Influence of plant diversity on soil organic carbon storage and microbial transformation of organic carbon in soils

Increasing plant diversity is known to be important for ecosystem functioning and an increase in soil organic carbon storage. The link between aboveground plant diversity and belowground diversity is currently under discussion. Furthermore, the mechanisms by which aboveground diversity impacts storage as well as the sustainability of storage are still not well understood. Addressing these issues the thesis contributes to a better understanding of the impact of plant diversity on belowground ecosystem functioning. For investigations the field site of The Jena Experiment was used. The species pool comprises 60 species common to the Central European Molinio-Arrhenatheretum grasslands. Between 2002 and 2007 organic carbon and nitrogen were stored in the top and sub soil. In the top soil the main drivers for storage were soil texture and plant diversity. While the root input was not important for storage in the top soil, it was found to significantly affect storage in the sub soil, where the system seemed to be input-limited. Due to the increased substrate use efficiency of microorganisms in the sub soil, the major part of the input was transformed and stored. Microbial transformation of input and sustainable sequestration of carbon was confirmed by the results of density fractionations. Soil microbial community was characterised by phospholipid fatty acids (PLFA). Although the abiotic factors were found to have an impact on microbial abundance, increased plant diversity lead to increased amounts of soil microbial biomass. For soil microbial biomass not only the amount of plant biomass input but also the quality and heterogeneity of input was important. The same result was found for the microbial composition and indicates that increasing diversity increases niche complementarity of soil microorganisms. The results newly establish the strong impact of plant diversity on the soil organic carbon and nitrogen storage beyond abiotic controls. Soil microorganisms were found to play the central role for transformation of organic input and were the main drivers for a sustainable storage at higher diversity levels. As specific interactions between the aboveground and belowground compartments are vital for the ecosystem functioning, this should strengthen our efforts to reduce species extinction

Neuroplasticity induced by peripheral nerve stimulation

PhD ThesisNon-invasive methods have been developed to induce plastic changes in the sensorimotor cortex. These rely on stimulating pairs of afferent nerves. By associative stimulation (AS) of two afferent nerves, excitability changes in the motor cortex occur as indicated by studies reporting changes in motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS). Repetitive stimulation of those nerves has a potential in rehabilitation and treatment of neurological disorders like stroke or spinal cord injury. Despite promising results and applications in human subjects using these methods, little is understood about the underlying basis for the changes which are seen. In the present study, behavioural, electrophysiological and immunohistochemical assessments were performed before and after paired associative and non-associative (NAS) median and ulnar nerve stimulation. Two macaque monkeys were trained to perform a skilled finger abduction task using refined behavioural methods. Monkeys were not able to move their thumb and index finger as selectively after one hour of paired AS as indicated by an increased number of errors and decreased performance measures. NAS however decreased error numbers and led to increased performances. Additionally, I recorded from identified pyramidal tract neurons and unidentified cells in primary motor cortex (M1), in two macaque monkeys before and after one hour of AS (and NAS) of the median and ulnar nerve. Cell discharge was recorded in response to electrical stimulation of each nerve independently. Some cells in M1 showed changed firing rates in response to nerve stimulation after AS (and NAS). Subsequently, structural changes in response to one week of paired AS were investigated. The laminar-specific density of parvalbumin-positive interneurons, perineuronal nets and the colocalisation of these two entities changed on the stimulated (in comparison to the non-stimulated) sensorimotor cortex. These findings suggest that the sensorimotor cortex undergoes plastic changes in response to AS (and NAS).Wellcome Trus

Decrease in TSH Receptor Autoantibodies during Antithyroid Treatment: Relationship with a Long Noncoding Heg RNA and Cdk1 mRNA in Mononuclear Cells

We have previously shown that a long noncoding RNA transcript Heg is negatively correlated with TSH receptor autoantibodies (TRAb) in patients with untreated Graves' disease and with CD14 mRNA in treated patients and controls. Thus patients with high concentrations of Heg RNA have low levels of TRAb or CD14 mRNA, respectively. Here we show that an additional factor, gene expression of Cdk1 in mononuclear cells, is positively related to concentrations of TRAb in patients with untreated Graves' disease. Cdk1 mRNA is very important for regulation of cell cycle activity. It is well known that TRAb decrease significantly during treatment with antithyroid drugs. This decrease during treatment cannot be explained by Heg RNA, which remains unchanged. Cdk1 mRNA decreased significantly during treatment to values below values obtained in normal subjects. Thus both Heg RNA and Cdk1 mRNA may influence the level of TSH receptor autoantibodies but by different mechanisms

How low can you go: Spatial frequency sensitivity in a patient with pure alexia

AbstractPure alexia is a selective deficit in reading, following lesions to the posterior left hemisphere. Writing and other language functions remain intact in these patients. Whether pure alexia is caused by a primary problem in visual perception is highly debated. A recent hypothesis suggests that a low level deficit – reduced sensitivity to particular spatial frequencies – is the underlying cause. We tested this hypothesis in a pure alexic patient (LK), using a sensitive psychophysical paradigm to examine her performance with simple patterns of different spatial frequency. We find that both in a detection and a classification task, LK’s contrast sensitivity is comparable to normal controls for all spatial frequencies. Thus, reduced spatial frequency sensitivity does not constitute a general explanation for pure alexia, suggesting that the core deficit in this disorder is at a higher level in the visual processing stream

Johannes Göderitz

Nachruf der Braunschweigischen Wissenschaftlichen Gesellschaft, in der Plenarsitzung am 13. Oktober 1978 vorgetrage