Site conditions, not parental phenotype, determine the height of Spartina foliosa

The effect of parental growth form on ramets introduced to new sites has br oad implications for ecological restoration. We asked whether transplants o f Spartina foliosa need to come from tall parents in order to produce tall stands for nesting by the Light-Footed clapper rail, one of southern Califo rnia's many endangered, salt-marsh-dependent species. Tan and short S. foli osa transplants, collected from local salt marshes, were grown in a common garden and in microcosms, with different results. In the common garden, whi ch had hypersaline soil, offspring of tall versus short clones did not diff er, but they did respond to soil variations among blocks. In blocks with le ss sandy soil, stems were taller and up to 5 times more numerous, and patch sizes were up to 3 times larger After two years in low-salinity microcosms , transplants receiving nitrogen additions produced more stems and over twi ce the total stem length of controls, regardless of parental height form. A slight parental effect was seen in this benign environment; the maximum he ight of tall-form transplants was 15 cm taller than that of short-form tran splants, but the effect did not persist through year 2. Results indicate th at both height forms of S. foliosa grew better (taller and more dense) with less environmental stress (lower salinity, more nutrients). We conclude th at environmental differences are more important than parental height form i n determining S. foliosa growth. This means that, for restoration purposes, S, foliosa ramets can and should be collected from short clones, rather th an from existing, prime nesting habitat.