The facilitative role of Kosteletzkya pentacarpos in transitioning coastal agricultural land to wetland during sea level rise

Rising sea level is increasing soil salinity and flooding frequency, directly impacting low-lying coastal farmlands. In response to reduced production of traditional crops, dikes may be built which will prevent inland migration of wetlands. Seashore mallow, Kosteletzkya pentacarpos, is being developed as an alternative crop for such areas. Eventually, when the crop can no longer be harvested because of flooding, we hypothesize that seashore mallow will facilitate the establishment of desirable wetland species by acting as a nurse crop through this transitional period. Four treatments were planted in flood-irrigated plots at an upland field site adjacent to a salt marsh. The control, Spartina patens, K. pentacarpos, and combined treatments were laid out in a complete randomized block design with replication. These were sampled for species percent vegetative cover, morphological traits, above-ground biomass, and leaf litter. The presence of seashore mallow enhanced S. patens and Baccharis halimifolia recruitment and did not negatively impact growth of planted S. patens. Communities established around K. pentacarpos were both productive and diverse, and leaf litter was increased by K. pentacarpos. Our findings support the use of K. pentacarpos as a low-cost nurse crop in salinized agro-ecosystems. Such a strategy would prolong agricultural function and minimize loss of ecological services by allowing gradual inland wetland migration

The regulation of ecosystem functions by ecotypic variation in the dominant plant: a Spartina alterniflora salt-marsh case study

Genetic differences among populations of a keystone species may affect ecosystem functional properties. We tested this by planting Spartina alterniflora from different geographical regions in a newly created salt marsh in Delaware, USA. Spartina alterniflora plants from morphologically distinct short-form (back marsh) populations were originally collected from Massachusetts (41°34′ N), Delaware (38°47′ N), and Georgia (31°25′ N) in the USA and vegetatively propagated for 6 years in a salt water-irrigated common garden in Delaware before transfer to a newly created salt marsh. The magnitude of the expression of marsh functions in the created marsh, measured over 5 years, remained distinct in patches of each ecotype. End of season aerial biomass, below-ground biomass, root and rhizome distribution, canopy height, stem density, and carbohydrate reserves were closer to values reported for the plants’ native sites than to those typical of Delaware. Thus, many of the plant features characteristic of particular latitudes appear to be under genetic control. Such ecotypic differentiation influences ecosystem function through keystone resource and keystone modifier activities. Respiration of the microbial community associated with either dead shoots or the soil varied with plant ecotype in the created wetland and the patterns reflected those reported for their native sites. High edaphic respiration under the Massachusetts ecotype was correlated with the high percentage of sugar in the rhizomes. Edaphic chlorophyll was greater under the canopies of the Massachusetts and Delaware ecotypes than under the Georgia canopy and exhibited a relationship similar to that of algal production rates reported for the native sites. Larval fish were most abundant in pit traps in the Massachusetts ecotype