A COMPARISON OF SPARTINA ALTERNIFLORA PRIMARY PRODUCTION ESTIMATED BY DESTRUCTIVE AND NONDESTRUCTIVE TECHNIQUES

Abstract

Individual live and dead culms of highmarsh Spartina alterniflora Loisel. within permanent 0.1 m2 quadrats were tagged. Growth data reveal leaf production, senescence and abscission are continuous processes throughout the year in this Georgia salt marsh. Leaf production of culms < 10 cm in height peaked in June (0.023 leaves culm-1 day-1) and of culms ≤ 10 cm in height in December (0.031 leaves culm-1 day-1). Leaf senescence peaked in August (0.047 leaves culm-1 day-1) as did leaf abscission (0.023 leaves culm-1 day-1). Production of new leaves from shoots ≤ 10 cm exceeded leaf production from older culms during fall and early winter. Recruitment of new shoots occurred throughout the year with a maximum rate of 71 culms m-2 56 days-1 in April and a total annual recruitment of 277 culms m-2 yr-1. Total annual mortality was estimated at 248 culms m-2 yr-1. Live standing biomass in grams dry weight (gdw) was estimated using the model, y = 0.63 - 0.05h + 0.002h2 where h = culm height. Field testing of the model suggested agreement between destructively and nondestructively estimated biomass within 95% confidence limits throughout the year, except during spring and early summer. Nondestructive estimation of net aerial primary production (NAPP) consisted of summing biomass losses to the dead component resulting from culm mortality and abscission of leaves from live culms. Leaf abscission from live culms accounted for 31% of the annual NAPP. Destructively estimated NAPP was 931 gdw m-2 yr-1 whereas the nondestructively estimated NAPP was 635 gdw m-2 yr-1. The difference in NAPP estimates appears to be related to sampling variability and leaf loss during the year, both of which are addressed by the nondestructive method.