SPATIAL DEPENDENCE OF SOIL ENZYME-ACTIVITIES ALONG A SLOPE

This study measured the spatial dependence of soil enzyme activities a nd other properties of the Ap horizon in a Gray Brown Luvisol (Hapluda lf), Soil samples were collected at 74 positions along a slope followi ng harvest of soybean [Glycine max (L.) Merr.] and fall tillage. Param eters measured were activity of dehydrogenase, urease, glutaminase, ph osphatase, arylsulfatase, and beta-glucosidase; water, organic carbon (OC), mineral N, and inorganic P contents; the light fraction of soil organic matter; and depth of the Ap horizon. Rank correlation indicate d significant relationships between water and dehydrogenase, urease, g lutaminase, phosphatase, and arylsulfatase activities, and between wat er and OC content, Depth of the Ap horizon, water content, and arylsul fatase activity were strongly spatially dependent; OC and inorganic P contents and phosphatase activity were moderately spatially dependent. Other properties showed little or no spatial dependence. re ranges of spatial dependence were similar for depth of the Ap horizon, inorgani c: P content, and phosphatase activity (approximate to 20 m), The rang e for arylsulfatase activity was 16 m, while that of OC content was 32 m, The relatively long range estimate for water content (98 m) was in fluenced by a trend along the slope. Maps of water and OC contents and phosphatase and arylsulfatase activities indicated similar spatial pa tterns along the slope, The magnitude of these soil properties was min imal in the middle or upper portion of the slope, and maximal at the f ootslope. Similarity in spatial patterns along the slope was interpret ed as evidence for influence of water or OC content on amounts of phos phatase and arylsulfatase at that scale.