Alfalfa roots and nitrogen transformations in peat

Accumulation of NH⁺₄ and NO^?₃ in peat was significantly reduced by living or decaying alfalfa roots. Alfalfa root extracts, alfalfa saponins, the carbohydrate fraction of alfalfa saponins and mono- and disaccharides inhibited NH⁺₄ production and NO^?₃ accumulation, in a casein-amended peat or enrichment cultures, and they enhanced denitrification in a flooded peat. NO^?₃ accumulation in peat was affected to a lesser extent by polysaccharides, the genine (aglycone) fraction of alfalfa saponins, and by the root extracts of Rhodes grass, clover and wheat. It is suggested that inhibition of accumulation in alfalfa-grown peat is mainly due to the relatively high concentrations of free sugars and saponins of alfalfa roots, which lead to NH⁺₄ immobilization, with a concomitant decrease in NO^?₃ accumulation.     

Studies on the constituents of Gliricidia sepium (Leguminosae) leaves and roots: isolation and structure elucidation of new triterpenoid saponins and aromatic compounds

Our research program on the Central American fooder plant Gliricidia sepium led to the discovery of two new triterpene saponins (1 and 2) and known aromatic compounds. The new compounds possess 3beta,21beta, 24-trihydroxy-22-oxoolean-12-ene as an aglycon. The oligosaccharide moiety linked to C-3 of the aglycon contained two pyranoses (glucuronic acid and xylose); in addition the glucose residue of both 1 and 2 is also linked to C-21. Structure elucidation of these new compounds through the extensive use of 1D and 2D NMR techniques have provided detailed information about the sapogenin and the saccharide chains, inclusive of sugar sequence and the position of glycosylation.     

Composition of carbon fractions and potential denitrification in drained peat soils

The organic matter of five low-moor peat soils and one eutrophic raised-bog peat soil was chemically characterized by C fractionation and ion-exchange chromatography of amino acids and carbohydrates. C fractions were related to potential denitrification, D_pot, as a measure of microbial activity and C availability, determined by the acetylene inhibition technique. Chemical and physical properties vary distinctively between different kinds of peat, and show increasing C/N ratio and decreasing bulk density and ash content within the profile. Generally, the carbon composition reflects the geobotanical origin of the peat. In most samples more than 65% of organic C consists of non-hydrolysable C. Readily hydrolysable neutral sugar C represents up to about 12% of organic C, usually decreasing with depth. The recalcitrant fraction of neutral sugar C is much smaller (1 to 4.2% of organic C) and does not vary with depth. The content of readily hydrolysable glucose exhibits a strong profile differentiation that decreases with depth, whereas the higher contents of recalcitrant glucose carbon (12/0.5 M H₂SO₄) in the lower peat horizons reflect their cellulose character. Regression analysis between D_pot and single C components explains up to 51.5% of the variability. Combining fractions which point to C availability (readily hydrolysable glucose) and microbial metabolism (amino acids), it is possible to estimate D_pot with a certainty of more than 80%.     

Assessment of biochemical and antioxidant diversities in a shallot germplasm collection from Vietnam and its surrounding countries

The shallot is considered an important genetic resource for Allium breeding programs because, compared to the bulb onion, the shallot contains higher levels of several functional chemical compounds. However, there may be differences in content, composition and beneficial activity among shallot landraces. This study was carried out to characterize the differences in phenolic, quercetin, sugar, S-alk(en)yl-l-cystein sulfoxide (ACSO), and saponin contents and antioxidant capacities of a shallot germplasm including 31 strains derived from different regions of Vietnam and six other countries. A wide variation was observed in the quantitative analyses of the chemical contents. Shallots with high contents of polyphenols, saponins, and quercetins were found in the south of Vietnam and other low-latitude countries. Meanwhile, those possessing fairly high ACSO and sugar contents were observed in the north of Vietnam. Qualitative analysis of saponins via thin layer chromatography did not show clear variation among shallot strains, but polymorphism was observed between the shallot and other Allium species, such as A. roylei. The principal component analysis could clearly discriminate shallot strains by their geographical origins. All shallot strains showed potent antioxidant activities in a DPPH assay. The highest antioxidant capacity was in the strains possessing relatively high contents of polyphenol, quercetin, and saponin. Significant correlations were found between antioxidant capacity (IC ₅₀ ^?1 ) and four groups of chemical compounds (polyphenols, quercetins, saponins, and ACSOs) (r = 0.40–0.59). A strong correlation was observed between IC ₅₀ ^?1 and quercetin contents (r = 0.59, p < 0.01). The six Fusarium-inoculated shallot strains seemed to be adequately resistant against disease, and the levels of resistance may be related to the saponin content in the bulb tissues.     

Population responses of oribatids and enchytraeids to ectomycorrhizal and saprotrophic fungi in plant-soil microcosms

The oribatid mites Oppiella nova, Tectocepheus velatus and Nothrus silvestris and the enchytraeid worm Cognettia sphagnetorum are four common animal species in boreal forest soils. According to the literature, they respond differently to clear-cutting of forest stands. O. nova responds with population decreases, T. velatus and N. silvestris with small changes and C. sphagnetorum with population increases. We hypothesised that the presence/absence of ectomycorrhizal (EM) fungi is a major factor in explaining these reactions. The population responses of these soil animals to inoculation of five species of EM fungi growing in symbiosis with their host tree (Pinus sylvestris L.) and one saprotrophic fungus, Hypholoma capnoides, growing on wood were tested in pot microcosms with artificial soil (peat and vermiculite) for 70-84 days. Additionally, plants without inoculation of EM fungi, plants growing in forest soil (FS) and plant-free peat and vermiculite (PV) were included. O. nova increased significantly in abundance in the treatments with the EM fungi Suillus variegatus and Paxillus involutus, but not in the other treatments. T. velatus increased significantly in abundance in FS, but declined in most of the other treatments, and N. silvestris showed a similar, albeit not significant, response. C. sphagnetorum did not increase in abundance in any of the treatments with EM fungi but increased its abundance four times in both FS and PV. The results show that the fungivore O. nova preferentially feeds on certain EM fungi, especially S. variegatus, whereas the EM fungus Piloderma fallax and the saprotrophic H. capnoides are not preferred. In contrast, C. sphagnetorum is restricted in its population growth by the EM fungi studied, and this dominant microbi-detritivore is clearly favoured by the absence of EM fungi.     

Source and transformations of lignin in Carex-dominated peat

We identified the effects of vegetation changes, and aerobic and anaerobic decay on the lignin composition in the Penido Vello peat record (Galicia, Spain). The ombrotrophic part of this peat record was dominated by graminoids and has significant contributions of ericoids at some depths. The organic matter (OM) of different peat fractions (bulk, NaOH-extractable fraction, and non-extractable residues) of 15 samples from the upper meter was analysed with pyrolysis-gas chromatography/mass spectrometry (pyrolysis-GC/MS). In addition, the dominant plant species were analysed, including Carex durieui, Agrostis curtisii, Molinia caerulea, Deschampsia flexuosa, Festuca rubra, Eriophorum angustifolium, Erica mackaiana and Calluna vulgaris, and their lignin composition compared to that of the peat OM. The high abundance of guaiacol and 4-formylguaiacol in fresh plant tissue compared to peat OM suggests that in addition to p-coumaric and ferulic acid (which are abundant in graminoids), other non-lignin phenolic monomers are contributed by graminoid species. For the non-lignin phenolics, graminoids differed from ericoids in the high abundance of ferulic acid (4-vinylguaiacol), while p-coumaric acid (4-vinylphenol) showed high and similar abundances in ericoids and graminoids. This result suggests that ratios between p-hydroxyphenyl (or p-coumaric acid) and other lignin moieties in (pyrolysates of) peat cannot be used as source indicator. Comparison of plant and peat fractions using factor analysis allowed a distinction between the effects of source (plant identity) and decay on the lignin composition of the Penido Vello peat, and different stages of decomposition were identified. Preferential decay of guaiacyl over syringyl moieties was found for the first stage of decay. This preferential decay is probably related to the large abundance of guaiacyl moieties in easily degradable non-lignin phenolics. Preferential decay of syringyl moieties occurred during subsequent aerobic decay.     

Leachability of ra-226 from uranium mill tailings consolidated with naturally occurring materials and/or cement

Reduction of the fraction of Ra-226 leached from U mill tailings by one or two orders of magnitude was found possible by solidifying the mill tailings with cement and cement plus peat or clay. For the period of the leaching experiments (approximately 100 days) the leaching behavior of the solidified mill tailings could be described by an empirical equation of the form Q = αt ^α, where Q = fraction of activity leached, normalized with respect to the surface: volume ratio of the tailings, t = time, and α and α are constants. The most effective consolidation mixture investigated was a 70:30 tailings to consolidating mixture comprised of cement, peat and clay in the ratio of 50:30:20.     

Cytotoxic saponins from bulbs of Allium porrum L

An extensive phytochemical analysis of the saponin content has been undertaken on leek, Allium porrum L., sown and collected at different seasons. As a result of this investigation, eight saponins (1-8) have been isolated, four of them (5-8) being novel compounds. Compounds 5 and 6, possessing the same tetrasaccharide moiety of compounds 1 and 3, display very unusual spirostane aglycones, 12-ketoporrigenin and 2,12-diketoporrigenin (named porrigenin C), respectively, recently isolated for the first time as free sapogenin in the same plant. Compounds 7 and 8 are rare cholestane bidesmosides possessing a di- and trisaccharide residues linked to a polyhydroxycholesterol aglycone, respectively. The structures of the isolated compounds have been determined by nondegradative spectroscopic analysis, mainly based on NMR. All the eight saponins isolated from leek were tested for their cytotoxic activity against two different cell lines in vitro, and compounds 1, 2, and 6 resulted particularly active.     

Domestication and saponins contents in a gradient of management intensity of agaves: <Emphasis Type="Italic">Agave cupreata</Emphasis>, <Emphasis Type="Italic">A. inaequidens</Emphasis> and <Emphasis Type="Italic">A. hookeri</Emphasis> in central Mexico

Saponins occur in numerous plants, including agaves, determining benefic and harmful properties to humans; their presence may favor using plants as soap and other products, but also they may cause caustic effects producing contact dermatitis. In domestication, favorable and unfavorable properties of saponins may cause an increase or decrease of their content, respectively. This study quantified and identified saponins among wild and managed populations of three agave species: A. cupreata Trel. et Berger, A. inaequidens Koch with wild and cultivated populations used for mescal production, and A. hookeri Jacobi, existing exclusively cultivated, used for production of the fermented beverage pulque. We studied 272 plants from 19 populations, quantifying contents of crude saponins through spectrometry. In 12 populations, the saponins types were identified by High Performance Liquid Chromatography–Mass-Spectrography-Time-of-Flight HPLC-MS-TOF. The highest crude saponins content was recorded in A. hookeri (26.09 mg/g), followed by A. cupreata (19.85 and 15.17 mg/g in wild and cultivated populations, respectively). For A. inaequidens, we recorded 14.21, 12.95, and 10.48 mg/g in wild, silvicultural managed and cultivated populations, respectively. We identified 18 saponins types, A. inaequidens showing all of them. A hecogenin glycoside (HG1) is found in high amounts in A. hookeri but in low quantities in A. inaequidens and A. cupreata. A. inaequidens had the greatest diversity of saponins. The contents of crude saponins in A. inaequidens and A. cupreata decrease with management intensity, but contrarily to what we expected, it was the highest in A. hookeri. We hypothesize that such high amount could be due to some saponins, probably HG1, may be precursors of sugars.     

Role of cation exchange in preventing the decay of anoxic deep bog peat

The major bog systems in northern areas are dominated by Sphagnum species, the partially decomposed remains of which form the bulk of deep peat. By adding mono- and di-valent cations to deep peat cores (2.0-2.5 m) and measuring CH₄ and CO₂ concentrations in the manipulated peat cores using quadrupole mass spectrometry (QMS) we demonstrate that the lack of availability to microorganisms of essential cations is limiting decay in deep peat. The cations with the highest binding strength displaced the most cations and stimulated decay. Decay in deep peat cores was also stimulated by a C source (acetate), but not by NH₄⁺. The addition of cations and acetate resulted in a less than additive stimulation of decay. The stimulatory effect of acetate and copper decreased in the presence of ammonium. The addition of EDTA to surface bog peat (where cations are conserved) decreased decay rates in surface peat (0.0-0.5 m) to that of the untreated deep peat (2.0-2.5 m). Deep peat was unaffected by treatment with EDTA. The effect of adding Cu²⁺differed with the depth from which the peat was collected. Cu²⁺ did not stimulate decay in surface bog peat (0.0-1.5 m) but stimulated decay in peat from 1.5-3.5 m. Below 3.5 m to the bottom of the profile (5.0 m) no positive effect was observed. By comparing deep peat with surface peat we have shown that cation limitation because of high cation exchange capacity is specific to the main mass of deep bog peat and may explain differences in decay rates between anoxic surface peat and deep peat.     

Earthworm distribution and abundance along a mineral-peat soil transect

The earthworm fauna along a gradient from undisturbed mineral soil to an artificial acid peat soil up to 25 cm deep and ca. 30 yr old was studied in the Phoenix Park, Dublin. The peat held only 15% of the total numbers of worms in the mineral soil and 9% of the biomass, but 9 out of the 12 species recorded were present in the peat. Aporrectodea caliginosa, A. tuberculata and Allolobophora chlorotica were the most numerous species in the mineral soil but were scarce in the peat where the surfaced-welling, pigmented species L. rubellus, L. castaneus and Satchellius mammalis were most abundant. Low pH and shortage of suitable food were considered to be the main factors limiting earthworm populations in the peat.     

FTIR spectroscopy can be used as a screening tool for organic matter quality in regenerating cutover peatlands

Vegetational changes during the restoration of cutover peatlands leave a legacy in terms of the organic matter quality of the newly formed peat. Current efforts to restore peatlands at a large scale therefore require low cost and high throughput techniques to monitor the evolution of organic matter. In this study, we assessed the merits of using Fourier transform infrared (FTIR) spectra to predict the organic matter composition in peat samples at various stages of peatland regeneration from five European countries. Using predictive partial least squares (PLS) analyses, we were able to reconstruct peat C:N ratio and carbohydrate signatures with reasonable accuracy, but not the micromorphological composition of vegetation remains. Despite utilising different size fractions, both carbohydrate (<200 μm fraction) and FTIR (bulk soil) analyses report on the composition of plant cell wall constituents in the peat and therefore essentially reveal the composition of the parent vegetational material. The accuracy of the FTIR-based PLS models for C:N ratios and carbohydrate signatures was adequate to allow for their use as initial screening tools in the evaluation of the present and future organic matter composition of peat during monitoring of restoration efforts.     

The Geochemistry of Ombrotrophic Sphagnum Species Growing in Different Microhabitats Of Eight German and Belgian Peat Bogs and the Regional Atmospheric Deposition

Comparing today’s atmospheric deposition records with the elemental concentration and the net-uptake rates of ombrotrophic Sphagnum mosses from eight German and Belgian peat bogs revealed that most of all the quality and number of regularly obtained deposition monitoring data is not satisfactory. Moreover, it seems likely that the deposition rate, determined by Sphagnum mosses, does not reliably reflect the record of the total open field deposition indicated by the deposition monitoring data. The moss data, too, show a distinct spatial variability possibly because the geochemistry of peat mosses differs according to the annual growth in height, the total surface area and the surface roughness of the receptor ‘peat moss’ (special interception deposition). Increased Ti concentration values, for example, combined with a high annual growth rate in height at the hollow moss S. cuspidatum resulted in generally high Ti net-uptake rates and a high Ti inventory (total Ti in sample). We, therefore, suggest that productive Sphagnum species might be able to fix more Ti particles on their larger surface area than less productive species do. Moreover, the results demonstrate that for reliably calculating Sphagnum elemental net-uptake rates, as well as for all quantification of Sphagnum or peat geochemistry on a time and area basis, an accurate knowledge of the period the collected samples were exposed to atmospheric deposition is required. In particular, to do reliable reconstructions of past atmospheric deposition rates using peat deposits, further studies are needed to precisely specify the spatial variability in the geochemistry of living Sphagnum mosses.     

Determination and toxicity of saponins from Amaranthus cruentus seeds.

The concentrations of four triterpene saponins present in amaranth seeds were determined with high-performance liquid chromatography. It was shown that the total concentration of saponins in seeds was 0. 09-0.1% of dry matter. In germinating seeds an increase in concentration to 0.18% was observed after 4 days of germination, which remained stable for the next 3 days and later dropped to 0.09%. Highly purified extracts from the seeds were tested for their toxicity against hamsters. The hydrophobic fraction obtained by the extraction of seeds with methylene chloride showed no toxicity; the behavior of tested animals was similar to that of the group given an equivalent dose of rapeseed oil. A crude saponin fraction, containing approximately 70% of pure saponins in the matrix, showed some toxicity; the approximate lethal dose was calculated as 1100 mg/kg of body weight. It is concluded that low contents of saponins in amaranth seeds and their relatively low toxicity guarantee that amaranth-derived products create no significant hazard for the consumer.     

Bacterial diversity and community structure along different peat soils in boreal forest

Bacteria in peat forest soil play important role in global carbon cycling. The distribution of bacteria population in different peat soils as a whole and how forest management practices alter the bacterial populations are still poorly known. Using pyrosequencing analysis of 16S rRNA gene, we quantified the diversity and community structure of bacteria in eight peat forest soils (pristine and drained) and two mineral forest soils from Lakkasuo, Finland with either spruce-dominant or pine-dominant tree species. In total, 191,229 sequences which ranged from 15,710 to 22,730 per sample were obtained and affiliated to 13 phyla, 30 classes and 155 genera. The peat forest soils showed high bacterial diversity and species richness. The tree species seems to have more strong impact on the bacterial diversity than the type of peat soil, which drives the changes in bacterial community structure. The dominant taxonomic groups across all soils (>1% of all sequences) were Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, Planctomycetes and Verrucomicrobia. The relative abundance of bacteria phylum and genus differed between soil types and between vegetation. Significant differences in relative abundance of bacteria phyla were only found for Gemmatimonadetes and Cyanobacteria between the pristine and the drained peat forest soils. At genus level, the relative abundance of several genera differed significantly between the peat soils with same or different tree species, including Burkholderia, Caulobacter, Opitutus, Mucilanginibacter, Acidocella, Mycobacterium, Bradyrhizobium, Dyella and Rhodanobacter.     

Ecological conditions for Saxifraga hirculus in Central Europe: A better understanding for a good protection

Saxifraga hirculus is a postglacial relict in Central Europe, whose populations suffered a dramatic decrease in the 19th and 20th centuries. However, few researchers have been interested in its ecological requirements in Central Europe. This article synthesizes previous knowledge supplemented by original data from the last large population (Switzerland).S. hirculus is a weak competitor which needs precise ecological conditions. It grows on bryophyte carpets in neutral to slightly acid wetlands, with stable water table close to the soil surface (optimum between 8 and 14 cm) but does not stand long flooding. However, it requires a good oxygen supply, with roots 2-3 cm under the soil surface, generally not reached by water, with running, cold water through loose, fibric peat. Its optimal conditions are in spring fens, but it grows in other types of wetlands as well. However, overgrowing by shrubs, sedges or Sphagnum in natural successions may threaten the species with extinction, as did drainage and peat extraction previously. Now, its survival in Central Europe depends on an adequate management of the ecosystems. Moderate grazing (cattle or sheep) or mowing help to limit competition with taller Carex species. Reintroduction of disappeared populations or creation of new ones from cultivation in botanical garden is possible, but appropriate sites are rare. In some cases, substrate management could improve the conditions in somewhat inadequate situations. This management in four directions can be flexibly applied in different situations to progress to optimal conditions for the conservation of this valuable species.     

Failure of peat-covered hillslopes at Dooncarton Mountain,Co. Mayo,Ireland: Analysis of topographic and geotechnical factors

Shallow landslides involving loss of blanket peat are relatively uncommon but can nevertheless be environmentally and geomorphologically significant. This paper describes a cluster of 40 shallow landslides, including significant peat failures, which occurred within 2.5 km² on Dooncarton Mountain (Republic of Ireland) in the evening of 19 September 2003 during an exceptional rainfall event. It examines two hypotheses: (i) that the combination of topography and local soil catena characteristics were the primary site factors that led to the occurrence of most of the failures, and (ii) that anthropogenic disturbance to the slopes in the form of boundary ditches or peat-cutting activities may have contributed to three of the largest peat failures. All of the landslides were mapped and sampled within 4 months of the event. Physical, hydrological and geotechnical properties of the slope materials were determined from samples obtained from nine representative failures. Possible controls on the stability of the slopes were investigated by modelling seven of the landslides and a series of hypothetical slopes using standard limit equilibrium methods. The humified blanket peat was underlain by a dominantly sandy mineral material, including a buried soil horizon, derived from weathering of the mainly schist bedrock. Direct shear tests established the respective shear strengths to be ?′ = 50°, c′ = 0 (buried soil) and ?′ = 21–25°, c′ = 8–11 kPa (basal peat), although back-analyses suggested that the average peat cohesion was lower than this on the failed slopes. Analyses of separate slope segments of the landslides showed that the main slope convexity, where the peat cover gives way to thin peaty soil, defined the zone of minimum stability. Failure of the slope segment immediately above the convexity was controlled by the depth of peat and the hydrostatic or possibly artesian water pressures within the slopes. Thus catena characteristics coupled with local topography (gradient and peat depth) were important determinants of slope instability. Two of the failed slopes were crossed by boundary ditches but, contrary to accounts from elsewhere, stability analyses suggested that these ditches did not contribute significantly to the landslides. Stability analysis of a slope affected by peat extraction also suggested no direct causal association, but the hydrological conditions developed in the vertical tine cuts did probably contribute to a large peat slide. At other locations, therefore, similar anthropogenic factors should be incorporated in landslide hazard assessments.     

Effects of Nitrogenous Fertilizer Application on the Establishment of Vegetation System in Weathered Particles of Coal Gob in Shanxi Mining Areas, China

We conducted a greenhouse experiment to investigate the effects of nitrogenous fertilizer application on weathered particles of coal gob (WPCG). Different rates of nitrogenous fertilizer??low N (0.034 g?N?kg^?1 WPCG), medium N (0.068 g?N?kg^?1 WPCG), and high N (0.136 g?N?kg^?1 WPCG)??were applied, and two native grasses (Orchardgrass and Alfalfa) were mix-planted in each pot. The results showed that the biomass production were all significantly increased in low and medium N group compared with that in the control group, respectively, in aboveground or underground part (p?<?0.01), but it was slightly increased in high N group. Compared with the control group, chlorophyll concentrations of Orchardgrass in medium N group and Alfalfa in low N group were all significantly increased (p?<?0.05), but it was the lowest in high N group. N uptake efficiency was the highest in low N group. However, N, P, and K uptake efficiencies were all lowest in high N group. Moreover, the microorganism population in WPCG was greatly improved in low N group. Compared with the control group, the numbers of bacteria, actinomycete, fungi, and nitrogen-fixing bacteria were significantly increased by 438%, 125%, 20%, and 258%, respectively (p?<?0.05). After 120 days growth of Orchardgrass and Alfalfa, the percentage of particle diameter of WPCG was changed. The percentage of fine particles (<3 mm) was increased by 99.4%. In conclusion, it will be a more efficient approach for the quick establishment of vegetation system to apply low nitrogenous fertilizer (0.034 g?N?kg^?1 WPCG) as an immediate treatment for nitrogen deficiency during the primary reclamation period on a large scale.     

Population status of the Bornean orang-utan (Pongo pygmaeus) in the Sebangau peat swamp forest, Central Kalimantan, Indonesia

A survey of the density and population size of Bornean orang-utan (Pongo pygmaeus) was carried out in 1995 and 1996 in an area of peat swamp forest in the Sungai (River) Sebangau catchment, Central Kalimantan, Indonesia. Densities were calculated for four forest sub-types by counts of orang-utan sleeping platforms (nests) along line transects. Densities were found to be highest in the tall interior and mixed swamp forest sub-types. Low pole forest supported the lowest density. Habitat disturbance caused by logging was shown to affect orang-utan density within mixed swamp forest. The orang-utan population for a larger peat covered landscape unit (9200 km²), including the Sebangau catchment, was estimated to be between 5671 (±955) and 8951 (±1509) individuals, based upon the area of each forest type, the level of disturbance in each area and corrected to prevent overestimates. This study identifies the presence of a very large, self-sustaining orang-utan population in this region and emphasises the urgent requirement for greater protection of Kalimantan's peat swamp forests in the light of recent and rapid habitat degradation.