Soil organic matter biochemistry and potential susceptibility to climatic change across the forest-tundra ecotone in the Fennoscandian mountains

We studied soil organic carbon (C) chemistry at the mountain birch forest‐tundra ecotone in three regions of the Fennoscandian mountain range with comparable vegetation cover but contrasting degrees of continentality and latitude. The aim of the study was to identify functional compound classes and their relationships to decomposition and spatial variation across the ecotone and latitudinal gradient. Solid‐state ¹³C nuclear magnetic resonance (CPMAS ¹³C NMR) was used to identify seven functional groups of soil organic C: alkyls, N‐alkyls, O‐alkyls, acetals, aromatics, phenolics and carboxyls. N‐alkyls, O‐alkyls and acetals are generally considered labile substrates for a large number of saprotrophic fungi and bacteria, whilst phenolics and aromatics are mainly decomposed by lignolytic organisms and contribute to the formation of soil organic matter together with aliphatic alkyls and carboxyls. All soils contained a similar proportional distribution of functional groups, although relatively high amounts of N‐alkyls, O‐alkyls and acetals were present in comparison to earlier published studies, suggesting that large amounts of soil C were potentially vulnerable to microbial degradation. Soil organic matter composition was different at the most southerly site (Dovrefjell, Norway), compared with the two more northerly sites (Abisko, Sweden, and Joatka, Norway), with higher concentrations of aromatics and phenolics, as well as pronounced differences in alkyl concentrations between forest and tundra soils. Clear differences between mountain birch forest and tundra heath soil was noted, with generally higher concentrations of labile carbon present in tundra soils. We conclude that, although mesic soils around the forest‐tundra ecotone in Fennoscandia are a potential source of C to the atmosphere in a changing environment, the response is likely to vary between comparable ecosystems in relation to latitude and continentality as well as soil properties especially soil nitrogen content and pH.     

TEXTURE-FLAVOR INTERACTIONS IN LOW FAT STIRRED YOGURT: HOW MECHANICAL TREATMENT, THICKENER CONCENTRATION AND AROMA CONCENTRATION AFFECT PERCEIVED TEXTURE AND FLAVOR

The influence of thickening agent (0 and 7g/L), mechanical treatment (low and high) and flavoring agent concentration (2.2 to 63.2 μL/kg) on texture, taste and aroma of low fat stirred yogurts was investigated through sensory profiling by a panel of ten subjects trained on 13 attributes. Two assessment conditions were used: either in the presence or in the absence of olfactory perception (nostrils closed with nose clips). Sensory differences were greater for texture than for the other perception modalities. Olfactory perception enhanced yogurt astringency. If both thickener addition and mechanical treatment influenced texture attributes and rheology, the second factor had the strongest effect. Texture attributes were highly correlated with rheological parameters. Increasing flavoring agent concentration tended to decrease thickness and the addition of thickening agent depressed green apple notes and sweet taste, suggesting texture/flavor interactions.     

Assessing phylogenetic relationships in extant heterosporous ferns (Salviniales), with a focus on Pilularia and Salvinia

Heterosporous ferns (Salviniales) are a group of approximately 70 species that produce two types of spores (megaspores and microspores). Earlier broad‐scale phylogenetic studies on the order typically focused on one or, at most, two species per genus. In contrast, our study samples numerous species for each genus, wherever possible, accounting for almost half of the species diversity of the order. Our analyses resolve Marsileaceae, Salviniaceae and all of the component genera as monophyletic. Salviniaceae incorporate Salvinia and Azolla; in Marsileaceae, Marsilea is sister to the clade of Regnellidium and Pilularia– this latter clade is consistently resolved, but not always strongly supported. Our individual species‐level investigations for Pilularia and Salvinia, together with previously published studies on Marsilea and Azolla (Regnellidium is monotypic), provide phylogenies within all genera of heterosporous ferns. The Pilularia phylogeny reveals two groups: Group I includes the European taxa P. globulifera and P. minuta; Group II consists of P. americana, P. novae‐hollandiae and P. novae‐zelandiae from North America, Australia and New Zealand, respectively, and are morphologically difficult to distinguish. Based on their identical molecular sequences and morphology, we regard P. novae‐hollandiae and P. novae‐zelandiae to be conspecific; the name P. novae‐hollandiae has nomenclatural priority. The status of P. americana requires further investigation as it consists of two geographically and genetically distinct North American groups and also shows a high degree of sequence similarity to P. novae‐hollandiae. Salvinia also comprises biogeographically distinct units – a Eurasian group (S. natans and S. cucullata) and an American clade that includes the noxious weed S. molesta, as well as S. oblongifolia and S. minima. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157 , 673–685.     

Characterization of eight microsatellite loci in the maize stalk borer Busseola fusca Fuller, 1901 (Lepidoptera: Noctuidae)

The noctuid stem borer Busseola fusca occurs throughout sub‐Saharan Africa, where it is considered as a major pest of corn and sorghum. To understand B. fusca phylogeography, we isolated and characterized eight microsatellite loci in this species. We investigated these loci for polymorphism on a subset sample of individuals from different geographic populations. All loci were polymorphic, showing between four and 10 alleles. Cross‐species amplification of four of these loci was tested on 11 other noctuid species.     

Characterization of seven polymorphic microsatellites for the study of two Ranunculaceae: Ranunculus nodiflorus L., a rare endangered species and Ranunculus flammula L., a common closely related species

Ranunculus nodiflorus and Ranunculus flammula are two closely related Ranunculaceae. In France, the first one is rare and endangered, whereas the second is common. To compare their population genetic structure, seven polymorphic microsatellite markers were characterized. We found no polymorphism in R. nodiflorus, whereas R. flammula was polymorphic at each locus. The total number of alleles per locus varied from three to eight. Observed heterozygosities ranged from 0 to 0.261. This set of microsatellites offers an efficient tool to study population genetic structure and to compare the results between closely related endangered and common species.