Assessing Aboveground Net Primary Production of Vascular Plants in Marshes

Abstract

Information of aboveground net primary production (ANPP) in marshes has been limited by the lack of accurate methods for assessment. Most popular methods have weaknesses that cause either underestimates or overesti- mates of ANPP values. The nondestructive growth kinetics monitoring method used by Williams and Murdoch (W-M) has provided, perhaps, a most ideal and reasonable assessment of ANPP in Juncus roemerianus marshes. Unfortunately, the W-M procedure is difficult to carry out and it is restricted to Juncus marshes. I present here a modification of the W-M procedure. The modified procedure applies the principle of the original W-M method while eliminating the need to monitor growth kinetics of individual plants. The modified ANPP procedure requires monthly harvests of the above- ground plant biomass over a period of 1 yr and the estimation of mean residence time of the plant. The modified W-M procedure was comparable to the original procedure in j roemerianus marshes of northern Florida. This modified pro- cedure has the potential to be applied to marshes other than those dominated byJuncus.