| Abstract: | Some glycoside hydrolase activities, dehydrogenase activities, and oxygen uptakes were studied in New Zealand topsoils under pasture, arranged in two zonal soil sequences: one in which mean annual temperature varied (5 soils), and another in which mean annual rainfall varied (7 soils). Differences in other site factors were small. All the biochemical activities were negatively, but not usually significantly, correlated with mean annual temperature. Activities did not appear to be influenced by differences in the proportions of grasses and legumes (mainly clovers) or in the clay contents at the different sites. Activities of glycoside hydrolases (a) without added substrate and (b) with added starch were significantly correlated with mean annual rainfall, and with soil moisture and organic C contents; activities of (c) enzymes hydrolysing sucrose were significantly correlated only with soil organic C contents. The ratios of (c) to (b) declined significantly with increasing mean annual rainfall. Dehydrogenase activities were highest in winter samples and significantly correlated with both soil moisture content and pH. Oxygen uptakes were significantly correlated with numbers of viable bacteria in soils of the rainfall sequence although they were not significantly correlated with annual rainfall nor with soil organic C contents. Oxygen uptakes and dehydrogenase activities were not significantly interrelated. Results were compared with previous studies of grassland soils. |
