SPATIAL AND TEMPORAL VARIABILITY IN CHEMICAL-PROPERTIES OF A PODZOLICB-HORIZON OF AN OLD-GROWTH MAPLE FOREST

A Podzolic soil from an old-growth maple hardwood forest in eastern Ca nada was systematically sampled from a 16.5-m-long trench in 1975. In 1986, the upper 10 cm of the B horizon was resampled from two sampling lines located on each side and parallel to the 1975 trench, one at a distance of 1 m downhill and the other at a distance of 4 m uphill. To tal N, organic C, pH, and exchangeable Ca, Mg and K were measured. The objectives were to evaluate the change in the chemical status of the B horizon from 1975 to 1986 and to characterize the spatial variabilit y of the horizon. No significant change was found in the soil chemical properties tested during this 11-yr period. No significant autocorrel ation was observed between soil samples 60 cm apart, except for the do wnhill sampling line, which was located 1 m from the trench. For most properties, the magnitude of the difference between two soil sampling units was not proportional to the distance separating them over the ra nge of 0.6-4.2 m. Except for pH, a difference in soil properties of mo re than 30% was observed in 37-56% of sample pairs 60 cm apart. Resamp ling near (1 m) an old soil pit may not be valid because of possible l ocal modifications of soil properties created by the pit, even when it is filled in.