Copepods in summer platelet ice in the eastern Weddell Sea,Antarctica

Copepods in platelet-ice layers underlying fast ice and in the water column below were studied at Drescher Inlet, eastern Weddell Sea in February 1998. Three copepod species were found: Drescheriella glacialis and Paralabidocera antarctica occurred in platelet-ice layers, while Stephos longipes was only present in the water column. The distribution of all species varied considerably between station and depth. D. glacialis dominated the platelet-ice community and occurred at all five platelet-ice sampling sites, except one, with numbers of up to 26 ind. l^–1. In contrast, P. antarctica was only found in low numbers (up to 2 ind. l^–1) at one site. The total copepod abundance in the platelet ice was not associated with algal biomass, although it was strongly correlated with high ammonium concentrations (up to 9 M) in the interstitial water between the platelets. This is the first indirect evidence to support the hypothesis that zooplankton excretion can partly account for the high ammonium values often found in platelet-ice layers.     

林分密度对新津文峰山马尾松人工林林下物种多样性和生物量的影响

以四川省新津文峰山马尾松(Pinus massoniana)人工林为研究对象,用典型抽样法探究5种林分密度(A:1000株/hm~2;B:1125株/hm~2;C:1250株/hm~2;D:1375株/hm~2;E:1500株/hm~2)对林下植被物种多样性和生物量的影响及林下植被物种多样性和生物量的相关性。结果显示:(1)共调查到植物124种,隶属于74科115属,灌木层物种少于草本层。(2)灌木或草本层在不同林分密度下的优势种都较一致。(3)灌木层物种丰富度指数D值、Shannon-Wiener多样性指数H值及草本层4个多样性指数均在密度B、E分别有最大和最小值;灌木层D值随密度增大而先增后减,其他3个指数变化规律不明显。灌、草层J_(sw)值较稳定。(4)灌木层生物量比草本层多。总体上灌、草层地上生物量大于地下生物量,都在密度B达最大;灌木地下生物量保持较稳定,而草本层变化幅度较大。(5)除灌木层J_(sw)值与该层各生物量呈负相关外,其余各指标均显示正相关。不同林分密度对马尾松林下植物多样性和生物量产生不同的影响,经综合研究分析认为,林分密度1125株/hm~2相对更利于该地马尾松人工林的可持续健康发展。     

Estuarine benthic invertebrates of Indian river and Rehoboth Bays,Delaware

From 1968 to 1970, 273 quantitative samples of macroscopic benthic invertebrates were collected seasonally (winter and summer) from Indian River and Rehoboth Bays, Delaware. A total of 103, 485 individuals representing 11 phyla and 149 species was taken. Mobile carnivores comprised 30.9% (46 species) of the fauna, selective deposit feeders 28.2% (42 species), sedentary suspension feeders 18.1% (27 species), nonselective deposit feeders 3.4% (5 species), and sessile carnivores 2.7% (4 species). In terms of number of individuals, selective deposit feeders and sedentary suspension feeders comprised 49.2% (51,442 individuals) and 43.7% (44,647 individuals), respectively. The average density (no./m²) was generally significantly higher in Indian River than Rehoboth Bay. Maximum density for the former was 106,871/m² and for the latter 60,192/m². Evenness diversity was normally slightly higher in summer than winter and higher in Rehoboth Bay than in Indian River Bay. The top three species, ranked by density and frequency of occurrence, were Ampelisca abdita, Gemma gemma, and Tellina agilis. Annual and seasonal changes in density and dominance (exclusive of the top three species) were substantial. Biomass patterns were very similar to areas north (Moriches Bay, New York) and south (Beaufort, North Carolina). It was suggested that larger invertebrates have been deemphasized in biomass estimates in past studies. It was concluded that Rehoboth and Indian River Bays contained an Ampelisca — bivalve (Gemma gemma, Tellina agilis, Mercenaria mercenaria) community.     

The influence of resprouting forest canopy species on richness in Southern Cape forests, South Africa

We investigated the relationship between species richness and numbers and types of individuals and species present in forests with different physiognomies in the southern Cape Province, South Africa. Data were collected from three different ‘plot’ types: 400 m², canopy‐scaled (plot length is directly proportional to canopy height) and per 100 individuals closest to a point. Plots were designed to control for the effect of scale on local richness. Canopy species richness was inversely proportional to the abundance of resprouting species. The strength of the relationship between the abundance of resprouters and canopy species richness increased progressively from the 400 m² plots to the canopy‐scaled plots and finally to the plots of 100 individuals. Resprouter abundance decreased, while canopy species richness increased, with increasing canopy height. Resprouters are able to retain their in situ position in the forests for longer periods of time than do reseeders. This reduces individual and species turnover, thus reducing species richness in resprouter‐dominated forests.     

Chaff piles of harvester ant (Messor spp.) nests in a desert ecosystem

Summary The plant species composition of the chaff piles of three species of harvester ant (Messor spp.) and the contribution of the chaff to the organic pool were studied from August 1985 to July 1987. There were distinct differences in the plant species composition of the chaff of the three species. We attribute this to the different diets of the three species, which reflect the relative sizes of their individuals and their foraging strategies. The amount of chaff accumulated varies greatly between the three species (Messor rugossus: 127–196 g · ha^–1 · y^–1;Messor ebeninus: 2823–4437 g · ha^–1 · y^–1;Messor arenarius: 2165–2535 g · ha^–1 · y^–1), although the number of nests per hectare is virtually the same. We found that the amount of chaff is related to the rate of activity and the size of the individuals of each of the three ant species. The total chaff accumulated during the study period was 19.2 kg · ha^–1, which is an important contribution to the organic matter in the soil in the Negev desert ecosystem.     

Diversity,habitats and size-frequency distribution of the gastropod genus Conus at Dahab in the Gulf of Aqaba,Northern Red Sea

Topographically complex subtidal reefs of the Indo-West Pacific region are characterised by a high species richness of cone snails of the genus Conus (up to 36 on some reefs) but low population densities (≤1 individual/m²), whereas Conus assemblages on reef flats usually support fewer species (5–9) and high population densities (up to 5.2 individuals/m²). Subtidal sand areas are known to be least species-rich (1–6 species). Although the diversity of this predatory gastropod genus has been described previously from different areas of the Indo-Pacific, little ecological information is available on Conus in the Northern Red Sea. Therefore, data from five habitat types were obtained along 73 line-transects (245?m²⁾, which yielded ecological data for a total of 175 individuals of 9 species. In accordance with former findings, our results demonstrate that the reef flat was the habitat with the highest observed population densities (6.15 individuals/m²) but low species diversity (H’ = 0.9; 5 species); subtidal reefs, in contrast, were characterised by low densities (0.13 individuals/m²) and a relatively high species diversity (H ‘= 1.5; 6 species). This suggests that Conus diversity and species richness in the Northern Red Sea around Dahab is lower than in other parts of the Indo-West Pacific region. Furthermore, hardand soft substrata were dominated by different Conus species in accordance to the distribution of favourable microhabitat patches, the degree of physical stress and the availability of refuges and prey organisms. The fact that these Conus were predominantly small-bodied vermivores (size range: 6–85?mm; mean shell size: 15?mm; SD = 9?mm) suggests that this size class possesses an advantage over molluscivores and piscivores. Except for subtidal reefs, which showed a highly variable species composition, the studied habitat types around Dahab were characterised by distinct assemblages of Conus.     

Carbon, nitrogen, and hydrogen isotope ratios in creekside trees in western Kansas

Three species of creekside trees were monitored weekly during the 2007 and 2008 growing seasons. The 2007 growing season was wet early, but became drier as the season progressed. In contrast, the 2008 growing season was dry early, but became wetter as the season progressed. Creekside trees were measured to determine effects of changing water regimes on leaf-level processes. Lonicera tatarica plants were compared to Morus alba and Celtis occidentalis trees. Leaves were monitored for changes in stomatal conductance, transpiration, δ¹³C, δ¹⁵N, δD, leaf temperature, and heat losses via latent, sensible, and radiative pathways. δD of creek water was more similar to ground water than to rain water, but the creek was partially influenced by summer rains. δD of bulk leaf material was significantly higher in individuals of C. occidentalis compared to the other species, consistent with source water coming from shallower soil layers. Despite decreasing water levels, none of these tree species showed signs of water stress. There were no significant differences between species in stomatal conductance or transpiration. Leaf δ¹³C was significantly lower in individuals of L. tatarica compared to the other species. Differences in δ¹³C were attributed to a lower carboxylation capacity, consistent with lower leaf nitrogen content in L. tatarica plants. Leaf δ¹⁵N was significantly lower in individuals of L. tatarica compared to the other species, consistent with uptake of a different N source. Two of the three sites appeared to be affected by inorganic N from fertilizer run-off. Evidence is presented that these species acquired water and nitrogen from different sources, resulting from differences in root uptake patterns.     

Ingestion Rates of Some Daphnia Species in a Shallow Lake (Lake Balaton,Hungary)

Filtering rates of three species of Daphnia were studied in situ by the ¹⁴C technique during the summer in a lake with a water temperature of 20-25°C (Lake Balaton, Hungary). The renewal time of gut contents proved to be 3-5 min in each of the three species whether fed on natural or artificial food. From May to September, filtering rates of D. cucullata, D. hyalina and D. galeata averaged 7.8, 10.3 and 9.2 ml ind.⁻¹ day⁻¹, respectively. Identically long individuals of all three species had almost the same filtering rates in spring, whereas in summer animals of identical weights had similar filtering rates regardless of species because of the length variability of the helmets. The grazing rate of adult filter-feeding crustaceans is suggested to be approximately 7 % per day.     

Hoverfly (Diptera: Syrphidae) community of a cultivated arable field and the adjacent hedgerow near Debrecen,Hungary

A hoverfly (Syrphidae) community was investigated in a cultivated wheat field and the adjacent hedgerow near Debrecen (Hungary). We monitored the change of species richness and abundance of hoverflies along three transects in the hedgerow and in the wheat field in different distances (10 m, 20 m) from the hedgerow. The effect of sampling methods on the number of hoverfly species and individuals was analyzed. Two sampling methods were used to catch hoverflies: netting and pan traps. The whole sampling period was divided into three subperiods, which are early (22^nd April–2^nd June), middle (11^th June–1^st August) and late (6^th August–11^th September). Altogether 1,214 individuals of 22 species were sampled. Fourteen species with 78% of individuals belonged to the aphidophagous group, feeding on aphids as larvae. Altogether 861 individuals of 22 hoverfly species were sampled by netting and 353 individuals of 10 species by pan traps. The total number of hoverfly species was significant lower in the late period than in the early. The total abundance was higher in the middle period compared to the early. The species richness and abundance of aphidophagous species followed a similar pattern as the total species values. The species richness and abundance of hoverflies were significant higher in 10 m and 20 m distance in the wheat field than along the hedgerow. The results suggest that the pan traps were less efficient in the hedgerow than the netting, but in the wheat field they sampled more hoverflies because of visually alluring effect on hoverflies in the absence of flowers.     

Obesity, white blood cell counts, and platelet counts among police officers

Objective: To determine the association between several obesity indices (BMI, waist circumference, waist‐to‐hip and waist‐to‐height ratios, and abdominal height) and hematologic parameters [white blood cell (WBC) and platelet counts] among police officers. Research Methods and Procedures: The authors conducted this cross‐sectional study among 104 randomly selected officers (41 women and 63 men) from the Buffalo, NY, Police Department. Anthropometric measures were performed by clinic staff, and fasting blood samples were drawn for complete blood counts. Pearson's correlation, Student's t tests, ANOVA, analysis of covariance, and linear regression were used to assess the associations. Results: Officers ranged in age from 26 to 61 years old and were predominantly white. Among women, current smokers had significantly higher WBC counts (7.4 × 10³ cells/µL ± 1.4) than former (5.2 × 10³ cells/µL ± 1.4) or never smokers (5.6 × 10³ cells/µL ± 1.5) (p = 0.002). Women had similar WBC counts but higher mean platelet counts than men (p = 0.005). Among women, abdominal height was positively associated with platelet count after adjustment for depression (p for trend = 0.039). Among women and men, a non‐significant step‐wise trend was observed between abdominal height and mean WBC counts before and after adjustment for smoking, race, and physical activity. No association was observed between obesity and platelet count among men. Discussion: Abdominal height was significantly associated with increased platelet counts among female officers. No significant associations were observed between obesity and WBC or platelet counts among male officers.     

Home range and habitat use of translocated endangered species,Cottus koreanus,in South Korea

The home range and characteristics of Cottus koreanus were investigated using passive integrated transponder (PIT) telemetry in the Gulji Stream, Korea, where the target species was artificially translocated. After release, tagged individuals moved up to 78?m away from the release site in search of proper habitats. The average distance moved until settlement was 17.1?m. The observed home range of settled individuals had longitudinal sections of 9.9?±?3.6?m and surface areas of 7.2?±?2.7?m². This is comparable to congeneric species that inhabit similar ecological habitats. Once individuals had settled, they rarely moved from that site except during the spring season. The typical microhabitat characteristics of the sites where the released individuals settled are: water depth of 5–10?cm, water velocity of 0.1–0.3?m?s^?1, and the size of boulders and cobbles of 10–20?cm in diameter. This study of translocated C. koreanus individuals provides detailed information about habitats that can be used for effective habitat restoration and successful translocations attempts of this species.     

Predation on reef-building corals: multiscale variation in the density of three corallivorous gastropods, Drupella spp.

 Feeding aggregations of three corallivorous gastropods, Drupella cornus, D. fragum and D. rugosa, have caused considerable coral damage on reefs across the Indo-West Pacific. Distribution and abundance of these three species were explored at Lizard Island, Great Barrier Reef, to determine within-reef variations in density, and spatial relationships between Drupella and their prey corals. The scales of greatest variation were between reef habitats (combinations of exposure and depth) and individual coral colonies. Density varied 12-fold among four habitats: exposed crests (2.55/m²), exposed slopes (0.22/m²), sheltered crests (0.34/m²) and sheltered slopes (2.07/m²). Species composition also varied markedly between habitats. Individuals were highly aggregated, usually forming small clusters (<10 individuals) on live coral colonies and other substrata, and occasional large aggregations of=200 to>2000. Five basic tenets for sampling Drupella are established, based on patterns of variation in density and species composition, and small-scale habitat use. Accepted: 8 February 1999     

Seasonal, altitudinal and host plant-related variation in the abundance of aphids (Insecta, Hemiptera) on sub-Antarctic Marion Island

Although aphids are the most species-rich group of invasive alien insects across the Southern Ocean Islands, their biology on the islands is poorly known. In this study, host plant-related, seasonal and altitudinal variation in the abundance of the three aphid species (Macrosiphum euphorbiae, Myzus ascalonicus, Rhopalosiphum padi) found on sub-Antarctic Marion Island is examined. Myzus ascalonicus is the most abundant of the species, reaching densities of c. 2,400 individuals per 1,200 cm² on the indigenous Acaena magellanica (Rosaceae) and 479 individuals per 1,200 cm² on the indigenous Cotula plumosa (Asteraceae), with lower numbers at elevations up to 300 m and a pronounced seasonal peak in December-February. Macrosiphum euphorbiae occurs on the same plant species in densities of between c. 11 individuals per 1,200 cm² on C. plumosa and c. 200 individuals per 1,200 cm² on A. magellanica, and with a pronounced summer peak in December. In both species, small numbers of winged forms are found (c. 1–5%), although they are permanently parthenogenetic on the island. Rhopalosiphum padi is also permanently parthenogenetic on the island and likewise shows a December peak in abundance. The current data suggest that low ambient temperatures, which are close to the lower development threshold of R. padi, and other temperate aphid species, limit development in winter, thus leading to a decline in abundance.     

Physiological and morphological characterisation of Limonium species in their natural habitats: Insights into their abiotic stress responses

Background and aims

Morphological and biochemical traits of four halophytes of the genus Limonium were analysed in plants sampled from salt marshes in SE Spain. This work aimed to explore the mechanism(s) behind the adaptation of these species to stressful habitats, with particular emphasis on responses to drought.

Methods

Plants of each species together with soil samples were collected in summer, which is the most stressful season in the Mediterranean. Soil parameters and plant morphological traits were determined, and the levels of several biochemical stress markers in plants were measured using spectrophotometric assays. A multivariate analysis was performed to correlate soil and plant data.

Results

Morphological characteristics regarding the underground system topology and several biochemical traits (higher foliar Ca²⁺, sucrose and glucose, and lower proline, glycine-betaine and fructose) clearly separate L. santapolense individuals from plants of the other three species.

Conclusions

Drought tolerance of L. santapolense in the field is mostly dependent on morphological adaptations: when growing in an arid location, plants of this species develop long taproots that can extract water from the deep, moist layers of the soil.

     

Estimating the relative nutrient uptake from different soil depths in Quercus robur, Fagus sylvatica and Picea abies

The distribution of fine roots and external ectomycorrhizal mycelium of three species of trees was determined down to a soil depth of 55 cm to estimate the relative nutrient uptake capacity of the trees from different soil layers. In addition, a root bioassay was performed to estimate the nutrient uptake capacity of Rb⁺ and NH₄⁺ by these fine roots under standardized conditions in the laboratory. The study was performed in monocultures of oak (Quercus robur L.), European beech (Fagus sylvatica L.) and Norway spruce [Picea abies (L.) Karst.] on sandy soil in a tree species trial in Denmark. The distribution of spruce roots was found to be more concentrated to the top layer (0–11 cm) than that of oak and beech roots, and the amount of external ectomycorrhizal mycelia was correlated to the distribution of the roots. The uptake rate of [⁸⁶Rb⁺] by oak roots declined with soil depth, while that of beech or spruce roots was not influenced by soil depth. In modelling the nutrient sustainability of forest soils, the utilization of nutrient resources in deep soil layers has been found to be a key factor. The present study shows that the more shallow-rooted spruce can have a similar capacity to take up nutrients from deeper soil layers than the more deeply rooted oak. The distribution of roots and mycelia may therefore not be a reliable parameter for describing nutrient uptake capacity by tree roots at different soil depths.     

鼎湖山南亚热带常绿阔叶林20公顷样地群落特征研究

 鼎湖山南亚热带常绿阔叶林是北回归线附近保存较完好的地带性植被,是在南亚热带季风湿润型气候条件下发育的植被类型,具有热带向亚热带的过渡性质,群落结构相对复杂,组成种类相对丰富。参照巴拿马巴洛科罗拉多岛（Barro Colorado Island, BCI） 50 hm²热带雨林样地的技术规范,采用中国森林生物多样性监测网络的统一调查研究方法,于2005年在鼎湖山南亚热带常绿阔叶林建立了20 hm² 固定监测样地,调查并鉴定了样方内胸径 （Diameter at breast height, DBH）大于1 cm的木本植物。首次调查结果表明,群落内共有木本植物210种,71 617个活的个体,分属于56科119属。从乔木区系的组成及其特点可以看出,其南亚热带的区系成分占绝对优势,并呈现出由亚热带向热带过渡的趋势。群落垂直结构复杂,地上成层现象较明显,乔木可分为3层,其中重要值最大的锥（Castanopsis chinensis）、木荷（Schima superba）和黄杞（Engelhardtia roxburghiana）均是乔木上层的优势种;中层是群落的主要层,由厚壳桂（Cryptocarya chinensis）、黄叶树（Xanthophyllum hainanense）和华润楠（Machilus chinensis）等中生和耐阴树种组成;下层成分较复杂,物种多样性高,不同地段的物种组成差异较大。样地内物种十分丰富,种-面积曲线拟合显示其物种数量接近于BCI。稀有种比例极高,有110种,占总物种数的52.38%,其中有45%的稀有种源于物种本身的特性,有20%源于区系交汇,人为或自然干扰造成的稀有种占30%以上。样地中所有个体的径级分布(以1 cm等级排列)明显呈倒“J"形,表示群落稳定与正常生长状态。根据对优势种径级结构的分布分析,将各树种的径级结构归纳为4种类型：1）峰型（中径级个体储备型）,此类物种为乔木上层优势种;2）倒“J"型 （正常型）,此类物种为乔木中层的优势种;3）类倒“J"型（偏正常型）,此类物种占据乔木的中、下层; 4）“L”型（灌木型）,此类物种分布于乔木下层和灌木层。点格局分析得出优势种在各个层上的绝大部分尺度都是聚集分布的,而不同径级的空间分布随物种的不同而呈现出明显的差异性,点格局显示了优势种在相同径级的分布（特别是DBH=10～40 cm）具有一定的空间互补性。对大径级（DBH＞40 cm）的504个个体进行空间分布格局分析,结果表明,所有这些个体随机分布于整个样地,但不同的物种在空间分布上存在一定的规律。     

Seed and microsite limitation in Rheum nobile,a rare and endemic plant from the subnival zone of Sino-Himalaya

Background: Species persistence, particularly in monocarpic species, depends on the successful recruitment of individuals. An understanding of the factors that limit the recruitment of rare monocarpic plant species is therefore vital for their conservation.

Aims: To identify the factors limiting the recruitment of Rheum nobile, a rare and highly specialised monocarpic giant herb endemic to the high eastern Himalayas.

Methods: Seed sowing (seeds added or not added) and seedling transplanting experiments were conducted in disturbed (vegetation removed) and undisturbed plots in the vicinity of established populations of R. nobile to explore the mechanisms of recruitment limitation. Four levels of photosynthetically active radiation (0, 15, 30 and 50 μmol m^?2 s^?1) and two sowing positions (beneath and above grass litter or moss layer) were manipulated in the laboratory to determine how ground cover limited seedling emergence.

Results: Seed addition increased seedling recruitment. Disturbance significantly increased seedling emergence and establishment. Seed germination significantly decreased with the reduction of light availability, but 31.7% of all seeds germinated in complete darkness. Seedling emergence was close to zero when seeds were sown on top of a layer of grass litter or moss, but rose to 34.5% when the seeds were sown beneath such layers.

Conclusions: Our results indicate that the recruitment of R. nobile is limited by a combination of seed and microsite availability. Therefore, in order to conserve this species, we suggest adding seeds to suitable sites and implementing soil disturbances in existing populations to create suitable microsites.     

Benthic ctenophores (Platyctenida: Coeloplanidae) in South Florida: predator–prey interactions

The primary goal of this study was to demonstrate, from field observations and laboratory experiments, some key trophic roles of benthic ctenophores as predators and prey in subtropical communities. We examined individuals of two benthic platyctenid species: Coeloplana waltoni, a minute epibiont on octocorals in exposed, open‐water settings; and Vallicula multiformis, an associate of calm‐water biofouling communities and floating Sargassum spp. Laboratory observations of individuals of both ctenophore species revealed frequent capture and ingestion of diverse zooplankton taxa, especially crustaceans. Laboratory predation trials demonstrated the capture of dolphinfish (Coryphaena hippurus) eggs and larvae by both ctenophore species. Dolphinfish eggs and larvae larger than individuals of C. waltoni were captured but not ingested during 2‐h trial periods. These prey items were sometimes purloined and ingested by polyps of the ctenophore's octocoral host. Ingestion of dolphinfish eggs and larvae by individuals of C. waltoni was observed, however, after longer periods of exposure to prey. In predation trials, dolphinfish eggs and larvae were both captured and ingested by larger individuals of the ctenophore species V. multiformis. Field and laboratory observations revealed diverse invertebrate and fish taxa that prey on both ctenophore species. In the laboratory, the mean daily per capita consumption of individuals of C. waltoni by a pomacanthid fish ranged 0.5–2.8 individuals, and ranged 2.6–3.6 individuals for predation by an ovulid mollusc. Field population densities of these predators ranged 0.1–0.7 individuals per m² for the pomacanthid, and 0.2–1.1 individuals per m² for the mollusc. Laboratory feeding observations demonstrated frequent consumption of individuals of V. multiformis by a sea anemone, and by three species of brachyuran crabs. Field observations revealed eight fishes that probably feed incidentally on individuals of V. multiformis. These findings add to the limited knowledge base of predator–prey dynamics in both C. waltoni and V. multiformis.