Variation in Seed Production and Germination of Spartina Anglica Within a Zoned Saltmarsh

Abstract

(1) The coastal saltmarsh at Southport, Merseyside, supported four zones of Spartina anglica sward which, from seaward to landward, were named pioneer, transitional, mature, and invaded zones, respectively. (2) The mean density of inflorescences varied from nearly 4 m-2 in the pioneer zone to more than 112 m-2 in the adjacent transitional zone. The upper reaches of the marsh had intermediate densities. (3) Inflorescences from the upper zones were large and bore at least twice as many spikelets as those from lower zones. However, the proportion of mature, filled seeds per inflorescence was inversely related to the number of spikelets borne on it resulting in a marked difference between zones in the production of viable seed. The zone of most vigorous vegetative growth and largest inflorescences thus produced the smallest proportion of viable seed. (4) Germination of seeds was accelerated by cool (5 IC), moist and brief (60 day) storage. The length of photoperiod had no significant effect on germination whereas salt water was inhibitory. There were significant interactions between factors. Overall production of viable seeds was low (<6%) and 77% of potentially viable seed was produced in 16% of the total marsh area examined.