Net aerial primary production (NAPP) of the marsh macrophyteScirpus maritimus estimated by a combination of destructive and non-destructive sampling methods

Net aerial primary production (NAPP) of marsh macrophytes is usually estimated either by destructive sampling techniques or by phenometric techniques. 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 determine end-of-season biomass and phenometric techniques to estimate the mortality of biomass before the end of the season. NAPP is derived through summation of these two estimates. Techniques needed to calculate the precision of the NAPP estimate are provided. The so called hybrid technique was used to estimate NAPP ofScirpus maritimus L. in a brackish marsh along the Westerschelde estuary, the Netherlands. Estimated NAPP was 1372 g m-2. End-of-season biomass accounted for 1106 g m-2, while mortality contributed 266 g m-2. Precision of the end-of-season biomass and the mortality estimates, expressed as coefficient of variation, was 18.2 and 26.0% respectively. The precision of the resultant, 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.