Angiogenesis-independent endothelial protection of liver: role of VEGFR-1

The vascular endothelium was once thought to function primarily in nutrient and oxygen delivery, but recent evidence suggests that it may play a broader role in tissue homeostasis. To explore the role of sinusoidal endothelial cells (LSECs) in the adult liver, we studied the effects of vascular endothelial growth factor (VEGF) receptor activation on mouse hepatocyte growth. Delivery of VEGF-A increased liver mass in mice but did not stimulate growth of hepatocytes in vitro, unless LSECs were also present in the culture. Hepatocyte growth factor (HGF) was identified as one of the LSEC-derived paracrine mediators promoting hepatocyte growth. Selective activation of VEGF receptor-1 (VEGFR-1) stimulated hepatocyte but not endothelial proliferation in vivo and reduced liver damage in mice exposed to a hepatotoxin. Thus, VEGFR-1 agonists may have therapeutic potential for preservation of organ function in certain liver disorders.     

Schätzung des Humusgehaltes nach der Munsell-Farbhelligkeit

Calculation of the humus content of soil samples by the Munsell-value The log values of humus contents (0.1–15%) and the Munsell-values of 156 dry or moist soil samples from Northern Germany were strongly correlated, especially in additional consideration of Munsell-chromas and soil texture.     

A simple mixed model for trend analysis in wildlife populations

This article is concerned with a test for time trend in ecological surveys conducted at multiple sites across several years. The test is useful for studying long-term trends in wildlife populations. We propose a modification of a mixed model—recently suggested by Van Leeuwen, Murray, and Urquhart—which leads to invariance to translation in the origin of the time covariate. The modified model is easily fitted using standard software. Using simulation, the performance of the procedure for un balanced data is shown to be satisfactory. Data on the population density of Thomson’s gazelles (Gazella thomsoni Günther) are used as an example.     

A simulation study on tests of hypotheses and confidence intervals for fixed effects in mixed models for blocked experiments with missing data

This article considers the analysis of experiments with missing data from various experimental designs frequently used in agricultural research (randomized complete blocks, split plots, strip plots). We investigate the small sample properties of REML-based Wald-type F tests using linear mixed models. Several methods for approximating the denominator degrees of freedom are employed, all of which are available with the MIXED procedure of the SAS System (8.02). The simulation results show that the Kenward-Roger method provides the best control of the Type I error rate and is not inferior to other methods in terms of power.     

Mikrobielle Aktivitäten in landwirtschaftlich genutzten Böden Niedersachsens. I. Einfluß der ackerbaulichen Nutzung

Microbial activity of arable soils in Lower Saxony, Germany. I. Influence of agricultural practice A range of microbial functions were measured over four years in field trials on three soil types in Lower Saxony. Generally, glucose-induced short-term respiration and dehydrogenase activity were most susceptible to environmental influences. Higher microbial activity occurred under cereals than under sugar beets. Some microbial functions were affected by soil type and vegetation period. Furthermore, pesticide treatments of sugar beets inhibited some microbial functions.     

Entwicklung einer Kleinstdurchlaufküvette und ihre Anwendung zur Phosphatbestimmung bei der systematischen Bodenuntersuchung

In dreijährigen Versuchen auf zwei Standorten des nordostdeutschen Tieflandes (Müncheberg, Kreis Märkisch‐Oderland und Berge, Kreis Havelland) konnte gezeigt werden, daß Zwischenfrüchte (Gelber Senf, Ölrettich, Phacelia), die über Winter absterben, den Gehalt an mineralischen N‐Verbindungen im Boden bis Frosteintritt wirksam verringerten. In kurzer Zeit nach dem Abfrieren bis etwa Mitte Januar setzten sie jedoch bis zu 60% der aufgenommenen N‐Menge wieder frei. Die damit dem N_min‐Pool des Bodens zugeführte N‐Menge unterlag nur zeitlich verzögert der Verlagerung in Form von NO₃. Die Freisetzungsintensität wurde durch die Höhe der N‐Gabe zur Zwischenfrucht beeinflußt. Steigende N‐Mengen führten zu einer Verringerung des C/N‐Verhältnisses in den Zwischenfrüchten und zu höherer Freisetzungsintensität.

Winterharte Zwischenfrüchte wie Winterraps und Winterrübsen speicherten im Vergleich dazu die aufgenommene N‐Menge wirksam in der Biomasse, so daß die NO₃‐ Verlagerung im Boden bis zur Aussaat der Folgefrucht auf ein Minimum reduziert wurde.     

Drought sensitivity of Norway spruce is higher than that of silver fir along an altitudinal gradient in southwestern Germany

Context

For Central Europe, climate projections foresee an increase in temperature combined with decreasing summer precipitation, resulting in drier conditions during the growing season. This might negatively affect forest growth, especially at sites that are already water-limited, i.e., at low elevation. At higher altitudes trees might profit from increasing temperatures.

Aims

We analyzed variations in radial growth of silver fir (Abies alba Mill.) and Norway spruce (Picea abies (L.) Karst.) along an altitudinal gradient from 400 until 1,140 m a.s.l. in the Black Forest, to assess climate responses with increasing elevation.

Methods

Climate–growth relationships were analyzed retrospectively using tree-ring and climate data. In total, we sampled stem discs of 135 trees to build 27 species- and site-specific chronologies (n _fir?=?13, n _spruce?=?14).

Results

Our results indicate distinct differences in climate–growth relations between fir and spruce along the gradient. Growth of high-altitude fir was positively related to temperature from January till March. Growth of low-altitude fir and spruce at all elevations was positively related to precipitation and negatively to temperature during the growing season, particularly in July. A self-calibrating Palmer drought severity index underlined summer drought sensitivity of these trees.

Conclusion

Overall, we found that climatic control of tree growth changes over altitude for fir. For spruce, a remarkable synchrony in growth variation and climate response was shown, which indicates that this species is drought sensitive at all studied elevations. In a future warmer climate, the growth of low-altitude fir and spruce along the entire studied gradient may be negatively affected in the Black Forest, if an increased evaporative demand cannot be compensated by increased water supply.     

Short-term and long-term effects of human trampling on above-ground vegetation, soil density, soil organic matter and soil microbial processes in suburban beech forests

Understanding the effects of disturbance by human trampling on ecosystem processes is essential for the management of recreational areas. Discussions on recreational impacts are based either on data from trampling experiments or on field survey data from sites subjected to long-term recreational use, but rarely on a combination of both. We examined whether results from a short-term trampling experiment reflect the impact of long-term trampling around frequently used fire places. We compared short- and long-term effects of human trampling on above-ground forest vegetation and soil physical, chemical and microbial characteristics. We found both similarities and differences in short- and long-term trampling effects. Both short- and long-term trampling reduced plant cover, plant height and species density, though long-term effects were more pronounced than short-term effects. In both approaches, leaf litter biomass decreased, whereas soil density increased with trampling intensity. Other soil characteristics including soil moisture, total soil organic matter content and total organic nitrogen content were not or only marginally affected by short- and long-term trampling. Furthermore, soil microbial biomass and the activity of dehydrogenase did not change in both approaches. In contrast, the activity of β-glucosidase was only reduced by short-term trampling, whereas activity of phosphomonoesterase was reduced only by long-term trampling. Soil compaction was one factor reducing microbial activities at low and medium trampling intensities in our experiment and in the highly compacted area around the fire rings. We conclude that it could be problematic to use the results of short-term trampling experiments to predict general long-term trampling effects. Our results imply also that the restoration of degraded sites might be hampered by the low nutrient turnover resulting from the reduced litter layer and changes in enzyme activities, mitigating a successful re-establishment and growth of plants.     

Concentrations and uptake of macronutrients by oat and pea in intercrops in response to N fertilization and sowing ratio

Intercropping is of increasing interest in temperate-arable farming systems. The influence of nitrogen (N) fertilization and sowing ratio on concentrations and uptake of calcium (Ca), potassium (K), magnesium (Mg) and phosphorus (P) by oat and pea was assessed in three substitutive intercrops on a fertile soil in eastern Austria. N decreased Ca in oat grain and increased P in pea grain as well as Ca and Mg in oat residue and Mg and P in pea residue. Intercropping did not affect nutrient concentrations of oat grain, whereas a lower pea share in intercrops increased P in pea grain. In residue, Ca, K and Mg concentrations were higher in oat and Ca and K partly lower in pea with a lower share of each crop. The oat-dominated intercrops could partly achieve a slightly higher total grain nutrient yield than pure stands at no or low N; however, these benefits diminished with a higher pea share and N input. In comparison to pure stands, higher residue nutrient yields were obtained by intercropping in all sowing ratios and fertilization levels. Consequently, oat–pea intercropping can be a strategy for increasing the macronutrient yield of grain and especially of residue for ruminant feeding.