首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 770 毫秒
1.
The integration of agroforestry plots with ephemeral crops such as vegetables on the farm scale can probably serve as a refuge and source of beneficial insects. Therefore, agroforestry systems possibly represent an alternative that favors ecosystem services and help growers in the transition process from conventional to agro-ecological agriculture. This study aimed to understand the role of introducing agroforestry systems in structuring insect communities, with consequences for the abundance of herbivore and natural enemies, contributing to farm management and favoring biological control as an ecosystem service. Field surveys showed that agroforestry systems can harbor more species than horticultural crops, independent of the functional group. They also contain a greater diversity of herbivores and an even greater diversity profile of natural enemy communities. Agroforestry systems served as a source of natural enemies that can colonize horticultural crops when herbivores are present. As a consequence, natural enemies can establish a numerical response to herbivore abundance, but their communities are also affected by stochastic factors related to climatic conditions. Thus, agroforestry systems and agro-ecological practices might favor an agriculture based on the maintenance and conservation of ecosystem services.  相似文献   

2.
In olive orchards, which are very common in the Mediterranean region, cover crops are becoming increasingly used to counter problems of erosion. Although such plant covers can provide food and shelter for beneficial insects, mites, and spiders, they may also attract pests. In order to determine their relationships with the main pests in olive orchards, an analysis was made of adult population levels and damage caused in five olive-cultivation zones, in olive orchards with cereal-crop covers and in olive orchards with conventional tillage. The effects of the cereal cover crops on insect pest populations were different and in some cases in opposite direction. Thus cereal cover crops had no impact on the different studied pests, including all those that spend part of their development cycle in the soil, such as Bactrocera oleae, Prays oleae, or Otiorrhynchus cribicollis. However, under certain conditions some pests did show an increase in abundance. Diverse trophic relationships should be investigated in this agroecosystem in future studies in order to develop appropriate crop-management policies.  相似文献   

3.
Despite widespread recognition of linkages between vegetation and insects, understanding of the ecological mechanisms underlying these relationships is limited. Better comprehension of relationships linking abundance and biomass of insects to vegetation would increase accuracy of predictions of the effects of forest management activities on insect communities. This knowledge could also be pivotal to understanding predator–prey dynamics linked to insect populations. We sampled nocturnal flying insects and measured vegetation characteristics in 34 stream reaches in conifer-dominated forests of the Oregon Coast Range in the Pacific Northwest of the United States. We considered five a priori hypotheses (resource quality, resource diversity, resource abundance, resource concentration, and stream cover hypotheses) that could explain mechanisms underlying associations between riparian vegetation and nocturnal flying insects, and used an information-theoretic approach to determine the relative strength of evidence for each. The resource quality hypothesis, which predicts that abundance and biomass of insects increases with cover of deciduous vegetation, explained substantial variation for nearly every order of insect investigated, whereas the remaining hypotheses explained relatively little. Abundance and biomass of insects had stronger associations with characteristics of canopy trees than with characteristics of shrub or understory trees, suggesting that deciduous trees are an important habitat element for nocturnal flying insects in these areas. Resource managers planning riparian vegetation management in conifer-dominated forests should be aware that manipulation of the cover of deciduous trees in riparian areas could have a large impact on these insects and their vertebrate predators. By providing information on forest canopy composition, remote sensing may offer a low-cost tool for identifying areas with high abundance and biomass of insects during conservation planning.  相似文献   

4.

The indirect effect of seminatural habitats on pest suppression has been widely studied in agricultural landscapes. By contrast, the role of crop diversity on pest suppression by predators has seldom been explored, particularly using molecular gut-content analysis (MGCA). In addition, differences between early- and late-season effects of landscape complexity on pest control, crucial to ensure season-long control, have received little attention. During 2014 and 2015, we investigated the effect of agricultural landscape complexity and crop diversity on cereal leaf beetle (CLB, Oulema melanoplus) predation early in the season using sentinel egg cards and late in the season by assessing larval predation using MGCA. Early-season CLB egg predation and late-season abundance of Nabis americoferus and coccinellids in wheat fields were positively correlated with amount of woodland habitat in these landscapes. Contrary to our predictions, crop diversity had negative associations with the late-season frequency of larval predation and the abundance of N. americoferus. Predator diversity and the abundance of Hippodamia lady beetles had negative associations with CLB abundance, highlighting the significant contribution of some generalist predators to CLB suppression. Our results suggest that the proportion of woodland and a few major crops (e.g., canola and non-cereal crops), rather than crop diversity, are associated with higher predation at different temporal scales. Overall, our results suggest that a habitat management strategy could be implemented to adjust the crop rotation regime to add the right kind of crop diversity in the landscape to support the natural control of CLB.

  相似文献   

5.
We examined the effects of nonhost plant diversity and predators on the potato leafhopper, Empoasca fabae (Harris), the pea aphid, Acyrthosiphon pisum (Harris), and their primary host plant, alfalfa, Medicago sativa L. Potato leafhopper intensity (i.e., leafhoppers/alfalfa stem density) and plant damage (i.e., hopperburn) were significantly greater in alfalfa mono- than in polycultures of alfalfa mixed with nonhost plant species. There was no significant effect of nonhost plant diversity on pea aphid intensity or on predator abundance. Predator:prey ratios were higher in poly- than in monoculture. One predator, Nabis sp., was selected for further study. A microcosm experiment indicated that Nabis is an effective predator of both herbivores, and suggested that nonhost plant diversity may enhance the predation of leafhoppers by Nabis. These results suggest that nonhost plant diversity and Nabis limit leafhopper populations and protect alfalfa from herbivory. The potential for nonhost plants to increase herbivore movement and vulnerability to predation is discussed.  相似文献   

6.
The aphid–natural enemy interaction in winter wheat fields constitutes a complex system that has been frequently studied because of its implication for biological control. However, not all of the aphids living in cereal fields are crop pests, as there are also aphids living on weeds that may serve as alternative hosts or prey for aphid parasitoids or predators. In this context, a concomitant survey of the plant and insect communities was conducted to understand how different plant communities affect the abundance and richness of aphids and the interactions with their natural enemies. The plant community was split into functional groups (grasses, legumes and forbs), and the aphid community was divided into feeding groups according to their host preferences (specialists in grasses or forbs). The grass aphids, which dominated the total aphid catches, responded positively to grass cover, which was particularly enhanced in the conventional fields. Conversely, the forb aphids, which mainly conditioned the total species richness of the aphids, were closely correlated with the local abundance of legumes. The system of cereal aphid-parasitoids was enhanced in the conventional fields, where the abundance of grasses was higher, whereas the legumes of the organic fields indirectly played a key role in enhancing the richness of the parasitoids and the abundance of predators. Our findings indicate that a bottom-up effect exists throughout the plant community, aphids, and aphidophagous insects and that plant community characteristics should be considered to better understand cereal aphid control.  相似文献   

7.
蛀干害虫是园林植物的毁灭性害虫,严重阻碍城市园林植物的健康生长。由于蛀干害虫长期营隐蔽性生活,化学防治难度较大,本文从寄生性天敌昆虫、捕食性天敌、病原微生物、昆虫病原线虫、植物性杀虫物质、基因工程等方面对园林蛀干害虫生物防治的研究和应用进行了论述,对存在的问题及其应用前景进行了展望。  相似文献   

8.
In eastern North Carolina, USA, intensively managed pine (Pinus spp.) forests, a primary forest type in the Southeastern United States, often are established where water levels are maintained via ditching. In these landscapes, water occurs in numerous linear ditches and several small ponds (heliponds), used by helicopters for the suppression of forest fires. Changes to the physical structure of water sources may be important to bats that use these sources for drinking and foraging. Therefore, we examined bat activity in a managed pine landscape and an adjacent natural wetland in relation to water source type (heliponds, ditches, and natural wetland) and insect abundance. We sampled bat activity using remote acoustic detectors; we sampled insects using passive traps. Insect abundance did not differ among water source types. Bat activity was most concentrated at modified water sources within the managed pine landscape (heliponds and ditches). Feeding activity was highest at heliponds. Heliponds and ditches were important sources of open water and insect prey for bats in the managed pine forest landscape. We suggest management for bats in similar forest landscapes should include maintenance of open and accessible water sources such as heliponds.  相似文献   

9.
Generalist arthropod predators are potential drivers of population dynamics in a wide variety of ecosystems but their feeding habits are often difficult to reveal as they are small, mobile, and live among dense vegetation or in soils. DNA-based gut-content analysis is a powerful tool that enables studies on arthropod predator–prey interactions. We studied lycosid spiders (Pardosa spp.) in agroecosystems to see if they consumed cereal aphids (Rhopalosiphum padi) and Collembolans at random, i.e., in proportion to their abundance in the field. We also tested if consumption of the target prey items was affected by the presence of alternative food. Spiders were captured in farmers’ fields and their gut-contents screened by PCR with R. padi and Collembola primers. On all sampling occasions, concurrent assessments of total prey availability were carried out. Spider predation rates on R. padi always exceeded 50 %. Spiders also tested positive for Collembola but to a lower and more varying degree. In general, Pardosa did not consume R. padi and Collembolans in relation to their abundance in the field. Aphid predation was much higher than expected whereas consumption of Collembolans was considerably lower. The presence of alternative prey influenced consumption of the aphid. It was concluded that prey consumption by Pardosa spiders generally cannot be assumed to simply mirror prey availability. The spatial distribution of the target prey needs to be considered as well as the abundance, composition, and nutritional content of potential alternative food items.  相似文献   

10.
Because natural regeneration of oak is strongly dependent on jay abundance and distribution, we need to understand the determinants of jay abundance and occurrence as a first step to assess oak regeneration. In this paper we modelled the jay population distribution and abundance in a Mediterranean landscape mosaic of the eastern Iberian Peninsula (Valencia, east Spain). The methodology was based on assessing landscape attributes (habitat composition and configuration variables) on seven 9-km2 sites and registering jay fledgling locations. Using a stepwise regression model we determined the variables that best explained the jay density. The probability of occurrence of jay nests within each site was assessed by comparing the landscape attributes of jay and non-jay areas within each site. Results were validated by predicting each site on the basis of data from the remaining six sites and then calculating the deviation between the predicted and the observed values in the field. The results suggest that jay density correlates positively with forest cover and landscape heterogeneity variables, and negatively with shrubland cover. Validation of the results showed that the model is reasonably effective in predicting both jay abundance and distribution at the extent and resolution used.  相似文献   

11.
Wireworms, the larvae of click beetles are world-wide pests of arable and vegetable crops. Many studies have shown that arthropods are influenced by landscape context. Therefore, for successful wireworm risk assessment, it is important to gain more information on relationships between landscape structure and wireworm infestation level. The aim of this study was to investigate if different landscape variables are related to wireworm infestation, represented by the proportion of wireworm damaged potato tubers. Based on aerial photographs and field surveys landscape variables, such as landscape composition, landscape complexity and ecological variables were characterised around 14 randomly selected potato field plots alongside the gradient from the lower warm-dry “Weinviertel” (region 1) to the cool-humid “Waldviertel” (region 2) in the North-East of Austria at three scales (1, 9 and 25 ha). Relationships between landscape variables and wireworm damage ratings were described by Spearman correlations coefficients. Our results showed that wireworm damage was higher in region 2 than in region 1 and tended to be higher in soils with higher sand content. Among the tested landscape variables only landscape composition, especially grassy field margins were significantly positively correlated with wireworm damage at the 25 ha scale. In areas with high proportion of such grassy habitats, farmers should pay more attention to field characteristics, such as sand content in soil, and management, like crop rotation. Further investigations on appropriate management regimes for grassy landscape elements suppressing wireworm populations but ensuring the maintenance of natural pest control should be conducted.  相似文献   

12.
Lepidoptera larvae are important prey for capercaillie chicks {Tetrao urogallus), but utilization varies among habitats. This field experiment investigates the effects of larval feeding behaviour, abundance and the density of bilberry (Vacciniwn myrtillus) on utilization of larvae by a group of four capercaille chicks and also tests whether chick utilization differs between wet and dry coniferous forest. In fenced plots, four hand‐raised chicks were released for a 15 min feeding period. Reduction of geometrid larvae was correlated positively with their abundance but correlated negatively with bilberry density. Geometrids had a much higher predation risk than pyralids and tortricids, probably because they are exposed while feeding, in contrast to pyralids and tortricids. Total reduction of lepidoptera was higher in wet than dry forest, probably due to a higher proportion of geometrid larvae, and lower density of bilberry in the wet forest. The manner of insect feeding and habitat type (e.g. wet and dry forest), which influence bilberry density, therefore may be important factors to consider when assessing or managing habitat quality for capercaillie chicks.  相似文献   

13.
Monitoring populations of pests and their natural enemies under different management situations and seasonal weather parameters provides extremely useful information for taking preventive measures against pest outbreaks. The abundance, spatial and temporal distributions of herbivorous insects and arthropod natural enemies on Alnus species were monitored at four sites in Kabale district, Uganda between June 1999 and August 2000. Chewing insects, dominated by Coleoptera (75%), constituted the majority of insect herbivores sampled. Dominant and potentially serious pests of Alnus included Apion globulipenne, an unidentified Chrysomelidae (Coleopt. 27), Phymateus viridipes, Coloborrtics corticina and a Cacopsylla species (Homoptera: Psyllidae). Spiders were the predominant natural enemies accounting for 64% of the total natural enemies encountered, followed by parasitic Hymenoptera (30%). There were marked spatial and temporal variations in arthropod abundance. Among sites, mean abundance of total insect herbivores and total natural enemies on A. acuminata over 15 months ranged from 3.8–8.5 and 3.3–4.7 individuals per 1-m branch length respectively. Over the same period, mean number of total insect herbivores and total natural enemies on A. nepalensis that was studied at only one site were 11.9 herbivores and 4.2 natural enemies per 1-m branch length. Populations of most insect orders increased in the wet season although the greatest herbivore abundance was evident in the dry season. Further studies are necessary on the impact and management strategies of the potentially important insect pests and natural enemies on Alnus.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

14.
Analysing food webs in agricultural habitats is essential for the development of natural control strategies. Several molecular tools to investigate trophic interactions on a species-specific level have been developed in recent years and their advantages and limitations have been discussed. With this study we introduce another tool, terminal restriction fragment length polymorphism (tRFLP). Generalist predators found in Australian brassica crops, their prey and abundant parasitoids were chosen as a model system to adapt and evaluate the tRFLP approach. Using general primers and selecting six restriction enzymes, we obtained species-specific tRF patterns for 21 of the most abundant arthropods in brassica crops. We detected up to three prey species in the gut contents of laboratory-fed predators. Detection rates differed among predators, ranging between 28 and 100%. The identification of a species-specific tRF pattern was strongly affected by the presence and concentrations of DNA from other species. In a preliminary field study, prey could be identified from 20% of the collected brown lacewings. The advantage of the tRFLP method is the possibility of identifying multiple species at once. This advantage is counterbalanced by methodological limitations, among which the most critical one is the fact that it will be difficult to maintain specificity in highly diverse ecosystems. However, if species diversity is limited and the target sequence and the primers are chosen to increase detection success, the tRFLP method can be used to study trophic interactions in the field.  相似文献   

15.
The most important literature on the ecological importance of spiders for forest ecosystems was compiled and analyzed. Forest spiders normally live in densities of 50 to 200 individuals/m2 and prey, at least in Europe, predominantly on small soft-bodied insects (Diptera and Collembola mainly). However, bigger insects, including various forest pests, are also found in their prey. According to the present stand of knowledge the spiders of the soil surface seem to be important insect predators, whereas the ecological importance of spiders living on the trees is still controversial.  相似文献   

16.
Present study was designed to assess the prey preference behaviour of three most dominant hunting spiders [Lycosa terrestris Butt, Anwar and Tahir 2006 (Araneae: Lycosidae), Pardosa birmanica Siman 1884 (Araneae: Lycosidae) and Oxyopes javanus (Thorell 1887) (Araneae: Oxyopidae)] of rice ecosystems both in the laboratory and in the field. Two types of laboratory experiments, i.e., choice and no choice feeding, were performed using only adult male and female specimens of the spiders. No choice test showed that each of the three hunting spiders readily consumed larvae and nymphs of rice pests offered. Female hunting spiders consumed more prey compared to male hunting spiders. Results of choice feeding test indicated that L. terrestris and P. birmanica preferred nymphs of rice insect pests while O. javanus preferred larvae of rice insect pests. Results of direct observations showed that in August, dipterous insects were the most numerous rice pests consumed by L. terrestris, P. birmanica and O. javanus, comprising over 56.3, 38 and 48% of their respective diets. In contrast, in September, the proportion of dipterous insects decreased dramatically and hoppers become the most numerous pests, comprising over 50, 51 and 41% of all prey and spiders consumed by L. terrestris, P. birmanica and O. javanus, respectively. In October, aquatic Heteroptera were frequently observed in their diets. Predatory potential of these hunting spiders differed statistically in the laboratory as well as in the field. It is concluded from the results of present project that studied species of spiders could successfully be used to control insect pests of rice ecosystems.  相似文献   

17.
We examined mortality patterns of two conifer species in relation to tree abundance and species composition in a declining spruce-fir forest in Akan National park, Hokkaido, northern Japan. The data taken from eleven 58 m × 58 m square study plots showed that percentage basal area (BA) of dead trees of canopy trees during the last decade was 49% forPicea jezoensis (Sieb. et Zucc.) Carr and 30% forAbies sachalinensis (Fr. Schm.) Masters. InP. jezoensis, percentage basal area (BA) of dead trees was positively related to both BA of its own species and proportion of it to BA of all species, whereas it was not significantly related to both of these variables inA. sachalinensis. Multiple logistic regression with dbh as a confounding factor also indicated that, inP. jezoensis, the proportion of dead stems was positively affected by the stem density of conspecific trees, whereas it was negatively affected by the stem density of the other species in each study plot. However, inA. sachalinensis, the proportion of dead stems was significantly related to neither of these factors. The different mortality pattern between two conifer species suggests that the spruce bark beetle,Ips typographus (L.), which is a serious pest of spruce, may have caused theP. jezoensis decline. Instead of wind-throw or thinning that usually initiate this bark beetle attack, some unknown factors seemed to predispose the trees to insect attack. These unknown factors may also explain the high mortality ofA. sachalinensis in this forest. This research was supported by FFPRI Project, Ministry of Agriculture, Forestry and Fishery.  相似文献   

18.
湖州青梅害虫及天敌种类调查和结构分析   总被引：1，自引：0，他引：1  
通过详细的林间样地踏查,调查了浙江省湖州长兴地区青梅林的昆虫及蜘蛛的种类,分析了各类群的组成结构。共采集到昆虫98种(青梅害虫67种,天敌昆虫26种,中性昆虫5种)、蜘蛛5种。调查表明,青梅害虫主要有黑蚱蝉C ryptotympana atrata、八点广翅蜡蝉Ricania speculum、杨梅球坚蚧Eulecanium kunoensis、褐刺蛾Setora postornata及太谷桃仁小蜂Eurytoma maslovskii5种,其中又以黑蚱蝉和太谷桃仁小蜂最为主要。青梅林昆虫群落功能结构分析表明,青梅林昆虫群落中以植食性昆虫占主导地位,占全部种类的65.05%。首次报道了青梅林害虫及天敌的种类和结构,为青梅害虫的防控提供了参考。  相似文献   

19.
The natural enemy hypothesis predicts a positive correlation between plant species diversity and natural enemy control. This study aimed to evaluate the role of traditional cacao agroforests, known as “cabrucas,” on the conservation of the predatory beetle community compared to that of monodominant rubber agroforests. Predatory beetles were sampled in three habitats in Southeastern Bahia, Brazil: cabrucas and rubber agroforests and native Atlantic forests. In each habitat, 18 10 m2 plots were established, in which canopy cover was measured and beetles were sampled with a modified Malaise/window trap. Land use intensification did not affect the composition of predatory beetles, with the presence of widely distributed species that are also capable of colonizing simpler environments such as the rubber agroforest. Canopy cover had a positive effect on generalist predator diversity and we observed a reduction in the abundance and species richness of generalist predators with increasing habitat homogenization. Despite the simplified structure of the habitat, the remaining tree diversity and canopy cover in cabrucas supported a community of generalist predators similar to the one found in the native forest. Species diversity of bark beetle predators was higher in cabrucas, which may be due to the high diversity of bark beetles and the favorable abiotic conditions, whereas the low abundance of prey in the native forest and severe abiotic conditions in the rubber agroforest probably determined the lower diversity of generalist predators in these habitats. Cabrucas play an important role in the conservation, supporting a community of predatory beetles more similar to the one found in native forest and that is more effective at controlling populations of herbivores than in homogeneous rubber agroforests.  相似文献   

20.
We assessed the effect of abandonment of sylvo-pastoral practices in chestnut orchards (Castanea sativa) on bats in southern Switzerland to determine practical recommendations for bat conservation. We compared bat species richness and foraging activities between traditionally managed and unmanaged chestnut orchards, testing the hypothesis that managed orchards provide better foraging opportunities and harbour more bat species. Echolocation calls of foraging bats were sampled simultaneously at paired sites of managed and unmanaged orchards using custom made recorders. Vegetation structure and aerial insect availability were sampled at the recording sites and used as explanatory variables in the model. In a paired sampling design, we found twice the number of bat species (12) and five times higher total foraging activity in the managed chestnut orchards compared to the unmanaged ones. Bat species with low flight manoeuvrability were 14 times more common in managed orchards, whereas bats with medium to high manoeuvrability were only 5 times more common than in abandoned orchards. The vegetation structure was less dense in managed orchards. However, management did not affect relative insect abundance. Bats primarily visited the most open orchards, free of undergrowth. As a result of restricted access into the overgrown forests, the abandonment of chestnut orchards leads to a decline in bat species richness and foraging activities. Continued management of chestnut orchards to maintain an open structure is important for the conservation of endangered bat species in the southern Swiss Alps.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号