Herman A. Verhoef

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The loss of biodiversity can have significant impacts on ecosystem functioning, but the mechanisms involved lack empirical confirmation. Using soil microcosms, we show experimentally that functional dissimilarity among detritivorous species, not species number, drives community compositional effects on leaf litter mass loss and soil respiration, two key(More)
The abundance and micro-stratification of bacteria and fungi inhabiting the organic layers of a Scots pine forest (Pinus sylvestris L.) were investigated. An experiment using stratified litterbags, containing organic material of four degradation stages (fresh litter, litter, fragmented litter and humus) was performed over a period of 2.5 years. Dynamics and(More)
*The impact of various agricultural practices on soil biodiversity and, in particular, on arbuscular mycorrhizal fungi (AMF), is still poorly understood, although AMF can provide benefit to plants and ecosystems. Here, we tested whether organic farming enhances AMF diversity and whether AMF communities from organically managed fields are more similar to(More)
Elevated levels of nitrogen input into various terrestrial environments in recent decades have led to increases in soil nitrate production and leaching. However, nitrifying potential and nitrifying activity tend to be highly variable over space and time, making broad-scale estimates of nitrate production difficult. This study investigates whether the high(More)
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)
Wekerom forest shows a high nitrogen (N) load, and the first signs of N saturation. This characterization is based on the high N content of the needles, the high nitrate-N (NO3-N) mobilization and low cation mobilization from the organic horizon. The N cycle in this forest has been transformed into an „open flow” system, in which the ammonium-N, deposited(More)
The direct contribution made by soil arthropods to nutrient dynamics was investigated in pine forests that differed in soil nutrient status. Nutrient concentrations (K+, Ca2+, Mg2+, PO 4 3− , N, C) in the most abundant species and groups of arthropods in two Pinus nigra forests were compared, and distinct differences were found among taxonomic groups. In(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)
In a previous study, ammonia-oxidizing bacteria (AOB)-like sequences were detected in the fragmentation layer of acid Scots pine (Pinus sylvestris L.) forest soils (pH 2.9–3.4) with high nitrification rates (>11.0 μg g−1 dry soil week−1), but were not detected in soils with low nitrification rates (<0.5 μg g−1 dry soil week−1). In the present study, we(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)