ASSESSING ABOVEGROUND NET PRIMARY PRODUCTION OF VASCULAR PLANTS IN MARSHES

Information of aboveground net primary production (ANPP) in marshes ha s been limited by the lack of accurate methods for assessment. Most po pular methods have weaknesses that cause either underestimates or over estimates of ANPP values. The nondestructive growth kinetics monitorin g method used by Williams and Murdoch (W-M) has provided, perhaps, a m ost ideal and reasonable assessment of ANPP in Juncus roemerianus mars hes. 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 or iginal W-M method while eliminating the need to monitor growth kinetic s of individual plants. The modified ANPP procedure requires monthly h arvests of the above ground plant biomass over a period of 1 yr and th e estimation of mean residence time of the plant. The modified W-M pro cedure was comparable to the original procedure in J. roemerianus mars hes of northern Florida. This modified procedure has the potential to be applied to marshes other than those dominated by Juncus.