Comparison of pitfall traps and litter bags for sampling ground-dwelling arthropods

Abstract:  For their simplicity and effectiveness, pitfall traps have become a standard technique to measure the activity and relative abundance of ground-dwelling arthropods. Permeable screen or mesh bags filled with plant material, referred to as litter bags, have also recently been employed as a complementary sampling technique for epigeal taxa. The anticipated need for increased field research on arthropod populations, particularly in transgenic crops with insecticidal properties, suggests that a relative assessment of both sampling methods could contribute to the design of future studies. Comparisons among pitfall traps, and litter bags placed above- or below-ground indicated that above-ground litter bags most frequently succeeded in collecting certain groups of arthropods associated with moisture and sheltered areas, including centipedes (Chilopoda) and beetle larvae (Carabidae, Staphylinidae). Conversely, pitfall traps most often captured taxa considered active at ground level, such as adult carabids or harvestmen (Opiliones). For taxa collected in >40% of all three trap types, bootstrap confidence intervals for the coefficient of variation (CV; used to assess precision or sampling efficiency) showed that above-ground litter bags were significantly more precise than pitfall traps for sampling elongate springtails (Collembola) and adult rove beetles (Staphylinidae), but only during the first year of sampling. While below-ground litter bags often appeared similar to one or both of the other trap types, in no case were below-ground litter bags best based on frequency of collection or CV. Though differences were not always consistent between years, results suggest that the additional effort required to sample using litter bags may be justified for the collection of some ground-dwelling taxa.     

Reproducibility and variation of morphometric analysis of carcinoembryonic antigen staining in histopathology. The influence of standardized microscopic fields

Using morphometric methods, five pathologists analyzed the positive staining for carcinoembryonic antigen (CEA) in sections from 17 ovarian tumors, with the intraclass correlation coefficient (ICC) and the mean values of the coefficients of variation (CV) used to assess reproducibility and variation. First, field and point scores for epithelium and mucin were estimated using 25 randomly selected square fields in sections from each of the tumors. The ICC range in the whole sample field was 0.53 to 0.81 (slight to substantial reproducibility) while the mean values of CV were 0.50 to 0.75. Second, the results of using random and standardized individual fields for the measurements were studied in three tumors. In random fields, the ICC was 0.57 to 0.71 (slight to moderate reproducibility) and the mean values of CV were 0.53 to 0.65. The corresponding values in standardized fields were 0.71 to 0.73 (moderate reproducibility) and 0.41 to 0.57, respectively. The results show that the variation is smaller and the degree of reproducibility higher in standardized fields. Considerable variation remains, however, revealing human factors as an important source of variation in practical morphometry.     

云南芒果种质基因组大小测定与变异分析

为了解云南芒果(Mangifera indica L.)种质资源的基因组的变异情况, 采用流式细胞术对35 份云南芒果种质资源的基因组大小进行了测定和变异分析。结果表明, 云南芒果种质资源的基因组大小存在一定差异, 基因组的平均C值是0.445110 pg, 0.4353177×10⁹ bp, 最小的是采自景洪的半栽培种YSM-44 (0.434567 pg, 0.4250060×10⁹ bp), 最大的是采自红河的野生种YSM-25 (0.458679 pg, 0.4485881×10⁹ bp)。基因组C值变异程度最大的是野生种(CV=1.65%), 其次为半野生种(CV=1.26%)、半栽培种(CV=1.21%)和栽培种(CV=0.11%)。与芒果具有相近基因组大小的多为苔藓植物, 与"C值悖论"观点相一致。因此, 应用流式细胞术能准确、快捷地测定芒果基因组大小, 而且云南野生、半野生及半栽培芒果种质资源遗传变异类型丰富, 有较大的挖掘利用潜力。     

Effects of Land Crabs on Leaf Litter Distributions and Accumulations in a Mainland Tropical Rain Forest1

The effect of the fossorial land crab Gecarcinus quadratus (Gecarcinidae) on patterns of accumulation and distribution of leaf litter was studied for two years in the coastal primary forests of Costa Rica's Corcovado National Park. Within this mainland forest, G, quadratus achieve densities up to 6 crabs/m² in populations extending along the Park's Pacific coastline and inland for ca 600 m. Crabs selectively forage for fallen leaf litter and relocate what they collect to burrow chambers that extend from 15 to 150 cm deep (N= 44), averaging (±SE) 48.9 ± 3.0 cm. Preference trials suggested that leaf choice by crabs may be species‐specific. Excavated crab burrows revealed maximum leaf collections of 11.75 g dry mass– 2.5 times more leaf litter than collected by square‐meter leaf fall traps over several seven‐day sampling periods. Additionally, experimental crab exclosures (25 m²) were established using a repeated measures randomized block design to test for changes in leaf litter as a function of reduced crab density. Exclosures accumulated significantly more (5.6 ± 3.9 times) leaf litter than did control treatments during the wet, but not the dry, seasons over this two‐year study. Such extensive litter relocation by land crabs may affect profiles of soil organic carbon, rooting, and seedling distributions.     

Litter production in an Avicennia Gerrninans (L.) stearn forest in Guyana, South America

Litter production of A. germinans was determined during a twelve month period (July, 1994 to June, 1995). Litter traps of 25 cm by 25 cm, with a 1.0 mm mesh size, were suspended above high tide level. Collection of litter was done every two weeks. The litter was dried at 103°C to constant weight and separated into leaves, flowers, fruits and woody parts. Total litter biomass was 1771 (SD 66.7) g m^–2y^–1, with leaf litter constituting 61.41% of the total. Fruits contributed 24.84%, flowers (8.88%) and woody parts (4.87%). Leaf litter production showed two peaks (a major one in August, 1994 and a minor one in February, 1995). High flower litter production was observed in October and November, 1994, while peak fruit litter was produced in January, 1995. The production of woody parts was spread between November, 1994 and March, 1995 with a slight peak in February, 1995. Great variation was observed in the production of the plant organs within and between sampling stations. It seems litter production is influenced by the inflowing rivers which drain the Amazon Basin, rather than by rainfall in the area.     

The variability of mating signals and preferences in the brown planthopper,Nilaparvata lugens (Homoptera: Delphacidae)

Male and female brown planthoppers, Nilaparvata lugens(Stål) (Homoptera: Delphacidae), exchange substrate-transmitted signals prior to mating. The pulse repetition frequency of the male song is known to be involved in mate recognition and also to vary among geographical populations. Here the variability of male signals, female signals, and female preferences has been examined within a population. Female preference variation has been partitioned into variation in mean preference and variation in the window of preference of individuals. The genetic component of variation has been examined using isofemale lines. Male signal variation was limited (CV=8%) and was mainly within individuals. Female signal variation was greater (CV=15%). Female mean preference varied little (CV=10%) and was closely matched to the male signal mean, but the preference window was wide (> 4 male signal standard deviations on average) and variable (CV=56%). There was evidence for genetic variation only for preference window. These results are discussed in relation to theories of signal system evolution.     

造林密度对米老排凋落物量及动态的影响

在2015年10月~2016年9月,采用90个凋落物收集器,研究不同造林密度对米老排人工林凋落物总量、组分及动态特征的影响。结果表明：年凋落物总量及各组分的产量与造林密度呈线性相关。随着造林密度的增加,林分的年凋落物总量、叶、花果和杂物的年凋落物量均呈现降低的趋势,而枝条的年凋落物量呈增加的趋势。不同造林密度米老排人工林的年凋落物量为6.52~8.17 t·hm^-2·a^-1,其中叶为主要组分,占总量的86.2%~87.85%,枝条占0.35%~5.43%,花果占0.46%~4.67%,杂物占6.69%~8.89%。不同造林密度叶凋落物量的月动态变化均呈单峰型,最大值出现在9月,最小值在3~4月。枝条凋落物量的月动态变化呈不规则型,花果和杂物凋落物量均呈双峰型,花果的凋落主要集中在5和10月,而杂物的凋落量高峰在6和9月。凋落物总量与叶凋落物量的月动态变化基本相似,但在6月杂物凋落物量的影响下,有些密度的林分也会呈双峰型。当林分完全郁闭后,随着造林密度的增加,林分枝下高的增加,胸径、树冠比以及冠幅的减小,可能会导致凋落物总量、叶、花果及杂物凋落物量的下降,而枝条的凋落物量增加。     

Determination of protein and amino acid requirements of lactating sows using a population-based factorial approach

Determination of appropriate nutritional requirements is essential to optimize the productivity and longevity of lactating sows. The current recommendations for requirements do not consider the large variation between animals. Therefore, the aim of this study was to determine the amino acid recommendations for lactating sows using a stochastic modeling approach that integrates population variation and uncertainty of key parameters into establishing nutritional recommendations for lactating sows. The requirement for individual sows was calculated using a factorial approach by adding the requirement for maintenance and milk. The energy balance of the sows was either negative or zero depending on feed intake being a limiting factor. Some parameters in the model were sow-specific and others were population-specific, depending on state of knowledge. Each simulation was for 1000 sows repeated 100 times using Monte Carlo simulation techniques. BW, back fat thickness of the sow, litter size (LS), average litter gain (LG), dietary energy density and feed intake were inputs to the model. The model was tested using results from the literature, and the values were all within ±1 s.d. of the estimated requirements. Simulations were made for a group of low- (LS=10 (s.d.=1), LG=2 kg/day (s.d.=0.6)), medium- (LS=12 (s.d.=1), LG=2.5 kg/day (s.d.=0.6)) and high-producing (LS=14 (s.d.=1), LG=3.5 kg/day (s.d.=0.6)) sows, where the average requirement was the result. In another simulation, the requirements were estimated for each week of lactation. The results were given as the median and s.d. The average daily standardized ileal digestible (SID) protein and lysine requirements for low-, medium- and high-producing sows were 623 (CV=2.5%) and 45.1 (CV=4.8%); 765 (CV=4.9%) and 54.7 (CV=7.0%); and 996 (CV=8.5%) and 70.8 g/day (CV=9.6%), respectively. The SID protein and lysine requirements were lowest at week 1, intermediate at week 2 and 4 and the highest at week 3 of lactation. The model is a valuable tool to develop new feeding strategies by taking into account the variable requirement between groups of sows and changes during lactation. The inclusion of between-sow variation gives information on safety margins when developing new dietary recommendations of amino acids and protein for lactating sows.     

Biogeochemical cycles in natural forest and conifer plantations in the high mountains of Colombia

Plant litter production and decomposition are two important processes in forest ecosystems, since they provide the main organic matter input to soil and regulate nutrient cycling. With the aim to study these processes, litterfall, standing litter and nutrient return were studied for three years in an oak forest (Quercus humboldtii), pine (Pinus patula) and cypress (Cupressus lusitanica) plantations, located in highlands of the Central Cordillera of Colombia. Evaluation methods included: fine litter collection at fortnightly intervals using litter traps; the litter layer samples at the end of each sampling year and chemical analyses of both litterfall and standing litter. Fine litter fall observed was similar in oak forest (7.5 Mg ha/y) and in pine (7.8 Mg ha/y), but very low in cypress (3.5 Mg ha/y). Litter standing was 1.76, 1.73 and 1.3 Mg ha/y in oak, pine and cypress, respectively. The mean residence time of the standing litter was of 3.3 years for cypress, 2.1 years for pine and 1.8 years for oak forests. In contrast, the total amount of retained elements (N, P, S, Ca, Mg, K, Cu, Fe, Mn and Zn) in the standing litter was higher in pine (115 kg/ha), followed by oak (78 kg/ha) and cypress (24 kg/ha). Oak forests showed the lowest mean residence time of nutrients and the highest nutrients return to the soil as a consequence of a faster decomposition. Thus, a higher nutrient supply to soils from oaks than from tree plantations, seems to be an ecological advantage for recovering and maintaining the main ecosystem functioning features, which needs to be taken into account in restoration programs in this highly degraded Andean mountains.     

Why are antlion larvae rare under the leaf litter? Testing the hypothesis of improper trap maintenance¿Por qué las larvas del león de las hormigas son tan raras bajo la hojarasca? Probando la hipótesis del mantenimiento inadecuado de las trampas

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中国森林生态系统凋落叶分解速率的分布特征及其控制因子

凋落物分解是森林生态系统碳循环的重要组成部分。建立中国森林凋落叶分解速率数据库, 分析凋落叶分解速率与其主要影响因素之间的关系, 对精确地预测中国森林生态系统碳收支具有重要意义。该研究通过收集已报道的中国森林凋落叶分解常数(k)及其相关变量, 分析探讨地理因素(纬度、经度和海拔)、气候因素(年平均气温和年降水量)、凋落叶质量(氮、磷、钾、木质素、木质素:氮和碳氮比)和叶特性(常绿与落叶、阔叶与针叶)对中国森林凋落叶分解速率的影响。结果表明, 在国家尺度上, k随年平均气温、年降水量、氮、磷和钾的增加而增加, 随纬度、经度、海拔、碳氮比、木质素和木质素:氮的增大而减小, 叶特性对k的影响不显著。气候与地理因素(年平均气温、年降水量和纬度)能解释k值变异的34.1%, 凋落叶质量(氮、钾、木质素和木质素:氮)能解释k值变异的21.7%, 它们能共同解释k值变异的74.4%。了解森林凋落叶分解速率在国家尺度上的格局和主控因素可为中国森林生态系统碳循环相关模型提供基础参数。     

Supplementation of dextrose to the diet during the weaning to estrus interval affects subsequent variation in within-litter piglet birth weight

Effects of supplementation of dextrose to the diet of sows during the weaning-to-estrus interval (WEI) on subsequent litter size and within-litter variation were investigated. After weaning, 223 sows (first to fifth parity) were fed 3.5 kg/d. Half of the sows additionally received 150 g of dextrose per day as topdressing on the feed. WEI and estrus duration were determined as well as subsequent pregnancy rate and litter size. Piglets were weighed individually at birth and at weaning (day 26.4; S.D.: 2.5). Supplementation of dextrose to the diet during the WEI did not affect WEI (106 h), pregnancy rate (88.2%), farrowing rate (84.2%), subsequent litter size (total born: 13.70), or birth weight (1599 g). The within-litter variation in birth weight was lower in sows on the dextrose treatment (CV: 17.5% versus 21.2% for the dextrose and control group, respectively, P=0.03). From this experiment, we concluded that addition of dextrose during the weaning to estrus interval did not increase litter size, but seems to affect the uniformity in birth weight of the litter.     

Spatial characteristics in decomposition rate of foliar litter and controlling factors in Chinese forest ecosystems

凋落物分解是森林生态系统碳循环的重要组成部分。建立中国森林凋落叶分解速率数据库, 分析凋落叶分解速率与其主要影响因素之间的关系, 对精确地预测中国森林生态系统碳收支具有重要意义。该研究通过收集已报道的中国森林凋落叶分解常数(k)及其相关变量, 分析探讨地理因素(纬度、经度和海拔)、气候因素(年平均气温和年降水量)、凋落叶质量(氮、磷、钾、木质素、木质素:氮和碳氮比)和叶特性(常绿与落叶、阔叶与针叶)对中国森林凋落叶分解速率的影响。结果表明, 在国家尺度上, k随年平均气温、年降水量、氮、磷和钾的增加而增加, 随纬度、经度、海拔、碳氮比、木质素和木质素:氮的增大而减小, 叶特性对k的影响不显著。气候与地理因素(年平均气温、年降水量和纬度)能解释k值变异的34.1%, 凋落叶质量(氮、钾、木质素和木质素:氮)能解释k值变异的21.7%, 它们能共同解释k值变异的74.4%。了解森林凋落叶分解速率在国家尺度上的格局和主控因素可为中国森林生态系统碳循环相关模型提供基础参数。     

Evaluation of surveillance methods for monitoring house fly abundance and activity on large commercial dairy operations

Relative house fly, Musca domestica L., activity at three large dairies in central California was monitored during the peak fly activity period from June to August 2005 by using spot cards, fly tapes, bait traps, and Alsynite traps. Counts for all monitoring methods were significantly related at two of three dairies; with spot card counts significantly related to fly tape counts recorded the same week, and both spot card counts and fly tape counts significantly related to bait trap counts 1-2 wk later. Mean fly counts differed significantly between dairies, but a significant interaction between dairies sampled and monitoring methods used demonstrates that between-dairy comparisons are unwise. Estimate precision was determined by the coefficient of variability (CV) (or SE/mean). Using a CV = 0.15 as a desired level of estimate precision and assuming an integrate pest management (IPM) action threshold near the peak house fly activity measured by each monitoring method, house fly monitoring at a large dairy would require 12 spot cards placed in midafternoon shaded fly resting sites near cattle or seven bait traps placed in open areas near cattle. Software (FlySpotter; http://ucanr.org/ sites/FlySpotter/download/) using computer vision technology was developed to count fly spots on a scanned image of a spot card to dramatically reduce time invested in monitoring house flies. Counts provided by the FlySpotter software were highly correlated to visual counts. The use of spot cards for monitoring house flies is recommended for dairy IPM programs.     

Objective analysis of stallion sperm motility

An image-analysis system utilizing a microcomputer and CellSoft computer-assisted semen analysis software package was evaluated to assess stallion sperm motility characteristics. Analyses were performed at 37°C on a 6 μl drop of diluted semen placed on a glass slide and covered with an 18 mm² coverslip. Four groups of 25 cells each per slide, four slides per ejaculate and four ejaculates from each of three stallions were analyzed in a nested model. The percentage of motile sperm cells, mean velocity (μm/sec), mean linearity, and mean angular head displacement (μm) were measured. Statistical analysis of variance components showed that within ejaculates, more variation was accounted for in the differences among groups of 25 cells than among slides. Predicted standard deviations calculated for combinations of slides and groups of cells showed that a combination of two slides from which a total of 400 cells were analyzed resulted in a mean intra-assay coefficient of variation (CV) of 5.7% for the four measured variables. The following are individual coefficients of variation: percentage of motile cells (7.8%), mean velocity (6.4%), mean linearity (1.9%) and mean angular head displacement (6.6%). When ejaculate differences were included in the model and predicted standard deviations were calculated for a single ejaculate, the mean inter-assay CV was 9.2%. Mean velocity (6.4%) and mean linearity (4.7%) were more repeatable among ejaculates than either the percentage of motile sperm (14.4%) or angular head displacement (11.2%). It was concluded that this system is precise enough to determine differences in motility characteristics of stallion semen samples.     

广西英罗湾红海榄群落凋落物研究

本文主要研究广西合浦山口英罗湾红树林保护区红海榄群落的凋落物,结果表明:(1)红海榄群落1989年凋落物量为631.26 g/m~2,其中落叶561.50 g/m~2,说明落叶在红海榄群落物质归还中起着关键性作用。(2)年凋落物中各组分占总量的比例分别为叶88.95％、花3.68％、果(含胚轴)3.0％和枝4.26％。(3)月凋落物量(Y_1,g/m~2)与月平均气温(X_1,℃)呈线性正相关,其回归公式为Y_1=3.071 x_1-16.804(r=0.77,df=14),相关极显著;月凋落物量(Y_1)与月降水量(X_2,mm)的回归公式为Y_1=0.116 x_2+34.381(r=0.62,df=14),相关极显著。高温高湿季节的凋落物量明显高于低温干燥季节的凋落物量。     

Litter dynamics and its effects on the survival of <Emphasis Type="Italic">Castanopsis sieboldii</Emphasis> seedlings in a subtropical forest in southern Japan

Based on direct field measurement, this study quantitatively estimated the litter dynamics on the forest floor for a 1-year-period and then investigated its influence on the seedling dynamics of Castanopsis sieboldii, as well as interactions with adults in a subtropical forest in southern Japan. Litter dynamics is composed of three major components: falling litter, transport, and decomposition on the forest floor. Litterfall was measured by litter traps and did not exhibit clear spatial tendency. Lateral input was assessed by newly accumulated litter beneath the traps and showed no spatial variation, either. In contrast, lateral output of litter, which was quantified from disappearance of artificial litter, was correlated with local topography. Consequently, we found considerable spatial variations and seasonal changes in litter dynamics on the forest floor. In addition, we constructed survival models of C. sieboldii seedlings at the individual level. The lateral movement of accumulated litter had an influence on the survival of seedlings, which mostly occurred in periods of typhoons with heavy rain. Meanwhile, the distance from canopy trees, which is assumed to be a spacing mechanism due to seedling/adult interactions, played a lesser role in this subtropical forest. Our results suggest that the stability of accumulated litter on the forest floor was a predominant factor in the spatial dynamics of the early life stage of C. sieboldii.     

Dispersion theory and the sterile insect technique: application to two species of fruit fly

Dispersion theory is applied to the distribution of two kinds of sterile insect, Mediterranean fruit fly (Medfly), Ceratitis capitata (Wiedemann), and Queensland fruit fly (Qfly), Bactrocera tryoni (Froggatt) (Diptera: Tephritidae). Dispersion theories are an essential basis of sampling theory and sampling plans, but this paper looks at them from another direction and uses data from arrays of sterile insect technique (SIT) monitoring traps to compare the utility of different measures such as coefficient of variation (CV), the exponent b of Taylor's power law, and exponent k of the negative binomial distribution and also derives predictions pertaining to the density (and hence release rate) of sterile insects that would be required to achieve effective coverage of the target area. This is far more useful than reliance on just the mean values of trap catches because such reliance takes no account of the fact that sterile flies distribute themselves unevenly with many patches inadequately covered despite the impression given by the mean. Data were used from recapture rates following either ‘roving releases’ of Medfly or releases from fixed points of Qfly. The relation of recapture rate to CV indicated that a doubling of release rate in order to double average recapture rate from 150 per trap per week to a value of 300 would have very little effect in terms of reducing CV and that there appears to be no practical prospect of reducing CV to below unity with the current methods of release without incurring a manifold increase in cost. Similarly, models derived from the negative binomial equation indicated that a law of diminishing returns applies in terms of the increase in the amount of adequate coverage (such as the percentage of traps catching >50 flies per week) that can be obtained by increasing release rates.     

Density dependence constrains mean growth rate while enhancing individual size variation in stream salmonids

The objective of this study was to elucidate the effects of density dependence on the individual size variation of brown trout (Salmo trutta) juveniles. Recruitment (the abundance of the youngest juveniles in May when they were 2 months old); the mean size attained by those individuals in September (6 months old) and the corresponding size variability around the mean size quantified with the coefficient of variation (CV) were examined in 22 year-classes at seven sites of two contrasting tributaries of the Rio Esva drainage (north-western Spain). Both mean size and CV tended to be site-specific but density dependence in the form of recruitment dependence affected both mean size and CV: the mean size depicted negative power relationships with increased recruitment whereas the CV increased positively with increased recruitment. However, this pattern differed among sites. At two out of seven sites, there was no obvious relationship between the mean size and recruitment. The CV increased positively with increased recruitment at all sites, although at several sites the CV described linear relationships and at others described power relationships. As a consequence, the stronger effects of density dependence on mean size occurred at low densities with minor effects at high densities, whereas density dependence operated on CV with continuous effects within the whole range of recruitment variation except at several sites where lower effects occurred at high densities. Thus, the occurrence, shape and intensity of competitive interactions underlying density dependence as a major cause of size variation differed across temporal and spatial scales.     

Genotype × Herbivore Effect on Leaf Litter Decomposition in Betula Pendula Saplings: Ecological and Evolutionary Consequences and the Role of Secondary Metabolites

Plant genetic variation and herbivores can both influence ecosystem functioning by affecting the quantity and quality of leaf litter. Few studies have, however, investigated the effects of herbivore load on litter decomposition at plant genotype level. We reduced insect herbivory using an insecticide on one half of field-grown Betula Pendula saplings of 17 genotypes, representing random intrapopulation genetic variation, and allowed insects to naturally colonize the other half. We hypothesized that due to induced herbivore defence, saplings under natural herbivory produce litter of higher concentrations of secondary metabolites (terpenes and soluble phenolics) and have slower litter decomposition rate than saplings under reduced herbivory. We found that leaf damage was 89 and 53% lower in the insecticide treated saplings in the summer and autumn surveys, respectively, which led to 73% higher litter production. Litter decomposition rate was also affected by herbivore load, but the effect varied from positive to negative among genotypes and added up to an insignificant net effect at the population level. In contrast to our hypothesis, concentrations of terpenes and soluble phenolics were higher under reduced than natural herbivory. Those genotypes, whose leaves were most injured by herbivores, produced litter of lowest mass loss, but unlike we expected, the concentrations of terpenes and soluble phenolics were not linked to either leaf damage or litter decomposition. Our results show that (1) the genetic and herbivore effects on B. pendula litter decomposition are not mediated through variation in terpene or soluble phenolic concentrations and suggest that (2) the presumably higher insect herbivore pressure in the future warmer climate will not, at the ecological time scale, affect the mean decomposition rate in genetically diverse B. pendula populations. However, (3) due to the significant genetic variation in the response of decomposition to herbivory, evolutionary changes in mean decomposition rate are possible.