EFFECTS OF PREVIOUS INTENSIVE AGRICULTURAL MANAGEMENT ON MICROORGANISMS AND THE BIODIVERSITY OF SOIL FAUNA

In this study effects of previous intensive management on microorganis ms and soil fauna were investigated. It was hypothesized that a former but now abandoned intensive management practice still causes negative effects years after conversion into conventional management. Two agri cultural fields were investigated. Until 1990 one field (preINT) had b een managed with the intensive crop hops (Humulus lupulus), whereas th e second one (preCON) had been under crop rotation. In consequence the main difference between the two fields was the high copper load of pr eINT. In the period during this study both fields were cultivated the same way (1991: winter wheat, 1992: spring barley). Microbial biomass, species numbers and abundances of collembola as well as of earthworms were much lower in preINT in the first year of investigation. In 1992 , earthworm biomass was still extremely low, whereas the microbial bio mass and total collembola had reached the values of preCON. Between th e collembola populations there were still distinct differences in spec ies abundances. In preCON, Folsomia quadrioculata, Onychiurus armatus, and the Mesaphorura krausbaueri group each made up about 1/4 of the t otal population. In preINT nearly 60 % of the population consisted of the Mesaphorura krausbaueri group, followed by Isotoma notabilis and O nychiurus armatus. Folsomia quadrioculata and Isotomiella minor in pre INT exhibited extremely small abundances during o the whole investigat ion period. Thus, in comparative field studies their abundances could serve as indicators for copper contamination. Supplementary microcosm studies had shown that severe reductions of earthworm numbers, especia lly with simultaneous high mesofauna abundances, will be accompanied b y increased mineralization rates. Therefore changes in soil fauna comp osition caused by copper contamination could have pronounced effects o n mineralization rates and nutrient fluxes.