Estimates of N2 Fixation in Ecosystems: The Need for and Basis of the 15N Natural Abundance Method

Abstract

Absolute instantaneous rates of biological N2 fixation can be measured accurately under carefully controlled laboratory conditions. Seeking an integrated value of the quantity of N2 fixed over, for example, a growing season adds enormously to the problem. These difficulties are considerably magnified in natural field settings, compared to agricultural settings. Several articles have reviewed available methods for use in the field (Burris 1974; Hardy and Holsten 1977; Bergersen 1980; Turner and Gibson 1980; Knowles 1980, 1981; Rennie and Rennie 1983; Silvester 1983) with the authors expressing various degrees of satisfaction with the available methods.