Comparison of in situ methods to measure N mineralization rates in forest soils

Nitrogen mineralization is a critical ecosystem process that is difficult to measure. Among several in situ methods used to estimate N mineralization rates in soils, the buried bag and covered-cylinder methods are two of the most common. Few studies have compared N mineralization rates from these two in situ methods, and it is still unclear if they provide analogous results. We compared both techniques, and two different core diameters, to determine if the different methods produce comparable results. Contrary to our expectations, larger cores were not more representative than smaller due to the importance of site-specific soil characteristics, especially rockiness. Dissimilarities in means, and weak and inconsistent correlations between methods, suggested that the different methods may not be equivalent. Our results suggest that the method optimization depends on specific site conditions, at least in forest soils, and that comparison among studies using different in situ methods should be made with caution until more standardization is achieved.