Cultivable bacteria isolated from apple trees cultivated under different crop systems: Diversity and antagonistic activity against Colletotrichum gloeosporioides

This study evaluated the diversity of cultivable plant growth-promoting (PGP) bacteria associated with apple trees cultivated under different crop management systems and their antagonistic ability against Colletotrichum gloeosporioides. Samples of roots and rhizospheric soil from apple trees cultivated in organic and conventional orchards in southern Brazil were collected, together with soil samples from an area never used for agriculture (native field). Bacteria were identified at the genus level by PCR-RFLP and partial sequencing of the 16S rRNA, and were evaluated for some PGP abilities. The most abundant bacterial genera identified were Enterobacter (27.7%), Pseudomonas (18.7%), Burkholderia (13.7%), and Rahnella (12.3%). Sixty-nine isolates presented some antagonist activity against C. gloeosporioides. In a greenhouse experiment, five days after exposure to C. gloeosporioides, an average of 30% of the leaf area of plants inoculated with isolate 89 (identified as Burkholderia sp.) were infected, whereas 60 to 73% of the leaf area of untreated plants was affected by fungal attack. Our results allowed us to infer how anthropogenic activity is affecting the bacterial communities in soil associated with apple tree crop systems, and to obtain an isolate that was able to delay the emergence of an important disease for this culture.     

Fire‐sensitive species dominate seed rain after fire suppression: Implications for plant community diversity and woody encroachment in the Cerrado

Woody encroachment is becoming common in tropical savannas. We studied natural seed rain and performed seed addition experiments in a Brazilian savanna that had not been burned for several decades. We found greater abundance of fire‐sensitive species in the seed rain, likely contributing to woody encroachment. Flexible fire management policies that allow for natural and prescribed fires may be required to maintain savanna diversity.     

Wood formation in urban Norway maple trees studied by the micro-coring method

Intra-annual wood formation in healthy and affected Norway maple (Acer platanoides L.) street trees in the City of Ljubljana, Slovenia, was studied by the micro-coring method. Samples were taken with a Trephor instrument at weekly intervals during the 2005 growing season. The beginning of wood formation corresponded to the initiation of cambial activity in the middle of April in all investigated Norway maple trees. In healthy trees, the period of wood formation was finished in mid-September, persisting 7 weeks longer than in affected ones. Small destructivity and sufficient quality of micro-cores confirmed that sampling with a Trephor is a convenient method for the study of wood formation in diffuse-porous hardwoods, growing in the harsh conditions of an urban environment.     

Tree-ring analysis of traditional native bark-stripping at Ship Island, Southeast Alaska, USA

Tree-ring analyses of 23 bark-stripped trees, mostly Thuja plicata (western red cedar) but also Chamaecyparis nootkatensis (yellow cedar) and Picea sitchensis (Sitka spruce), help describe traditional Native tree-bark exploitation at a site north of Ketchikan in southeast Alaska, USA. Tree-ring samples exposed 36 cultural scars dating from between a.d. 1718 and 1912, showing that Natives landed on this hazardous stretch of Clarence Strait to take tree bark in 29 (about 15%) of the 195 years spanned by the sample. One-third of these culturally modified trees had multiple scars indicating repeated use of individual trees. The most intensive forest use occurred between 1852 and 1895, while the lack of bark scars after 1912 marks a decline in traditional Native craft. A burst of bark-stripping between 1779 and 1787 may be associated with the legendary last battle between the Stikine Tlingit of Alaska and the Tsimshian of British Columbia. The sample is compared with dated samples from British Columbia (Canada) and Washington State, USA.     

浙江磐安红叶树种资源及其应用调查

对浙江省磐安县红叶树种资源及其应用情况进行初步调查,结果表明,该县共有乔木、灌木、藤本红叶木本植物37种,分属19科26属,其中,落叶乔木所占比例最大,有21种,占该县红叶树种的56.8%。根据叶片变色规律可分成秋叶变红、嫩叶红色、秋叶和嫩叶均呈红色、常年有红叶等四大类型,种数最多的是秋叶变红类,有26种,占该县红叶树种的70.3%。本文对部分重要的红叶树种的园林应用价值进行综合评价,并对该县红叶树种资源的开发利用提出建议。     

Latitudinal Variation in Leaf and Tree Traits of the Mangrove Avicennia germinans (Avicenniaceae) in the Central Region of the Gulf of Mexico

The variation in leaf mass per area, leaf nutrients (% carbon, nitrogen and phosphorus), and the allometric relation between tree height and diameter of the black mangrove, Avicennia germinans, were explored in nine mangrove forests in similar environments along a 5° latitudinal gradient in the central region of the Gulf of Mexico, as indicated by a southward increase in temperature and precipitation. There was no correlation between leaf nitrogen or phosphorus content and latitude. Leaf mass per area and leaf carbon content were positively correlated with latitude and negatively correlated with temperature and annual rainfall, whereas asymptotic tree height and maximum diameter showed the opposite trend. Such patterns suggest a trade-off between leaf traits and tree size which may be constrained by the same environmental factors along a dry-cold to humid-warm latitudinal gradient.     

Seasonality and resource availability control bacterial and archaeal communities in soils of a temperate beech forest

It was hypothesized that seasonality and resource availability altered through tree girdling were major determinants of the phylogenetic composition of the archaeal and bacterial community in a temperate beech forest soil. During a 2-year field experiment, involving girdling of beech trees to intercept the transfer of easily available carbon (C) from the canopy to roots, members of the dominant phylogenetic microbial phyla residing in top soils under girdled versus untreated control trees were monitored at bimonthly intervals through 16S rRNA gene-based terminal restriction fragment length polymorphism profiling and quantitative PCR analysis. Effects on nitrifying and denitrifying groups were assessed by measuring the abundances of nirS and nosZ genes as well as bacterial and archaeal amoA genes. Seasonal dynamics displayed by key phylogenetic and nitrogen (N) cycling functional groups were found to be tightly coupled with seasonal alterations in labile C and N pools as well as with variation in soil temperature and soil moisture. In particular, archaea and acidobacteria were highly responsive to soil nutritional and soil climatic changes associated with seasonality, indicating their high metabolic versatility and capability to adapt to environmental changes. For these phyla, significant interrelations with soil chemical and microbial process data were found suggesting their potential, but poorly described contribution to nitrification or denitrification in temperate forest soils. In conclusion, our extensive approach allowed us to get novel insights into effects of seasonality and resource availability on the microbial community, in particular on hitherto poorly studied bacterial phyla and functional groups.     

A java applet for exploring the new higher level classification of eukaryotes with emphasis on the taxonomy of protists

ABSTRACT. We have converted the hierarchically organized new higher level classification of eukaryotes with emphasis on the taxonomy of protists proposed by Adl et al. into an interactive and dynamic Java applet. The current version of the applet can be accessed via http://phylogenetics.bioapps.biozentrum.uni-wuerzburg.de/etv . We use the layout from a Degree-of-Interest tree (DOITree) that effectively displays all the taxonomic information as well as the phylogenetic relationships described in the original article by Adl et al. The tree was made using the Prefuse Toolkit for interactive information visualization. All browsers capable of using Java applets will be able to view the tree. The applet is freely available for scientists, teachers, and students.