IMPACT OF HEAVY-METALS ON MASS AND ENERGY FLUX WITHIN THE DECOMPOSITION PROCESS IN DECIDUOUS FORESTS

Laboratory experiments on microbial decomposition and on the contribut ion of diplopods to organic matter decomposition in soil were combined with field studies to reveal the major points of heavy metal effects on the leaf litter decomposition process. The study focused on the acc umulation of organic litter material in heavy metal-contaminated soils . Microbial decomposition of freshly fallen leaves remained quantitati vely unaffected by artificial lead contamination (1000 mg kg-1). The s ame was true for further decomposed leaf litter material, provided tha t the breakdown of this material was not influenced by faunal componen ts. Although nutrient absorption in diplopods is affected by high lead contents in the food, this effect alone, however, was shown not to be sufficient for the massive deceleration of the decomposition process under heavy metal influence which could not only be observed in the fi eld but occurred in microcosm studies as well. Reduced reproduction an d lower activity of the diplopods most likely were responsible for the observation that lead-influenced diplopods enhanced microbial activit y in soil only in a lesser degree than uncontaminated animals did. Thi s effect is assigned to represent the main reason for decreased decomp osition rates and the subsequent accumulation of organic material in h eavy metal-contaminated soils.