H. R. Zoomer

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One of the most important areas in ecology is to elucidate the factors that drive succession in ecosystems and thus influence the diversity of species in natural vegetation. Significant mechanisms in this process are known to be resource limitation and the effects of aboveground vertebrate herbivores. More recently, symbiotic and pathogenic soil microbes(More)
The relation between environmental factors and the presence of ammonia-oxidising bacteria (AOB), and its consequences for the N transformation rates were investigated in nine Scots pine (Pinus sylvestris L.) forest soils. In general, the diversity in AOB appears to be strikingly low compared to other ecosystems. Nitrosospira cluster 2, as determined by(More)
 Enhanced UV radiation did not show any effect on the decomposition of a mixed litter of the dune grassland plant species Calamagrostis epigeios and Carex arenaria. Also, leaching of nutrients from lysimeters filled with dune grassland soils was not affected by enhanced UV radiation. Negative UV effects on the fungal biomass in the first part of the(More)
Forest soils show a great degree of temporal and spatial variation of nitrogen mineralization. The aim of the present study was to explain temporal variation in nitrate leaching from a nitrogen-saturated coniferous forest soil by potential nitri®cation, mineralization rates and nitrate uptake by roots. Variation in nitrate production in time and space,(More)
 High spatial variation in nitrification potentials has been observed in forest soils, but explanations for this variability have remained speculative. In the present study we determined whether sample treatment, sample size, denitrification or small-scale variations in abiotic properties could explain spatial variation in nitrogen transformations in the(More)
In microcosm studies the organic layers of coniferous forest soils show high nitrate and low ammonium mobilization, in accord with the presence of high numbers of autotrophic nitrifiers. The fungivorous collembolan Tomocerus minor (Lubbock) increases ammonium mobilization, probably through its excretion products, and has an indirect effect on nitrate(More)
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