荒漠草原地面节肢动物功能群对草地封育的响应

以宁夏盐池国家级草原资源生态监测站为依托,选择荒漠草原典型植被类型的封育与未封育样地调查了地面节肢动物、植被及土壤特征,同时根据动物食性对节肢动物功能群进行了划分.结果表明:荒漠草原地面节肢动物可划分为捕食性、植食性、腐食性和杂食性4种营养功能群.其中,植食性和捕食性节肢动物在数量上占优势,植食性和腐食性节肢动物生物量所占比例较大,表明荒漠草原地面节肢动物区系以植食性动物分布为其主要特征.围栏封育增加了捕食性、植食性和杂食性节肢动物个体数量和类群数,增加了捕食性和杂食性节肢动物的生物量,提高了捕食性和植食性节肢动物的物种多样性,这与植被恢复和土壤环境改善密切相关,说明荒漠草原围栏封育增加了地面节肢动物功能群的多样性和复杂性.但是围栏封育后,腐食性节肢动物个体数量减少,生物量降低,反映了腐食性节肢动物对放牧草地生境的依赖性.     

林丹烟剂干扰下毛竹(Phyllostachys heterocycla cv.pubescens)林节肢动物群落的结构与组成

对林丹烟剂干扰下毛竹（Phyllostachys heterocycla cv.pubescens）林节肢动物群落结构与组成的系统定位观察与分析表明：长期使用林丹烟剂明显增加了群落主要物种（Pi≥0.05）的植食性种类及其优势度,显著降低群落总体的物种多样性,减少蜘蛛目、膜翅目、鞘翅目和双翅目或捕食性、寄生性和中性功能集团的物种数,削弱林冠层寄生性和捕食性物种在种类和数量上对植食性物种的制约潜能,引起叶部植食性害虫的暴发。因此,在毛竹害虫控制中应避免长期大量使用林丹烟剂。     

沙障对流动沙丘区地表节肢动物分布及多样性的影响

沙障作为人工固沙植被恢复与保护绿洲和道路安全的一种手段,可以有效阻止沙丘移动,改变流动沙丘地表生态水文过程,进而影响节肢动物多样性及营养结构及功能变化。鉴于此,选取临泽县中部沙带为研究区,利用陷阱法系统调查了生物、物理沙障和流动沙丘区沙丘不同部位地表节肢动物分布及多样性。研究结果表明,沙障营建强烈影响了流动沙丘区地表节肢动物组成,生物和物理沙障区地表节肢动物的活动密度、物种丰富度及多样性均显著高于流动沙丘区,捕食性和其它食性节肢动物较植食性节肢动物对沙障营建的响应更为敏感。沙障还改变了沙丘地表节肢动物的分布规律,生物和物理沙障区地表节肢动物的活动密度从沙丘底部到顶部依次增加,而流动沙丘区地表节肢动物主要分布在沙丘中下部。谢氏宽漠王和尖尾东鳖甲在流动沙丘区主要分布沙丘的中下部,沙障营建导致沙丘顶部谢氏宽漠王和尖尾东鳖甲的活动密度大幅提高。此外,研究还发现生物和物理沙障对地表节肢动物的影响不同,生物沙障区地表节肢动物活动密度显著高于物理沙障区,捕食性和东鳖甲属等其它食性节肢动物的活动密度在生物沙障区均高于物理沙障区。总之,沙障营建及类型差异强烈影响地表节肢动物的分布及多样性,它通过资源上行效应和土壤物理环境的改变提高了地表节肢动物的多样性及营养结构,从而影响了土壤生态系统结构及功能变化过程。     

生态护理对山地桔园节肢动物群落结构及多样性的影响

采用扫网、目测和手捕的方法,调查了山地桔园生态护理区和常规管理区节肢动物种群结构和多样性,获得生态护理区节肢动物2851只,隶属于2纲11目60科143种,常规管理区节肢动物2311只,隶属于2纲11目50科99种。生态护理区捕食性、寄生性和中性类亚群落节肢动物的种类增加了123.9%～168%,数量增加了83.5%～330.7%;捕食性、寄生性和中性类亚群落优势种群增多,而植食性亚群落相对减少;3—10月各亚群落消长动态相对平稳,害虫优势种柑桔红蜘蛛和桔蚜种群数量一直低于常规管理区,柑桔粉虱则相反;除植食性外,各亚群落的相对丰富度均大于常规管理区、优势集中度均小于常规管理区;总群落、捕食性、中性和植食性亚群落的Shannon指数分别比常规管理区高,而寄生性亚群落则低0.56,Hill多样性指数N1、N2与Shannon指数趋势相似;总群落、中性和植食性亚群落的均匀度指数高0.01～0.21,捕食性和寄生性的低0.03～0.04。因此,生态护理对增加桔园节肢动物种群结构和多样性效果明显,对害虫的持续控制和柑桔安全生产具有实际意义。     

转双抗虫基因741杨节肢动物群落营养结构及生态位变化

转双抗虫基因741杨（简称转基因741杨）节肢动物群落中,基位物种的植食性昆虫丰富度显著降低,但中性节肢动物丰富度却明显增加.高抗和中抗的节肢动物群落中位物种和顶位物种较之对照有所增多.转基因741杨节肢动物群落的害虫功能团,其优势状况,与对照相比有所改变：天敌优势度高于对照,中性节肢动物丰富度增加,并在天敌-害虫的营养链中起着重要的调控作用.鳞翅目害虫的空间生态位宽度最小,其它各功能类群的生态位宽度较大;捕食性和寄生性天敌与鳞翅目害虫的生态位重叠均较小,而与腐生和游逛种类的生态位重叠较大;各类害虫之间、捕食性天敌与寄生性天敌之间亦存在激烈竞争.转基因741杨对寄生性天敌和捕食性天敌在利用时间资源上有正作用.各种功能类群的时-空二维生态位宽度和生态位重叠均不如单维生态位宽度和生态位重叠值大,但抗性株系天敌类群对环境的适应性优于对照.     

林丹烟剂干扰下毛竹（Phyllostachys heterocycla cv. pubescens）林节肢动物群落的结构与组成

对林丹烟剂干扰下毛竹（Phyllostachys heterocycla cv. pubescens）林节肢动物群落结构与组成的系统定位观察与分析表明：长期使用林丹烟剂明显增加了群落主要物种（P_i≥0.05）的植食性种类及其优势度,显著降低群落总体的物种多样性,减少蜘蛛目、膜翅目、鞘翅目和双翅目或捕食性、寄生性和中性功能集团的物种数,削弱林冠层寄生性和捕食性物种在种类和数量上对植食性物种的制约潜能,引起叶部植食性害虫的暴发。因此,在毛竹害虫控制中应避免长期大量使用林丹烟剂。     

大蒜-小白菜间作套种对菜田节肢动物功能团的影响

2004年9-11月于福建省琅岐岛针对大蒜与小白菜间作(CG1)套种(CG2)对节肢动物群落功能团影响进行调查和分析。结果显示:CG1提高了植食性昆虫、寄生性和捕食性天敌丰盛度,CG2可在降低植食性昆虫数量的同时提高寄生性天敌的数量;多作田寄生性天敌物种丰富度、丰盛度和多样性指数均高于单作田;优势类群动态表现为菜蚜茧蜂与蚜虫种群在CG1出现"天敌跟随现象",多作田在整个生长期都有利于提高捕食者球腹蛛的控制效能;中性昆虫在生长前期和中期是菜蚜虫茧蜂和球腹蛛的替代寄主或猎物。因此合理的间作或套种,有利于提高菜田生境的多样化,强化自然天敌对害虫的生态控制作用。     

作物多样性对害虫及其天敌多样性的级联效应

植物物种丰富度对植食性、寄生性和捕食性节肢动物多样性的影响是群落生态学的一个重要研究内容.探讨了作物物种丰富度对害虫及其天敌多样性的影响.通过连续4年5个作物物种丰富度水平的野外实验,发现作物物种丰富度显著性影响害虫物种丰富度,但对天敌物种丰富度的影响甚微.然而,害虫物种丰富度却显著影响天敌物种丰富度.这些发现表明,相邻营养层之间的级联效应较强,而不相邻营养层之间的作用关系被中间营养层所弱化.此外,本研究还发现,混栽田中节肢动物群落稳定性高于单一种植田中节肢动物群落稳定性.本研究结果突出了不同营养层之间复杂的作用关系以及作物多样性在农业生态系统食物网中的关键性角色.     

广东地区春季大豆节肢动物种类调查分析

对广东地区大豆田节肢动物进行了系统调查.结果表明,广东地区春季大豆节肢动物物种十分丰富,共计3纲15目93科201种.其中植食性害虫分属于8目38科78种,捕食性天敌8目28科71种,寄生性天敌2目9科14种,中性昆虫4目19科38种.     

板蓝根田节肢动物群落的结构与多样性研究

为了解河南省板蓝根田节肢动物群落的结构组成及物种多样性,该研究采用5点随机取样,通过网捕法和目测法调查并记录了板蓝根植株及地面上的节肢动物种类和数量。结果表明:河南省板蓝根田节肢动物群落物种丰富,共采集到2 613头,隶属于2纲10目39科61种。其中,植食性种类和捕食性种类均为24种(各占39.34%),寄生性种类4种(占6.56%),中性种类9种(占14.75%)。蜘蛛的种类占群落总种数的比例最高(为21.31%),表明田间的蜘蛛种类最丰富。鳞翅目物种的个体数量远大于其他的目,占群落个体数的43.78%。菜青虫和小菜蛾的相对丰盛度最高,分别为0.184 8和0.162 6,说明二者是河南省板蓝根田的优势害虫。捕食性集团的均匀度指数最高,寄生性集团的优势度指数最高,其中小菜蛾幼虫的寄生性天敌菜蛾盘绒茧蜂的数量最大。     

Comparison of survey methods for wintering grassland birds

ABSTRACT Although investigators have evaluated the efficacy of survey methods for assessing densities of breeding birds, few comparisons have been made of survey methods for wintering birds, especially in grasslands. In winter, social behavior and spatial distributions often differ from those in the breeding season. We evaluated the degree of correspondence between density estimates based on different survey methods. Surveys were conducted during two winters (2001–2002 and 2002–2003) on 16 grassland sites in southwestern Oklahoma. Line‐transect (using a detection function to account for birds present but not detected) and area‐search (where density was based on the total count within a given area) methods were employed. Observations on line transects were also analyzed as strip transects, where density was based on total count within a given strip width and no detection function was used. Savannah Sparrows (Passerculus sandwichensis), LeConte's Sparrows (Ammodramus leconteii), Song Sparrows (Melospiza melodia), Smith's Longspurs (Calcarius pictus), Chestnut‐collared Longspurs (C. ornatus), and Eastern Meadowlarks (Sturnella magna) were sufficiently abundant to allow comparison. Area‐search density estimates tended to be higher than line‐transect estimates for Savannah Sparrows, Song Sparrows, and Eastern Meadowlarks, suggesting that some individuals initially located close to the transect line were not detected on line transects. The area‐search and line‐transect methods gave similar density estimates for Chestnut‐collared and Smith's longspurs. Area‐search estimates of Eastern Meadowlarks were significantly higher in the second year of the study only. For this species, area‐search estimates did not differ from those of strip transects covering an equal area, so the reason for the differing meadowlark estimates is not clear. Higher density estimates using the area‐search method likely resulted from: (1) birds that might escape detection by hiding were more likely detected (flushed) during area searches because of the repeated passes through the area, and (2) birds close to the line in line transects escape detection by hiding, biasing those estimates low. We also evaluated the correspondence of density rankings for the six species as determined by the different survey methods and for the same species across survey sites. Correlations among the six species of the area‐search results with those of line transects and strip transects generally were high, increasing in 2002–2003 when densities of birds were greater. All three methods provided similar density rankings among species. Density rankings within species across sites for the four non‐longspur species generally were concordant for the three methods, suggesting that any of them will adequately reflect among‐site differences, especially when densities vary greatly across sites. Further research is needed to determine the extent to which grassland birds are missed on line transects. We suggest that workers using line transects to study these species give careful consideration and make additional efforts to satisfy the distance‐sampling assumption that all birds on or near the line are detected. If density is measured as a total count in a fixed area, we recommend that observers pass within <10 m of all points in the area.     

Seasonal variation in detectability of butterflies surveyed with Pollard walks

Monitoring protocols should be designed to maximize the probability of detecting target species with limited resources. Most species are imperfectly detected, hence, they will often be overlooked at sites where they actually occur, resulting in false-negative errors (i.e. false absences). Uncertain detection of target species has profound implications for conservation, but can be dealt with by using adequate survey designs and statistical models. Butterflies often are monitored with repeated, fixed-route transect counts (Pollard walks). Even though this survey method is widely used in temperate regions, its efficiency in terms of detection probability has never been rigorously assessed in part owing to a lack of suitable analysis methods. Here, I use site-occupancy models to explore the seasonal patterns in detection probability of four California butterflies using Pollard walks. In an effort to inventory the butterfly fauna in two natural areas in the eastern foothills of the Santa Cruz mountains (California), I surveyed twelve 250 m long transects weekly for 22 weeks. I estimated the detection probability (the probability of recording a species during a single transect walk, given it is present) of four species. The probability of detecting each species depended mostly on the monitoring week. Average detection probability across the season was 64% for Cercyonis pegala, 56% for Limenitis lorquini, 76% for Euphydryas chalcedona, and 50% for Lycaena arota. Based on the mean detection probability, I then inferred the number of visits necessary to be statistically confident that a given species was indeed absent from a transect where it was not observed (i.e. obtaining a false absence rate <5%). Knowledge of detection probabilities is fundamental to the optimal design of monitoring programs and the interpretation of their results. The methods applied in this study provide an efficient and evidence-based method to optimally allocate butterfly monitoring resources across space (number of transects) and time (number and timing of visits).     

A new potential method to estimate abundance of small game species

This study tested the hypothesis that nonlinear transects, such as the L‐, V‐ and W‐shaped transect, which are widely used in soil sampling but rarely in ecology, may perform better in capturing habitat heterogeneity potentially resulting in more accurate small game species estimates, than straight‐line transects. To test this, we computed and compared the Normalized Difference Vegetation Index (NDVI) captured by the straight‐line, L‐shaped, V‐shaped and W‐shaped transects for Kyle Game Reserve (Zimbabwe), inside the home ranges of two small game species, namely species A and species B. These transects differed in geometry but had the same length. We also performed simulations in a geographic information system environment to compare the detection ability of the different transect geometry. One‐way analysis of variance followed by Tukey's honest significant difference test was used to test for significant differences in the mean number of detections and NDVI variance captured by each transect geometry. Simulations results indicate that for both home ranges, the V‐shaped transect resulted in significantly higher detections than the widely used straight‐line transect. Nonlinear transects also yielded higher NDVI variances than the straight‐line transect in both home ranges.     

Species-richness patterns of vascular plants along seven altitudinal transects in Norway

Altitudinal richness patterns were investigated along altitudinal gradients located in northern Norway (two transects) and along a west–east gradient in southern Norway (five transects). The transects were sampled for vascular plant species richness using a uniform sampling method. Each transect consisted of 38–48 5×5 m sample plots regularly spaced from sea level or valley bottom to a local mountain top. In five transects species richness peaked at mid-altitudes, whereas in the two northern transects species richness decreased with altitude. The observations were qualitatively evaluated in relation to the influence of the area of the species pool, hard boundaries, temperature and precipitation, and mass effect. The observed patterns cannot be fully accounted for by any of these factors. However, the altitude of the peak in species richness was above the forest-limit for all the humped relationships, which may suggest that species richness above the forest-limit might be enhanced by a mass effect from forest taxa. The two monotonic relationships found in the north may be caused by the relatively low number of alpine species at these sites. The monotonic pattern may result from a decrease in "forest species" towards the mountain tops.     

Altitudinal zonation of Andean cryptogam communities

To test whether cryptogamic plant communities in tropical Andean rain forests are distributed in floristically discrete communities corresponding to altitudinal belts, I subjected the elevational distribution of pteridophytes along two elevational gradients in Bolivia, and of bryophytes and lichens along two transects in Peru and Colombia (data from Gradstein & Frahm, 1987 ; Wolf, 1993 ) to an analysis of deviance. All well‐defined elevational boundaries in floristic composition were related to marked ecological changes: the transition from the steep mountains to the hilly lowland zone coupled with a change in geological substrate at 400 m along the Bolivian Carrasco transect, a strong humidity gradient at 1000 m at the Bolivian Masicurí transect and at 1250–1980 m along the Colombian transect, and the transition from mixed cloud forests to forests dominated by Polylepis or Podocarpus at 3400–3600 m in Carrasco, at 1650–1800 m in Masicurí, and at 3670 m in Colombia. Consequently, floristic elevational belts appear to be well‐defined at strong environmental boundaries and in fairly species‐poor forest communities where the presence or absence of one or a few tree species influences the whole ecosystem while they are ill‐defined in species‐rich communities such as tropical forests at low to mid‐elevations.     

Influences of transect relocation errors on line-point estimates of plant cover

The line-point transect method has been used to estimate plant cover for about nine decades. In particular, the method is often used to determine baseline plant cover and monitor for changes in plant cover over time. In such cases, detection of change requires both the initial transect starting position and angle of orientation are exact in relocation without error. A study was conducted on influences of errors in basal cover estimates that resulted from inexact relocation and orientation of a resample transect. Simulation studies of actual field data showed that variation in plant cover estimates from relocated line-point transects increased with each source of error and combinations of these errors. Relocated transects resulted in unbiased estimates of total-plant cover only when means over all transects are used to detect changes over time. Substantial errors were observed when the mean cover of individually relocated transect was compared to its original transect.     

Zonation of spiders (Araneae) and carabid beetles (Coleoptera: Carabidae) in island salt marshes at the North Sea coast

The specific communities of spiders and carabid beetles of island salt marsh habitats of the East Frisian Island chain at the German North Sea coast were investigated. During the vegetation periods of 1997 and 1998 three pitfall trapping transects were installed on the islands of Borkum and Wangerooge. Within the salt marshes, transects extended from 0 m to 175 m. Elevation gradients varied between 10 cm and 232 cm above MHT (mean high tide). On Borkum, 35 traps were exposed in two transects, on Wangerooge 25 traps were placed in one transect. Three to five elevations above MHT were investigated per transect, each one with five traps. Highest species numbers were recorded in the higher elevated salt marshes. In contrast, highest activity values were noticed in the medium elevated salt marshes. Within both groups, spiders and carabids, four communities were distinguished by indirect gradient analysis. Indicator species were assigned to the different communities that were mainly assorted to different elevations of the salt marshes. Thus, the communities of both taxa corresponded well to the vegetational formations. The importance of sea level rise for structuring the communities of salt marsh arthropods is discussed. Overall, still great uncertainties exist on how arthropod communities and salt marshes themselves will develop.     

Tropical metacommunities along elevational gradients: effects of forest type and other environmental factors

Elevational gradients provide a natural experiment for assessing the extent to which the structure of animal metacommunities is molded by biotic and abiotic characteristics that change gradually, or is molded by aspects of plant community composition and physiognomy that change in a more discrete fashion. We used a metacommunity framework to integrate species‐specific responses to environmental gradients as an approach to detect emergent patterns at the mesoscale in the Luquillo Mountains of Puerto Rico. Elements of metacommunity structure (coherence, species turnover and range boundary clumping) formed the basis for distinguishing among random, checkerboard, Gleasonian, Clementsian, evenly spaced and nested patterns. Paired elevational transects (300–1000 m a.s.l.) were sampled at 50 m intervals to decouple underlying environmental mechanisms: a mixed forest transect reflected changes in abiotic and biotic conditions, including forest type (i.e. tabonuco, palo colorado and elfin forests), whereas another transect reflected changes in environmental conditions but not forest type, as its constituent plots were located within palm forest. Based on distributional data (presence versus absence of species), the mixed forest transect exhibited Clementsian structure, whereas the palm forest transect exhibited quasi‐Gleasonian structure. In contrast, the distribution of modes in species abundance was random with respect to the latent environmental gradient in the mixed forest transect and clumped with respect to the latent environmental gradient in the palm forest transect. Such contrasts suggest that the environmental factors affecting abundance differed in form or type from those affecting distributional boundaries. Variation among elevational strata with respect to the first axis of correspondence from reciprocal averaging was highly correlated with elevation along each transect, even though axis scores were not correlated between mixed forest and palm forest transects. This suggests that the identity of the environmental characteristics, or the form of response by the fauna to those characteristics, differed between the two elevational transects. Despite the proximity of the transects, the patchy configuration of palm forest, and the pervasive distribution of the dominant palm species, the relative importance of abiotic variables and habitat in structuring gastropod metacommunities differed between transects, which is remarkable and attests to the sensitivity of metacommunity structure to environmental variation.     

Line transect sampling from a curving path

Cutting straight line transects through dense forest is time consuming and expensive when large areas need to be surveyed for rare or highly clustered species. We argue that existing paths or game trails may be suitable as transects for line transect sampling even though they will not, in general, run straight. Formulas and software currently used to estimate local density using perpendicular distance data can be used with closest approach distances measured from curving transects. Suitable paths or trails are those for which the minimum radius of curvature is rarely less than the width of the shoulder in the detection probability function. The use of existing paths carries the risk of bias resulting from unrepresentative sampling of available habitats, and this must be weighed against the increase in coverage available.     

Effect of sampling grain on patterns of species richness and turnover in Amazonian forests

Grain (size of sampling units) affects the spatial resolution at which ecological patterns can be observed and analysed, and potentially has an important effect on the results of broad‐scale studies on diversity gradients. Here we examine the effect of grain on patterns of species richness and turnover in lowland rainforests of western Amazonia (Peru and Colombia). We inventoried pteridophytes (ferns and lycophytes), melastomes (Melastomataceae) and palms (Arecaceae) in four line transects of 22–29 km length. Different grains were obtained by aggregating original 100‐m‐long sampling units into larger segments up to 19.2 km long. With any given grain and plant group, local species richness varied considerably both within and among transects, and a transect segment that was species‐rich with one grain could be relatively species‐poor with another. Which transect had the highest vs lowest mean species richness per sampling unit (α richness) differed among plant groups. It also varied to some degree with grain, as transects differed in how rapidly local species richness increased with increasing grain. Patterns of species turnover were more consistently correlated among plant groups than patterns of species richness were, and NMDS ordinations were rather similar with all grains and plant groups. Floristic heterogeneity within the Amazonian terra firme rainforest seems to contain a general compositional pattern that is sufficiently robust to be detectable with various sampling schemes, but patterns of species richness appear more case‐specific. Therefore, using one plant group as an indicator for patterns in other plant groups can be expected to work better for species turnover than for species richness.