Micro-arthropod seasonally in streams of varying pH

SUMMARY. 1. Micro-arthropods were sampled seasonally (January, May, August and October) during 1986 from ten, stony riffle sites on streams in the Ashdown Forest of southern England, using both standard benthic and interstitial samplers.
2. Total densities peaked at most sites in summer. Species richness reached a maximum at acid sites in summer but at cireumneutral sites in autumn, when Hydrachnellae and Cladocera were particularly species rich.
3. Individual species showed no obvious differences in seasonally between sites; the majority peaking in summer or autumn, regardless of pH. However, cyclopoid copepods were particularly numerous at acid sites in summer, a pattern not observed at circumneutral sites.
4. Multivariate ordination and classification of data sets from the separate seasons, and all four seasons combined, showed that mean site pH, conductivity, and aluminium and calcium concentrations were the most important variables explaining between-site variation in species composition. This clear distinction between the community structure at acidic and circumneutral sites was evident in all seasons except winter. Species composition was also more predictable throughout the year at low-pH sites.
5. A number of species were taken consistently in interstitial samples and the cyclopoids Diacydops languidus and D. languidoides were restricted to the hyporheos at circumneutral sites. The similar faunal composition of the hyporheos and the epibenthos indicated that the separation of these communities was not well defined in Ashdown Forest streams.     

The impact of changing the season in which cereals are sown on the diversity of the weed flora in rotational fields in Denmark

1. Surveys have shown that there has been a dramatic decrease in the weed flora of fields under rotational cultivation during the last 30 years. This trend has been particularly noticeable in winter cereals, a crop of increasing importance in the landscape.
2. The weed flora of spring and winter cereals was compared in 19 unsprayed fields during a 5-year study to test the hypothesis that cereal type exerts no effect on the flora or on the absolute and relative abundance of single species.
3. Plant and species densities, and accumulated species richness, were lower in winter than in spring cereals.
4. Floristic similarity was greater among spring cereal fields and between spring and winter cereals within the same fields than among winter cereal fields.
5. Species that occurred with unequal density in spring and winter cereals occurred at higher densities in the spring cereals; these species germinated mainly in the spring. However, for a few species the relative plant abundance was highest in winter cereals; these species were able to germinate both in the spring and autumn.
6. Some species – on the relative scale – occurred indifferently of season of sowing; all but one of these species were able to germinate both in the spring and autumn.
7. Plant species and taxa that are important food resources for arthropod herbivores occurred at greater densities in spring than in winter cereals and, in addition, occurred with the highest relative abundance in spring cereals.
8. Change in land use from spring to winter cereals involves not only an immediate reduction of more than 25% in the density of plants and species, but also a change and increased uncertainty in the composition of the weed flora. These findings may have serious implications for the ecology of wildlife in the agricultural landscape.     

闽江口鱼类功能多样性

根据2016年春季(5月)、夏季(8月)、秋季(11月)和冬季(2月)在闽江口海域进行底拖网作业的渔业资源调查样品,应用鱼类形态功能特征点数据分析了福建闽江口海域的鱼类功能多样性现状及时空变异.结果表明: 功能多样性与物种丰度具有相同的变化趋势,各站位鱼类物种丰度分别为:春季(17.8±5.1);夏季(22.4±5.6);秋季(17.7±6.3);冬季(12.1±2.3).鱼类集群功能多样性指数夏季最高,为(33.94±28.70),冬季最低(9.93±8.83),春季为(11.30±7.55),秋季为(19.05±19.32).群落内功能种呈现显著的季节演替,春季为太的黄鲫(占比为26%),夏季为六指马鲅(26%),秋季为龙头鱼,占比高达69%,显著高于其他物种的总和,冬季为棘头梅童鱼(38%).鱼类功能的季节性变动主要受其生活史及与其他物种之间的种间关系影响.     

The effects of bankside management on chalk stream invertebrate communities

SUMMARY 1. Communities of aquatic macroinvertebrates and the terrestrial adult phases of aquatic insects were investigated from short stretches of English chalk streams with two different bankside vegetation types: simply structured grazed grass (grazed) and structurally complex herbaceous vegetation with scattered trees (ungrazed). Macroinvertebrates were sampled in spring, summer, autumn and winter 1996–97 from three aquatic habitats: mid-channel gravel, patches of the aquatic macrophyte Ranunculus and marginal emergent macrophytes. The terrestrial adult phases of aquatic insects were sampled in spring, summer and autumn from bankside vegetation.
2. Total macroinvertebrate abundance did not differ between stretches with different bankside vegetation. Taxon richness of mid-channel gravel was, however, significantly higher in ungrazed compared with grazed stretches and Shannon diversity ( H ') of mid-channel gravel and marginal vegetation was significantly higher in ungrazed compared with grazed stretches. Total abundance, taxon richness and Shannon diversity ( H ') of the terrestrial adult phases of aquatic insect were significantly higher from the bankside vegetation of ungrazed compared with grazed stretches.
3. Ordination of communities of aquatic macroinvertebrates and terrestrial adults demonstrated that individual families of both groups were generally more abundant in ungrazed stretches. Many more families were significantly associated with ungrazed stretches than with grazed stretches.
4. This investigation has shown that high structural diversity of bankside vegetation along lowland chalk streams is accompanied at the reach scale by increased diversity of both aquatic macroinvertebrates and the terrestrial adult phases of aquatic insects. The conservation potential of such streams may thus be lowered by management practices that result in the removal or simplification of bankside vegetation along extensive stream stretches.     

Seasonal patterns in species richness of herbivores: Macrolepidopteran larvae on Finnish deciduous trees

Abstract. 1. The seasonal distribution of macrolepidopteran species richness on Finnish deciduous trees vaned from positively skewed (peak in spring) to negatively skewed (peak in autumn).
2. The skewness values of species richness had a significant negative correlation ( r = - 0.98) with the duration of the seasonal shoot-growth period of the tree species.
3. Trees which complete their shoot growth early in the season ( Quercus type) produce new leaves only during spring, while trees whose shoot growth continues to autumn ( Populus type) do so throughout the summer.
4. Consequently, there is a difference in the number of available resources in the late summer foliage of different tree species, Trees ceasing leaf production early such as oak ( Quercus robur ) and bird cherry ( Prunus padus ) have one major resource type (mature leaves) in late-season foliage while trees like birches and alders have two Ooung and mature leaves).
5. Because young leaves formed late in the season are preferred to mature ones by some species of herbivores and because other species prefer mature leaves at the same time, the species richness of Populus-type trees is higher later in the season than the species richness of Quercus-type of trees, which have just one type of resource available.     

遂渝铁路边坡草本植物多样性季节动态和空间分布特征

以遂渝铁路边坡植物群落为研究对象,自然边坡为对照,分别于2008年9月、12月、2009年3月和6月对其进行植物调查。采用Margalef指数、Simpson指数、Shannon-Wiener指数和Pielou指数等指标评价不同季节、坡位和植被类型条件下草本植物多样性的变化。结果表明：在时间尺度上,铁路边坡坡中物种丰富度呈现明显的季节性差异(P<0.05),以秋季最大为2376;铁路边坡各坡位草本植物多样性和均匀度指数也呈现显著季节性变化(P<0.05),且变化规律一致：春季>夏季>冬季>秋季;与铁路边坡不同,自然边坡草本植物丰富度、多样性和均匀度指数变化趋势不明显(P>0.05)。在空间分布上,坡位对铁路边坡物种丰富度影响显著(P<0.05),其中,夏季坡上植物丰富度最大为2.164,春季、秋季和冬季丰富度最大值均在坡中最大,分别为2.261、2.376和1.983;坡位仅对自然边坡秋季物种丰富度和均匀度影响显著(P<0.05),其中,物种丰富度表现为坡上>坡下>坡中,而均匀度为坡中>坡上>坡下。不同植被类型的物种丰富度、多样性和均匀度也有较大差异,自然边坡物种多样性明显大于铁路边坡,总体上自然边坡植被恢复优于铁路边坡。因此,加强对植被恢复的管理是铁路边坡生态恢复的重要环节。     

Seasonal population dynamics of Pallisentis (Neosentis) celatus (Acanthocephala: Quadrigyridae) in the intestine of the rice-field eel Monopterus albus in China

Studies on the seasonal population dynamics of Pallisentis (Neosentis) celatus (Acanthocephala: Quadrigyridae) in the intestine of the rice-field eel Monopterus albus from the paddies and ditches in the Dong-ting Lake basin of China, were carried out with samples taken from June 2002 to May 2003. Prevalences were above 21% in all seasons sampled and with a distinct seasonal trend, which was highest (45.81%) in the spring and decreased by degrees. The mean intensity of infection was above 4.0 worms per fish. The maximum intensity of worms recovered from a single fish was 86 in the autumn of 2002. No significant seasonal differences were found in mean intensities, and differences in the mean abundance between winter and spring, winter and autumn were significant. Over-dispersed distributions of P. (N.) celatus in the host population, due to heterogeneity and feeding habits, were observed in all seasons. The size composition of both sexes of P. (N.) celatus showed males between 2.0 mm and 14.0 mm and females between 2.2 mm and 22.2 mm, with the main recruitment phase in the worm populations occurring in the summer and autumn, especially in the autumn, with the lowest recruitment occurring in the winter. The maturation and copulation of worms were mainly focused in the spring season. The sex ratio of female to male was both high in summer (1.09:1) and autumn (1.08:1). The higher proportion of females and the change in the worm sex ratio in summer can be attributed to the reduced longevity of male worms. As immature male worms exhibit a higher proportion of the worm population than females in all seasons, further studies are needed to determine if such a situation compensates for the shorter life span of males.     

梁子湖浮游甲壳动物的生物多样性

基于2006年8月至2008年3月对梁子湖浮游甲壳动物的采样调查,记录了该湖区浮游甲壳动物22种,隶属9科18属,其中枝角类(Cladocera)16种,桡足类(Copepoda)6种,包括9属新记录.物种多样性季节性动态变化明显:枝角类优势种在春、夏和秋冬季依次为透明溞(Daphnia hyalina,优势度Y = 0.80±0.01),小栉溞(Daphnia cristata,Y = 0.50±0.03)和长额象鼻溞(Bosmina longirostris,Y = 0.58±0.04);而桡足类优势种在夏、秋和冬春季依次为长江新镖水蚤(Neodiaptomus yangtsekiangensis,Y = 0.41±0.01)、近邻剑水蚤(Cyclops vicinus,Y = 0.46)和特异荡镖水蚤(Neutrodiaptomus incongruens,Y = 0.65±0.18).浮游甲壳类个体密度以春季最高((292±85) ind/L),夏、秋、冬季渐低(依次为(169±104)、(140±53)、(120±0) ind/L).物种多样性冬春季较低(物种数S≤12,丰富度指数D = 0.77和0.71,香农-威纳指数H = 1.79和1.45),夏秋季较高(S≥17,D = 0.98和0.88,H = 1.78和1.83).梁子湖浮游甲壳类动物多样性年际差异不显著,表明湖区环境条件较为优越、稳定.     

Grasshopper response to a 40-year experimental burning and mowing regime, with recommendations for invertebrate conservation management

Grasshopper assemblages were sampled in 44 plots in each of three adjacent sites in a 40-year-old southern tall grassland experimental area in South Africa. Specific plots received particular mowing and/or burning treatments over the 40-year period. Grasshopper responses to vegetation type, and to different burning and mowing practices, were site-specific, despite the close proximity of sites. This suggests that grasshopper assemblage composition is not entirely deterministic and depends on the trajectory of plant succession. Grasshopper species richness and abundance decreased from annually to triennially burnt plots, and increased in plots mown once per year to plots mown three times per year. Burning in the first week of August (winter) was more favourable for grasshopper assemblages than burning in autumn or after the first spring rains. Mean grasshopper species richness was highest in plots mown after the first spring rains, and the mean number of individuals was highest i n plots mown early in summer. When annually burnt plots were compared with annually mown plots, grasshopper abundance and species richness were highest in the burnt plots. A rotational winter burning programme, which is practical under African conditions, is recommended for the conservation of grasshoppers and other invertebrates.     

Phosphorus inactivation in a eutrophic lake by the direct addition of ferric aluminium sulphate changes in phytoplankton populations

SUMMARY. 1. Reduced total phosphorus concentrations in the summer which followed the addition of iron aluminium sulphate to White Lough failed to reduce significantly the phytoplankton. which continued to be dominated by Oscitlatoria agardhii var. isothrix Skuja.
This species was present throughout the 4 years studied, forming over 50% of the algal volume in 80% of samples. In contrast, species which occurred principally in the summer months were found to be severely curtailed when sediment release of phosphorus was suppressed.
2. The phosphorus: carotenoid ratio was used to assess the extent of phosphorus limitation because laboratory studies on O. agardhii var. isothrix showed that this ratio was a much beter indicator of cell phosphorus content than the phosphorus: chlorophyll a ratio. Reduced summer phosphorus concentrations in White Lough caused a transition from intermittent to continuous phosphorus limitation rather than a proportional reduction in the summer phytoplankton.
3. Reduced autumn grazing pressure by Daphnia hyatina Leydig allowed large algal populations to develop in the winters following phosphorus reduction despite a 50% decline in total phosphorus. The combination of increased winter phytoplankton and lower total phosphorus reduced soluble reactive phosphorus concentrations to less than 5,μg P l⁻¹ which in turn curtailed the spring diatom pulse.     

Sexual size dimorphism, sex ratio and the relationship between seasonality and water quality in four species of Gordiida (Nematomorpha) from Catamarca, Argentina

A total of 687 adult nematomorphs of four species of Gordiida: Chordodes brasiliensis (393 specimens), Noteochorododes cymatium (47 specimens), N. talensis (162 specimens) and Pseudochordodes dugesi (85 specimens) were collected during a period of 1 year from El Simbolar stream, Argentina. Free-living worms were abundant during autumn and spring, but their number decreased during winter and summer. Males were shorter and significantly more abundant than females. The presence of N. cymatium, N. talensis and P. dugesi was correlated with water temperature and these species were most abundant in winter and spring. The presence of C. brasiliensis was correlated with flow rate and pH; this species was more abundant in autumn and winter. These four species are sympatric.     

生境片段化对千岛湖地表甲虫物种多样性的影响

在千岛湖片段化景观中选取20个陆桥岛屿和8个大陆样点,从2012年7月到2014年4月,按季度(春、夏、秋季)6次采用巴氏陷阱法收集地表甲虫,分析其物种多度、组成、多样性和季节动态,以及不同岛屿上的地表甲虫的物种多样性与岛屿面积和隔离度等岛屿空间特征的关系.结果表明: 共收集记录到地表甲虫26科101种3370头.大陆和大岛地表甲虫的物种丰富度有显著差异,且小岛地表甲虫密度显著高于大陆;大陆地表甲虫的物种组成变化较大,而岛屿上分布的地表甲虫的物种组成则变化较小.地表甲虫的物种丰富度与岛屿面积呈显著正相关,密度与隔离度呈显著正相关.夏季岛屿上地表甲虫物种丰富度高于春秋两季,岛屿与大陆样地的Shannon指数、Simpson指数和Pielou均匀度指数均在夏季最高、秋季最低.     

Seasonal Abundances of Naked Amoebae in Biofilms on Shells of Zebra Mussels (Dreissena polymorpha) with Comparative Data from Rock Scrapings

ABSTRACT. In North America, zebra mussels ( Dreissena polymorpha ) are notoriously known as invasive species. The abundance of naked amoebae sampled from the shells of zebra mussels was compared with abundances from rock scrapings at approximately monthly intervals for 1 year. The sites were 2 km apart along the same shoreline. No significant difference in abundance of naked amoebae ( F =1.44; P ≤0.270) was detected for the two sampling sites. The combined data showed a minimum density of naked amoebae in winter, followed by peaks in early spring. The percent encysted increased from a low of 1% in the summer to 80% in early winter.     

Feeding ecology of rooks (Corvus frugilegus) on the Heretaunga Plains,Hawke's Bay,New Zealand

Abstract

The food resources of rooks were measured and related to changes in the birds' feeding behaviour during 1968-1970. In all, 381 birds were individually marked with wing tags and colour-coded leg bands and released; their activities were recorded for set periods. Rooks preferred to eat invertebrates and walnuts, but also took seed of cereals, pulses, and stock feeds. They spent at least 40% of their feeding time (75-80% in spring) eating invertebrates, 30-60% finding or hiding walnuts and sometimes acorns in autumn and winter, and 45% eating seed during hot, dry weather in summer. Up to 6% of feeding time was spent eating newly sown or ripening seed. Throughout winter rooks frequently searched for hidden nuts, which they ate or moved to new positions. The proportion of time they spent feeding and the kind of food taken varied seasonally and, in summer and winter, hourly; there were only slight differences between morning, mid-day, and afternoon periods. Rooks spent 65% of the time feeding in autumn, but only 25-30% in spring. Conversely, they spent longer at nest sites from late autumn, peaking at 60% in spring, then less time at nests as they spent longer searching for food. The size of flocks altered with the food being eaten and therefore with season and time of day. Small flocks were widespread where favoured food was plentiful in autumn, winter, and spring, but flocks were larger where food was unevenly abundant in summer and sometimes in winter. During early autumn each bird usually ate and stored walnuts in a selected area of 1-2 km3, returning there later in the season to recover stored nuts. The areas formed only part of the total range used by the study population, and were usually shared with other birds. Tests in aviaries showed that rooks preferred earthworms and walnuts to acorns, maize, and wheat (in that order), and field tests confirmed that rooks preferred walnuts to maize. The numbers of each food item required to sustain a rook for a daylight hour were estimated. Summer is the most difficult season for rooks to find food.     

Food habits and habitat selection of suburban badgers (Meles meles) in Japan

A study of the Japanese badger Meles meles anakuma was undertaken in Hinode, a suburb of Tokyo, between 1992 and 1998. Faecal analysis, based on 82 samples, revealed that during spring and summer, earthworms ( Megaseolocidae spp.) occurred at high frequency in the diet, with berries ( Rubus spp.), beetles and persimmon Dymopyrus kaki also eaten during summer months. Scavenged food was eaten in early spring when earthworm availability was low, and badgers switched from worms when persimmon became abundant in autumn. Twenty-one Japanese badgers (14 males and seven females) were radio-tracked. Adult badger home ranges were stable, and those of males [40±19 ( sd ) ha, n =7] were larger than those of females [11±6 ( sd ) ha, n =4]. Badger resting sites in each home range were located within 630 m of each other and categorized as setts or couches. Setts were sited within core areas (30% adaptive kernel method) of home ranges. Most setts were on a sub-ridge and avoided west-facing slopes. Couches, mainly in deciduous forest and forest edge, were generally sited towards the periphery of home ranges. Most badger foods were distributed along ecotones between forestry plantations and farmland; earthworms, their main food from late spring to summer, and berry thickets were both concentrated at the edge of conifer plantations. Persimmon trees, the main food source for badgers in autumn, were also found in agricultural land bordering forest edge. Badger home range size was related to forest edge density.     

珠江口及邻近海域大型底栖动物多样性随盐度、水深的变化趋势

利用2006年7-8月(夏季)、2007年4-5月(春季)和2007年10-12月(秋季)珠江丰水期、平水期和枯水期3个航次在南中国海北部珠江口附近海域4条由河口、近岸到深水区调查断面的数据, 研究大型底栖动物多样性由河口-近岸-深水的变化趋势及与环境因子的关系。春季、夏季和秋季分别获得大型底栖动物273、256和148种, 各季节均以环节动物种类最多, 节肢动物次之。大型底栖动物种类数、丰度、生物量和Shannon-Wiener多样性指数均由河口向近岸海域升高, 再由近岸向外海深水区降低。Pielou均匀度深水区最高, 其次为近岸。河口和深水区大型底栖动物k-优势度曲线位于近岸浅水域曲线之上, 表明生物多样性由河口向近岸升高, 而由近岸向深水则降低。大型底栖动物与环境因子Pearson相关性分析表明, 春、秋季大型底栖动物种类数、丰度和生物量与水深呈显著的负相关, 秋季种类多样性指数和均匀度也与水深呈显著的负相关性, 而夏季仅生物量与水深呈显著的负相关; 春、秋季大型底栖动物种类数、生物量、丰度、多样性指数和种类均匀度与盐度的相关性不显著, 但是夏季大型底栖动物种类数、丰度、多样性指数和种类均匀度与盐度呈显著正相关。单位面积(0.2 m²)内, 珠江口及邻近海域大型底栖动物在近岸浅水区较深水区和河口生物多样性高, 且生物量丰富。     

Effect of burning and mowing on grass and forb diversity in a long‐term grassland experiment

Abstract. Disturbance may be an important determinant of plant community composition and diversity owing to its effects on competitive interactions, resources, dominance and vigour. The effect of type, timing and frequency of disturbance on grass and forb species richness was examined using data from a long‐term (> 50 yr) grassland burning and mowing experiment in KwaZulu‐Natal, South Africa. Grass species richness declined considerably (> 50%) in the absence of disturbance, whereas forb species richness was unaffected. Annual burning in sites not mown in summer tended to increase grass species richness relative to triennial burning (22% increase) with the reverse being true in sites mown twice in summer (37% decline). Forb species richness declined by 25% in sites mown twice in summer relative to sites mown in early summer only. Disturbance was necessary to achieve maximum grass species richness presumably by removing litter and increasing the availability of light. The interaction of time of mowing in summer (early versus late) and time of burning during the dormant period (spring versus winter) had the most dramatic effect on species richness. Time of burning had no effect on richness in sites mown in early summer, but winter burning resulted in a dramatic decline (27–42%) in richness in sites mown in late summer. This effect may be related to possible greater soil desiccation with this combination of disturbances.     

Landscape level processes driving carabid crop assemblage in dynamic farmlands

Landscape heterogeneity has been shown to be a major factor in the maintenance of biodiversity and associated services in agricultural landscapes. Farmlands are mosaics of fields with various crop types and farming practices. Crop phenology creates asynchrony between fields sown and harvested in different periods (winter vs. spring crops). The present study was conducted to examine the influence of such spatio-temporal heterogeneity on biodiversity, with the hypothesis that it would lead to spatio-temporal redistribution (shifting) of species. Species richness and activity-density of carabid beetles in winter cereal (winter) and maize (spring) crops were compared across 20 landscapes distributed along a double gradient of relative area and spatial configuration of winter and spring crops. Maize fields were sampled in spring and late summer for comparison over time. The response of carabid species richness to landscape heterogeneity was weak in spring, but maize field richness benefited from adjacencies with woody habitat, in late summer. In spring, increased length of interfaces between winter and spring crops lowered carabid activity-density in winter cereal fields, suggesting that maize fields acted as sinks. Interfaces between woody habitats and crops increased activity-density in both crop types. We found no evidence of spatio-temporal complementation, but different species benefited from winter cereals and maize in spring and late summer, increasing overall diversity. These findings confirm the role of adjacencies between woody and cultivated habitats in the conservation of abundant carabid assemblage in winter cereals and maize. We conclude that between-field population movement occurs, and advocate for better consideration of farmland heterogeneity in future research.     

Seasonal dynamics of Proteocephalus sagittus in the stone loach Barbatula barbatula from the Hana River, Czech Republic

The seasonal cycle of the cestode Proteocephalus sagittus (Cestoda: Proteocephalidae) was studied for the first time in the stone loach Barbatula barbatula from the Hana River, Czech Republic. A total of 180 loaches were examined monthly from January to December 2001. The parasite occurred in loaches throughout the year but infection parameters differed significantly among seasons, with the highest values of prevalence and abundance from the late winter to the early summer. Parasite recruitment took place in the winter and early spring and the worms sexually matured in the late spring and early summer. In contrast to P. torulosus, the gravid worms of which laid eggs only at the end of the spring/beginning of the summer, gravid worms of P. sagittus were also found, although in low numbers, in the autumn and early winter. The rate of infection of loach with P. sagittus was neither dependent on the sex nor on the size of its fish host.     

The variability in the catches of charr, Salvelinus alpinus L., and perch, Perca fluviatilis L., from multi-mesh gill nets

Multi-mesh gill nets set at Rawlinson's Nab in the south basin of Windermere for 24 months from 1979 to 1981 caught predominantly charr and perch. Nets set parallel to the shore caught significantly fewer fish than those set perpendicular to the shore. Variability in the mean catches of perch increased from winter to summer when the size of the catches also increased. Charr were mostly caught from November until February. Estimates of variance associated with the geometric mean catch of a single net (set perpendicular to the shore) were calculated for the periods winter for the charr and winter, summer, spring and autumn for the perch. These variances were used to calculate 95 and 99% C.L. of the geometric mean. For limits to be below half or twice the geometric mean, 12 nets would have to be used for charr during winter. For perch the number of nets needed would be six in winter, 20 in spring and autumn and 40 in summer. It is concluded that the nets are of little value in assessing changes in stock abundance.