The dynamics of stiff clubmoss Lycopodium annotinum L. patches in clumps of trees left on the clear-cutting in pine forest Leucobryo-Pinetum

Clumps of trees left on the clear-cuttings have an important role in protecting populations of endangered plant species against destruction during silviculture activities. The aim of this study is to describe the changes in the area of the Lycopodium annotinum patches. The area of L. annotinum patch in clump of trees, have been significantly reduced during 5 years after clear-cut. In the first year of the observations, the studied population occupied an area of 69.8 m2 whereas in 2012, it was only 37.5 m2. Most of the shoots were withered away on the south side of the clump. The probable reason was too strong insolation. Shoots that survived were located in the north part of the clump – shielded by young trees and shrubs layer. At this time, the control patch of L. annotinum located inside the forest increased its area. Before the clear-cuttings, the annual growth of vertical shoots of clubmoss was higher in the patch located in future tree clump. After the clear-cutting, growth of shoots in this patch was shorter than in patch located all the time inside the forests. The most effective growth was observed in the third studied patch located in the clear-cutting border. The explanation for this phenomenon could be the higher humidity of habitat on this site. Clumps of trees left after the clear-cutting contribute to the protection of endangered populations, but do not eliminate the significant microhabitat changes. The clubmoss patches located in moist habitats are more likely to survive even if they are partially exposed to the sunlight.

Changes in vegetation and soil seed bank of meadow after waterlogging caused by Castor fiber

<p>Soil waterlogging is among abiotic stresses that influence species composition and productivity in numerous plant communities. The aim of the study was to find answer to the question of how waterlogging caused by beavers’ activity induces quantitative and qualitative changes of vegetation and soil seed bank levels of variable-moist meadows.</p><p>An immediate effect of the waterlogging at the level of vegetation was the decline in species richness and a decrease in the values of the biodiversity index. Water stress inhibited growth and development of plants already present and, primarily, impeded recruitment of new individuals of species characteristic of variable-moist meadows, e.g. <em>Cirsium rivulare</em>, <em>Filipendula ulmaria</em> and <em>Lythrum salicaria</em>, which were replaced by <em>Carex acutiformis</em>. Prolonged waterlogging did not induce equally substantial changes in the soil seed bank as in the vegetation. Both in the waterlogged and control patches, slightly decreased species richness and biodiversity index were recorded. After waterlogging withdrawal, the reserves of the soil seed bank were slightly higher than the initial values. The differences were not statistically significant.</p><p>In the waterlogged patch, the qualitative floristic similarity between taxa identified in the soil seed bank and vegetation cover declined, which was evidenced by the value of Jaccard’s index decreasing from 0.46 to 0.36. A reverse relationship was found in control patch, where the value of the similarity index slightly increased from 0.41 to 0.48.</p>

Familiarity affects social network structure and discovery of prey patch locations in foraging stickleback shoals

Numerous factors affect the fine-scale social structure of animal groups, but it is unclear how important such factors are in determining how individuals encounter resources. Familiarity affects shoal choice and structure in many social fishes. Here, we show that familiarity between shoal members of sticklebacks ( Gasterosteus aculeatus ) affects both fine-scale social organization and the discovery of resources. Social network analysis revealed that sticklebacks remained closer to familiar than to unfamiliar individuals within the same shoal. Network-based diffusion analysis revealed that there was a strong untransmitted social effect on patch discovery, with individuals tending to discover a task sooner if a familiar individual from their group had previously done so than if an unfamiliar fish had done so. However, in contrast to the effect of familiarity, the frequency with which individuals had previously associated with one another had no effect upon the likelihood of prey patch discovery. This may have been due to the influence of fish on one another's movements; the effect of familiarity on discovery of an empty ‘control’ patch was as strong as for discovery of an actual prey patch. Our results demonstrate that factors affecting fine-scale social interactions can also influence how individuals encounter and exploit resources.

Active vibration suppression of flexible structure using a LMI-based control patch

Based on the linear matrix inequality, a linear feedback control is presented to realize active vibration suppression of a class of flexible structure. By introducing an appropriate modal transformation, the controller design procedure can be simplified greatly. A specific Lyapunov function is adopted to induce the asymptotical stability of the flexible structure. Simulation results for flexible spacecraft are provided to illustrate the effectiveness of the proposed scheme.

Nitrogen dynamics of cattle dung and urine patches on intensively managed boreal pasture

SUMMARYThe aim of the present study was to investigate the nitrogen (N) dynamics in soil and N utilization by grass in dung pats and urine patches, and to quantify the amount of soluble organic N (SON) in grassland soil. The experiment was conducted in 2003/04 at MTT Agrifood Research, Maaninka, Finland. The study consisted of three treatments: dung pats, urine patches and a control patch without excreta. The soil (to a depth of 0·6 m) and herbage were sampled on 10 occasions over the course of 1 year. TN and SON in soil averaged 14 400 and 60 kg/ha N, respectively. Changes in soil mineral N were short-lived and a large proportion of excreta N was immobilized. The grass took up 27 kg excretal N/ha from the dung pat and 71 kg N/ha from the urine patch, which equals 0·07 and 0·19 of the excretal N given to each treatment, respectively. As a large proportion of the excretal N is immobilized and accumulates in soil, re-evaluation of the recommendations for N fertilization of pastures older than 2 years is justified.

A Direct Comparison of Whole Cell Patch and Sharp Electrodes by Simultaneous Recording From Single Spinal Neurons in Frog Tadpoles

High-impedance, sharp intracellular electrodes were compared with whole cell patch electrodes by recording from single spinal neurons in immobilized frog tadpoles. A range of neuron properties were examined using sharp or patch test electrodes while making simultaneous recordings with a second control patch electrode. Overall, test patch electrodes did not significantly alter the activity recorded by the control electrode, and recordings from the two electrodes were essentially identical. In contrast, sharp electrode recordings differed from initial control patch recordings. In some cases, differences were due to real changes in neuron properties: the resting membrane potential became less negative and the neuron input resistance ( Ri) fell; this fall was larger for neurons with a higher Ri. In other cases, the control patch electrode revealed that differences were due to the recording properties of the sharp electrode: tip potentials were larger and more variable; resting potentials appeared to be more negative; and spike amplitude was attenuated. However, sharp electrode penetration did not, in most cases, significantly alter the pattern of neuron firing in response to injected current or the normal pattern of activity following sensory stimulation or during fictive swimming. We conclude that sharp electrodes introduce a significant leak to the membrane of tadpole spinal neurons compared with patch electrodes but that this does not change the fundamental firing characteristics or activity of the neurons.