The relation between various detritus inputs and soil enzyme activities in a Central European deciduous forest

Within the framework of Síkfőkút DIRT (Detritus Input and Removal Treatments) Project, we have been examining the extent to which microbial activities of soils are influenced by detritus inputs of diverse quantities and qualities. The experimental site is located in the south part of the Bükk Mountains in North Eastern Hungary. This forest is a semi-natural stand (Quercetum petraeae-cerris community) without forest management. The six treatments established are as follows: three treatments involving detritus removal (No Litter, No Roots, No Inputs), two treatments involving detritus duplication (Double Litter, Double Wood) and a control treatment. The study intends to present the results of saccharase and arylsulphatase activity examinations. Our hypothesis was that detritus reduction causes significantly greater influence on soil enzyme activities than detritus increase of the same extent. The general purpose of the project is to reveal the connection between modifications of detritus production and changes of climatic conditions and land use. It also studies how the modifications, decreases or increases in detritus production influence organic material content, and physical, chemical or biological processes of soils. Saccharase and arylsulphatase activities were measured three and a half years after the establishment of the plots; thus having enough time for the development of different ecological conditions at our disposal. Significant differences were detectable between the treatments for both enzymes. Two separate groups of treatments could be distinguished. The treatments with additional aboveground inputs (Double Litter, Double Wood) and the control (C) revealed higher activities, while a lower – sometimes significantly lower – enzyme activity characterized the other three, removal treatments (No Litter, No Roots, No Inputs). As for the Double Litter, Double Wood and Control treatments, no significant difference was detectable, although the latter two revealed higher values of enzyme activities than the former one. We found that soil moisture content was correlated with the two soil enzyme activities, especially that of the arylsulphatase. A much weaker correlation was found between the enzyme activities and soil moisture content in the soils that were wetter and poorer in substrates (No Roots and No Inputs treatments). Seasonal differences also involved the diverse moisture contents, while the effect of temperature could hardly be observed during the examinations (due to the nature of methods). In the case of both enzymes, the highest activities were detected during the wetter period, in spring. The three detritus removal treatments influenced enzyme activities in different ways. As for saccharase, it was the removal of belowground detritus that caused the greatest influence. However, in the case of arylsulphatase, it was the soil moisture content that influenced activity to the greatest extent in detritus removal treatments.