Molecular phylogeny of the lionfish genera Dendrochirus and Pterois (Scorpaenidae,Pteroinae) based on mitochondrial DNA sequences

This study investigates the molecular phylogeny of seven lionfishes of the genera Dendrochirus and Pterois. MP, ML, and NJ phylogenetic analysis based on 964 bp of partial mitochondrial DNA sequences (cytochrome b and 16S rDNA) revealed two main clades: (1) "Pterois" clade (Pterois miles and Pterois volitans), and (2) "Pteropterus-Dendrochirus" clade (remainder of the sampled species). The position of Dendrochirus brachypterus either basal to the main clades or in the "Pteropterus-Dendrochirus" clade cannot be resolved. However, the molecular phylogeny did not support the current separation of the genera Pterois and Dendrochirus. The siblings P. miles and P. volitans are clearly separated and our results support the proposed allopatric or parapatric distribution in the Indian and Pacific Ocean. However, the present analysis cannot reveal if P. miles and P. volitans are separate species or two populations of a single species, because the observed separation in different clades can be either explained by speciation or lineage sorting. Molecular clock estimates for the siblings P. miles and P. volitans suggest a divergence time of 2.4-8.3 mya, which coincide with geological events that created vicariance between populations of the Indian and Pacific Ocean.     

The effect of sewage-enriched river Ganga water on the biomass production of theAzolla-Anabaena complex

The biomass formation ofAzolla was greatly enhanced by water of the River Ganga and by prevailing environmental conditions. It increased gradually from January to April (first maximum 2.409 g.m^–2.day^–1), declined during June (1.185 g.m^–2.day^–1), and reached a second its maximum during September (2.629 g.m^–2.day^–1). The biomass formation was related to the nutrient availability in the medium in a particular season (measured were: nitrate-N, available phosphorus, total suspended solids, and conductivity). The average annual production of 6.73 ton.ha^–1.yr^–1 is equivalent to the average production of 0.025 ton.ha^–1.yr^–1 phosphorus, 0.252 ton.ha^–1.yr^–1 nitrogen, and 1.57 ton.ha^–1.yr^–1 crude protein.     

Growth rates and energy demands in captive juvenile arctic foxes Alopex lagopus in Svalbard

Four arctic fox Alopex lagopus pups (two males and two females) were caught at dens when about 25–53 days old and kept in outdoor pens at NyÅlesund, Svalbard. Their growth in body size (as measured by the length of a front foot), increase in weight, and food consumption were monitored from July to December, 1987. The pups grew rapidly and reached 97.5 ± 0.1% of their maximum adult size when they were 99–127 days old. Increase in body weight took longer (130 days). Food consumption generally increased until about 90 days old, after which it was highly variable. Pups consumed on average 266 kcal kg^–1 day^–1 growing 34g/day until 95 days old. Subsequently, until about 200 days old, they consumed 202 kcal kg^–1 day^–1 and grew 6.8 g/day.     

Ammonia-nitrogen excretion in Daphnia pulex

Ammonia-nitrogen excretion rates were measured in natural summer and cultured populations of Daphnia pulex from Silver Lake, Clay County, Minnesota, USA during 1973. The mean rate of ammonia-nitrogen excretion for the summer populations was 0.20 µg N animal^–1 day^–1 or 5.11 µg N mg^–1 dry body weight day^–1 (N = 80) measured at 15°, 20°, and 25°C. These rates appear to be temperature and weight dependent, but they are probably affected by factors other than temperature and dry body weight. Ammonia-nitrogen excretion rates of Daphnia pulex cultured on Chlamydomonas reinhardi yielded the following relationship with temperature: Log₁₀E = (0.061) T 1.773, where E is µg N animal^–1 day^–1 and T is temperature °C. The ammonia-nitrogen excretion on a mg^–1 dry body weight day^–1 basis was related to temperature according to the following similar expression Log₁₀E = (0.043) T + 0.153, where E is µg N mg^–1 dry body weight day^–1, and T is temperature °C. The length-weight relationship of Daphnia pulex for the summer populations (N = 1583) was log₁₀W = (0.526) Log₁₀L + 1.357, where W is weight in µg and L is length in mm.     

Comparison of growth rate in culture,dry matter content,agar content and agar quality of two New Zealand red seaweeds,Gracilaria chilensis Bird,McLachlanet Oliveira andGracilaria truncata Kraft

Plant growth rates and agar characteristics were compared for two agarophytes,Gracilaria chilensis (Gracilariales, Rhodophyta) andG. truncata, so that the suitability ofG. truncata for mariculture could be assessed.G. chilensis plants grew steadily in the laboratory culture system at rates of 5–8% day^-1 (mean Relative Growth Rate) throughout the 6 week experimental period, with no decline in health.G. truncata plants grew at rates of 2–4% day^-1 for 5 weeks, but during the sixth week their apical tips became necrotic and growth rates fell to zero. There was no significant difference in the dry matter content (as a percentage of their wet weight) between the two species ofGracilaria, with values falling in the range of 16–19%. Slightly higher agar yields were obtained from alkali-treatedG. chilensis (17–20% dry matter) than from untreatedG. truncata (16–18%) although the agar fromG. truncata formed softer gels from which it was more difficult to recover. The gel strength of untreated agar extracted fromG. chilensis was very low (ca. 100 g cm^-2 for a 1% gel) but when an alkali treatment step was included in the extraction process, it increased to 520 g cm^-2 for a 1% gel. Contrary to an earlier report, untreatedG. truncata agar also had a very low gel strength (ca. 100 g cm^-2 for a 1.5% gel), but it rose to only 167 g cm^-2 after alkaline treatment.     

Ontogenetic changes in food intake and digestion rate of the herbivorous marine iguana (Amblyrhynchus cristatus,Bell)

Young reptiles have higher relative energy demands than adults, but the proposed ontogenetic changes in diet to fulfil these demands were not found in the algae-eating Galápagos marine iguanas on Santa Fé. Feeding and digestion rates were investigated to analyse how young achieve higher energy intake. Daily food intake of free ranging marine iguana hatchlings (6–11 months old) was about one third that of adults, but relative intake (g dry mass · g^–1 wet mass · day^–1) was four times higher in the hatchlings. During feeding experiments, relative daily food intake of hatchling marine iguanas was approximately three times higher than that of adults (0.042 vs 0.013 g dry mass · g^–0.8 wet mass · day^–1), and mean gut passage time was two times shorter (5 vs 10 days). The hatchlings also maintained high body temperatures (36.7° C) even under relatively cool day-time air temperatures of 32° C. Apparent digestibility of algal food measured both during feeding trials and by Mn²⁺ AAS (atomic absorption spectrometry) for free-ranging iguanas was 70%, independent of body size and temperature. The red algae prevailing in the diet were high in protein (30% dry mass) and energy (12.1 kJ/g dry mass). Diving iguanas had higher rates of energy intake than intertidal foragers, but daily intake was less. Maintenance of high body temperature enabled hatchlings to achieve high digestion rates and, combined with high relative intake, thus achieve sufficient energy intake for rapid growth despite higher mass specific metabolic rates. Estimates of biomass of marine iguanas and their algal food are given for a section of coastline on Santa Fé.     

Energy requirements of the red kangaroo (<Emphasis Type="Italic">Macropus rufus</Emphasis>): impacts of age,growth and body size in a large desert-dwelling herbivore.

Generally, young growing mammals have resting metabolic rates (RMRs) that are proportionally greater than those of adult animals. This is seen in the red kangaroo (Macropus rufus), a large (>20 kg) herbivorous marsupial common to arid and semi-arid inland Australia. Juvenile red kangaroos have RMRs 1.5–1.6 times those expected for adult marsupials of an equivalent body mass. When fed high-quality chopped lucerne hay, young-at-foot (YAF) kangaroos, which have permanently left the mother's pouch but are still sucking, and recently weaned red kangaroos had digestible energy intakes of 641±27 kJ kg^–0.75 day^–1 and 677±26 kJ kg^–0.75 day^–1, respectively, significantly higher than the 385±37 kJ kg^–0.75 day^–1 ingested by mature, non-lactating females. However, YAF and weaned red kangaroos had maintenance energy requirements (MERs) that were not significantly higher than those of mature, non-lactating females, the values ranging between 384 kJ kg^–0.75 day^–1 and 390 kJ kg^–0.75 day^–1 digestible energy. Importantly, the MER of mature female red kangaroos was 84% of that previously reported for similarly sized, but still growing, male red kangaroos. Growth was the main factor affecting the proportionally higher energy requirements of the juvenile red kangaroos relative to non-reproductive mature females. On a good quality diet, juvenile red kangaroos from permanent pouch exit until shortly after weaning (ca. 220–400 days) had average growth rates of 55 g body mass day^–1. At this level of growth, juveniles had total daily digestible energy requirements (i.e. MER plus growth energy requirements) that were 1.7–1.8 times the MER of mature, non-reproductive females. Our data suggest that the proportionally higher RMR of juvenile red kangaroos is largely explained by the additional energy needed for growth. Energy contents of the tissue gained by the YAF and weaned red kangaroos during growth were estimated to be 5.3 kJ g^–1, within the range found for most young growing mammals.Abbreviations BMR basal metabolic rate - DEI digestible energy intake - MER maintenance energy requirement - MER_g maintenance plus growth energy requirement - PPE permanent pouch exit - RMR resting metabolic rate - YAF young-at-foot Communicated by I.D. Hume     

Root turnover as determinant of the cycling of C,N, and P in a dry heathland ecosystem

Root production and turnover were studied using sequential core sampling and observations in permanent minirhizotrons in the field in three dry heathland stands dominated by the evergreen dwarfshrub Calluna vulgaris and the grasses Deschampsia flexuosa and Molinia caerulea, respectively. Root biomass production, estimated by core sampling, amounted to 160 (Calluna), 180 (Deschampsia) and 1380 (Molinia) g m^-2 yr^-1, respectively. Root biomass turnover rate in Calluna (0.64 yr^-1) was lower compared with the grasses (Deschampsia: 0.96 yr^-1; Molinia 1.68yr^-1)). Root length turnover rate was 0.75–0.77 yr^-1 (Deschampsia) and 1.17–1.49 yr^-1 (Molinia), respectively. No resorption of N and P from senescing roots was observed in either species. Input of organic N into the soil due to root turnover, estimated using the core sampling data, amounted to 1.8 g N m^-2 yr^-1(^Calluna), 1.7 g N m^-2 yr^-1 (Deschampsia) and 19.7 g N m^-2 yr^-1 (Molinia), respectively. The organic P input was 0.05, 0.07 and 0.55 g P M^-2 yr^-1, respectively. Using the minirhizotron turnover estimates these values were20–22% (Deschampsia) and 11–30% (Molinia) lower.When the biomass turnover data were used, it appeared that in the Molinia stand root turnover contributed 67% to total litter production, 87% to total litter nitrogen loss and 84% to total litter phosphorus loss. For Calluna and Deschampsia these percentages were about three and two times lower, respectively.This study shows that (1) Root turnover is a key factor in ecosystem C, N, and P cycling; and that (2) The relative importance of root turnover differs between species.     

Estimated feeding rates and energy requirements of gentoo penguins,Pygoscelis papua,at Macquarie Island

Summary Water and sodium turnovers of 6–7 week old gentoo penguin chicks and breeding adults were measured using isotopically labelled water and sodium. Influx rates for chicks averaged 188 ml·kg^-1·day^-1 and 13.9 mmol·kg^-1·day^-1 for water and sodium, respectively. Chicks consumed an estimated 228 g·kg^-1·day^-1 fresh food or 886 kJ kg^-1 day. These values correspond to 761 g·day^-1 or 2945 kJ·day^-1 for a gentoo chick mid-way through the growth period. Flux rates for adults attending chicks ranged from 199 to 428 ml·kg^-1·day^-1 for water and from 15 to 36 mmol·kg^-1·ay^-1 for sodium.     

Respiration, nutrient excretion and filtration rate of tropical freshwater mussels and their contribution to production and energy flow in Lake Kariba, Zimbabwe

The productivity and ecological role of benthos in man-made Lake Kariba was assessed through the use of P/B-ratios and by measuring the metabolism (respiration, N and P excretion) of the most abundant mussel species (Aspatharia wahlbergi, Corbicula africana and Caelatura mossambicensis) in laboratory experiments. For A. wahlbergi also filtration rate was estimated.The annual production of benthos for the populated 0–12 m interval was estimated at 11.0 g m ^–2 yr^–1 (shellfree dry weight) of which mussels contributed for 8.81 g (80%), snails 2.16 g (20%) and insects 0.03 g (0.3%) respectively. The most important mussel species in the lake were Caelatura mossambicensis (4.97 g m^–2 yr^–1) and Corbicula africana (3.33 g). The dominant snail species was Melanoides tuberculata (1.63 g). For the total lake, also including deeper unpopulated bottoms, the annual production of benthos was 2.70 g m^–2 yr^–1 (shell-free dry weight).Respiration and excretion varied with temperature displaying a bell-shaped relationship. Metabolic rates in Aspatharia wahlbergi increased about 5× between 16.5 °C and the maximum at 34.0 °C and then decreased again at 39.0 °C, when the mussels showed signs of severe stress. Metabolism in Corbicula africana had a lower optimum with fairly constant activity between 18.6 and 29.2 °C, rapidly decreasing above this temperature.The average respiration, nutrient excretion and water filtration rates for mussels in Lake Kariba at 25.2 °C were estimated to about 0.6 mg O₂ 85 µg NH₄–N, 1.5 µg PO₄–P and 0.51 water filtered h^–1 g^–1 shellfree dry weight. This gives that a volume corresponding to about the total epilimnion of the lake is filtered by the mussels annually. Further, mussels can be estimated to remineralise % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0Jf9crFfpeea0xh9v8qiW7rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaGymaiaac+% cacaaI0aaaaa!3A2B!\[1/4\] of the total load of phosphate, and 8 times the total load of nitrogen every year. The population needs 3.5 × 10⁴ tons of organic carbon for its maintainance, which indicates that about 5% of the annual phytoplankton production is channeled through mussels. We conclude that the mussels, rather than being an important food source for fish, seem to play a large role in the nutrient dynamics of Lake Kariba.     

Forest floor mass,litterfall and nutrient return in Central Himalayan high altitude forests

Dynamics of forest floor biomass, pattern of litter fall and nutrient return in three central Himalayan high elevation forests are described. Fresh and partially decomposed litter layer occur throughout the year. In maple and birch the highest leaf litter value was found in October and in low-rhododendron in August. The relative contribution of partially and more decomposed litter to the total forest floor remains greatest the year round. The total calculated input of litter was 627.7 g m^-2 yr^-1 for maple, 477.87 g m^-2 yr^-1 for birch and 345.9 g m^-2 yr^-1 for low-rhododendron forests. 49–61% of the forest floor was replaced per year with a subsequent turnover time of 1.6–2.0 yr. The annual nutrient return through litter fall amounted to (kg ha^-1 yr^-1) 25.5–56.1 N, 2.0–5.4 P and 9.9–23.3 K. The tree litter showed an annual replacement of 26–54% for different nutrients and it decreased towards higher elevation. The nutrient use efficiency in terms of litter produced per unit of nutrient was higher in present study compared to certain mid- and high-elevation forests of the central Himalaya.     

Dry matter and nutrient inputs through litter fall in a dry tropical forest of India

The present paper elucidates the pattern of leaf and non-leaf fall and quantifies of the total annual input of litter in a dry tropical forest of India. In addition, concentration of selected nutrients in various litter species and their annual return to the forest floor are examined. Total annual input of litter measured in litter traps ranged between 488.0–671.0 g m^-2 of which 65–72% was leaf litter fall and 28–35% wood litter fall. 73–81% leaves fall during the winter season. Herbaceous litter fall ranged between 80.0–110.0 g m^-2 yr^-1. The annual nutrient return through litter fall amounted (kg ha^-1): 51.6–69.6 N, 3.1–4.3 P, 31.0–40.0 Ca, 14.0–19.0 K and 3.7–5.0 Na, of which 71–77% and 23–29% were contributed by leaf and wood litter fall, respectively for different nutrients. Input of nutrients through herbaceous litter was: 13.0–16.6 for N, 1.0–1.4 for P, 4.0–5.0 for Ca, 7.9–10.5 for K and 0.8–1.0 kg ha^-1 yr^-1 for Na.     

Performance of a hybrid anaerobic reactor,combining a sludge blanket and a filter,treating slaughterhouse wastewater

A column reactor, in which the bottom two-thirds were occupied by a sludge blanket and the upper one-third by submerged clay rings, was evaluated using slaughterhouse wastewater as substrate. The reactor was operated at 35°C at loading rates varying from 5 g to 45 g chemical oxygen demand (COD) 1^–1 × day^–1 at an influent concentration of 2450 mg COD 1^–1. A maximum substrate removal rate of 32 g COD 1^–1 × day^–1, coupled with a methane production rate of 6.91 × 1^–1 × day^–1 (STP), was obtained. This removal rate is significantly higher than those previously reported. The rate of substrate utilization by the biomass was 1.22 g COD (g volatile suspended solids)^–1 day^–1. COD removal was over 96% with loading rates up to 25 g COD 1^–1 × day^–1, at higher loading rates performance decreased rapidly. It was found that the filter element of the reactor was highly efficient in retaining biomass, leading to a biomass accumulation yield coefficient of 0.029 g volatile suspended solids g^–1 COD, higher than reported previously for either upflow anaerobic sludge-blanket reactors or anaerobic filters operating independently.     

Biology ofChironomus piger Str. (Diptera: Chironomidae) and its role in the self-purification of a river

Chironomus piger larvae are widespread in small rivers and canals strongly polluted with domestic sewage. Despite this, almost nothing is known concerning the biology of the species under natural conditions and its role in the process of river self-purification. For two years, benthic samples were collected in the Sestra River at a site about 250 m downstream of the effluent discharge drains of a sewage treatment installation where the greatest concentrations of the larvae occurred. The number and biomass ofC. piger larvae were subject to marked fluctuations,viz. 96,000–348,000 ind m^–2 and 420–1,800 g m^–2. 460 degreedays (on average) was required for development of one generation.C. piger has 5 or 6 generations per year depending on the hydrometeorological conditions during the growing season.C. piger larvae play an important role in self-purification of the river. They utilize precipitating seston for food and for building their dwelling tubes. According to our calculations the amount of organic matter assimilated in the area of maximum larval concentration ranged 80–177 g wet weight m^–2 day^–1, and 32–71 g wet weight m^–2day^–1 was mineralized.     

Renewal rate and nutrient concentration as tools to modify productivity and biochemical composition of cyclostat cultures of the marine microalga Dunaliella tertiolecta

A factorial experimental design with two nutrient concentrations (2 and 4 mmol Nl^–1 in the form of NaNO₃) and five rates of daily renewal of the cultures (10%, 20%, 30%, 40% and 50%) was carried out in cyclostat, light/dark-synchronized cultures of the marine microalga Dunaliella tertiolecta Butcher. Steady-state cellular density was a linear function inversely proportional to renewal rate. Maximal cellular productivity, 3 × 10⁹ cells1^–1 day^–1, equivalent to 0.24 g1^–1 day^–1 dry weight and 0.17 g1^–1 day^–1 organic weight, was found with renewal rates of 20%–30% and 4mmol N1^–1, but maximal protein productivity, 0.066 g1^–1 day^–1, was obtained with a renewal rate of 40% for both nutrient concentrations. The protein content ranged between 30% and 70% of the organic fraction depending on the culture conditions. Carbohydrates were the only fraction accumulating in response to nutrient stress, ranging from 57% to 10% of the organic fraction, meanwhile the lipid content was increased by increase of nutrient availability. Under non-nitrogen-limited conditions the C:N ratio stabilized around 5.2–5.3 and the protein content of the organic fraction around 70%, but the cell nitrogen quota decreased under these conditions with increasing renewal rates, owing to the lower organic content of cells obtained with high growth rates. The high capacity for changing the biochemical composition, demonstrated for D. tertiolecta in the cyclostat system, has interesting implications for the management of continuous cultures of microalgae and its applications in biotechnological processes.     

Steady-state sodium absorption and chloride secretion of colon and coprodeum,and plasma levels of osmoregulatory hormones in hens in relation to sodium intake

Summary The plasma levels of four osmoregulatory hormones and their target ion-transport systems in the lower intestines of the domestic fowl were determined in order to elucidate their interrelationship and their setpoints in relation to NaCl intake. White Plymouth Rock hens were adapted to six intake levels of NaCl (0.20±0.02–24.7±1.9 mmoles Na⁺·kg bw^–1·day^–1) for 6 weeks. The Na⁺ absorption and the Cl^– secretion of colon and coprodeum were characterized in vitro by the effects of hexoses, amino acids, amiloride, and theophylline on the short-circuit current (SCC) and electrical potential difference (PD). The NaCl-conserving system of the adult chicken is set at low intake levels of NaCl as the 80% range (quantitized by non-linear, logistic regression analyses) of the change in the plasma [ALDO], the amiloride-inhibitable Na⁺ absorption of coprodeum and colon ( SCC), occurred from 0.18 to 2.3, from 0.9 to 4.3, and from 1.2 to 7.3 mmoles Na⁺·kg bw^–1·day^–1, respectively. These results demonstrate that the amiloride-inhibitable Na⁺ absorption of coprodcum is more closely linked to plasma [ALDO] than that of colon. The aminoacid-Na⁺ coabsorption of colon increased over exactly the same range of Na⁺ intake as the colonic amiloride-inhibitable Na⁺ absorption decreased, whereas the hexose-Na⁺ coabsorption increased at higher levels of Na⁺ intake, from 2 to 11 mmoles Na⁺·kg bw^–1·day^–1. Both these Na⁺ absorption types had reached their maximums at 24.7 mmoles Na⁺·kg bw^–1·day^–1, whereas the plasma [AVT] and plasma [PRL], although significantly increased, apparently had not; their 80% range of change occurred from 9.9 to 99 mmoles Na⁺·kg bw^–1·day^–1, and the main changes in plasma osmolity were predicted to occur from 5.4 to 107 mmoles Na⁺·kg bw^–1·day^–1. These results suggest that these colonic and hormonal variables conserve osmotically-free water and operate at high NaCl intake. The theophylline-induced colonic Cl^– secretion did not change with NaCl intake, whereas the stimulation of SCC in coprodeum decreased with increasing NaCl intake: The main change occurred between 0 and 3.2 mmoles Na⁺·kg bw^–1·day^–1. Thus, all ion-transport capacity disappears in coprodeum with increased dietary NaCl intake, whereas colon maintains its ion-transport capacity (although the nature of the Na⁺ transport changes). It is suggested that hormones defending the extracellular volume and composition are regulated close to zero input and output of both NaCl and water, regardless of whether they are NaCl conserving or free-water conserving. Therefore, changes in their stable plasma concentrations occur at the extremes of tolerable range of NaCl intake.Abbreviation AA aminoacids - ALDO aldosterone - AMI amiloride - AVT arginine vasotocin - bw body weight - CS corticosterone - HEX hexoses - INDO indomethacin - PD potential difference - PRL prolactin - R resistance - SCC short-circuit current - SD standard deviation - SEM standard error of mean - THEO theophylline     

Effects of Body Size and Food Ration on Over-winter Survival and Growth of Age-0 Atlantic cod, Gadus morhua

This study examined the effects of body size and food ration on over-winter survival of age-0 Atlantic cod. Cod were divided into two groups based on standard length (large=76.95±1.10 mm SL; small=57.65±1.02 mm SL; mean±1 SE) and wet weight (large=4.02± 0.21 g; small=1.52±0.09 g). Replicate tanks (n=2) of 10 large and 10 small cod were exposed to one of two food rations (0.25% and 1.0% body weight day^-1) for the entire experiment (December to June). Tanks were examined daily for mortalities and feeding was adjusted accordingly. The experiment was run under ambient light and seawater conditions. All but large age-0 cod exposed to the low food ration grew over the course of the experiment. The specific growth rate (SGR) of small cod was significantly higher (0.2425% wet weight day^-1) than that of the large fish (0.0443% wet weight day^-1). Food ration had no significant influence on SGR or over-winter survival. Significantly more of the large age-0 cod survived the winter (58.5% of those originally introduced) compared to the smaller fish (14%). Our results are consistent with those from studies of several other fish species, and are discussed in relation to the ecology of age-0 cod, and their potential use in aquaculture in Newfoundland.     

Production estimates of the dominant taxa of Chironomidae (Diptera) in the modified,River Widawka and the natural,River Grabia,Central Poland

Production and community composition of selected taxa of Chironomidae were estimated in cross-sections of the lower course of two lowland rivers, the Widawka and the Grabia. At the selected site, the Grabia has not changed its morphometry for many years, whereas the discharge of the Widawka has increased (mainly due to inputs of coal mine water) by 75% in comparison with its hypothetical natural discharge. In the Widawka, the production value, for 76.7% of total Chironomidae abundance, amounted to 12.45 g dry wt m^–2 yr^–1, while in the Grabia it amounted to 11.91 g dry wt m^–2 yr^–1 The annual P : B ranged from 14.5 for large-sized species (Chironomus in the Widawka) to 82.0 for small-sized species (Eukiefferiella in the Grabia). The similar production values estimated for both rivers, despite a three times higher density of Chironomidae in the Grabia, is noteworthy.     

Cation distribution,cycling, and removal from mineral soil in Douglas-fir and red alder forests

Overstory species influence the distribution and dynamics of nutrients in forest ecosystems. Ecosystem-level estimates of Ca, Mg, and K pools and cycles in 50-year old Douglas-fir and red alder stands were used to determine the effect of overstory composition on net cation removal from the mineral soil, i.e. cation export from the soil in excess of additions. Net cation removal from Douglas-fir soil was 8 kg Ca ha^–1 yr^–1, 1 kg Mg ha^–1 yr^–1, and 0.3 kg K ha^–1 yr^–1. Annual cation export from soil by uptake and accumulation in live woody tissue and O horizon was of similar magnitude to leaching in soil solution. Atmospheric deposition partially off-set export by adding cations equivalent to 28–88% of cation export. Net cation removal from red alder soil was 58 kg Ca ha^–1 yr^–1, 9 kg Mg ha^–1 yr^–1, and 11 kg K ha^–1 yr^–1. Annual cation accumulation in live woody tissue and O horizon was three times greater than in Douglas-fir, while cation leaching in soil solution was five to eight times greater. The lack of excessive depletion of exchangeable cations in the red alder soil suggests that mineral weathering, rather than exchangeable cations, was the source of most of the removed cations. Nitric acid generated during nitrification in red alder soil led to high rates of weathering and NO₃-driven cation leaching.     

Response of understory vegetation to variable tree mortality following a mountain pine beetle epidemic in lodgepole pine stands in northern Utah

We analyzed the long-term dynamics of aboveground biomass ofLeymus chinense steppe in relation to interannual variation of precipitation and temperature during 1980–1989 at levels of community, growth form and species in the Xilin river basin, Inner Mongolia Autonomous Region, China. Annual aboveground net primary production (ANPP) varied from 154.00 g m^-2 yr^-1 in 1980 to 318.59 g m^-2 yr^-1 in 1988, with a mean of 248.63 g m^-2 yr^-1 and the coefficient of variation of 25%. ANPP was not significantly correlated to annual precipitation and total precipitation during April–September atp0.05 level, but precipitation in May and August accounted for 69% of interannual variation of ANPP. The means of rain use efficiency and water use efficiency ofL. chinense steppe were 8.1 kg DM ha^-1 mm^-1 yr^-1 and 0.89 mg DM g^-1 H₂O respectively. Aboveground biomass of various growth forms and species had different response patterns to interannual variation of precipitation and temperature. Monthly and seasonal distribution of precipitation and temperature were the key controls of aboveground biomass of species.