Salt stress limitation of seedling recruitment in a salt marsh plant community

Abstract

Seedling recruitment in salt marsh plant communities is generally precluded in dense vegetation by competition from adults, but is also relatively rare in disturbance-generated bare space. We examined the constraints on seedling recruitment in New England salt marsh bare patches. Under typical bare patch conditions seed germination is severely limited by high substrate salinities. We examined the germination requirements of common high marsh plants and found that except for one notably patch-dependent fugitive species, the germination of high marsh plants is strongly inhibited by the high soil salinities routinely encountered in natural bare patches. Watering high marsh soil in the greenhouse to alleviate salt stress resulted in the emergence of up to 600 seedlings/225 cm. The vast majority of this seed bank consisted of Juncus gerardi, the only common high marsh plant with high seed set. We tested the hypothesis that salt stress limits seedling contributions to marsh patch secondary succession in the field. Watering bare patches with fresh water partially alleviated patch soil salinities and dramatically increased both the emergence and survival of seedlings. Our results show that seedling recruitment by high marsh perennial turfs is limited by high soil salinities and that consequently their population dynamics are determined primarily by clonal growth processes. In contrast, populations of patch-dependent fugitive marsh plants which cannot colonize vegetatively are likely governed by spatially and temporally unpredictable windows of low salinities in bare patches.

Infection by the systemic fungus Epichloë glyceriae alters clonal growth of its grass host, Glyceria striata

“…Clonal growth can benefit the host by extending longevity of a genotype by spreading the risk of mortality among many ramets, and by potentially increasing the relative fitness of a genotype locally through daughter ramet production (Harper 1977;Cook 1979;Pan & Price 2001). Moreover, daughter ramets have a higher probability of establishment than seeds, particularly in harsh environments, because daughter ramets can be subsidized by mother ramets until they are established (Shumway & Bertness 1992;Shumway 1995;Pennings & Callaway 2000).…”

Seed production, germination rate, and seedling establishment ofScirpus pungens in tidal brackish marshes

“…There is a general trend for seed banks to be smaller and less diverse as salinity increases (Leck 1989). Shumway and Bertness (1992) have also observed that increasing salinity inhibits germination and emergence of Juncus gerardi Loisel. Bertness et al (1987) have reported that insect herbivory on flowers and seeds of Spartina alterniflora Loisel., S. patens (>,it.)…”

“…Colonization of bare patches through sexual reproduction has been reported for a variety of species including ,/. gerardi and Scirpus deltarum Schuyler (Shumway andBertness 1992, White 1993). However, the overall impact of this colonization on the development of Scirpus marshes along the St.Lawrence River estuary is unknown and would require a long-term study.…”

Flora Y Vegetacion Del Salar De Ascotan, Andes Del Norte De Chile

“…Luego, la ausencia de terófitas en el salar de Ascotán podría deberse al escaso espacio disponible para colonizar y a la alta salinidad de sus suelos en los espacios abiertos sin vegetación. Al respecto, Shumway & Bertness (1992) mencionan que, en general, en los hábitats de salar y de marismas salinas, la frecuencia de perturbaciones es baja y los espacios abiertos son sólo micrositios con alta concentración de sales. Por otra parte, la mayor proporción de caméfitas en el salar respecto de la vegetación zonal, podría estar relacionada con algunas particularidades fisiológicas de especies caméfitas del salar tales como Lycium humile Phil.…”