Effect of vegetation manipulation of abandoned arable land on soil microbial properties

The effect of vegetation composition on various soil microbial properties i n abandoned arable land was investigated 2 years after agricultural practic e had terminated. Microbial numbers and processes were determined in five r eplicate plots of each of the following treatments: continued agricultural practice (monoculture of buckwheat in 1997), natural colonization by the pi oneer community (arable weeds), and manipulated colonization from low (four species, three functional groups: grasses, forbs and legumes) or high dive rsity (15 species, three functional groups) seed mixtures from plant specie s that are characteristic of abandoned fields in later successional stages. The results indicated that differences in above-ground plant biomass, plan t species composition and plant species diversity had no significant effect on soil microbial processes (net N mineralization, short-term nitrificatio n, respiration and Arg ammonification), microbial biomass C and N (fumigati on-incubation) or colony-forming units of the major microbial groups. Hence , there were no indications that soil microbial processes responded differe ntly within 2 years of colonization of abandoned arable land by later succe ssional plants as compared to that by plants from the natural pioneer weed community. Therefore, it seems that during the first few years after arable field abandonment, plants are more dependent on the prevailing soil microb iological conditions than vice versa.