昆嵛山腮扁叶蜂发生与赤松纯林林分因子的关系

为了解林分因子与昆嵛山腮扁叶蜂发生的关系,为昆嵛山赤松纯林的营林措施和昆嵛山腮扁叶蜂的防控技术提供理论指导,本研究在昆嵛山区域选取林龄相对一致(34±2 a)的赤松纯林为对象,调查林分密度、郁闭度、草本盖度、树高、枝下高、胸径、冠幅7个林分因子以及昆嵛山腮扁叶蜂虫巢数。依据虫情指数的分布范围,将样地分为4组,通过方差分析和多重比较研究了4组样地中各项林分因子的差异性。采用逐步回归法,筛选出影响昆嵛山腮扁叶蜂虫情指数的关键因子,在此基础上通过偏相关分析和单因素方差分析法进一步阐明关键因子与虫情指数之间的关系。结果表明,7个林分因子在4组样地中均存在极显著的组间差异。逐步回归筛选出冠幅、枝下高和林分密度为影响昆嵛山腮扁叶蜂发生的关键因子,根据关键因子建立了虫情指数的线性预测方程。冠幅和枝下高对昆嵛山腮扁叶蜂虫情指数的影响均达到极显著正相关水平(P0.01),林分密度对昆嵛山腮扁叶蜂虫情指数的影响为极显著负相关(P0.01)。影响虫情指数的关键因子可能会因林分的不同而不一致,因此要根据关键因子调整林分结构,以达到控制虫害流行的目的。     

鞭角华扁叶蜂自然种群生命表

鞭角华扁叶蜂Chinolydaflagellicornis（F．Smith）是危害柏木的主要害虫,近年来在长江沿岸柏木防护林区发生严重,造成灾害。为了解该虫的种群动态规律及影响虫口数量变动的致死原因,并为该虫的预测预报提供资料,笔者于1995～1996年在忠县、云阳两县对鞭角华扁叶蜂自然种群进行了观察,现将结果整理于后。1生命表的研制过程1．1生命表观察虫期的划分[1]：根据鞭角华扁鞭角华扁叶蜂平均生命表叶蜂的发育进度和生活习性,将整个世代划分为卵期,1、2、3、4～6龄幼虫期,预蛹期,蛹期和成虫期共8个发育阶段。l．2观察方法。于1995—1996…     

鞭角华扁叶蜂蜕皮甾类激素滴度的变化

用放射免疫分析法测定了鞭角华扁叶蜂Chinolyda flagellicornis末龄幼虫及滞育预蛹血淋巴中蜕皮甾类激素滴度。结果表明,末龄幼虫血淋巴中蜕皮甾类激素滴度在第2和4天各有一高峰;滞育预蛹血淋巴中保持一定滴度的蜕皮甾类激素,并随发育时期的不同有所波动;预蛹化蛹前一周血淋巴中蜕皮甾类激素滴度存在两个与变态相对应的峰值。表明鞭角华扁叶蜂的滞育与蜕皮甾类激素相关。     

鞭角华扁叶蜂幼虫期的呼吸代谢

报道了鞭角华扁叶蜂Chinolyda flagellicornis幼虫不同发育时期的耗氧量.试验表明,鞭角华扁叶蜂的耗氧量随着幼虫的生长发育而增加,在同一龄期内,耗氧量与虫体鲜重呈2次曲线相关;在不同的龄期之间,耗氧量则与虫体鲜重的0.8299次方成正比.在同一龄期内,幼虫的代谢速率呈抛物线状;在整个幼虫期随着龄期的增加而呈下降趋势.     

鞭角华扁叶蜂幼虫的营养成分分析

采用现代分析技术手段对鞭角华扁叶蜂Chinolydaflagellicornis(F.Smith)幼虫的主要营养成分进行分析,结果表明其鲜虫浆的蛋白质、氨基酸、粗脂肪、糖类及灰分含量分别为17.1%,13.5%,6.7%,1.0%和1.5%,胆固醇含量为0.3mg/g;含有7种人体必需氨基酸,其必需氨基酸占总氨基酸含量的43.0%,必需氨基酸与非必需氨基酸含量的比值为75.3%,第一限制性氨基酸为含硫氨基酸,即蛋氨酸和胱氨酸;同时,其不饱和脂肪酸与必需脂肪酸分别占总脂肪的61.3%和24.3%,特别是油酸和亚麻酸含量较高,分别达37.0%和18.4%;此外,还含有K,Ca,Mg,Fe,Zn,Cu,Mn等多种矿物质和微量元素。最后在分析其营养价值的基础上,对鞭角华扁叶蜂幼虫的开发利用价值进行了评价。     

鞭角华扁叶蜂对自然生境柏木挥发物释放的影响

植物挥发物（Volatile organic compounds;VOCs）在植物抵御害虫侵袭的过程中具有重要作用。本研究以重庆市云阳县长江林场人工林中健康和受害柏木为研究对象,通过VOCs测定分析发现鞭角华扁叶蜂虫害发生之前,两种柏木共计有37种VOCs成分,主要为萜类化合物,其次为醇、酯、醛、烷烃等类化合物;其中健康柏木特有驱赶作用的2-莰醇（龙脑）,受害柏木特有吸引作用的顺式-2-癸烯醛,其余35种为共有成分;各成分浓度在两种柏木中存在较大差异。虫害发生之后,两种柏木共计有32种VOCs成分,而2-莰醇、顺式-2-癸烯醛、薄荷醇、臭樟脑和α-石竹烯等5种成分消失;许多成分的浓度变化趋势与虫害发生前的相反。结果表明健康与受害柏木VOCs释放的差异可能是柏木能否抵御鞭角华扁叶蜂侵害的主要防御机制之一,这将为优良抗虫柏木选育提供理论依据和参考指标。     

塔里木河下游林地树冠QuickBird影像信息提取与分析

基于QuickBird影像,采用人机交互方法提取了塔里木河下游不同离河距离胡杨、柽柳树冠信息,以实测数据为真值检验遥感提取冠幅、郁闭度及混交比精度;并建立了胡杨冠幅、胸径、树高关系模型,为塔里木河流域植被调查、生物量估测及生态恢复评价提供依据和方法借鉴.结果表明:胡杨、柽柳冠幅提取精度分别为84.00%、76.24%;林分郁闭度、混交比提取精度分别为69.45%、66.96%.基于实测数据建立的冠幅与胸径、胸径与树高模型相关显著(R2>0.8,P<0.01);根据遥感解译因子反演胡杨胸径、树高的平均精度分别为80.33%、89.25%.     

两种相容性生物量模型的比较——以广东省3个阔叶树种为例

基于广东省樟树、木荷和枫香3个阔叶树种共270株样木的生物量实测数据,采用多元非线性联合估计,按分量相加和总量控制两种方法,分别构建了一元(胸径)和二元(胸径、树高和胸径、冠幅)的相容性生物量模型,比较分析了这两种相容性生物量模型的拟合效果和预估精度。结果表明:(1)分量相加和总量控制构建相容性模型对3个树种拟合效果均较好,预估精度均较高,二者之间差别不大,但总体上分量相加模型拟合效果较优。(2)二元模型拟合效果和预估精度普遍优于一元模型,但加入第二个变量的异同,在各个分量中的表现不一。加入树高因子,显著改进树干和树皮的拟合效果;加入冠幅因子,显著改进树枝、树叶和地上部分的拟合效果。选择胸径和冠幅因子建立二元生物量模型可以获得较高的拟合精度。(3)基于最优独立模型构建的相容性模型拟合和预估效果最优,地上部分总量甚至优于最优独立模型。因此,各分量相加构建的相容性模型略优于总量控制。对于阔叶树种自变量的选取,二元模型加入冠幅因子的精度高于加入树高因子。     

基于神经网络的马尾松叶绿素含量高光谱估算模型

分析不同生长期的马尾松冠层反射光谱特征与相应叶绿素含量的相关关系.利用36个红边参数逐一筛选,最终确定7个与叶绿素含量相关性较高的红边参数作为光谱特征参数,分别应用逐步分析法与BP神经网络构建叶绿素含量的高光谱估算模型;同样,筛选出4个植被指数作为光谱特征参数,同时,将对原始光谱进行主成分分析降维后的前4个主成分作为BP神经网络的输入变量,分别应用逐步分析法与BP神经网络构建叶绿素含量的高光谱估算模型.结果表明: 将红边参数作为输入变量建立的逐步回归模型和BP神经网络模型的决定系数(R²)分别为0.5205、0.7253,均方根误差(RMSE)分别为0.1004、0.0848,相对误差分别为6.3%、5.7%.将植被指数作为输入变量建立的逐步回归模型和BP神经网络模型的R²分别为0.5392、0.7064,RMSE分别为0.0978、0.0871,相对误差分别为6.2%、6.0%.基于主成分分析的BP神经网络模型的预测效果最好,R²为0.7475,RMSE为0.0540,相对误差为4.8%.     

青海云杉(Picea crassifolia)种群格局的分形特征及其影响因素

应用计盒维数、信息维数和关联维数对祁连山主要森林类型青海云杉(Picea crassifolia)种群空间格局进行的研究表明:青海云杉种群格局计盒维数在0.992～1.938之间,平均值为1.716,信息维数在0.996～1.860之间,平均值为1.632, 关联维数在1.418～1.759之间,平均值为1.568.计盒维数与样地海拔和土壤水分含量呈显著的负相关,与样地坡向呈显著的正相关,信息维数与样地海拔呈显著负相关而与坡向呈显著的正相关,关联维数与样地坡度呈显著的负相关,主成分分析表明,海拔和土壤含水量是影响青海云杉种群格局分形维数第一主成分,坡向是第二主成分,坡度是第三主成分,这3个主成分累计解释率为87.6%.     

Effects of temperature and humidity on the development of eggs of Toxocara canis under laboratory conditions

The influence of temperature and humidity on the survival and development of Toxocara canis eggs in an in vitro model system was investigated. Two soil samples were inoculated with T. canis eggs and maintained at 3% and 50% humidity and temperatures of 19-24 degrees C. Nine soil samples were inoculated with T. canis eggs of which three samples were kept at 4 degrees C with humidities at 3%, 15%, and 30%; three were maintained at 21 degrees C and three more were incubated at 34 degrees C, and at the same three humidity levels. Samples were monitored every 7 days for a total of 2 months, for the presence and development of eggs. With increasing temperature, the number of eggs undergoing development increased (P<0.01); the number of deformed eggs decreased, the number of infective eggs increased (P<0.01), and egg maturation was accelerated. A decrease in the survival of infective eggs occurred at 34 degrees C. An increase in humidity produced a rise in the number of developed eggs at all three temperatures (P<0.01). This study suggests that elevated temperatures accelerated the development as well as the degradation of eggs of T. canis, whereas the range in humidity was directly correlated with egg development.     

The avoidance of superparasitism in four species of parasitic wasp—Mathematical models and experimental results

Experimental results, and interpretation, are presented which relate to oviposition behaviour in four species of parasitic wasp (Hymenoptera: Chalcidoidea). All lay their eggs in pupae of the common house fly (Musca domestica) and of other flies associated with man. Probability models suggested byD. J. Daley for describing the avoidance of superparasitism are used to analyse the data. Certain of the models considered by previous authors appear as specieal cases. A satisfactory fit was obtained either by assuming a fixed probability of oviposition in an already parasitised pupa, or by using a model motivated by supposing that a female will tolerate without oviposition some fixed number of visits to already parasitised pupae. A third model was considered which makes the probability depend on the number of previous ovipositions in the pupae now visited. In all four species the presence of other females (with parasite: host ratio unchanged) increased the probability of oviposition upon encountering an already parasitised pupa. In the presence of other females Spalangia endius laid an increased number of eggs, whereas the other three species laid fewer eggs.     

The influence of tactile and other non-chemical factors on the ovipositional responses of the generalist herbivore Epiphyas postvittana

A bioassay to test the ovipositional responses of the generalist herbivore, Epiphyas postvittana, was developed, and various non-chemical factors that influenced the laying, and number of eggs laid, by females were tested. In choice experiments using various models, surface texture was found to be an important factor influencing ovipositional behaviour, with females preferring to lay on smoother rather than rougher surfaces. Another surface texture feature that influenced oviposition was a raised wax ridge on a smooth surface. The wax ridge stimulated more eggs to be laid within close proximity to the ridge. Observations of females showed that the increased numbers of eggs laid on models with a wax ridge resulted not from increased landing, time spent, or numbers of eggs laid per ovipositional bout, but rather through an increased probability of ovipositing after landing on models with a wax ridge compared to models without the ridge. Spatial features of the models were also found to influence egglaying by females. Females showed a tendency to lay on the upper rather than the lower surface of models, although this appeared to depend upon how stimulatory the upper surface of the model was. Females also laid more eggs on models with a dense array of leaves than on models with a more spread-out array.     

Visual aspects of egg care behaviour in Cichlasoma nigrofasciatum (Günther)

Egg size was found to be an important visual stimulus eliciting egg care behaviour in substrate-spawning Cichlasoma nigrofasciatum. Egg size was manipulated by the use of artificial wax ‘eggs’ while maintaining other visual spects of the spawn unchanged. Egg-care behaviour was compared under two experimental and three control conditions. The experimental conditions consisted of exchanging the eggs for larger or smaller models. The control groups included a baseline record of egg care toward natural eggs, a situation without eggs and one with model ‘eggs’ similar in size to the natural. The results showed that models larger or smaller than real eggs were discriminated; a considerable decrement in several fanning parameters occurred relative to the baseline or natural size model groups. The absence of eggs resulted in the greatest decrement of fanning. These results suggest some hormonal control of egg care behaviour. The length of time spent fanning eggs is a function of the time the eggs are in view; the adaptive significance of this result is discussed.     

Influence of rearing hosts on host size acceptance by Trichogramma australicum

We investigated the acceptance of different sized host models by Trichogramma australicum in the laboratory. We used isoline cultures of T. australicum reared in hosts of different sizes. Helicoverpa armigera represent relatively large hosts, and those of Sitotroga cerealella are small, termed the Ha and Sc biotypes, respectively. Five sizes of glass beads were tested for acceptance: diameter 0.5, 0.75, 1.0, 1.5 and 2.0 mm. The acceptance of a host model was determined by persistent attempted drilling of a glass bead by a female. The relationship between host egg size and number of eggs laid by a female was also investigated. We used three sizes of artificial egg (diameter 0.75, 1.00, and 1.50 mm of hemispherical cupules) each containing artificial diet. Ha biotype wasps accepted host models in the range 0.75--1.50 mm dia. (vol. 0.166--1.325 l), whereas those of the Sc biotype accepted host models in the range 0.50--1.00 mm dia. (vol. 0.05--0.393 l). This evidence suggests a lineal (possibly genetic) influence to host size acceptance for T. australicum, dependent on the size of the host in which the wasp has been reared. Also T. australicum lay fewer eggs in smaller artificial eggs than in larger ones. The role of host size in host acceptance and number of eggs delivered, and its implications, is discussed.     

Fecundity and egg density in the redd for sea trout

The relationship between fecundity and length for sea trout Salmo trutta from three streams in NW England was curvilinear and, after logarithmic transformation of both variables, was well described by a linear regression model. Regression equations for the fish from the three streams were not significantly different ( p >0.05). The relationship between estimated eggs per redd and female size in a tributary of one of the streams was also well described by a linear regression model after logarithmic transformation. Fecundity was usually higher than estimated eggs per redd, and this difference increased with female size so that the mean number of eggs per redd expressed as a percentage of mean fecundity decreased from 100% for a female with a length of 240 mm to 79% for one of 650 mm. The power function in its logarithmic form has now been fitted to fecundity-length data for sea trout from 12 streams and rivers in England, Scotland, Ireland and Norway. Comparisons between fecundity estimates for the same sizes of females revealed a large variation between populations and possible reasons for this are discussed.     

Physical features of grass leaves influence the placement of eggs within the plant by the Hessian fly

Hessian fly eggs are more likely to be found on adaxial rather than abaxial surfaces of wheat leaves. These leaf surfaces differ in their physical features: the adaxial side of the leaf has parallel grooves and ridges while the abaxial side is relatively smooth. We used leaf models to investigate the relationship between Hessian fly egglaying and these physical features. When both sides of a green paper leaf model were treated with a wheat leaf extract, but only one side of the model was scored with parallel grooves, the grooved side received more eggs than the smooth side. As the number of grooves per surface increased from 0 to 10, eggs per model increased. When grooves and the wheat leaf extract were tested together and separately, the grooves significantly increased egg numbers in the presence, but not the absence, of wheat extract. In contrast, wheat extract increased egg numbers both in the absence and presence of grooves. Molding techniques were used to recreate the physical features of the adaxial and abaxial leaf surfaces of five grasses. For four of the grass genotypes (a triticale, two common wheats, and a durum wheat), patterns of egglaying on real leaves and molded models were similar, i.e., adaxial leaf surfaces and adaxial molded models were preferred over abaxial leaf surfaces and abaxial models. On the fifth grass, oat, preferences for the adaxial side of real leaves and for adaxial models were not as obvious. We conclude that the adult female Hessian fly obtains information about the leaf surface through her tactile and/or kinesthetic senses and uses this information when making egglaying decisions.     

Reproduction and the energy cost of defense in a Batesian mimicry complex

Summary The amount of energy invested in reproduction and in defense was examined in a Batesian mimicry complex consisting of the modelEleodes obscura and the mimicStenomorpha marginata (both Coleoptera: Tenebrionidae). Models live up to 4 y as adults while mimic adults live only 3 mo. The energy content of the eggs of the model and mimic was determined by microbomb calorimetry. The energy content of the defensive secretions produced by the model was determined by computational chemistry and MNDO computer programming. Contrary to the predictions of some life-history theory, the long-lived model annually produces many small eggs each of low energetic content, while the short-lived mimic annually produces fewer, larger eggs each of high energetic content. However, in terms of total energy, the long-lived model has an annual investment in reproduction equal to that of the short-lived mimic. During the 3 mo of co-ocurrence of models and mimics within a year, an average individual model's cost in using defensive secretions against potential predators is 12% of the amount of energy tied up in the eggs that it produces within the year. The annual cost of defense for the model is 18% of the energy contained in the mean number of eggs produced. When the energy allocated to eggs is added to that allocated to defense, the model has an annual investiment that is greater than the annual investment in reproduction by the mimic. Although the energy invested in defense by the model is small relative to the energy invested in egg production, it buys the model considerable protection from predation. Nevertheless, the cost of defense does not explain the deviations from the predictions of life-history theory.     

Contest and Scramble Competition and the Carry-Over Effect in Globodera spp. in Potato-Based Crop Rotations Using an Extended Ricker Model

The Ricker model extended with a linear term was used to model the dynamics of a potato cyst nematode population on different potato cultivars over a wide range of population densities. The model accounts for contest and scramble competition and between-year carryover of unhatched eggs. Contest competition occurs due to the restricted amount of available root sites that are the feeding source of the female nematode. Nematodes not reaching such a feeding site turn into males and do not contribute to a new generation. Scramble competition results in a decrease of the number of eggs per cyst at high densities due to the decrease in the food supply per feeding site. At still higher densities, the size of the root system declines; then dynamics are mostly governed by carryover of cysts between subsequent years. The restricted number of three parameters in the proposed model made it possible to calculate the equilibrium densities and to obtain analytical expressions of the model''s sensitivity to parameter change. The population dynamics model was combined with a yield-loss assessment model and, using empirical Bayesian methods, was fitted to data from a 3-year experiment carried out in the Netherlands. The experiment was set up around the location of a primary infestation of Globodera pallida in reclaimed polder soil. Due to a wide range of population densities at short distances from the center of the infestation, optimal conditions existed for studying population response and damage in different cultivars. By using the empirical Bayesian methods it is possible to estimate all parameters of the dynamic system, in contrast to earlier studies with realistic biological models where convergence of parameter estimation algorithms was a problem. Applying the model to the outcome of the experiment, we calculated the minimum gross margin that a fourth crop needs to reach in order to be taken up in a 3-year rotation with potato. An equation was derived that accounted for both gross margin changes and nematode-related yield loss. The new model with its three parameters has the right level of complexity for the amount and type of collected data. Two other important models from the literature, containing five and 10 parameters respectively, may at this point turn out to be less appropriate. Consequences for research priorities are discussed and prediction schemes are taken in consideration.