Showing papers by "Heikki Setälä published in 1990"

Effects of soil fauna on leaching of nitrogen and phosphorus from experimental systems simulating coniferous forest floor

Abstract: Long-term experiments (97–98 weeks) were carried out in macrocosm systems simulating the complexity of coniferous forest soil. The macrocosms were partially sterilized by freezing, thawing and drying, then re-inoculated with microbes alone or microbes + soil fauna. Removable microcosms containing birch litter, spruce litter, or humus were inserted into the substrate humus in the macrocosms. Two experiments used organic matter only, and in the third there was mineral soil below the humus. The macrocosms were incubated in climate chambers that simulated both summer and winter conditions. At 4- to 6-week intervals the substrates were irrigated for analyses of pH, total N, NH 4 + −N, NO 3 − −N, and PO 4 3− −P in the leachates. At the end of each growing season a destructive sampling was performed, including analyses of KCl-extractable N and P. Leaching of NH 4 + and PO 4 3− from both the litter and the total systems was significantly enhanced by the soil fauna. There were also differences in mineralization of N and P between the refaunated systems, apparently due to divergent development of the faunal communities. In general, fauna affected KCl-extractable nutrients from the litter positively, although this effect was less evident than in the leaching water. In the humus and mineral soil the fauna significantly increased the release of N and P, especially in the later stages of the experiments. Soil pH was higher in the presence of fauna, but there was no difference in the pH of the leachates. Not only invertebrate-microbial interactions, but also mutual relationships among fauna were important in the nutrient dynamics.

Evaluation of the soil fauna impact on decomposition in a simulated coniferous forest soil

Abstract: Long-term experiments (ca. 2 years) were carried out in laboratory systems that simulated the complexity of a coniferous forest floor. The test materials were partially sterilized by freezing and thawing, and reinoculated with (1) microbes alone or (2) microbes with fauna. Removable microcosms containing birch litter, spruce litter, or humus were inserted into a humus substrate. Two experiments used organic matter only, and another included a layer of mineral soil below the humus. Both were incubated in climate chambers that simulated both summer and winter conditions. The evolution of CO2 was measured at regular intervals. In order to determine the C content of the leachates, the macrocosms and the microcosms were watered periodically.

Laboratory design to simulate complexity of forest floor for studying the role of fauna in the soil processes.

Abstract: We developed a technique for simulating the complexity of the soil system under controlled laboratory conditions Removable microcosms were inserted in a homogeneous substrate soil in a large plastic box This macrocosm was sealed, except for an inlet and outlet for air flow, and an aperture for collecting leachates The system can be designed and manipulated in various ways according to the needs of a particular experiment Respiration and nutrient fluxes can be measured either from the whole macrocosm or separately from the microcosms We have performed three experiments in order to evaluate the role of animals in the soil processes A set of macrocosms was constructed from components of coniferous forest soil These were partially sterilized by freezing and then thawing, and re-inoculated with (1) microbes alone, or (2) microbes and fauna The animal populations became well established, average densities per area approaching those in natural forest soils However, there were considerable differences in community structure between the experiments The sterilization did not eliminate microfauna; nematodes reproduced to high densities in the control macrocosms