Impact of heavy metals on mass and energy flux within the decomposition process in deciduous forests

Abstract

: Laboratory experiments on microbial decomposition and on the contribution 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 accumulation of organic litter material in heavy metal-contaminated soils. Microbial decomposition of freshly fallen leaves remained quantitatively unaffected by artificial lead contamination (1000 mg kg(-1)). The same was true for further decomposed leaf litter material, provided that the breakdown of this material was not influenced by faunal components. 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 field but occurred in microcosm studies as well. Reduced reproduction and lower activity of the diplopods most likely were responsible for the observation that lead-influenced diplopods enhanced microbial activity in soil only in a lesser degree than uncontaminated animals did. This effect is assigned to represent the main reason for decreased decomposition rates and the subsequent accumulation of organic material in heavy metal-contaminated soils.

Selection favours low hsp70 levels in chronically metal-stressed soil arthropods

“…Mean metal (Pb, Zn, Cd) concentrations per site refer to the border between the O and A h horizons and were obtained by graphite furnace atom absorption spectrophotometry (method according to Gräff et al ., 1997 ), from the data of Müller et al . (1987 ) and Köhler et al . (1995 ), or have been provided by the Baden‐Württemberg Research Agency for Forestry, Freiburg, Germany, or the District Magistracy of Tübingen, Germany.…”

Energy Reserves and Metal-storage Granules in the Hepatopancreas of Oniscus asellus and Porcellio scaber (Isopoda) from a Metal Gradient at Avonmouth, UK

“…These types of spherites are most likely derived from lysosomes, as supported by the presence of acid phosphatase in these organelles (summarized in Dallinger, 1993) and the observed fusion of granule-containing vesicles with lysosomes (Ko¨hler et al, 1995). Since storage of metals seems to be a more energy efficient way of detoxification than active transport and subsequent excretion via faeces (Simkiss, 1976(Simkiss, , 1977, the number and size of Type B-granules increases with increasing metal input (Brown, 1982).…”