Effects of agroecosystem diversification on natural enemies of soybean herbivores

This study evaluated the effects of agroecosystem diversification through no-tillage and strip intercropping on the abundance of natural enemies of soybean (Glycine max Merrill) herbivores. Twenty-four plots (289 m² each) were arranged in a randomized complete block design for a 3 by 2 factorial experiment. Factors were cropping systems (corn monoculture, soybean monoculture, and strip intercropping of corn and soybean) and tillage systems (no-tillage and conventional tillage). Natural enemies were sampled during 1988, 1989 and 1990 by sweep net, suction net (D-Vac), pitfall traps and quadrat samples. Analyses of variance indicated that of 15 taxa analyzed, most foliage-inhabiting natural enemies were significantly more abundant in intercropping than in monoculture plots, whereas soil-inhabiting natural enemies had higher numbers in no-tillage plots than conventional tillage plots. Therefore, the results support the theory of greater abundance of natural enemies in more complex agroecosystems. Better environmental conditions in diversified treatments was the possible reason for these results. Corn in intercropping plots provided shade, reduced wind speed, alternate food, and possibly higher humidity and lower temperatures for soybean natural enemies. A similar effect was likely cuased by the stubble and weeds, in no-tillage plots.     

Consumption of carrot weevil,Listronotus oregonensis, [Coleoptera: Curculionidae] by four species of carabids on host plants in the laboratory

Four carabid species,Anisodactylus santaecrucis, Bembidion quadrimaculatum oppositum, Pterostichus lucublandus andPterostichus melanarius, abundant in carrot fields in southwestern Quebec, were tested for predation against the carrot weevil,Listronotus oregonensis, on host plants. The largest species,Pterostichus melanarius, consumed the greatest number of carrot weevil larvae and pupae.Bembidion quadrimaculatum oppositum did not prey on carrot weevil eggs laid on carrot leaves.      

A field experiment on the effectiveness of spiders and carabid beetles as biocontrol agents in soybean

1 Spiders and carabid beetles are abundant generalist predators that prey upon insect pests of soybean. A field experiment was conducted to determine the impact of spiders and carabids on soybean yield. Prior to planting, three 7 × 7 m plots were fenced in order to reduce spider and carabid immigration. Carabids that emerged within the plots were not removed, but spiders that ballooned into these predator‐reduction plots or that entered by climbing the fence were removed by pitfall trapping and searching the vegetation. Three unmanipulated, unfenced plots served as the control treatment. 2 Densities of spiders on soybean vegetation, and activity‐densities of spiders and carabids determined by pitfall trapping, were c. 75% lower in the spider‐carabid reduction treatment than in control plots. Despite clear differences between treatments in numbers and activity of these major generalist predators, the weight of soybeans harvested did not differ between control and spider‐carabid reduction plots. 3 Paralleling the absence of an effect of predator reduction on soybean yield was the absence of any significant difference between treatments in densities of whiteflies (Aleyrodidae), leafhoppers (Cicadellidae), thrips (Thysanoptera), Lepidoptera larvae and herbivorous Coleoptera. 4 Our experiment provides no evidence that spiders and carabid beetles at ambient densities affect soybean yield. Low populations of pest species or low predation pressure on soybean pests by spiders and carabids at the ambient densities of this experiment could be responsible for this result.     

Pitfall trap catches of and aphid predation byPterostichus melanarius andPterostichus madidus in insecticide treated and untreated potatoes

Aphids were countedin situ and carabid beetle populations assessed by pitfall trapping betwen 1983–1985 in potato fields in Scotland treated with demeton-S-methyl (DSM) or untreated.Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae) was the most abundant aphid. Nineteen species of carabid beetles were trapped but the fauna was dominated byPterostichus melanarius (Ill.) andPterostichus madidus (Fabr.) (Coleoptera: Carabidae). Pitfall trap catches of these carabids were variable but generally lower in sprayed than unsprayed plots for a few days after DSM application and higher a week or two later. Of 1800P. melanarius and 910P. madidus dissected, 14.4 per cent and 30.5 per cent respectively, contained aphid remains. The proportion that had eaten aphids often was higher in sprayed than unsprayed plots immediately after treatment. In additional experiments, aphids treated with DSM fell from plants; four to five per cent of the theoretically applied dose of DSM reached the ground in a closed-canopy potato crop; and no mortality occurred whenPterostichus spp. were exposed to DSM in a field bioassay. It is proposed that observed patterns in trap catch ofPterostichus spp. around times of pesticide application may be due in part to aphids falling to the ground after treatment. Beetles that eat these fallen aphids may be less hungry, less active and less likely to be trapped. Later increases in catches may be attributed to hungry, more active beetles, a consequence of prey removal by the insecticide. Although this hypothesis requires further research, it is clear that the effects of insecticide treatment on carabid populations cannot be measured by pitfall trapping alone.     

Carabid beetle (Coleoptera: Carabidae) assemblages in the intermediate successional stage after Mt. Bandai eruption of 1888: Effects of environmental variables on carabid beetles in the Urabandai area

We studied carabid beetle assemblage structure and species diversity in an intermediate successional stage (seral) forest established in areas affected by the 1888 eruption of Mt. Bandai and a climax forest that had not been affected by the eruption at the Urabandai area, Fukushima Prefecture, Japan. In total, 2,131 carabid beetles representing 31 species were collected using pitfall traps without bait. A comparison of carabid beetle assemblages between the two forest types revealed that the number of species observed was comparable, but their abundance was greater in the seral forest. The assemblage structure clearly differed between the two forest types. In the seral forest, forest generalists, such as Synuchus arcuaticollis and Pterostichus prolongatus, along with forest specialists including Carabus vanvolxemi and Pterostichus asymmetricus, were collected. In the climax forest, forest generalists, such as Synuchus cycloderus and Carabus albrechti tsukubanus, were more abundant than forest specialists. This suggests that the current seral forest in the Urabandai area possesses environmental variables that enable the coexistence of both forest specialist and generalist beetle species. A redundancy analysis showed that six species from the genera Synuchus and Pterostichus were associated with high canopy openness and high understory vegetation cover, whereas species recorded only in the climax forest were associated with deep litter. Therefore, it seems likely that carabid beetles in the Urabandai area were affected by these three environmental variables.     

Tillage differentially affects the capture rate of pitfall traps for three species of carabid beetles

The influence of tillage, gender, and microclimate on capture rates of pitfall traps for the beetles Poecilus scitulus LeConte, Poecilus lucublandus (Say), and Pterostichus melanarius Illiger (Coleoptera: Carabidae) were assessed in mark–release–recapture experiments in spring pea and spring wheat. Experiments were conducted during June, July, and August of 2003 in the Palouse region of northern Idaho, USA. Rates of capture in pitfall traps for the three carabid species were differentially affected by crop‐tillage systems. Capture rates for P. scitulus and P. lucublandus were higher in no‐till (NT) than in conventional tillage (CT) peas, whereas capture rates for P. scitulus and Pt. melanarius were higher in CT than in NT wheat. Ground‐level temperatures and relative humidity (r.h.) differed little among tillage systems. Nevertheless, capture rates were generally positively correlated with ground‐level temperature and negatively correlated with r.h., with correlations more often significant in NT than in CT systems. The response of the thermophilic Poecilus spp. to temperature provides a possible mechanistic explanation for capture rate patterns in legumes during June, but not in other months for peas or any month in wheat during the experiments. Movement impedance due to residue could explain lower capture rates of P. scitulus and Pt. melanarius in NT than in CT spring wheat. These results suggest that researchers using pitfall trapping for carabid populations should take into account potential capture biases their treatments can introduce.     

Influence of compaction from wheel traffic and tillage on arbuscular mycorrhizae infection and nutrient uptake by Zea mays

Interactive effects of seven years of compaction due to wheel traffic and tillage on root density, formation of arbuscular mycorrhizae, above-ground biomass, nutrient uptake and yield of corn (Zea mays L.) were measured on a coastal plain soil in eastern Alabama, USA. Tillage and soil compaction treatments initiated in 1987 were: 1) soil compaction from tractor traffic with conventional tillage (C,CT), 2) no soil compaction from tractor traffic with conventional tillage (NC,CT), 3) soil compaction from tractor traffic with no-tillage (C,NT), and, 4) no soil compaction from tractor traffic with no-tillage (NC,NT). The study was arranged as a split plot design with compaction from wheel traffic as main plots and tillage as subplots. The experiment had four replications. In May (49 days after planting) and June, (79 days after planting), root biomass and root biomass infected with arbuscular mycorrhizae was higher in treatments that received the NC,NT treatment than the other three treatments. In June and July (109 days after planting), corn plants that received C,CT treatment had less above-ground biomass, root biomass and root biomass infected with mycorrhizae than the other three treatments. Within compacted treatments, plants that received no-tillage had greater root biomass and root biomass infected with mycorrhizae in May and June than plants that received conventional tillage. Corn plants in no-tillage treatments had higher root biomass and root biomass infected with mycorrhizae than those in conventional tillage. After 7 years of treatment on a sandy Southeastern soil, the interactive effects of tillage and compaction from wheel traffic reduced root biomass and root biomass infected with mycorrhizae but did not affect plant nutrient concentration and yield. ei]J H Graham     

Effects of alternative food on cannibalism and herbivore suppression by carabid larvae

1. Predator and alternative food density are important factors influencing herbivore suppression by generalist predators. Herbivore suppression can be reduced if predators forage preferentially on alternative foods. Cannibalism can increase at high predator densities, further reducing herbivore suppression. However, complex interactions are possible, as alternative food can increase predator abundance and survival restoring top‐down effects on herbivores. 2. In two species of carabid larvae (Poecilus chalcites and Anisodactylus ovularis), we studied how alternative foods (fly pupae and grass seeds) and predator density affect predation of black cutworm larvae and how alternative foods affect cannibalism among carabid larvae. 3. Adding alternative food to microcosms generally reduced total predation of cutworms. However, the strength of this effect was dependent on carabid species, larval density, and food type. 4. Increasing larval density from one to three per microcosm reduced per‐capita predation by both species irrespective of alternative food treatment. 5. Alternative food reduced cannibalism in both carabid species and increased survival of carabid larvae in field plots, such that twice as many were captured in plots subsidised with pupae than plots with no alternative food. 6. These results provide new insight into the complex interactions that influence predator survival and herbivore suppression in resource diverse habitats by demonstrating the primacy of intraguild interactions among carabid larvae.     

冬小麦免耕覆盖与生物有机肥施用对土壤细菌群落的影响

为揭示保护性耕作措施对土壤细菌群落结构及多样性的影响规律,选取免耕覆盖＋施生物有机肥（NF）、免耕覆盖＋不施生物有机肥（NC）、传统耕作不覆盖＋施生物有机肥（TF）和传统耕作不覆盖＋不施生物有机肥（TC）4个处理,以农田土壤生态系统为研究对象,利用16S rDNA基因Illumina MiSeq高通量测序技术,研究了冬小麦免耕覆盖与生物有机肥施用对土壤细菌群落结构及多样性的影响。结果表明：1）与TC处理相比,NF处理显著降低了土壤pH （P=0.03^*）,增加了土壤全氮（P=0.002^**）、总碳含量（P=0.0001^**,P=0.007^**）,影响了土壤碳/氮比分配（P=0.003^**）。2）从16个土壤样本中共获得细菌27门、86纲、125目、213科和315属,其中放线菌门（Actinobacteria）、酸杆菌门（Acidobacteria）、绿弯菌门（Chloroflexi）和变形菌门（Proteobacteria）为优势菌门,其相对丰度约占总丰度的82.40%。3）与传统耕作施生物有机肥处理相比,免耕覆盖施生物有机肥增加了土壤细菌的多样性指数（Simpson指数和Shannon指数）,降低了ACE丰富度指数。4）NMDS及多元分析结果表明：土壤细菌群落丰富度指数、多样性指数均与土壤pH、速效磷和土壤碳/氮比成正相关,与土壤微生物生物量碳（SMBC）和土壤总碳成负相关;其中,土壤pH和SMBC分别是影响酸杆菌门和放线菌门的主要驱动因子。施生物有机肥和耕作措施两种因素均对土壤细菌群落结构组成产生了影响,但以施用生物有机肥对土壤细菌群落多样性的影响较明显;此外,施用生物有机肥在传统耕作和免耕覆盖两种情况下均增加了冬小麦产量,但以传统耕作施生物有机肥处理最明显。因此,传统耕作配施生物有机肥是宁夏南部山区改善土壤理化性质、增加土壤细菌群落丰富度和多样性的重要途径。     

Effects of tillage on the activity density and biological diversity of carabid beetles in spring and winter crops

The effects of tillage regimen (conventional [CT] and no-tillage [NT]) on the activity density and diversity of carabid beetles (Coleoptera: Carabidae) was studied by pitfall trapping within a rain-fed cropping system in northwestern Idaho, 2000-2002. The cropping rotation consisted of a spring cereal (barley, Hordeum vulgare L., in 2000 and 2001; and wheat, Triticum aestivum L., in 2002), spring dry pea (Pisum sativum L.) 2000-2002, and wheat (T. aestivum), spring in 2000 and 2001, and winter in 2002. A total of 14,480 beetles comprised of 30 species was captured, with five numerically dominant species [Poecilus scitulus L., Poecilus lucublandus Say, Microlestes linearis L., Pterostichus melanarius Ill., and Calosoma cancellatum (Eschscholtz)], accounting for 98% of all captures. All species including the dominants responded idiosyncratically to tillage regimen. Adjusting for trapping biases did not significantly change seasonal activity density of Poecilus spp. or Pt. melanarius to tillage. More beetles were captured in CT than in NT crops because of the dominance of P. scitulus in CT, whereas species richness and biological diversity were generally higher in NT crops. Observed patterns suggest that direct effects of tillage affected some species, whereas indirect effects related to habitat characteristics affected others. CT may provide habitat preferable to xerophilic spring breeders. A relationship was found between beetle species size and tillage regimen in pea and to a lesser extent across all spring crops, with large species (>14 mm) conserved more commonly in NT, small species (<7 mm) in CT, and intermediate species (7-14 mm) conserved equally between tillage systems.     

Organic mulches vs. black plastic in organic strawberry: does it make a difference for ground beetles (Col., Carabidae)?

Abstract:  Carabid beetles were sampled by pitfall traps in May–September 2002 and 2003 in an experimental organic strawberry field in seven different mulching row treatments and in fescue-growing row spaces to determine the effect of mulches on carabid activity–density and species composition. There were no differences between treatments or row spaces in total numbers of all carabid species in either season. Of the 67 identified species and 4374 individuals, the most trapped ones were Clivina fossor (11.7% of total catch), Dyschirius globosus (10.2%), Patrobus atrorufus (9.3%), Pterostichus niger (8.8%), Bembidion properans (7.4%), Pterostichus melanarius (6.0%), Bembidion lampros (5.7%), Pterostichus crenatus (5.7%), Amara communis (4.1%), Trechus secalis (3.9%), Pterostichus strenuus (3.9%), Loricera pilicornis (3.1%), Harpalus rufipes (2.8%) and Carabus nemoralis (2.6%). Large carabid species P. niger and P. melanarius were trapped more in all mulched rows than in row spaces, and C. nemoralis was trapped more in the mixture of pine woodchip/buckwheat husk mulch than in row spaces, barley straw and birch woodchip mulch. The small but abundant species P. atrorufus was trapped more in buckwheat husk mulch than in row spaces and B. properans in row spaces than in buckwheat husk mulch. H. rufipes , being also a pest in strawberry, was trapped more in cut grass mulch than in row spaces. The Shannon H' diversity index was significantly higher in the mixture of pine woodchip/buckwheat husk mulch than in black plastic, buckwheat husk mulch or in row spaces, and in birch woodchip and cut grass mulches than in row spaces. The results of trapping studies show the species preference to the specific mulches, and reflect positive or negative effect of mulches on carabid diversity with consequences to plant protection.     

Influence of pest control pressure on occurrence of ground beetles (Coleoptera: Carabidae) in apple orchards

Bioindicators that reflect the level of chemical control have not been developed for use in apple orchards in Japan. In Japan, many carabid beetles and spiders are beneficial predators of a wide range of agricultural pest insects. In apple orchards, spider numbers are reflective of the level of control pressure, but there is no information on carabid beetles. To establish whether carabid beetles could indeed be useful bioindicators, the number of carabid beetles and spiders in six apple orchards (A–F) under different levels of control pressure was investigated in Akita prefecture, northern Japan, in 2008 and 2009. The negative impact on beneficial arthropods was assumed to decrease in the order of pyrethroids (A) > organophosphates (B) > neonicotinoids (C) > insect growth regulators (D) > fungicides only (E) > no spraying (F). Sprays were applied at 2-week intervals from mid-May to early August. Twenty species of carabid beetles were found in orchard F; about 50% of adults were Anisodactylus punctatipennis, and 30–40% were Amara chalcites. The number of Am. chalcites significantly decreased with increasing control pressure: (A–C) < (E, F) in 2008, (A–E) < F in 2009, and (A, B) < E in 2009. Most spiders collected were juvenile Tetragnathidae and Araneidae. The numbers of spiders and Am. chalcites adults were significantly highly correlated at each control pressure in both years. Thus, it was considered that only Am. chalcites adults can be used as bioindicators reflecting the control pressure in apple orchards in northern Japan, whereas the main diet of this species is probably C3 plants.     

Diversity and abundance of the coleopteran fauna from organic and conventional management systems in southern England

1 Studies of the epigeal coleopteran fauna on five pairs of organic and conventional farms were carried out between May and July 1994 in southern England using pitfall trapping. A total of 27 749 individuals and 140 species were identified. Overall, abundance of Coleoptera was greatest on organically managed farms. 2 Ground beetles (Coleoptera: Carabidae) and staphylinid beetles (Col. Staphylinidae) formed 79.7% and 16.7%, respectively, of the total catch. Pterostichus melanarius was the dominant carabid among the 45 species captured and significantly higher numbers were found in organic farms. Tachinus signatus was the most common of 44 staphylinid species, and was significantly more abundant on conventional farms. 3 For carabids, the log‐series α diversity index was higher on conventional farms but was not statistically different from that calculated for organic farms. The α index was identical for staphylinid species from organic and conventional farms. Diversity was significantly higher from conventional farms when data were combined for all of the recorded coleopteran species. 4 From this study, it appears that the main effect of farming practice is to influence the overall abundance and dominance of particular species, and the lower diversity of organic farms is a consequence of the large increase in dominance of a single species, namely P. melanarius.     

Impacts of Leaf-litter Addition on Carabids in a Conifer Plantation

As a fine-scale, manipulative model experiment leaf litter was added in plots to increase habitat heterogeneity in a 50-year-old Norway spruce plantation, established after the clear-cutting of a native beech forest, during a 2-year period in the Hungarian Mountain Range. Pitfall trap catches of carabids from leaf-litter plots were compared with those from control plots to explore the effect of leaf-litter addition. Difference in the species composition was revealed by ordination; scores of the samples of the two plot types were significantly separated along the first MDS axis. The most numerous species (Pterostichus oblongopunctatus) was significantly more abundant in the leaf-litter plots. However, there were no significant differences for the other most frequently obtained species. Habitat generalist species were the most abundant, followed by forest generalists, then forest specialists, and there were some open habitat species. Enhanced habitat heterogeneity (leaf-litter addition) in homogeneous plantations influenced the spatial distribution and composition of carabids, through altered abiotic (lower ground temperature in the leaf-litter plots) and biotic (more prey items) factors. Differences in abundance, species richness and Shannon diversity were not significant between the control and the manipulated plots, although carabid catch was higher in the leaf-litter plots during both years. Forestry practices to increase habitat heterogeneity should be considered to enhance biodiversity in managed forests.     

耕作和养分管理方式对冬小麦-夏玉米轮作农田春季杂草群落的影响

保护性耕作和杂草多样性是现代生态农业关注的热点问题.尽管保护性耕作下农田杂草多样性有所提高,但耕作方式与养分管理方式对农田杂草群落多样性的交互影响尚未探明.本研究以山东省济南市一块连续3年施行不同耕作方式(免耕、深松、旋耕、深耕)和不同养分管理措施(农户常规:年施氮肥480 kg·hm^-2,高产高效:年施氮肥360 kg·hm^-2,优化管理:年施氮肥300 kg·hm^-2)的冬小麦-夏玉米轮作农田为研究样地,调查并比较了不同管理模式下农田春季杂草群落特征.结果表明: 该冬小麦-夏玉米农田春季杂草群落共发现杂草15种,其中优势物种为马唐和稗;与深耕和旋耕相比,免耕和深松下杂草密度较高.在群落多样性方面,深耕处理下的物种丰富度和均匀度最低,而群落优势度高于其余3种耕作方式;在养分管理中,随着施肥量的增加,物种丰富度和均匀度均升高;深耕和旋耕处理下,随着施肥量的增加,群落优势度升高;而在免耕深松处理下,群落优势度会随着施肥量的增加而减少.在杂草群落生物量方面,免耕和深松的生物量显著高于深耕和旋耕,农户常规处理均高于其余两种养分管理方式,杂草生物量最高的组合是免耕+农户常规.免耕和施肥将提高农田春季杂草群落丰富度、均匀度和生产力.     

Impact of tillage on the incidence ofFusarium spp. in soil

The influence of several long-term conventional and conservation tillage treatments on the incidence and the diversity ofFusarium spp. in soil was studied. Soil samples were randomly collected from naturally contaminated field trials and Fusarium species were isolated by using the dilution plate method. The identification of the species was done by direct microscopic observation onFusarium-specific media. The isolation frequency ofFusarium species and the total number of colony forming units was affected by the sampling year and the cultivated crop and showed significant differences between the tillage treatments. Moldboard plough-treatments resulted in a lower diversity of Fusarium species than the chisel plough and rotary tiller treatments. Besides the tillage system the tillage depth also appeared to affect theFusarium populations. The deeper the tillage the lower was the number of isolatedFusarium spp. TwentyFusarium species were identified over both years of investigation. In conservation tillage plots a higher diversity ofFusarium species was found than in the moldboard plough-based tillage plots. A correlation betweenFusarium species producing the mycotoxin deoxynivalenol (DON) isolated from soil and the DON-content of grain could not be observed. However, these investigations indicate that conservation soil tillage results in conditions which increase the incidence ofFusarium species in soil.     

The carabid communities on peat and upland grasslands in northern England

During a two year period 13498 individuals of 66 species of carabids were taken from 44 sites on peat and upland grasslands over an altitude range of 11-847 m in the north of England. The similarities between the carabid faunas of each site have been assessed using a modified form of the Sørensen's Index and the sites clustered according to their similarities. Five carabid communities on peat and three on mineral soils have been identified and the more abundant species have been used to characterise them. Peat Community I occurs on dry heath and is characterised by peat associated species such as Trichocellus cognatus and Bradycellus ruficollis together with widespread open habitat species such as Pterostichus madidus, Notiophilus aquaticus, Calathus melanocephalus and Nebria salina. Peat Community II is found on areas where dry heath and deep wet peat are adjacent and is characterised by the species already mentioned together with typical wet habitat species such as Pterostichus diligens, P. nigrita, Patrobus assimilis. Agonum fuliginosum. Peat Community III is found on blanket bog and is characterised by the wet habitat species in the absence of the species present on the dry heath. Peat Community IV found on the lowland oligotrophic mires is characterised by the small number of species present and the addition of Pterostichus niger and Agonum ericeti to the few wet habitat species present. Peat Community V, on the scarp slope of Dun Fell, consists of the wet habitat species of Peat Community III together with Pterostichus madidus. Nebria salina, Notiophilus aquaticus and Calathus melanocephalus. Grassland Community I, on the fell tops, is characterised by the presence of Nebria gyllenhali, Notiophilus germinyi and Patrobus assimitis. Grassland Community II and III are less clearly defined but Grassland Community II may be present on wetter sites than III and is characterised by the presence of Pterostichus nigrita, P. diligens and P. strennus together with Notiophilus biguttatus. N. aquaticus, Pterosfichus madidus and Patrobus afrorufus. Grassland Community III consists of the latter group of species together with Nebria salina, Calathus melanocephalus and Notiophilus aestuans. The number of grassland sites studied was small and there may be further communities on the upland grasslands.     

耕作方式对玉-豆轮作地表节肢动物多样性及其营养结构的影响

为阐明长期不同耕作方式对轮作种植模式黑土农田地表节肢动物多样性及其营养结构的影响,2015年5月至9月间,利用陷阱法对连续13年玉米大豆轮作模式的定位试验站三种耕作方式(免耕、垄作、秋翻)的地表节肢动物群落进行了调查。共捕获动物1002只,隶属于3纲11目29科37个类群,凹唇蚁、玉米毛蚁和直角通缘步甲为优势类群。免耕(NT,no tillage)有利于增加蜘蛛类群密度,垄作(RT,ridge tillage)和秋翻(MP,mould board plough)显著增加了玉米毛蚁密度。耕作方式仅对群落密度有显著影响显著影响(P0.05),而大豆不同生育阶段显著或极显著的影响地表节肢动物群落组成特征(P0.05; P0.001)。长期玉米大豆轮作种植的地表节肢动物群落营养功能群在不同耕作方式中所占比例不同,保护性耕作方式(NT、RT)更有利于捕食性和植食性动物的生存和繁殖,常规耕作(MP)则是杂食性动物占据优势,明显呈现对不稳定环境的适应。大豆不同生育期,各功能群的个体数与类群数的动态变化不尽一致,不具有明显的规律性。研究结果表明,免耕轮作对维持地表节肢动物群落内部物种间的关系及其营养结构有着较为重要的作用,保护性耕作和轮作种植模式相结合可维持农田生态系统平衡。     

农田步甲的生物学研究

本文报道12种农田常见步甲的种群动态和捕食习性,施用杀虫剂对步甲的影响。     

陕北黄土丘陵沟壑区水土保持耕作及施肥下农田土壤种子库特征

为了探明多年免耕下农田恶性杂草发生的机理,提高保护性耕作下作物对农田恶性杂草持久稳定的抑制效果,依据陕西安塞田间4a的定位试验, 采用小区调查取样和室内实验相结合的方法,从物种组成、密度特征、多样性以及相似性特征等方面,研究了黄土丘陵旱作农区大豆(Glycine max)、玉米(Zea mays)、红小豆(Semen Phaseoli)、马铃薯(Solanum tuberosum)在翻耕化肥(CF)、翻耕有机肥(CM)、翻耕无肥(CN)、免耕化肥(NF)、免耕有机肥(NM)、免耕无肥(NN)等水平下的农田土壤种子库.结果表明: (1) 4种作物24种土样中共萌发出12个物种1965株幼苗,隶属于7科12属.1年生杂草占94%,棒头草(fugax nees ex steud)、苋菜(Acalypha australis)、马唐(Digitaria sanguinalis)、早熟禾(Poa sphondylodes)为优势种,占87%.(2)在0～20cm土层不同处理间,土壤种子库的密度变动于(282.9±63.4)～(7482.5±1078.3)粒·m- 2,其中,红小豆小区＞马铃薯小区＞大豆小区＞玉米小区;翻耕小区＞免耕小区;有机肥小区＞化肥小区＞无肥小区,差异极显著. (3)土壤种子库密度NM红小豆最高,NN玉米最低;丰富度指数CF大豆为2.30;NN红小豆为0.29;多样性指数NN大豆为5.56,CF红小豆为0.45;生态优势度NF玉米为1.35,CF大豆为0.17.玉米、大豆是黄土丘陵沟壑旱作农区免耕下农田抑制杂草最为适宜的作物, NM玉米、NF大豆和NM大豆是黄土丘陵沟壑旱作农区较优的耕作管理方式,其农田的生态效应是能够竞争性抑制恶性杂草的蔓延,优化土壤环境,杂草的多样性高且比较均衡,杂草的土壤种子库密度低.