Secondary production of an intertidal mussel (Mytilus edulis L.) population in the Eastern Scheldt (S.W. Netherlands)

We monitored an intertidal mussel (Mytilus edulis L.) population between June 1981 and June 1982 in the Eastern Scheldt estuary (S.W. Netherlands). Density and biomass of the population remained relatively constant over the study period. The shell length growth was described by a Gompertz growth curve. The parameters of this equation were estimated from a log-log-modified Ford-Walford plot of the growth-ring data. The slope of the relationship between animal weight and shell length is season-dependent, mainly due to the spawning cycle in larger mussels.Secondary production is estimated with the growth rate method. In the calculated growth rates the change in slope of the length-weight relationship is incorporated, as well as differences in length growth rates between summer and winter. Secondary production amounts to 156 g AFDW m^–2a ^–1 (expressed per m² of mussel bank). P:B is 0.50 a^–1. The mussel productivity is probably a limiting factor for the density of overwintering Oystercatchers (Haematopus ostralegus).     

Life cycle and growth ofTrichostegia minor (Curtis) in temporary woodland pools (Trichoptera: Phryganeidae)

Larvae of the caddisTrichostegia minor (Curtis) were collected from four woodland pools in The Netherlands, three of which are temporary, from August 1986 till June 1987. Eggs and larvae of this species proved to be very well adapted to drought, freezing, strongly fluctuating pH and alkalinity levels and prolonged oxygen deficit. The life cycle ofT.minor in a small woodland marsh overgrown byCalla palustris took one year. Adult flight period started at the end of May. Oviposition took place independent of water. Hatching of the eggs started in September and was probably induced by immersion. During the larval stage from September until May, 5 instars could be distinguished by the size of the head capsule. Growth of instars I, II and III during autumn was moderate. Most larvae overwintered as instar III or IV. Possibly there was a larval diapause during winter. In spring rapid growth to instar V took place prior to pupation. Growth rate, expressed as the increase of mean individual dry weight was highest from March to April (2.05±0.75% DW.m^–2.d^–1). In extremely shallow water growth in spring was initially more rapid compared to growth in deeper water. During winter the growth rate decreased to 0.038±0.071% DW.m^–2.d^–1. Net annual production based on the changes of momentary biomass was 183.2±31.7 mg DW.m^–2.y^–1 or 177.2±31.3 mg AFDW.m^–2.y^–1. Production loss during the winter season was 75.1±10.8 mg DW.m^–2.y^–1 or 72.3±10.6 mg AFDW.m^–2.y^–1.     

Kinetic analysis of ethanol production by an acetate-resistant strain of recombinant Zymomonas mobilis

Zymomonas mobilis ZM4/Ac^R (pZB5), a mutant recombinant strain with increased acetate resistance, has been isolated following electroporation of Z. mobilis ZM4/Ac^R. This mutant strain showed enhanced kinetic characteristics in the presence of 12 g sodium acetate l^–1 at pH 5 in batch culture on 40 g glucose, 40 g xylose l^–1 medium when compared to ZM4 (pZB5). In continuous culture, there was evidence of increased maintenance energy requirements/uncoupling of metabolism for ZM4/Ac^R (pZB5) in the presence of sodium acetate; a result confirmed by analysis of the effect of acetate on other strains of Z. mobilis. Nomenclature m Cell maintenance energy coefficient (g g^–1 h^–1)Maximum overall specific growth rate (1 h^–1)Maximum specific ethanol production rate (g g^–1 h^–1)Maximum specific total sugar utilization rate (g g^–1 h^–1)Biomass yield per mole of ATP (g mole^–1 Ethanol yield on total sugars (g g^–1)Biomass yield on total sugars (g g^–1)True biomass yield on total sugars (g g^–1)     

Production and decomposition of eelgrass (Zostera marina L.) in saline Lake Grevelingen

Summary During five 28-hours measurements in 1981, the oxygen production and consumption in an eelgrass community in saline Lake Grevelingen were investigated using light plexiglass enclosures. Applying a conversion factor of 0.29 the amount of carbon fixed and the amount of organic carbon mineralized were estimated. Gross and net production were estimated over 24-hours periods.There appeared to be a good correlation between production and insolation on the water surface. For every measurement period the production as a function of light and aboveground eelgrass biomass in the enclosure were calculated. This showed a maximum of 5.10^–6 mg C.J.^–1 g dry weight^–1 in April and minimum of 1.4.10^–6 mg C.J.^–1 g^–1 in August.Using the calculated production coefficients, the insolation and the eelgrass biomass the gross production, net production and consumption during the growing season of 1976 were calculated. Gross production amounted to 340 gC.m^–2, and net production came to 130 g C.m^–2. Approximately 60 gC.m^–2 was respired by the eelgrass plants while the remaining 150 gC.m^–2 was consumed or mineralized by other organisms on the sampling spot. Approximately 120 g C.m^–2.yr^–1 was transported by wind and wave action towards the eastern part of the lake where it became anaerobically degraded. This resulted in the formation of sulfide and methane.Communication no. 236 of the Delta Institute for Hydrobiological Research, Yerseke, The Netherlands.     

Fermentation of xylose and rice straw hydrolysate to ethanol byCandida shehatae NCL-3501

Candida shehatae NCL-3501 utilized glucose and xylose efficiently in batch cultures. The specific rate of ethanol production was higher with mixtures of glucose and xylose (0.64–0.83 g g^–1 cells d^–1) compared to that with individual sugars (0.38–0.58 g g^–1 cells d^–1). Although the optimum temperature for growth was 30°C, this strain grew and produced appreciable levels of ethanol at 45°C. A stable ethanol yield (0.40–0.43 g g^–1 substrate utilized) was obtained between 10 g L^–1 and 80 g L^–1 of initial xylose concentration. Conversion efficiency was further improved by immobilization of the cells in calcium alginate beads. Free or immobilized cells ofC. shehatae NCL-3501 efficiently utilized sugars present in rice straw hemicellulose hydrolysate, prepared by two different methods, within 48 h. Ethanol yields of 0.45 g g^–1 and 0.5 g g^–1 from autohydrolysate, and 0.37 g g^–1 from acid hydrolysate were produced by free and immobilized cells, respectively.     

Primary production dynamics of dominant hydrophytes in Lake Provala (Serbia)

The objective of this investigation was to analyze the primary production of the dominant hydrophytes by monitoring levels of organic matter and organic carbon and estimating photosynthetic potential via the total chlorophyll content. The survey was conducted in Lake Provala (Serbia) throughout the peak vegetation period of the year 2000. The contents of organic matter and organic carbon for Myriophyllum spicatum L. were 105.11 g m⁻² and 73.66 g m⁻², Nymphoides peltata (Gmel.) Kunt. were 95.51 g m⁻² and 45.26 g m⁻² and Ceratophyllum demersum L. were 52.17 g m⁻² and 29.75 g m⁻². Chlorophyll A (Chl a) and chlorophyll A+B (Chl a+b) pigments ranged from 1.54 mg g⁻¹(Chl a) and 2.1 mg g⁻¹(Chl a+b) in M. spicatum to 5.27 mg g⁻¹(Chl a) and 7.53 mg g⁻¹(Chl a+b) in C. demersum. At full leaf out, the latter aquatic plants exceeded 50% cover of the open water surface. All species achieved maximum growth in June, but significant differences in growth dynamics were observed. At the end of the vegetation period, these plants sink to the bottom and decompose     

Abundance,population dynamics and production of Chironomidae (Diptera) in an ul traoligotrophic lake in South Greenland

Macrozoobenthos of the ultraoligotrophic Lake 95 (61°N, 46°W, 8 ha, z_max=18 m, ) is composed of about 14 taxa dominated by 12 Chironomidae species. Abundance, life cycle, biomass and production were estimated for the six dominant taxa. Abundance declined fromca. 4150 at 2.5 m depth toca. 1400 ind m^–2 at 16 m depth and averagedca. 3200 ind m^–2 on a lakewide basis. By numbers,Heterotrissocladius changi andH. oliveri dominated the average fauna.H. changi was common at the 2.5 m and 5 m depth stations, whereasH. oliveri dominated from 5 m depth downwards. Chironomids showed mainly a 1-yr life cycle, but apparently bothHeterotrissocladius species had two contemporary cohorts with emergence in midsummer and late autumn/early spring, respectively. Average annual ratio was 4.2 and 4.6 forH. oliveri andH. changi, respectively. Annual production varied from 0.3 g ash-free dry weight (AFDW) m^–2 y^–1 at 16 m depth to 1.6 g AFDW m^–2 y^–1 at 2.5 m depthH. changi contributed 45%, fiveMicropsectra spp. 17% andH. oliveri 15% to total average production, which on a lakewide basis wasca. 1.1 g AFDW or 25 kJ m^–2 y^–1. Lake 95 thus belongs at the very low end of measured lake zoobenthic productions, which range from 10 kJ m^–2 y^–1 in Arctic lakes toca. 1600 kJ m^–2 y^–1 in highly eutrophic shallow lakes.     

Natural and constrainment-induced factors influencing the breakdown of dogwood and oak leaves

Breakdown rates and microbial colonization patterns of dogwood and oak leaves were measured between November and June of 1987–88 and 1988–89. Leaves were placed in artificial streams loose (unconstrained), in bags, or in packs. Discharge was maintained at approximately 0.25 s^–1, and no shredders were present in the streams. Average microbial biomass as ATP, for all species and treatments, increased from near 0 mg g^–1 AFDW in November to over 8 mg g^–1 AFDW in June. Microbial respiration increased from about 0.01 µg glucose respired hr-g^–1 AFDW in November to about 0.03 µg hr-g^–1 AFDW in June. Microbial biomass and activity were significantly greater on dogwood leaves than on oak leaves. Dogwood and oak leaf breakdown rates were fastest when unconstrained, –0.0034 and –0.0027 degree-day^–1 respectively. Breakdown rates of dogwood leaves were faster in bags (–0.0025 degree-day^–1) than in packs (–0.0015 degree-day^–1) while rates of oak leaves were not significantly different between bags and packs (–0.0014 and –0.0018 degree-day^–1 respectively). Breakdown rates of dogwood and oak leaves obtained in this study were much slower than those obtained by other investigators either in the presence or absence of shredders. A comparison of results from this study with results from other studies revealed that dogwood leaves may be affected more by turbulence, while oak leaves may be influenced more by shredder activity.     

Life-history strategies and production of Tinodes waeneri (L.) (Trichoptera) in Lake Esrom,Denmark

The life cycle and production of Tinodes waeneri (L.) was examined at five shallow littoral localities in Lake Esrom, Denmark, during 1979/80. Five larval instars were demonstrated. The differences in temporal composition of instars indicated three different life cycles. A bivoltine strategy was shown for the most exposed locality which also had the highest average abundance equal to 11 500 ind. m^–2. A univoltine population was found in the more sheltered NW part of the lake with an average density of 1 500 ind. m^–2. At the three remaining stations the life cycles were partly bivoltine with wintering populations of mixed cohorts and densities between 10 500 and 3 000 ind. m^–3. Two distinct flight periods with maxima in June and August were demonstrated for bi- and partly bivoltine populations. Differences in rates of growth and elimination added to the variability in life cycle. Growth rates peaked in August (5.0–7.4% d^–1) at an average temperature of 20°C. Estimates of production ranged from 1.9 to 17.5 g AFDW m^–2 a^–1 with an average of 8.0 g AFDW m^–2. The P/B ratios, which were within the expected range for uni- and bivoltine populations of trichopterans, were 5.73 for the bivoltine population and 3.31 for the univoltine population.Estimates of consumption revealed that the populations could be sustained by autochthonous epilithic production in the habitats. Variability in the quality and seasonal availability of food were judged to influence the type of life cycle.Lake Esrom Littoral Research Publ. No. 8. Publication No. 385 from the Freshwater Biological Laboratory, University of Copenhagen, 51, Helsingørsgade, DK-3400 Hillerød, Denmark.Lake Esrom Littoral Research Publ. No. 8. Publication No. 385 from the Freshwater Biological Laboratory, University of Copenhagen, 51, Helsingørsgade, DK-3400 Hillerød, Denmark.     

Structure and annual biomass production of Nymphoides peltata (Gmel.) O. Kuntze (Menyanthaceae)

In 1980, the monthly changes in biomass and plant surface area, together with aspects of production of Nymphoides peltata (Gmel.) O. Kuntze were studied in a backwater of the river Waal (The Netherlands). Furthermore, the seasonal changes in the vertical stratification of the biomass were studied in concrete tanks. These seasonal changes were studied with the harvest method, while the estimation of the net primary production was based upon biomass data and turnover rates of various plant parts. The data thus obtained are compared with those of other water plants, especially other floating-leaved macrophytes. In 1980, N. peltata reached its peak biomass in August being 372 g AFDW m⁻² (ash-free dry weight). The annual net productivity of Nymphoides was estimated to be 1036 g AFDW m⁻². The leaf blades and their petioles contributed most to the production.     

Periphyton production in an Appalachian river

Periphyton primary production was measured by ¹⁴C uptake on natural substrates in two sections of the New River, Virginia, U.S.A. Production ranged from 6.71 ± 0.43 mg C g^–1 h^–1 in summer to 1.47 ± 0.22 mg C g^–1 h^–1 in late autumn in the hardwater reach and from l.90 ± 0.10 mg C g^–1 h^–1 to 0.12 ± 0.08 mg C g^–1 h^–1 in the softwater reach. Production in the hardwater reach was 3–5 times greater than in the softwater reach and significantly correlated with dissolved inorganic carbon (DIC) concentration (r² = 0.506). No significant correlation was found between periphyton production and photosynthetically active radiation (PhAR). Extrapolation of periphyton production to a 135 km reach of the New River yielded an estimated annual input of 2 252 T AFDW from this source. Estimates of allochthonous (excluding upstream contributions) and aquatic macrophyte inputs to this same reach were 64 T AFDW and 2 001 T AFDW, respectively. While periphyton is not a large source of organic matter, its high food quality and digestibility make it an important component of the New River energy dynamics.     

A culture unit system for the study of responses of mycorrhizal and non-mycorrhizal seedling to treatments

The time-dependence of Mn accumulation was confirmed in potato foliage (Solanum tuberosum. L.cv. Norland) grown in solution culture. Older leaves grown at 0.61 mM Mn had substantially higher Mn concentrations than younger leaves and stem samples. Levels of Mn in older leaves increased steadily from 4000 µg g^–1 at one week to 8–10,000 µg g^–1 at 6 weeks, but were relatively constant in the emerging leaves. Even foliage grown at low Mn levels (0.01 mM Mn) had 4 fold gradients in Mn concentration from younger (40 µg g^–1) to older leaves (180 µg g^–1).At 0.61 mM Mn, concentrations of 3–4000 µg g^–1 in the youngest fully-developed leaves did not bring about any decline in yield, and levels of up to 5000 µg g^–1 occurred in individual potato leaves before Mn toxicity symptoms were observed. Potato foliage grown at the high Mn had similar leaf numbers, but showed an increased stem length and smaller leaves than foliage grown at 0.01 mM Mn. In particular, the leaf area of the middle and lower leaf fractions were affected by the high Mn level.The ability of rapidly growing plants to withstand high concentrations of Mn is discussed in relation to the pattern of dry matter and Mn accumulation shown by potato foliage.     

Life history, population dynamics and production of eastern mosquitofish, Gambusia holbrooki (Pisces, Poeciliidae), in rice fields of the lower Mondego River Valley, western Portugal

The introduced population of Gambusia holbrooki from the rice fields of the lower Mondego River Valley, Portugal, was studied for 15 months, relating their life cycle and population dynamics with its production, in order to assess the role of the species in the energy flow and secondary production in this type of agro-ecosystem. Two main annual cohorts (1995 and 1996 cohorts) were identified. The females outnumbered males and the average female/male-ratio was 4. The inspection of ovary developmental stages of this viviparous fish, revealed that the most important reproductive period was between April and August. The first recruits were recorded in June and were present thereafter until October. Males from the parental cohort died before August, whereas parental females could survive until October. Mean adjusted fecundity (number of embryos divided by female standard length) peaked in July 1996 (0.95) and in June 1997 (1.05). Females reached greater sizes, had a higher growth rate and lived longer than males. Annual production was estimated at 3.101 g.m^–2.year^–1 (ash-free dry weight, AFDW), the average biomass at 2.896 g.m^–2 (AFDW), and the P/B ratio was 1.071. A conjugation of life history, population dynamics, production and ecological traits (e.g. fast growth, reduced longevity, viviparity, high productivity, an intermediate position in food chain, and no special habitat requirements for reproduction) clearly show that the populations of G. holbrooki, introduced into rice fields all over the world, may play an important role in the structure and functioning of the biological communities of these important agro-ecosystems.     

Morphometry,Primary productivity and Energy flow in a Tropical Pond

Monthly changes in the morphometric features of pond Idumban reveal that total and littoral areas progressively decreased from 62.4 and 15.4 ha in October-November-December to 6.8 and 2.6 ha in September. The dominant macrophytic producers in the littoral area of the pond were Chara fragilis, Hydrilla verticillata and Ceratophyllum demersum, which flourished from October for a period of 8 to 10 months, exhibiting a typical exponential or J-shaped population growth curve. Biomass of Ch. fragilis increased to the maximum of about 420 g dry weight/m² in April, H. verticillata to 260 g/m² in June–July and that of Ce. demersum to 140 g/m² in April–May. In terms of unit weight, H. verticillata proved to be the most efficient, producing 156 mg dry substance/g plant/day; however, the mean values obtained for 1973-74 were 93, 54 and 53 mg/g/day for H. verticillata, Ch. fragilis and Ce. demersum; the corresponding NPP values 50, 29 and 30 mg/g/day. The GPP and NPP values, expressed in g dry weight/m²/day, were 7 and 4 for H. verticillata, 8 and 4 for Ch. fragilis, 3 and 2 for Ce. demersum. These values, expressed in mg C/m²/day, averaged to 8.2 and 4.6 for all the macrophytes and suggest that the macrophytes were photosynthetically faster and more efficient than phytoplankton. Total gross productivity for Idumban pond amounts to 1773 and 1449 ton (dry weight) for 1973 and 74, respectively: the corresponding values for the NPP were 953 and 825 ton. In other words, 44% of the GPP is lost on plant respiration. Plants equivalent to 56 ton (6% of NPP) are exposed to death in the periphery of the littoral area. The population of Pila globosa proved to be the dominant consumer of these macrophytes. Mean predation amounted to 64 ton/annum for Pila and 200 ton/ annum for other consumer animals. Solar energy known to enter the pond is 1,956,000 Kcal/m²/year. Of this, 24,682 Kcal/m²/year was fixed by the macrophytes, i.e. the photosynthetic efficiency is 1.3%. Of the total GPP, NPP amounted to 13,696 Kcal/m²/year; the net primary production efficiency is 56%. Consumption of the macrophytes by Pila population amounted to 2,943 Kcal/m year and the exploitation efficiency is only 21%.     

Transport of coarse particulate organic matter in an Idaho river,USA

I investigated organic matter transport in the Henry's Fork of the Snake River, Idaho, USA, from August 1987 to November 1988. Mean discharge during the study was 15 m³ s^–1. Screens were used to sample very coarse (> 6 mm) transported aquatic macrophyte material (VCTMM). Drift nets were used to sample coarse (1–6 mm) and fine (0.25–1 mm) transported particulate organic matter (CTOM and FTOM). Mean monthly concentration of VCTMM was 0.064 mg AFDWl^–1 and was significantly higher than CTOM (0.024 mg AFDW l^–1) and FTOM (0.036 mg AFDW l^–1). VCTMM concentration was highest in December (0.163 mg AFDW l^–1) and lowest in May (0.018 mg AFDW l^–1). The sample position along a transect across the channel had a significant effect on the amount of transported organic matter collected in many months. The concentration of debris from individual species tracked the standing stock of that species during the growing season. In Fall, a dramatic increase in VCTMM corresponded to a decrease in macrophyte standing stock. FTOM and CTOM concentrations were highest in January (CTOM: 0.048; FTOM: 0.111 mg AFDW l^–1), lowest in November 1988 (<0.006 mg AFDW l^–1), were not correlated with discharge, and were inversely correlated with the standing stocks of macrophytes upstream, probably because macrophyte beds influenced the retentiveness of the channel. Standing stock of aquatic macrophytes was highest in September–October (5.2 kg wet weight m ^–2) and lowest in February (1.7 kg wet weight m^–2). Annual movement of particulate organic matter past the sampling point was about 45 000 kg AFDW, of which 21 000 kg was VCTMM, 8 000 kg was CPOM, and 16 000 kg was FPOM.     

Hydrolysate detoxification with activated charcoal for xylitol production by Candida guilliermondii

A detoxification method using activated charcoal with concentrated rice straw hemicellulosic hydrolysate improved the conversion of xylose to xylitol by the yeast Candida guilliermondii by 22%. This was achieved when the hydrolysate:charcoal ratio was 40 g g^–1, resulting in removal of 27% of phenolic compounds. Under this condition, the xylitol yield factor (0.72 g g^–1) and volumetric productivity (0.61 g l^–1 h^–1) were close to those attained in a semi-defined medium simulating hydrolysate sugars.     

Feeding rates and energy deficits of juvenile and adult Japanese monkeys in a cool temperate area with snow coverage

Japanese monkeys, Macaca fuscata, living in a cool temperate forest experienced energy crises in winter. We measured feeding times and feeding rates (mass of foods eaten per unit time of feeding) in six different-sized, age–sex classes (1.2–12.6 kg body mass) in autumn and winter. One-, 2- and 3~4-year-olds spent 34–35% and 44–46% of the day feeding in autumn and winter, respectively. Monkeys less than 0 years old spent less time feeding (16–28%) than average in winter and autumn; adult females spent less (41%) in winter; and adult males spent less (25%) in autumn. All age–sex classes ate mainly fruits in autumn and the heavier classes fed more on tree bark than buds in winter. The feeding rate for fruits (2.3–53.5 g min^–1) was nine to 12 times faster than those for buds (1.0– 4.8 g min^–1) and bark (0.5–4.4 g min^–1), and energy content did not differ among fruits (22.1 kJ g^–1 dry mass), buds (19.9 kJ g^–1 dry mass) and bark (23.2 kJ g^–1 dry mass). Energy base feeding rates increased with body mass where the body mass exponent for buds (0.29) was smaller than those for bark (0.64) and fruits (0.63), which might be attributable to the unit size of food items and mass dependency of masticatory apparatus. Our monkeys obtained two to five times more energy in autumn (1567–1150 kJ day^–1) than in winter (604–3020 kJ day^–1). Adult females obtained 60% of expected energy expenditure and other classes obtained 77–88% of that in winter.     

Allochthonous input and retention in a small mountain stream,South Africa

Allochthonous input and benthic coarse particulate organic matter (CPOM) standing stocks were investigated in a first-order stream in South Africa between May 1984 and April 1985. Monthly falls into the stream of all litter types (total) ranged from 11 (September) to 79 g m^–2 (March). Total annual litter fall was 426 g dry weight, which corresponds to 1.2 g m^–2 d^–1. Flowers, fruits and seeds contributed 37 g m^–2, woody debris, 122 g m^–2, and leaves 267 g m^–2 to this total. Leaf fall from native trees, which accounted for approximately 57% of total litter input (244 g m^–2 a^–1), was significantly higher in summer than in winter. The summer peak in leaf fall recorded is far smaller and more protracted than the autumnal peak recorded for many Northern Hemisphere streams.Monthly total standing stocks of CPOM ranged from 14 g dry weight m^–2 in January to 69 g m^–2 in August, and a mean total CPOM standing stock of 41 g m^–2 mth^–1 was estimated. This comprised 18 g m^–2 mth^–1 soft litter, and 23 g m^–2 mth^–1 hard litter. CPOM standing stocks showed no seasonal trends, and with the exception of two species, standing stocks of endemic leaf species reflected their contributions to the total litter fall. Contrary to earlier reports for streams in the Fynbos Biome, Window Stream has CPOM standing stocks well within the ranges reported for low-order streams worldwide.     

Landscape patterns of CH4 fluxes in an alpine tundra ecosystem

We measured CH₄ fluxes from three major plant communities characteristic of alpine tundra in the Colorado Front Range. Plant communities in this ecosystem are determined by soil moisture regimes induced by winter snowpack distribution. Spatial patterns of CH₄ flux during the snow-free season corresponded roughly with these plant communities. InCarex-dominated meadows, which receive the most moisture from snowmelt, net CH₄ production occurred. However, CH₄ production in oneCarex site (seasonal mean=+8.45 mg CH₄ m^–2 d^–1) was significantly larger than in the otherCarex sites (seasonal means=–0.06 and +0.05 mg CH₄ m^–2 d^–1). This high CH₄ flux may have resulted from shallower snowpack during the winter. InAcomastylis meadows, which have an intermediate moisture regime, CH₄ oxidation dominated (seasonal mean=–0.43 mg CH₄ m^–2 d^–1). In the windsweptKobresia meadow plant community, which receive the least amount of moisture from snowmelt, only CH₄ oxidation was observed (seasonal mean=–0.77 mg CH₄ m^–2 d^–1). Methane fluxes correlated with a different set of environmental factors within each plant community. In theCarex plant community, CH₄ emission was limited by soil temperature. In theAcomastylis meadows, CH₄ oxidation rates correlated positively with soil temperature and negatively with soil moisture. In theKobresia community, CH₄ oxidation was stimulated by precipitation. Thus, both snow-free season CH₄ fluxes and the controls on those CH₄ fluxes were related to the plant communities determined by winter snowpack.     

Astragaloside IV and polysaccharide production by hairy roots of Astragalus membranaceus in bioreactors

Hairy roots of Astragalus membranaceus were grown in bioreactors up to 30 l for 20 d. Cultures from a 30 l airlift bioreactor gave 11.5 g l dry wt with 1.4 mg g^–1 astragaloside IV, similar to cultures from 250 ml and 1 l flasks, but greater than yields from a 10 l bioreactor (dry wt 9.4 g l^–1, astragaloside IV 0.9 mg g^–1). Polysaccharide yields were similar amongst the different bioreactors (range 25–32 mg g^–1). The active constituent content of the cells approached that of plant extracts, indicating that large scale hairy root cultures of A. membranaceus has the potential to provide an alternative to plant crops without compromising yield or pharmacological potential.