Study

Establishing brackish marshes on graded upland sites in North Carolina

  • Published source details Broome S.W., Seneca E.D. & Woodhouse W.W. (1982) Establishing brackish marshes on graded upland sites in North Carolina. Wetlands, 2, 152-178

Actions

This study is summarised as evidence for the following.

Action Category

Introduce seeds of non-woody plants: brackish/saline wetlands

Action Link
Marsh and Swamp Conservation

Add lime or similar chemicals before/after planting non-woody plants: brackish/saline wetlands

Action Link
Marsh and Swamp Conservation

Add inorganic fertilizer before/after planting non-woody plants: brackish/saline wetlands

Action Link
Marsh and Swamp Conservation

Directly plant non-woody plants: brackish/saline wetlands

Action Link
Marsh and Swamp Conservation
  1. Introduce seeds of non-woody plants: brackish/saline wetlands

    A replicated study in 1979–1981 on reprofiled borrow pits in North Carolina, USA (Broome et al. 1982) reported that smooth cordgrass Spartina alterniflora biomass developed in plots where sown cordgrass seeds germinated. Cordgrass seeds only germinated in some plots, which the authors suggested were those with suitable moisture levels (data not reported). In these plots, there was 304–1,163 g/m2 above-ground biomass of smooth cordgrass after one growing season. Methods: In spring 1979 and 1981, smooth cordgrass seeds were mixed into the surface of “several” plots on reprofiled coastal land (30 cm below to 60 cm above mean sea level; salinity <20 ppt). The seeds had been stored at 2–4°C, first dry, then in artificial sea water. The plots were dry during sowing but rewetted after. All plots were fertilized before or after sowing. In October 1979 and 1981, live vegetation was cut from the plots, then dried and weighed.

    (Summarised by: Nigel Taylor)

  2. Add lime or similar chemicals before/after planting non-woody plants: brackish/saline wetlands

    A controlled study in 1980–1981 on reprofiled borrow pits in North Carolina, USA (Broome et al. 1982) found that liming had no significant effect on the biomass of planted smooth cordgrass Spartina alterniflora. Limed and unlimed plots supported statistically similar above-ground cordgrass biomass in seven of seven comparisons after one growing season (limed: 7–172 g/m2; unlimed: 6–100 g/m2) and in one of one comparisons after two growing seasons (limed: 2,380 g/m2; unlimed: 1,804 g/m2). The result was the same when lime was applied to fertilized or unfertilized plots, and at two different lime doses (see original paper). Methods: In June 1980, wild-harvested smooth cordgrass plants were planted into coastal land that had been reprofiled (to 6–43 cm above mean sea level; salinity <20 ppt) after excavation of sediment for construction. The site was dry during planting but rewetted after. Some plants were limed after planting (dolomitic limestone; 2,240–4,500 kg/ha) whilst others were not limed. The study does not clearly report the experimental design (including number of plants and plots). In October 1980 and 1981, living cordgrass was cut from 0.25-m2 quadrats then dried and weighed.

    (Summarised by: Nigel Taylor)

  3. Add inorganic fertilizer before/after planting non-woody plants: brackish/saline wetlands

    A controlled study in 1979–1981 on reprofiled borrow pits in North Carolina, USA (Broome et al. 1982) found that adding fertilizer typically increased the biomass and height of planted cordgrasses Spartina spp., but typically reduced the biomass of planted black rush Juncus roemerianus and sometimes reduced survival of big cordgrass Spartina cynosuroides. After one growing season, fertilized cordgrasses produced more above-ground biomass than unfertilized cordgrasses in 40 of 53 comparisons (for which fertilized: 64–464 g/m2; unfertilized: 6–55 g/m2) with no significant difference in the other 13 comparisons (for which fertilized: 31–177 g/m2; unfertilized: 8–43 g/m2). In contrast, fertilized black rush produced less above-ground biomass than unfertilized black rush in four of six comparisons (for which fertilized: 4 g/m2; unfertilized: 18 g/m2) with no significant difference in the other two comparisons (for which fertilized: 11–12 g/m2; unfertilized: 18 g/m2). After two growing seasons, smooth cordgrass Spartina alterniflora was taller when fertilized (144–152 cm) than when not fertilized (113 cm). Black rush height was not measured. Finally, the study reported that adding standard fertilizer to the planting hole reduced survival of big cordgrass (standard fertilizer: 5–23%; slow-release fertilizer or unfertilized: 80% survival after one growing season). Methods: In June 1979 and 1980, greenhouse-grown or wild-harvested vegetation was planted into reprofiled borrow pits (salinity <20 ppt). Some plants were fertilized (one of 18 different type/dose combinations placed in planting holes, next to planting holes or mixed into soil surface). Other plants were left unfertilized. The study does not clearly report the experimental design (including numbers of plants and plots). In October 1980 and 1981, living vegetation was cut from 0.25-m2 quadrats then dried and weighed.

    (Summarised by: Nigel Taylor)

  4. Directly plant non-woody plants: brackish/saline wetlands

    A site comparison study in 1980–1981 involving reprofiled borrow pits in North Carolina, USA (Broome et al. 1982) reported 37–98% survival of four planted herb species after one growing season and that the biomass of survivors increased, but that vegetation in planted and natural marshes differed after two growing seasons. Statistical significance was not assessed. After one growing season, survival rates were 37–55% for smooth cordgrass Spartina alterniflora, 66–97% for big cordgrass Spartina cynosuroides, and 82–98% for saltmeadow cordgrass Spartina patens (data not clearly reported for black rush Juncus roemerianus). The above-ground biomass of surviving plants increased from 8–562 g/m2/species after one growing season to 297–3,105 g/m2/species after two growing seasons. Finally, planted and natural stands of big cordgrass and black rush were compared. After two growing seasons, planted stands contained only 297–1,525 g/m2 above-ground biomass (vs natural: 997–1,891 g/m2) and vegetation only 91–161 cm tall (vs natural: 155–293 cm). Planted stands contained more big cordgrass stems than natural marshes (planted: 223; natural: 44 stems/m2), but fewer black rush stems (planted: 509; natural: 884 stems/m2). Methods: In spring/early summer 1979–1980, four herb species were planted (60–90 cm apart) into reprofiled coastal land (dry during planting but rewetted after; salinity <20 ppt). Experimental design, including number of plants and plots, was not clearly reported. In October 1979–1981, planted vegetation and vegetation in a nearby natural marsh were surveyed. This included cutting, drying and weighing live vegetation from 0.25-m2 quadrats.

    (Summarised by: Nigel Taylor)

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