Hyphomycetes in the River Kelvin

Summary

The hyphomycete spora of the River Kelvin and its tributary, the Allander Water, was sampled during October 1986 to January 1987. Twenty spore types were found, the commonest being Flagellospora curvula and Lemonniera aquatica. Spore numbers were high in October and declined during the autumn to an undetectable level by the end of December, but leaves collected in December and January yielded spores on incubation in water.     

Resource availability controls fungal diversity across a plant diversity gradient

Despite decades of research, the ecological determinants of microbial diversity remain poorly understood. Here, we test two alternative hypotheses concerning the factors regulating fungal diversity in soil. The first states that higher levels of plant detritus production increase the supply of limiting resources (i.e. organic substrates) thereby increasing fungal diversity. Alternatively, greater plant diversity increases the range of organic substrates entering soil, thereby increasing the number of niches to be filled by a greater array of heterotrophic fungi. These two hypotheses were simultaneously examined in experimental plant communities consisting of one to 16 species that have been maintained for a decade. We used ribosomal intergenic spacer analysis (RISA), in combination with cloning and sequencing, to quantify fungal community composition and diversity within the experimental plant communities. We used soil microbial biomass as a temporally integrated measure of resource supply. Plant diversity was unrelated to fungal diversity, but fungal diversity was a unimodal function of resource supply. Canonical correspondence analysis (CCA) indicated that plant diversity showed a relationship to fungal community composition, although the occurrence of RISA bands and operational taxonomic units (OTUs) did not differ among the treatments. The relationship between fungal diversity and resource availability parallels similar relationships reported for grasslands, tropical forests, coral reefs, and other biotic communities, strongly suggesting that the same underlying mechanisms determine the diversity of organisms at multiple scales.     

Calcium Additions and Microbial Nitrogen Cycle Processes in a Northern Hardwood Forest

Evaluating, and possibly ameliorating, the effects of base cation depletion in forest soils caused by acid deposition is an important topic in the northeastern United States. We added 850 kg Ca ha⁻¹ as wollastonite (CaSiO₃) to an 11.8-ha watershed at the Hubbard Brook Experimental Forest (HBEF), a northern hardwood forest in New Hampshire, USA, in fall 1999 to replace calcium (Ca) leached from the ecosystem by acid deposition over the past 6 decades. Soil microbial biomass carbon (C) and nitrogen (N) concentrations, gross and potential net N mineralization and nitrification rates, soil solution and stream chemistry, soil:atmosphere trace gas (CO₂, N₂O, CH₄) fluxes, and foliar N concentrations have been monitored in the treated watershed and in reference areas at the HBEF before and since the Ca addition. We expected that rates of microbial C and N cycle processes would increase in response to the treatment. By 2000, soil pH was increased by a full unit in the Oie soil horizon, and by 2002 it was increased by nearly 0.5 units in the Oa soil horizon. However, there were declines in the N content of the microbial biomass, potential net and gross N mineralization rates, and soil inorganic N pools in the Oie horizon of the treated watershed. Stream, soil solution, and foliar concentrations of N showed no response to treatment. The lack of stimulation of N cycling by Ca addition suggests that microbes may not be stimulated by increased pH and Ca levels in the naturally acidic soils at the HBEF, or that other factors (for example, phosphorus, or Ca binding of labile organic matter) may constrain the capacity of microbes to respond to increased pH in the treated watershed. Possible fates for the approximately 10 kg N ha⁻¹ decline in microbial and soil inorganic pools include components of the plant community that we did not measure (for example, seedlings, understory shrubs), increased fluxes of N₂ and/or N storage in soil organic matter. These results raise questions about the factors regulating microbial biomass and activity in northern hardwood forests that should be considered in the context of proposals to mitigate the depletion of nutrient cations in soil.     

Vertical structure of Erica umbellata,a representative species of European Ibero-Atlantic dry heaths

The canopy structure of Erica umbellata was studied in order to (a) quantify biomass allocation among several organ types, (b) analyse the possible changes in vertical structure related to season and plant size, and (c) evaluate the effectiveness of non-destructive measures to estimate biomass for a species that is declining in some areas, due to fire and other human disturbances. The study was conducted in NW Spain, sampling E. umbellata plants belonging to three size groups. Destructive (biomass) and non-destructive (frequency, height, diameter) measures were used to characterise the vertical distribution and abundance of photosynthetic, woody, reproductive and dead organs. Allometric equations were calculated to estimate total mass using non-destructive measurements. As E. umbellata increases in size, those organs with a higher renewal rate (leaves, new stems, flowers) increase in the upper strata. Seasonal differences are recorded for the reproductive organs and new stems. A sharp decrease in the green/total phytomass ratio (from 0.51 to 0.17) is observed as plant size increases. Organ biomass can be accurately predicted from total weight and it is also possible to estimate the total weight from non-destructive measures, which provides an easier way of recording data in the field.     

High Volumetric Capacitance,Ultralong Life Supercapacitors Enabled by Waxberry‐Derived Hierarchical Porous Carbon Materials

Supercapacitors with fast charge/discharge rate and long cycling stability (>50 000 cycles) are attractive for energy storage and mobile power supply. In this paper, a facile strategy is developed to fabricate an Fe₂O₃/FeS‐decorated N, S‐codoped hierarchical porous carbon hybrid. Its microstructure and compositions can be readily controlled through adjusting the hydrothermal reaction between waxberry and iron sulfate. The constructed supercapacitors with the as‐prepared carbon materials from this reaction are able to exhibit outstanding capacitive performance with a superfast charge/discharge rate (<1 s), ultralong cycle life (>50 000 cycles, 80 A g⁻¹), ultrahigh volumetric capacitance (1320.4 F cm⁻³, 0.1 A g⁻¹), and high energy density (100.9 W h kg⁻¹, 221.9 W h L⁻¹). The outstanding performance makes it one of the best biomass‐derived supercapacitors. The superior capacitive behavior is likely to arise from the N and S codoping on the surface/edge/skeleton of the carbon microspheres and nanosheet composites coupled with the fast redox reaction of Fe₂O₃/FeS. Overall, this research presents a new avenue for developing the next generation of sustainable high‐performance energy storage device.     

Nutrient stoichiometry of aquatic hyphomycetes: Interstrain variation and ergosterol conversion factors

Ecological stoichiometry is a powerful concept. Rarely, however, has it been applied to fungi, despite their pivotal role in ecosystems. In view of the paucity of stoichiometric data, we grew 16 fungal isolates from streams in liquid culture (C:N:P = 160:16:1) and analysed them for nitrogen (N), phosphorus (P) and ergosterol as a fungal biomass marker. Interspecific differences explained up to 60% of the variation in N, P and ergosterol concentrations, and variation between strains of the same species accounted for up to another 16%. We found an average C:N:P of 136:10:1 in mycelia, while N:ergosterol and P:ergosterol ratios were 9.5 and 2.5, respectively. These ratios are an important step towards establishing reliable conversion factors to estimate the contribution of fungi to litter nutrient contents in complex field samples. Estimates could be further improved by applying the species-specific conversion factors we obtained. Additional analyses of fungal strains in conditions reflecting field situations are needed to strengthen the basis of such estimates of fungal nutrient pools in ecosystems; however, inherent variation within species limits the accuracy and precision that can be achieved.     

大兴安岭植被生物量的ALOS PALSAR估算

利用野外实测调查数据,系统分析了ALOS PALSAR L波段HH(L-HH)极化数据与大兴安岭地区森林各成分参数的关系,并采用简单线性模型、指数模型和加入地理因子模型建立森林生物量的估算模型进行最优反演.结果表明:后向散射系数与树木地上部分总生物量相关性最大,其次是干生物量,L-HH数据可以用来反演正确的树木地上部分总生物量.3种模型中,加入地理因子模型降低了植被生物量估算的误差,精度达0.851,反演结果与实际相符.在41.5°入射角L-HH极化数据下,大兴安岭塔河林业局和阿木尔林业局的森林生物量饱和点在15.4 kg·m-2.     

Effects of litter accumulation and water table on morphology and productivity of Phragmites australis

Phragmites australis (Common reed) occurs in the interface between water and land. The water depth gradient from deep water to dry land is inversely related to litter accumulation. Eutrophication can result in an excessive production of litter, which may have a large impact on the occurrence of P. australis in this gradient. In an outdoor pot experiment, it was investigated how water tables in combination with substrates containing variable amounts of litter affect morphology and productivity of P. australis. Vegetatively propagated P. australis was grown in pots filled with river sand, litter, and different mixtures of sand and litter (25, 50 and 75% by volume). Four water table treatments were applied; drained (–12 cm), waterlogged (0 cm), flooded (+12 cm), and weekly fluctuating drained and flooded conditions (–12/+12 cm of water relative to substrate level). When drained, no differences between substrate treatments were present. Waterlogging, flooding fluctuating water table treatments caused growth reduction in substrate containing litter. The plants formed short shoots and thin rhizomes. With increasing water table, allocation of dry matter to stems increased at the expense of leaves and rhizomes. At intermediate levels of litter in the substrate, allocation to leaves was lowest. In both instances a lower leaf weight ratio (LWR) was (partly) compensated for by a higher specific leaf area (SLA), resulting in less pronounced differences in leaf area ratio (LAR). Aquatic roots developed when plants were waterlogged or flooded, and increased when litter was present in the substrate. Aquatic roots were formed in the top soil layer when waterlogged. The percentage of aquatic roots increased with increasing amount of litter in the substrate when plants were flooded. It was concluded that the morphological responses of P. australis to litter strongly constrain its ability to maintain itself in deep water when the substrate contains litter. This might one of the explanations for the disappearance of P. australis along the waterward side of littoral zones.     

Phytoplankton distribution in the Caspian Sea during March 2001

Phytoplankton abundance, biomass and species composition of the Caspian Sea were evaluated by using samples collected from the Iranian (southern Caspian Sea) and southern Kazakhstan (eastern Caspian Sea) surface waters in March 2001. A total of 45 taxa were found in the samples (20 diatoms, 17 dinoflagellates and 8 others). Abundance and biomass of diatoms were high at the eastern stations, while dinoflagellates were dominant in terms of both biomass and abundance in the southern region. Average abundance and biomass were 40 000 ± 35 000 cell l⁻¹ and 580 ± 690 μg l⁻¹. The mean biomass value found here for the Middle and southern Caspian Sea in March are difficult to compare with the past due to limited information, but seems higher than previously registered values. Higher chlorophyll values were also apparent from the SeaWIFS images in 2001 compared to those in 1998. This is suggested to be due to decreased grazing of phytoplankton by zooplankton which is voraciously preyed by the recent invasive ctenophore Mnemiopsis leidyi.