PHENOLOGY OF THE EDAPHIC MICROARTHROPODS IN A CHILEAN COASTAL DESERT SITE AND THEIR RESPONSE TO WATER AND NUTRIENT AMENDMENTS TO THE SOIL

This work was aimed at (1) comparing the effect of experimental supple mentation of water and soil nutrients (N, P, K, Ca and Mg) on the rela tive numbers of soil microarthropods in a coastal desert ecosystem, (2 ) evaluating the effect of time (seasons) as an interacting factor, an d (3) describing the phenological patterns of the main taxa. We tested the hypothesis of no-treatment effects, The work was done in Lagunill as (30 degrees 06' S, 71 degrees 21'W, North-Central Chile), where two 1 ha-experimental plots were established in 1987. The plots differed in plant cover, soil characteristics and depth of an impermeable layer of calcium carbonate (hardpan). The study included a wet and a dry an nual cycle. Time (seasons) was the most important factor in determinin g the numerical response of soil microarthropods; but differences in t reatment effects between plots suggest that the depth of the hardpan l ayer may have played a role. The interaction water x time was signific ant for the prostigmatid mites and collembolans, but not for the remai ning taxa. For the two and a half years of the study, we were unable t o detect significant responses to the nutrient treatments. This lack o f response might have been due to the low artificial water input or to the resilience of the system.