Estimation of primary production using five different methods in a Spartina alterniflora salt marsh

The aboveground production of Spartina alterniflora in a salt marsh in Barataria Bay, Louisiana, USA was estimated using five different harvest methods: peak standing crop (PSC), Milner-Hughes, Smalley, Wiegert-Evans, and Lomnicki et al., and a non-destructive method based on measurement of stem density and longevity. Annual production estimates were 831 ± 41, 831 ± 62, 1231 ± 252, 1873 ± 147 and 1437 ± 96 g dry wt m−2 for each method, respectively. The average longevity of individually tagged young shoots was 5.2 ± 0.2 months, equivalent to an annual turnover rate of 2.3 crops per year. Among the five methods, Wiegert-Evans and Lomnicki et al. were considered more accurate than the other three because they corrected for mortality losses between sampling times. The Lomnicki et al. method was preferred over the Wiegert-Evans method because of its greater simplicity.