Is bodembiodiversiteit van belang voor herstel van beekdalvegetaties?

Effectgerichte maatregelen voor vegetaties richten zich doorgaans op het herstel van abiotische factoren in de bodem, zoals nutriënten- en waterhuishouding en tegengaan van verzuring. Lang niet altijd heeft dat het gewenste effect. Het is aannemelijk dat deze milieustress ook tot verstoring van het bodemleven kan leiden. De vraag is in hoeverre een goed functionerend bodemleven van belang is voor het herstel van de vegetatie. Het onderzoek richtte zich op blauwgraslanden en heischrale graslanden, vanwege hun gevoeligheid voor milieustress

De invloed van het bodemleven op plantengroei en natuurherstel

In de jaren zeventig van de vorige eeuw werd aangenomen dat natuurbeheer vooral de abiotische omgeving betrof. Vervolgens is de rol van begrazing uitgebreid onderzocht. Pas daarna ontstond belangstelling voor de invloed van het bodemleven op de groei van planten en de samenstelling van plantengemeenschappen. Het meest recent is het onderzoek naar de wijze waarop het bodemleven kan bijdragen aan natuurherstel (Harris, 2009). Hier presenteren we een overzicht van de bodembewoners, hun functies en effecten op plantengroei en natuurherstel. Naast inzichtvergroting beogen we suggesties te geven voor het toepassen van deze recent ontwikkelde kennis

Reinfection with severe acute respiratory syndrome coronavirus 2 without recurrence of multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children is a rare, potentially life-threatening postinfectious complication in children after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. It is currently unknown if multisystem inflammatory syndrome in children (MIS-C) can recur upon reinfection with SARS-CoV-2. Here, we report on a former MIS-C patient who was reinfected with SARS-CoV-2 without recurrence of MIS-C.Cardiovascular Aspects of Radiolog

Breadth and Dynamics of Human Norovirus-Specific Antibodies in the First Year of Life

We measured antibody binding to diverse norovirus virus-like particles over 12 months in 16 children. All had maternal antibodies at 2 months, with estimated lowest levels at 5 months of age. Antibody increases after 3 months suggested natural infections. This information could guide the timing of future norovirus vaccines

Itinerant Ferromagnetism in the Periodic Anderson Model

We introduce a novel mechanism for itinerant ferromagnetism, based on a simple two-band model. The model includes an uncorrelated and dispersive band hybridized with a second band which is narrow and correlated. The simplest Hamiltonian containing these ingredients is the Periodic Anderson Model (PAM). Using quantum Monte Carlo and analytical methods, we show that the PAM and an extension of it contain the new mechanism and exhibit a non-saturated ferromagnetic ground state in the intermediate valence regime. We propose that the mechanism, which does not assume an intra atomic Hund's coupling, is present in both the iron group and in some f electron compounds like Ce(Rh_{1-x} Ru_x)_3 B_2, La_x Ce_{1-x} Rh_3 B_2 and the uranium monochalcogenides US, USe, and UTe

Interactions among endoparasitic root-feeding nematodes; consequences for nematodes and host plant

Plants are influenced by above- and belowground herbivores and their interactions. Root feeders, among which are nematodes, generally occur in multi-species communities. The aim of this study was, to determine whether interspecific interactions among endoparasitic root-feeding nematodes ( Heterodera arenaria , Meloidogyne maritima and Pratylenchus penetrans ) would influence nematode abundance and dynamics and subsequently biomass of the shared host plant Ammophila arenaria .In a field experiment, different combinations of the endoparasitic nematodes and other soil organisms were added to A. arenaria . Subsequently, the feedback of the established soil communities was tested in bioassays. Soil from non-buried plants inoculated with a mixture of organisms from the root zone of A. arenaria reduced the biomass of newly planted seedlings. In contrast, a combination of the three endoparasitic nematodes did not affect plant biomass differently from the control. When in the field experiment M. maritima had been added to plants alone, juveniles and males of this species occurred in the new root layer earlier in the year and in higher densities than when H. arenaria and P. penetrans had been added as well. Addition of the other two species apparently forced M. maritima to develop under suboptimal conditions. Addition of the other endoparasite species did not affect H. arenaria and P. penetrans . Greenhouse experiments aimed at studying interactions between different pairs of the endoparasite species did not explain observations from the field experiment.Interestingly, in the field experiment M. maritima reduced plant biomass more when added alone than when added together with the other two endoparasites, whereas addition of root zone soil reduced plant biomass most. Heterodera arenaria and P. penetrans did not affect plant biomass. These results support the view that effects of species identity and diversity may be intermingled and that species traits rather than diversity determines the effect. The ectoparasitic nematode Tylenchorhynchus ventralis spontaneously colonised the field experiment in high densities, but the numbers declined when the experiment proceeded. In a greenhouse experiment, numbers of T. ventralis were reduced by adding an unnaturally high density of endoparasites. Thus, the observed decline in spontaneously established ectoparasite numbers was unlikely to be caused by the endoparasites, but by other (micro-) organisms that spontaneously colonised the soil. Despite their limiting effect, the endoparasites could not prevent T. ventralis from reducing plant biomass.In conclusion, it seems likely that in the field, abundance and dynamics of M. maritima are determined by interspecific competition with H. arenaria and P. penetrans . The latter two endoparasitic nematodes are less influenced by the presence of the other endoparasites than is M. maritima . Interestingly, M. maritima , when added alone, reduced plant biomass, whereas a combination of the three endoparasites did not. Addition of root zone soil of A. arenaria reduced plant biomass most, so that the negative soil feedback is likely to be caused by the whole soil community rather than by endoparasitic nematodes alone

Interactions between root-feeding nematodes depend on plant species identity

Root-feeding nematodes play an important role in structuring the composition of natural plant communities. Little is known about the role of intra- and interspecific interactions in determining the abundance of root-feeding nematodes in natural ecosystems. We examined interactions between two ectoparasitic root-feeding nematodes on two plant species: a good host plant for both nematode species and a good host for only one of the nematodes. We tested the hypothesis that root herbivore competitiveness depends on host suitability and related the experimental results to field data. In a greenhouse, we added different densities of the nematodes Tylenchorhynchus microphasmis and Tylenchorhynchus ventralis to Ammophila arenaria (the good host for both) and Carex arenaria (a good host for T. microphasmis only). Addition of T. ventralis did not significantly affect multiplication of T. microphasmis on both plant species. In contrast, on A. arenaria, T. ventralis experienced interspecific competition. However, on C. arenaria, T. microphasmis facilitated multiplication of T. ventralis. To explain this effect, we studied systemic plant-mediated effects in a split-root experiment. Nematode addition to one root compartment did not significantly influence nematode multiplication in the other root compartment, irrespective of nematode species identity. Therefore, the observed nematode interactions were not related to induced changes in the roots. In a two-choice experiment we tested whether host suitability was related to root attractiveness. Both nematode species were attracted to seedlings of A. arenaria, but not to C. arenaria. The low multiplication of T. ventralis on C. arenaria could be related to poor attraction to the roots. However, the poor attraction of T. microphasmis cannot be related to poor host suitability. Adding T. ventralis reduced shoot biomass of A. arenaria more than T. microphasmis did, whereas for C. arenaria the effect was the reverse. The interaction of the two nematodes on A. arenaria and C. arenaria shoot biomass was insignificant. However, the effect on root biomass of A. arenaria was interactive; adding T. ventralis to plants with high inoculation densities of T. microphasmis further decreased root biomass. Adding T. microphasmis further decreased root biomass of plants inoculated with low levels of T. ventralis. Depending on host plant identity, interactions between root-feeding nematodes may lead to competition or facilitation. Our results suggest that facilitation by T. microphasmis contributes to persistence of T. ventralis on C. arenaria. Thus, the population dynamics of root-feeding nematodes is influenced both by host plant identity and the presence of other root-feeding nematodes.