Defoliation and dieback of Sitka spruce in Reykjavík, Iceland

The green spruce aphid Elatobium abietinum is an important defoliating pest of Sitka spruce (Picea sitchensis) in Iceland. A comparison of two urban Sitka stands in Reykjavík, from 2013-2017, reveals a distinct defoliation difference between trees located near a main road (94% defoliated) and several hundred meters away from heavy traffic (47%). Chemical analyses of the spruce needles demonstrate substantially higher nitrogen ratios in trees near traffic. Furthermore, the recently warming winter temperatures promoted larger overwintering aphid populations since 2003, as well as a shift of mass outbreaks from autumn to spring, accompanied by distinct growth suppressions one year after an aphid population spike in the post-2003 tree-ring data. The results of this study indicate that the mechanisms triggering Sitka spruce dieback in Reykjavík include a combination of increasing winter temperatures, more frequent and severe green spruce aphid outbreaks, as well as elevated N values in the needles of urban trees.

Patterns of Eimeria excretion in young Icelandic calves

Faecal samples were collected from a total of 11 calves on three dairy farms (four from two farms and three from one) where calves generally thrive well and no anti-coccidial treatment is habitually carried out. One of the farms keeps calves in groups on hay/straw bedding, one keeps calves in pairs on plastic slats and then in groups on concrete slats, and the third one keeps calves in groups on concrete slats. Faecal consistency and the total number of Eimeria spp. oocysts per gram faeces (OPG) were determined and species identification was carried out by morphology. Eimeria oocysts were detected in all calves at some point of the study period, and diarrhoea was seen in 55% of the calves. The highest peak in oocyst excretion was 69,300 OPG. The first peak in oocyst excretion was seen 2-3 weeks after calves had been moved to group pens, and a second peak was seen 2-3 weeks later. Nine Eimeria species were found, including E. bovis and E. zuernii. The results are in accordance with previous studies showing that one of the risk factors for Eimeria infection in calves is entering a group pen where older calves are already being kept.

Lung nematodes of sheep (Ovis aries) in Iceland - prevalence, intensity and geographic distribution in 1992 and 1993

During the slaughter period in autumn 1992 and 1993 lungs and the gastrointestinal tract was collected from a single lamb originating from 96 sheep farms, selected to reflect the distribution of farms in Iceland. The results on the gastrointestinal helminths have already been published. The lungs were kept frozen until analysed in 2019. Nematodes were directly searched for in the lungs of 84 lambs. Results on larval counts were handed over to the present authors for comparison purposes. Three lungworm nematode species were detected: Muellerius capillaris (total prevalence 35.1%), Protostrongylus sp. (2.4%), and Dictyocaulus filaria (16.7%). M. capillaris was found in lambs from all parts of Iceland except from certain areas in the north and northeast. Protostrogylus sp. was detected on two adjacent farms in the north. D. filaria was frequently found in lambs from farms in the southern and western parts, whereas sporadic cases were found in north and east Iceland. As relatively few lambs were examined, the distribution area of sheep lungworm in the early 1990s is regarded to have been more extensive than indicated in the article.

The long-term effects of climatic factors on radial growth of downy birch (Betula pubescens) and rowan (Sorbus aucuparia) in East Iceland

The aim of this study was to investigate the tree-ring growth of rowan (Sorbus aucuparia L.) and downy birch (Betula pubescens Ehrh.) in Ranaskógur, a forest in East Iceland, and to determine its response to climate factors during the past century. Tree-core samples were collected in September 2018 and from those a tree-ring width (TRW) chronology and a standardized tree-ring index (TRI) chronology were produced. A statistical analysis between the chronologies and monthly mean temperatures and total monthly precipitation was carried out. The study found that both species had similar radial growth during the past century. The growth of birch responded significantly positively to June and July temperatures, while rowan responded significantly positively to July and August temperatures. The growth of neither species was significantly affected by precipitation across the whole period. However, in the 1940s to early 1960s, rowan growth correlated significantly with June precipitation, and birch with April and May precipitation.

Pyrosequencing investigation into the bacterial communities in the Qinghai-Tibet Plateau soils associated with soil characteristic factors

The Qinghai Tibet Plateau (QTP) is one of the most important regions of the earth’s ecosystem that is vulnerable to climate and human activities due to its complex climate and terrain. However, knowledge about soil bacterial communities and their effect on the ecosystem within the QTP environments is still scarce. Metagenomic approaches on the structure and diversity of bacterial communities and their relationship with the environment from eighteen selected sites of the five major QTP ecosystems (gray-cinnamon soils, chernozems, castanozems, mountain meadow soils, gray desert soils) are presented in this paper. The dominant bacterial phyla in five type soils were Proteobacteria and Actinobacteria, whereas Actinobacteria and Chloroflexi predominated in gray desert soils. The bacteria diversity in castanozeras and mountain meadow soils was significantly higher than that of the other three soil types (P < 0.05). Phylogenetic diversity in gray desert soil was significantly lower than that of other four soil types (P < 0.05). Phylotype richness was the lowest in gray-cinnamon soils. There were significant correlations between the phylotype richness and soil moisture (r = -0.578) and potassium (r = -0.529). Phylogenetic diversity (PD) was significantly correlated with total organic carbon (r = -0.548). The redundancy analysis (RDA) showed that the diversity and composition in the bacterial communities differed greatly among the five soil types and that they were closely correlated with the soil moisture, soil organic carbon and potassium. These results indicated that the bacterial community structures of QTP soils were obviously influenced by soil characteristics and soil environmental characteristics and provided a theoretical basis for the optimal management and sustainable utilization of the QTP soil ecosystem, which is of great significance.