The influence of mycorrhizal inoculation, inundation period, salinity and phosphorus availability on the growth of saltmarsh cordgrass Spartina alterniflora and big cordgrass Spartina cynosuroides in eastern USA
Published source details
McHugh J. M. & Dighton J. (2004) Influence of Mycorrhizal Inoculation, Inundation Period, Salinity, and Phosphorus Availability on the Growth of Two Salt Marsh Grasses, Spartina alterniflora Lois. and Spartina cynosuroides (L.) Roth., in Nursery Systems. Restoration Ecology, 12, 533-545
Published source details McHugh J. M. & Dighton J. (2004) Influence of Mycorrhizal Inoculation, Inundation Period, Salinity, and Phosphorus Availability on the Growth of Two Salt Marsh Grasses, Spartina alterniflora Lois. and Spartina cynosuroides (L.) Roth., in Nursery Systems. Restoration Ecology, 12, 533-545
Salt marsh restoration in order to mitigate damage caused by industrial development is of concern in some regions, such as the eastern United States. In this study, seedlings of two salt marsh grasses, saltmarsh cordgrass Spartina alterniflora and big cordgrass Spartina cynosuroides, were grown in soil with a commercial inoculum of arbuscular mycorrhizal fungi to see if this enhanced growth. The experiment was designed to make inoculation and growth procedures applicable to large-scale nursery production of seedlings, hence the use of a commercially available mycorrhizal inoculum.
Cordgrass seed collection: Seeds of saltmarsh cordgrass Spartina alterniflora and big cordgrass S.cynosuroides were obtained from Chesapeake Bay (northeast USA) in 1998. S.alterniflora seed was collected from tall-form plants near Poquoson (Virginia), and S.cynosuroides from Elliot's Island (Dorchester County, Maryland).
Mycorrhizal inoculum: A commercially available arbuscular mycorrhizal inoculum mix supplied in the form of a dry sandy loam (First Fruits (RD1, Box 156, Triadelphia, WV, USA.) was used. The predominant fungal species was Glomus etunicatum (95%) with Glomus claroideum (<2%) and Glomus intraradices (<2%), with an average spore count of 79 spores/cm³ of inoculum.
Cordgrass propogation: Cordgrass sowing medium comprised a peat moss and sand mix (1:1 ratio). Pulverized limestone (9 kg) was added to achieve a pH of around 6.5. Half of the soil was used to fill 1,600 pots (tapering 6 × 6 × 7.5 cm, approx. 175 ml). Another 1,600 pots were filled with the remaining soil that had been mixed with 20 l of mycorrhizal inoculum mix. Approximately 1.5 l of seed of each cordgrass was separately mixed with 50 l of a propagation soil mix (ProMix PGX, Premier, Inc.) and each was spread over 25 'ebb and flow' boxes (see original paper), containing either the straight soil mix or the inoculated soil mix. Plants were grown under conditions simulating three levels of tidal inundation, to which two levels of applied phosphorus (P) and two levels of salinity were imposed. Plants were harvested over 3 days, 2–4 December, after approximately 78 days of growth.
After 78 days S.alterniflora was poorly colonized by arbuscular mycorrhizae, developing only fungal hyphae and no arbuscules, S.cynosuroides became moderately colonized. Mycorrhizal inoculation marginally improved growth and P and nitrogen (N) content of both species at low levels of P supply, but significantly increased tillering. Greater P availability increased the mycorrhizal status of S.cynosuroides and improved P nutrition of both cordgrass species, despite a reduction in the root-to-shoot ratio. Increasing salinity reduced mycorrhizal colonization of S.alterniflora but not of S.cynosuroides. S.alterniflora growth and nutrient content improved at higher salinity, but this only increased nutrient content in S.cynosuroides. Increased inundation time decreased cordgrass growth, but tissue P and N concentrations were highest in plants with the longest inundation period.
Conclusions: Mycorrhizal colonization was low in both cordgrass species. Effects of mycorrhization on plant growth were slight and the root-to-shoot ratio of saltmarsh cordgrass was reduced. There was no influence of mycorrhizae on either species total P or total N acquisition, but the presence of mycorrhizae reduced tissue P concentration. The main effect of mycorrhizal inoculation on both cordgrass species was to induce greater tillering, resulting in a greater number of shoots. This could be beneficial in enhancing ground cover during restoration procedures.
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