NET AERIAL PRIMARY PRODUCTION (NAPP) OF THE MARSH MACROPHYTE SCIRPUS-MARITIMUS ESTIMATED BY A COMBINATION OF DESTRUCTIVE AND NONDESTRUCTIVESAMPLING METHODS

Net aerial primary production (NAPP) of marsh macrophytes is usually e stimated either by destructive sampling techniques or by phenometric t echniques. Destructive methods, however, are thought to be inaccurate while phenometric techniques are very labour intensive. In this study a new method is presented which allows an accurate and more efficient estimation of NAPP. The method combines destructive sampling to determ ine end-of-season biomass and phenometric techniques to estimate the m ortality of biomass before the end of the season. NAPP is derived thro ugh summation of these two estimates. Techniques needed to calculate t he precision of the NAPP estimate are provided. The so called hybrid t echnique was used to estimate NAPP of Scirpus maritimus i,. in a brack ish marsh along the Westerschelde estuary, the Netherlands. Estimated NAPP was 1372 g m(-2). End-of-season biomass accounted for 1 106 g m(- 2), while mortality contributed 266 g m(-2). Precision of the end-of-s eason biomass and the mortality estimates, expressed as coefficient of variation, was 18.2 and 26.0% respectively. The precision of the resu ltant, NAPP, was higher: 17.2%. These results indicate that NAPP could be estimated with a higher precision than end-of-season biomass. This contradicts the view that the accuracy of NAPP estimates can only be improved at the expense of its precision.