Determining species diversity of microfungal communities in forest tree roots by pure-culture isolation and DNA sequencing

Pure-culture isolation from roots was compared with transformation of total DNA from roots followed by sequence analysis of ITS 1/2 rDNA of representative clones as methods for determining the abundance and composition of microbiota in roots of Betula pendula, Fagus sylvatica, Larix decidua, Prunus serotina and Quercus petraea. The results from the two methods differed greatly, with no overlap between the taxa identified. Pure-culture isolation revealed greater species diversity (47 taxa), the most frequent fungi being Ascomycota, including Penicillium spp., Phialocephala fortinii, Pochonia bulbillosa, Sesquicillium candelabrum and Trichoderma spp. Transformation of total DNA and sequencing revealed less diversity (22 taxa), the most frequent taxa being Basidiomycota, including Coprinus fissolanatus and Mycena spp., and Ascomycota, including Podospora–Schizothecium spp., Helgardia anguioides and Microdochium sp. Communities characterized by either method showed slightly greater fungal diversity and less species dominance on F. sylvatica than on roots of other trees, whilst DNA sequencing showed least diversity and greatest species dominance on Q. petraea.     

Interactive effects of tree species and soil moisture on methane consumption

Methane consumption by temperate forest soils is a major sink for this important greenhouse gas, but little is known about how tree species influence CH₄ uptake by soils. Here, we show that six common tree species in Siberian boreal and temperate forests significantly affect potential CH₄ consumption in laboratory microcosms. Overall, soils under hardwood species (aspen and birch) consumed CH₄ at higher rates than soils under coniferous species and grassland. While NH₄⁺ addition often reduces CH₄ uptake, we found no effect of NH₄⁺ addition, possibly because of the relatively high ratio of CH₄-to-NH₄⁺ in our incubations. The effects of soil moisture strongly depended on plant species. An increase in soil moisture enhanced CH₄ consumption in soils under spruce but had the opposite effect under Scots pine and larch. Under other species, soil moisture did not affect CH₄ consumption. These results could be explained by specific responses of different groups of CH₄-oxidizing bacteria to elevated moisture.     

不同种植年限转基因抗虫棉对土壤中小型节肢动物的影响

2007~2008年,在分别于1999年、2002年和2006年种植Cry1Ac基因抗虫棉的棉田中,于棉花的苗期、蕾期、花铃期和吐絮期采集土壤样品,采用改良的Tullgren法收集土壤中的中小型节肢动物,以监测长期种植转基因抗虫棉对土壤节肢动物群落的影响。2年8次采样共获得12类中小型节肢动物,隶属于节肢动物门中的7纲10目,其中弹尾目、蜱螨目、蜘蛛目为本地区棉田中的优势类群,综合纲、双翅目、半翅目、双尾目、鞘翅目和同翅目为常见类群。广义线性混合模型分析结果表明,随着转基因抗虫棉种植年限的增加,各转基因抗虫棉田中的土壤主要类群中小型节肢动物的个体密度和多样性指数没有产生显著性差异,但是随着采样时期的不同各棉田土壤主要中小型节肢动物的个体密度和群落多样性指数均呈显著性季节变化。主成分分析表明,弹尾目、蜘蛛目、蜱螨目的得分值较高,可作为本地区未来转基因抗虫棉环境影响监测的重要指标生物。     

Protein precipitation by tannins in soil organic horizon and vegetation in relation to tree species

The aim of this study was to compare the concentration of tannins and their capacity to precipitate proteins in the dominant species of ground vegetation (Deschampsia flexuosa (L.) Trin., Pleurozium schreberi (Brid.) Mitt., Vaccinium myrtillus (L.), and Vaccinium vitis-idaea (L.)) and in different layers of the soil organic horizon (litter layer—L, fermentation layer—F, humified layer—H) under silver birch (Betula pendula Roth.), Norway spruce (Picea abies (L.) Karst.), and Scots pine (Pinus sylvestris L.). Total tannin concentrations were also measured in leaves or needles of birch, spruce, and pine. The study site is located in Kivalo, northern Finland, close to the Arctic Circle. Differences in total tannin concentrations in ground vegetation were due mainly to species, with Vaccinium species having the highest values. The influence of the dominant tree species was less important. Protein precipitating capacity was dependent on plant species; the highest values occurred in Vaccinium species and spruce. Because of their relatively high protein precipitating capacity but low total tannin concentration, D. flexuosa and P. schreberi seemed to have more astringent tannins. Concentrations of total tannin and hydrolyzable tannin in the soil organic horizon differed depending on the layer and tree species. In general, the highest concentrations of total tannins were found under birch and spruce in the L layer and the lowest concentrations under pine. Protein precipitating capacity was usually the lowest in the H layer and highest under birch and spruce in the F and H layers. We showed that lignin from rotted pine wood can also precipitate proteins but only small amounts; additionally, lignin can be an important source of error for soil total tannin measurements.