These explanations can now be tested.

10abiomass allocation10agoose herbivory10asubarctic salt marsh1 aMulder, Christa, P. H.1 aRuess, R., W.1 aSedinger, James, S. uhttp://www.jstor.org/stable/226136202808nas a2200253 4500008004100000245012900041210006900170300001400239490000700253520197600260653002602236653001702262653002502279653002002304653002402324653002302348653002202371653002402393653001702417100002402434700002302458700002302481856005002504 2004 eng d00aCommunity level engineering effects of Triglochin maritima (seaside arrowgrass) in a salt marsh in northern New England, USA0 aCommunity level engineering effects of Triglochin maritima seasi a589–5970 v923 a

1. Ecosystem engineers can influence other organisms indirectly by modifying their physical habitat and are common in all natural communities. We examined the mechanisms underlying the effects of engineering by seaside arrowgrass, Triglochin maritima (Juncaginaceae), in a northern New England forb panne. Within these waterlogged areas, T. maritima creates elevated rings that support high plant cover compared with nearly bare adjacent substrate.

2. The influence on vegetation patterns of ring height and facilitation by neighbouring vegetation were examined in the field with T. maritima rings (elevation + vegetation), experimentally lowered rings (vegetation only), artificially raised mud (elevation only) and bare mud. Transplants of four perennial species, along with naturally occurring seedlings, were followed to assess plant performance. We also monitored edaphic conditions, seed dispersal and plant cover in experimental plots over two growing seasons.

3. All transplanted species showed increased success in raised treatments (in which the substrate showed an increase in reductive potential and a decrease in waterlogging) while there was no significant relationship to the presence of neighbouring vegetation. Seed supply, however, was enhanced by both ring elevation and the presence of neighbours.

4. A glasshouse experiment to test the response of T. maritima to waterlogging showed an increased production of shallow roots, suggesting a mechanism that may contribute to ring formation.

5. Our results indicate that community consequences of engineering by T. maritima are predominantly due to raised ring formation that ameliorates waterlogging stress and thereby promotes increased species diversity. Consequently, T. maritima may be an important target species for conservation, as sea level rise is expected to increase waterlogging stress in marshes.

10aecosystem engineering10afacilitation10ahabitat modification10aphysical stress10areductive potential10asalt marsh ecology10aspecies diversity10aTriglochin maritima10awaterlogging1 aFogel, Benjamin, N.1 aCrain, Caitlin, M.1 aBertness, Mark, D. uhttps://juncaginaceae.myspecies.info/node/57800441nas a2200157 4500008004100000245005300041210004900094300001200143490000700155653001800162653001800180653001500198100001400213700001600227856004000243 1991 eng d00aTriglochin maritima L. (Triglochin maritimum L.)0 aTriglochin maritima L Triglochin maritimum L a531-5550 v7910aBritish Isles10aJuncaginaceae10aTriglochin1 aDavy, A J1 aBishop, G F uhttp://www.jstor.org/stable/2260731