The role of weathering and forestry in determining the acidity of Lakes in Sweden

The long term acidity level of a lake is determined by the balance between acidity input to the catchment and the generation of alkalinity in the catchment. If the input of acidity through biomass net production and the production of alkalinity through weathering of minerals can be estimated, then the steady-state acidity level can be calculated for the lake under a certain acid deposition rate. Such a calculation has been carried out for 8 lakes ranging from acid to neutral. For lakes with the most sensitive soils in the catchment, the critical acid deposition load that will permit the lake to stay neutral, may be less than zero acidity, indicating that the forest growth is contributing to the acidification of very sensitive system under the present forest managements methods.     

Taxonomy and evolution of cultivated plants: Literature review 1985/1986

Summary Important papers on taxonomy and evolution of cultivated plants published in 1985 and 1986 were compiled and briefly discussed.

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Taxonomie und Evolution der Kulturpflanzen: Literaturübersicht 1985/1986

Zusammenfassung Wichtige Arbeiten über Taxonomie und Evolution der Kulturpflanzen aus den Jahren 1985 und 1986 wurden zusammengestellt und kurz kommentiert.

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¶rt; : 1985–1986

¶rt; , 1985 1986 . .

     

Feeding deterrence and contact toxicity of Stemona alkaloids-a source of potent natural insecticides

On the basis of chronic feeding bioassays with neonate larvae of Spodoptera littoralis reared on an artificial diet, the methanolic leaf and root extracts from Stemona collinsae displayed very high insect toxicity compared to those of two Aglaia species, a commercial Pyrethrum extract, and azadirachtin, whereas S. tuberosa extracts demonstrated low activity in roots and no activity in leaves. Beyond that, in leaf disk choice tests against fifth instar larvae, S. collinsae showed strong antifeedant activity, whereas S. tuberosa was characterized by remarkable repellency. The anti-insect properties of both species were based on pyrrolo[1,2-a]azepine alkaloids, from which didehydrostemofoline (asparagamine A) was the major compound of the roots of S. collinsae, exhibiting the highest toxicity in feeding assays. Saturation and hydroxylation of the side chain in the co-occurring stemofoline and 2'-hydroxystemofoline, respectively, led to an increasing loss of activity. Contact toxicity tests with stemofoline and didehydrostemofoline exhibited even higher activities than those of Pyrethrum extract. Tuberostemonine was the dominating alkaloid in the roots of S. tuberosa, showing outstanding repellency but no toxic effects.     

Taxonomy and evolution of cultivated plants: Literature review 1983/1984

Summary Important papers on taxonomy and evolution of cultivated plants published in 1983 and 1984 were complied and briefly discussed.

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Taxonomie und Evolution der Kulturpflanzen: Literaturübersicht 1983/1984

Zusammenfassung Wichtige Arbeiten über Taxonomie und Evolution der Kulturpflanzen aus den Jahren 1983 und 1984 wurden zusammengestellt und kurz kommentiert.

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: 1983–1984

, 1983 1984 . .

     

Microbial biomass and activity on railway track and embankments

The spatial distribution of microbial biomass and microbial activity was studied in two Swedish railway embankments (located close to Mora and N?ssj?). Basal respiration and substrate-induced respiration (SIR) as well as the active (r) and dormant (K) fractions of the microbial biomass were determined in samples taken from the surface layer of the ballast. The SIR, r, K and basal respiration values were all of an overall low magnitude, but were highly variable over short distances on the track. Both the biomass and basal respiration were higher on the sides of the embankment than in the middle of the tracks. SIR, K and basal respiration were correlated to the organic matter content as measured by loss on ignition, whereas r was not. None of the parameters correlated with pH. It is proposed that organic matter content could be used as a predictor for microbial biomass in railway embankments.     

Impacts of salvage-logging on the status of deadwood after windthrow in Swiss forests

Downed and standing deadwood (DW) is a key resource for maintaining forest biodiversity. Although extreme events such as windthrow and fires produce large quantities of DW, this substrate is often drastically reduced by logging activities. To elucidate the respecting consequences of salvage-logging, we assessed both quantity and quality of storm-derived DW (storms Vivian 1990 and Lothar 1999) in Swiss forests using a sample of 90 windthrow sites with ≥3 ha complete windthrow and at elevations ranging from 350 to 1,800 m a.s.l. The majority had been salvage-logged (SL) a few years after the windthrow. On each site, we recorded DW amount and quality on six circular sample plots 20 or 50 m² in size. DW volume on SL sites was surprisingly high, with 76.4 m³ ha^?1 on average 20 years after Vivian and 73.8 m³ ha^?1 10 years after Lothar. In comparison, DW volumes on unsalvaged sites, that is, with no post-windthrow intervention (NI), amounted to 270 m³ ha^?1. A wide variety of wood decay stages and diameter classes (10 to ≥70 cm) was found on both NI and SL sites, suggesting considerable habitat diversity for DW-associated species irrespective of the treatment. The considerable amounts of DW left after salvage-logging distinctly exceed the minimum DW volumes in forest stands proposed by Müller and Bütler (Eur J For Res 129: 981–992, 2010) in a conservation context, which demonstrates the importance of wind disturbance for biodiversity. Further studies should quantify DW of individual tree species, since habitat requirements are species-specific.     

Concentrations and Flow of Free Amino Acids in Ruminal and Duodenal Liquid of Dairy Cows in Relation to Feed Composition,Time of Feeding and Level of Feed Intake

The main purpose of this study was to examine sources of variation in free amino acids (FAA) in the rumen and their relative contribution to the total duodenal amino acid supply. Six cannulated lactating dairy cows fed three concentrate mixtures differing in ruminally degradable intake protein (101, 114 and 134 g kg^-1 dry matter) at two levels of intake (19.3 vs 9.8 kg dry matter day^-1     

C and N turnover of fermented residues from biogas plants in soil in the presence of three different earthworm species (Lumbricus terrestris,Aporrectodea longa,Aporrectodea caliginosa)

A soil microcosm experiment was performed to assess (1) the C- and N- turnover of residues from biogas plants in soils in the presence of three earthworm species (Lumbricus terrestris, Aporrectodea longa and Aporrectodea caliginosa) and (2) the resulting changes in soil chemical and microbiological properties when using these residues as fertilizer in comparison to conventional slurry. Earthworms were exposed in soils, fertilized with an equivalent amount of 120 kg of NH₄-N ha^?1 from: (1) conventional cattle slurry and (2) a fermented residue derived from cattle slurry, grass (silage) and maize. Additional treatments without slurry and earthworms were used as controls.There was considerable evidence that soils fertilized by fermented slurry comprised fewer amounts of readily available nutrients for microbial C and N turnover. We observed significant stimulation of microbial biomass, basal respiration and nitrification in treatments with conventional slurry, especially in the presence of earthworms. However, the stimulation of microbial activity by manure and earthworms were significantly lower in treatments with fermented slurry. Moreover, the results showed clear interactions between different earthworm species and manures. While the biomass of the anecic species (L. terrestris and A. longa) increased in both slurry treatments, the biomass of A. caliginosa (endogeic) decreased, with a significantly stronger biomass decline in treatments with fermented slurry. The metabolic quotients revealed microbial stress metabolism in fermented slurry treatments, predominantly in treatments with A. caliginosa. We conclude that particularly A. caliginosa and soil microorganisms competed for labile C sources in treatments with fermented slurry. An application of these residues as fertilizer might result in a reduction of microbial activity in agricultural soils and in a decline of endogeic earthworms.     

Temporal disease dynamics and relative importance of sexual and asexual reproduction of grape downy mildew (Plasmopara viticola) in an isolated vineyard in the North Georgia Mountains,USA

The North Georgia Mountains are the southernmost region along the United States East Coast where European wine grapes (Vitis vinifera) are grown commercially. Epidemics of downy mildew, caused by Plasmopara viticola, are frequent and severe, but little is known about the epidemiology and population biology of the pathogen in this region. Disease monitoring in an experimental vineyard from 2015 to 2017 indicated that times of disease onset and progress rates were highly variable across years and cultivars. Oospores were observed microscopically, and simulation with a process-based model indicated presence of conditions favourable for oospore germination in the spring and early summer each year. A total of 409 P. viticola isolates collected over three  years were genotyped with seven microsatellite markers, revealing very high genotypic diversity, which when combined with the observation of oospores is indicative of a sexually reproducing population. Among the 409 isolates, 225 multilocus genotypes (MLGs) were identified, of which 164 were detected only once and 61 were repeated (clonal). Eight MLGs (represented by 28 isolates) were detected across years, suggesting the possibility of asexual overwintering of P. viticola in this region. Across sampling dates, the percentage of isolates belonging to nonrepeated (unique) MLGs ranged from 27.3% to 63.2%. Even towards the end of the annual epidemic, the percentage of isolates in nonrepeated MLGs was still relatively high, around 30%. These MLGs may have originated from oospores germinating late during the growing season, although incomplete sampling at earlier dates and contribution by immigration cannot be fully excluded.