Value of fallow farmlands as summer habitats for waterbirds in a Japanese rural area

Flooded rice fields, which occupy half of the total agricultural land in Japan, are known to be foraging habitats for waterbirds. We investigated the use of various fallow fields by birds in midsummer, when rice fields are generally full of grown rice plants and are of little use for foraging waterbirds. We distinguished four types of fallow fields based on the ground cover and vegetation: (i) tall-grass fields; (ii) wet short-grass fields; (iii) dry fields; and (iv) flooded open fields. In August 1998 we counted birds four times in 19 survey plots of fallow fields and in seven plots of rice fields in Ibaraki Prefecture, Japan, where 82% of the farmlands are devoted to rice production. We observed 590 individual birds of 22 species, of which 15 species were waterbirds, mostly herons and shorebirds. Flooded open fields supported the largest number of species and the highest bird density, while rice fields supported the fewest. Within flooded open fields, herons preferred open-water areas, while shorebirds used bare ground most often. Wet short-grass fields looked similar to flooded open fields, except for the amount of short grass, but supported far fewer birds than flooded open fields. The number of birds in dry fields was comparable to that in flooded open fields, but most of the birds were ground-foraging passerines. Our limited dataset suggests that fallow fields can serve as valuable supplemental habitats for waterbirds during summer, if they are appropriately managed to preserve flooded open fields and smaller areas of other habitats.     

Western corn rootworm adult movement and possible egg laying in fields bordering maize

Abstract:  Western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, larval damage in maize following soybean was observed in Croatia in 2003 along the edges and within soybean fields which bordered continuous maize fields in previous year. The explanation was that WCR adults moved from the continuous maize to the neighbouring soybean fields to lay eggs. This study was designed to measure how far WCR adults will enter into neighbouring fields to lay eggs. The WCR adult population was monitored in continuous maize fields in 2003 and 2005 by using Pherocon^® AM non-baited yellow sticky traps in the middle and on the borders of the maize field and at different distances and directions into neighbouring fields planted by wheat and soybean. Larval presence and root damage ratings (Iowa State University 1–6 ) were recorded at different locations within the maize field in following years. Approximately, the same concentration of WCR adults was recorded along the edges of the maize fields as recorded in the centres of those fields. A significant number of WCR adults was recorded up to a distance of 50 m into neighbouring fields. Regression analysis showed medium negative correlation between distance from previous maize field and root damage in the following year. Findings indicate that WCR egg lying can reach approximately 20 m into fields neighbouring maize fields and that significant root damage caused by WCR larvae in first-year maize following soybean and wheat can happen up to a distance of 20 m into those fields. Most farmers's fields in Croatia are up to approximately 50 m wide. As an edge effect for WCR egg laying can reach approximately 20 m into fields neighbouring maize fields, our research results indicate that it is possible to see WCR larval damage in rotated fields without those WCR's being the variant form.     

Extremely low frequency electric fields and cancer: Assessing the evidence

Much of the research and reviews on extremely low frequency (ELF) electric and magnetic fields (EMFs) have focused on magnetic rather than electric fields. Some have considered such focus to be inappropriate and have argued that electric fields should be part of both epidemiologic and laboratory work. This paper fills the gap by systematically and critically reviewing electric‐fields literature and by comparing overall strength of evidence for electric versus magnetic fields. The review of possible mechanisms does not provide any specific basis for focusing on electric fields. While laboratory studies of electric fields are few, they do not indicate that electric fields should be the exposure of interest. The existing epidemiology on residential electric‐field exposures and appliance use does not support the conclusion of adverse health effects from electric‐field exposure. Workers in close proximity to high‐voltage transmission lines or substation equipment can be exposed to high electric fields. While there are sporadic reports of increase in cancer in some occupational studies, these are inconsistent and fraught with methodologic problems. Overall, there seems little basis to suppose there might be a risk for electric fields, and, in contrast to magnetic fields, and with a possible exception of occupational epidemiology, there seems little basis for continued research into electric fields. Bioelectromagnetics 31:89–101, 2010. © 2009 Wiley‐Liss, Inc.     

The diversity of earthworms in 200 Scottish fields and the possible effect of New Zealand land flatworms (Arthurdendyus triangulatus) on earthworm populations

Earthworm populations from 200 fields (132 pasture and 68 arable) in Scotland are compared. Earthworms populations from two pasture fields at a Scottish farm infested with the New Zealand terrestrial planarian, Arthurdendyus triangulates (a predator of earthworms), are compared with a subset of these 200 fields (none of which had planarians at the time of the survey). A variety of univariate and multivariate methods are used for comparison. Results from the 200 fields show that the number of individuals, number of species, richness and diversity decline eastwards and northwards across Scotland. There is an overall difference between pasture and arable fields at the same farm, with fewer anecic earthworms (Aporrectodea longa and Lumbricus terrestris), but more Aporrectodea rosea, in arable fields. Conversely, species richness and cumulative species diversity is greater in arable fields, and sample similarity is less. The planarian‐infested fields show differences from the subset of western Scottish pasture fields and from each other. Both have fewer Aporrectodea caliginosa (and endogeic total) and A. longa (and anecic total) than the western pasture fields. One field has fewer L. terrestris and fewer earthworms in total. Univariate factors show no significant differences between the infested fields and similar non‐infested fields, but multivariate analysis suggests differences. Waterlogging and recent growth of rushes in the infested fields are discussed in relation to the reduced population of earthworms and to rainfall.     

Juniper fields in Sogn, Western Norway, a man-made vegetation type

Juniperus communis has been used e.g. as poles (posts), haysticks and wall-coating. In some districts it has even been an important export article. The fields of columnar juniper are the result of a long history of cultivation and grazing. In this article the main types of juniper fields in Sogn, Western Norway are presented, and their relationships to soil conditions and traditional use are discussed. According to structure, utilization and development four main types of juniper fields are recognized: I. Traditional juniper fields, II. Semi-cultural juniper fields, III. Secondary juniper fields and IV. Semi-natural juniper fields. Due to changes in agricultural methods, juniper fields are becoming rare.     

稻田生物灾害生态调控的综合效益研究

单季稻田生物灾害生态调控的综合效益研究结果表明：综防田的蜘蛛群落和土壤动物群落的生物多样性均高于化防田。两类稻田蜘蛛群落物种数和个体数的差异性均达显著水平,而两类稻田土壤动物群落类群数和个体数均达极显著水平以上。综防田的杂草群落生物多样性显著低于化防田。综防田蛛虱数量存在正相关,说明稻田蜘蛛具有重要的生态调控作用。综防田农药用量、农药费用和农药残留均低于化防田。综防田的土地生产率、产值利税率和农副产品商品率均高于化防田。以综防田为代表的稻田生物灾害生态调控具有良好的生态、经济和社会效益。     

Comparative study of movement patterns of Mastomys natalensis in irrigated rice and fallow fields in eastern Tanzania

A 2‐year capture–mark–recapture study was conducted to estimate home ranges and weekly travel distance of Mastomys natalensis (Smith 1834) in an irrigated rice ecosystem and fallow fields. We found that adults have larger home ranges than subadults in fallow fields but not in rice fields, indicating that fallow fields are more suitable for breeding. Travel distances were larger in rice fields, especially in the transplanting stage, during which rice fields are flooded and provide less food, causing movements into neighbouring fallow fields that then temporarily experience higher population density. A decrease in travel distance was observed in rice fields during the maturity stage, which can be explained by higher food availability and a more suitable, nonflooded situation. Movement of M. natalensis in rice‐fallow mosaic landscapes thus seems to be driven by food availability and flooding status of the rice fields, which can be attributed to land use practices.     

Estimation of 50-Hz Electrically Vs. Magnetically Generated Body Currents in Sleeping Subjects

The exposure from low-frequency electric and magnetic fields to sleeping subjects was analyzed at 343 sites. To establish the exposure due to electric fields, a new method was used to measure the current density on the body surface of the test subjects lying in their beds. The exposure due to magnetic fields was determined by short-term measurements of the magnetic flux density using induction coils. The exposures from the electric and magnetic fields were compared. The result was that, in general, the electric fields contribute much more to the total exposure than the magnetic fields.     

Effects of crop field characteristics on nocturnal winter use by American woodcock

Since the late 1960s, American woodcock (Scolopax minor) have undergone population declines because of habitat loss. Previous research suggested ridge and furrow topography in conventionally tilled soybean fields provided critical nocturnal cover as birds foraged on earthworms. However, the use of no-till technology has increased and many fields now lack ridge and furrow topography. We assessed woodcock winter nocturnal foraging habitat use given recent changes in agricultural technology, and investigated how field treatment, earthworm abundance, and environmental variables affect the selection of nocturnal foraging sites. We counted woodcock along transects in 5 field treatments twice in each of 67 fields during December–March 2008–2009 and 72 fields during December–March 2009–2010. During both seasons, we collected earthworm and soil samples from a subset of fields of each field treatment. Woodcock densities were at least twice as high in no-till soybean fields planted after corn and in undisked corn fields with mowed stalks than in other field treatments. No-till soybean planted after corn and undisked corn fields contained ridge and furrow topography, whereas other crops did not, and earthworms were at least 1.5 times more abundant in no-till soybean fields than other field treatments. Ridges and furrows in no-till soybean fields planted after corn and undisked corn fields may provide wintering woodcock with thermal protection and concealment from predators. No-till soybean fields planted after corn offered the additional benefit of relatively high food availability. The presence of ridge and furrow topography can be used to predict woodcock field use on the wintering grounds in agricultural areas. Farmers can provide nocturnal winter foraging sites for woodcock by delaying field disking and leaving ridge and furrow topography in crop fields. © 2011 The Wildlife Society.     

蚜虱净对苜蓿主要害虫及天敌种群数量的影响

在甘肃省定西市九华沟系统研究了喷施蚜虱净对苜蓿主要害虫及天敌种群数量动态的影响。结果表明,施药田蚜虫和蓟马的季节平均数量极显著高于对照田,而盲蝽和瓢虫、小花蝽、蜘蛛等大多数天敌的季节平均数量则极显著低于对照田,寄生蜂与对照田没有湿著差异。喷施蚜虱净对种群数量时序动态的影响在不同害虫和天敌种类中表现不同,5月底施药后7d对照田蚜虫和蓟马的种群数量分别为施药田的4．13倍和5．2倍,此后施药田害虫的种群数量开始迅速增加,到6月底2种害虫的种群数量均与对照田无显著差异,到7月中旬以后反而显著高于对照田。施药对盲蝽种群数量时序动态的影响与蚜虫和蓟马不同,5月底施药后盲蝽的种群数量一直显著低于对照田,直到7月下旬以后,种群数量才恢复到对照田的水平。喷施蚜虱净对天敌种群数量的时序动态有极显著的影响,大多数天敌的种群数量在5月底施药后到7月底都一直显著低于对照田,直到8月上旬才恢复到对照田的水平。施用杀虫剂在防治害虫的同时杀伤大量天敌,使害虫的种群数量迅速增加,甚至造成更严重的为害。因此在菖蓿上使用对天敌杀伤力小的杀虫剂对保持天敌的自然控制能力有重要作用。     

不同抗性品种稻田捕食性节肢动物的群落结构

对3个类型稻田早、晚稻捕食性节肢动物群落调查,结果表明:共有捕食性节肢动物67种,丰富度以蜘蛛高于捕食性昆虫类;早稻高于晚稻;中抗品种高于抗虫和感虫品种。早稻以皿蛛科Linyphiidae的食虫沟瘤蛛UlmmeliatainsecticepesBoes.etStr.占优势,晚稻则以狼蛛科Lycosidae的相对丰盛度最高。早稻捕食性天敌数量动态以中抗品种峰期最长;感性样田中天敌平均密度与中抗样田差异不显著,与抗虫品种差异显著;捕食性节肢动物多样性随着品种抗性的增强呈降低趋势,优势度随着品种抗性的增强而增强。晚稻3个品种样田中天敌的平均密度差异不显著;各品种样田的多样性明显高于早稻,且波动幅度小于早稻,品种之间多样性差异较小,晚稻群落可能具有较高的稳定性。     

R~3中的一类拟齐次向量场的性质

利用三维拟齐次向量场和三维齐次向量场之间的等价关系并借鉴对齐次向量场的研究方法,把齐次向量场的一些结论推广到拟齐次向量场.并运用这些理论分析了具有不同增长率的三种群竞争模型的动力学性质和生物意义,得到增长率最大的种群在此竞争系统中占优,增长率最小的种群在此竞争系统中灭绝的结论.     

Onion thrips colonization of onion fields bordering crop and non‐crop habitats in muck cropping systems

Onion thrips, Thrips tabaci Lindeman, colonization of onion fields may be influenced by bordering crop and non‐crop habitats. Identifying habitats adjacent to onion fields associated with high T. tabaci infestations would be valuable for improving scouting efforts and management decisions. A 3‐year study examined adult T. tabaci colonization patterns within onion fields early (June through early July) and late in the season (August) in three muck regions in New York (USA). We hypothesized that early‐season adult densities would be greater in onion fields bordering other crops (e.g. carrot, corn and potato) and non‐crops (e.g. woods) than those bordering other onion fields and that more adults would occur along onion field edges than field centres. Results indicated similar adult densities in onion fields regardless of bordering crop and non‐crop habitats in seven of nine muck region × year data sets; exceptions were more adults in onion fields bordering potato (Elba region only) and corn (Potter region only) than those bordering other onion fields. Adult densities decreased as distance into onion fields increased in only four of nine muck region × year data sets; in these cases only 38% more adults were found along field edges than field centres. Later in the season, we hypothesized that adult densities would be greater in non‐mature onion fields bordering mature onion fields, and densities would be greater along field edges than field centres. Results indicated that adult densities in non‐mature onion fields bordering mature onion fields were 54 times greater than those bordering other non‐mature onion fields, and four times more adults occurred along field edges than field centres; adult densities were similar along field edges and centres in non‐mature onion fields bordering other non‐mature onion fields. Implications for T. tabaci management in onion based on these colonization patterns are discussed.     

Spatial and temporal patterns of onion maggot adult activity and oviposition within onion fields that vary in bordering habitat

In New York, onion [ Allium cepa L. (Alliaceae)] fields often border woods or other vegetable fields. Because onion maggot adults, Delia antiqua (Meigen) (Diptera: Anthomyiidae), spend a significant portion of their time outside of onion fields, surrounding habitat may affect patterns of fly activity and oviposition within onion fields. To better understand these patterns throughout the onion-growing season, first-, second-, and third-flights maggot adult (male and female) activity was monitored using yellow sticky cards. Half of the monitored fields bordered woods, whereas the other half bordered other onion or vegetable fields. Within all fields, yellow sticky cards were placed at five distances along a transect beginning at the onion field edge extending into the field center. First-flight male and female adult activity was greatest along onion field edges and was especially high along edges bordering woods. This pattern diminished during the second flight and was absent during the third. To determine if spatial patterns of onion maggot oviposition by first-flight onion maggots were similar to first-flight adult activity patterns, potted onion plants were placed in onion fields that bordered or did not border woods in late May and early June 2003. The number of eggs laid in the soil at the base of each plant was recorded. Unlike spatial patterns of first-flight adult activity, oviposition patterns were not affected by bordering habitat or distance from the field edge. Based on the activity of onion maggot adults in onion fields, future and existing control strategies should consider targeting first-flight adults along field edges rather than across entire fields, especially in fields that border woods. In contrast, based on spatial patterns of oviposition within onion fields, controls targeting onion maggot larvae should be applied on a fieldwide basis.     

田埂留草控制稻飞虱效果及对捕食性天敌多样性影响

为探讨稻田田埂保留杂草控制稻飞虱的效果及对捕食性天敌多样性的影响,以稻田田埂周年性保留杂草为处理,以稻田田埂不保留杂草为对照,对处理区和对照区稻田稻飞虱成若虫、捕食性天敌种类和数量进行系统调查和分析。结果表明,在调查期内(6—10月),田埂留草稻田百丛稻株稻飞虱数量为(891.11±133.12)头,较非留草稻田减少35.31%;田埂留草稻田捕食性天敌隶属5目23科35种,而田埂非留草稻田隶属5目21科33种;田埂非留草稻田捕食性天敌优势种为食虫沟瘤蛛Ummeliata insecticepsBoes.etStr.、拟水狼蛛Pirata subpiraticus Boes.etStr.和黑肩绿盲蝽Cyrtorrhinus livdipennis Reuter,而田埂留草后优势种为食虫沟瘤蛛U.insecticeps、草间小黑蛛Erigonidium graminicolum(Sundevall)、拟水狼蛛和拟环纹狼蛛Lycosa pseudoamulata(Bose.etStr.);田埂留草稻田捕食性天敌的个体数量、丰富度、多样性指数分别为(128.89±13.52)、(33.67±0.50)、(4.53±0.04)头/百丛,较田埂非留草稻田分别增加31.96%、25.73%、5.59%,而优势度指数和均匀性指数没有显著变化。研究结果为发展稻田景观多样化控害提供依据。     

Nontarget effects of transgenic insecticidal crops: implications of source-sink population dynamics

Widespread planting of transgenic insecticidal (TI) crops for pest control has raised concerns about potential harm to nontarget arthropods. Because the first generation of TI crops produce single Bacillus thuringiensis (Bt) toxins causing little or no harm to most nontarget arthropods, they are not likely to cause such negative effects. However, varieties of transgenic crops with multiple Bt toxins or novel toxins might be more harmful to nontarget arthropods. Field studies assessing nontarget effects typically compare the relative abundance of nontarget arthropods in TI crop fields to non-TI crop fields. However, for nontarget arthropods that are killed by TI crops, such analyses may miss important effects. Results from simulations of a spatially explicit population dynamics model show that large-scale planting of TI crops could cause three types of negative effects on nontarget arthropods that suffer mortality caused by TI crops: (1) lower abundance in TI fields than non-TI fields with little or no effect on abundance in non-TI fields, (2) lower abundance in TI fields than non-TI fields and decreased abundance in non-TI fields, and (3) loss of the arthropod from TI and non-TI fields. Simulation results show that factors increasing the potential for negative effects of TI crops on nontarget arthropods in non-TI fields are low reproduction, high emigration, high adoption of TI crops, high mortality in TI fields, insecticide sprays, and rotation of TI and non-TI fields. The results suggest that risk assessment should consider the regional distribution of transgenic crops and the life history traits of nontarget arthropods to identify the most vulnerable regions and nontarget species.     

Influence of 50 Hz electric and magnetic fields on the pulse rate of human heart

This investigation studied the effects of 50 Hz electric and magnetic fields on the pulse rate of the human heart. The ECG (electrocardiograms) of 41 male volunteers were recorded with a Holter recorder. Twenty-six subjects were measured in and outside real fields, and 15 subjects were measured in and outside “sham” fields. The blood pressure and EEG (electroencephalogram) were also measured, but this article presents only the results of ECG recordings. The measurements took 3 h. The subjects were first sitting for 1 h outside the fields, then 1 h in the real or “sham” fields, and then, again, 1 h outside the fields. The electric field strength varied from 3.5 to 4.3 kV/m and the magnetic flux density from 1.4 to 6.6 μT. An analysis of the ECG recordings showed that the subjects' pulse rates were the same in and outside the fields. No response occurred when the subjects were exposed to real or “sham” fields. © 1994 Wiley-Liss, Inc.     

化学防治对不同类型棉田害虫和捕食性天敌群落多样性的影响

分析比较了化学防治对8种不同类型棉田害虫、捕食性天敌群落多样性的影响。研究结果表明,化学防治对棉田害虫、捕食性天敌群落的多样性指数、均匀性指数、丰富度及个体数的变化有较大的影响,尤其对捕食性天敌群落的影响显著。但这种作用依不同类型棉田或棉花不同生育阶段而异：化学防治对套作棉田害虫、捕食性天敌群落的影响较小,而对单作棉田和豆间棉棉田害虫、捕食性天敌群落的影响较大;晚播棉田害虫与捕食性天敌群落较早播棉田受化学防治的影响更大;化学防治对免耕棉田害虫、天敌群落的影响更大,非免耕棉田害虫、捕食性天敌群落受其干扰较小;春套棉边害虫、捕食性天敌群落与其它棉田类型相比,受化学防治的影响较少;棉花害虫在棉花生育前期对化学防治较棉花生育后期敏感,而捕食性天敌在棉花整个生育期均对化学防治敏感。     

Magnetic fields from steel-belted radial tires: implications for epidemiologic studies.

Magnetic fields emanate from radial tires due to the presence of reinforcing belts which are made of magnetized steel wire. When these tires spin, they generate alternating magnetic fields of extremely low frequency (ELF), usually below 20 Hz. The fundamental frequency of these fields is determined by tire rotation rate and has a sinusoidal waveform with a high harmonic content. The static field of radial tires can exceed 500 microT at the tread, and the tire-generated alternating fields can exceed 2.0 microT at seat level in the passenger compartment of vehicles. Degaussing the tires reduces both the static and alternating fields to low levels, but the fields increase gradually over time after degaussing. The tire-generated fields are below the frequencies detected by most of the magnetic field meters used in previous studies of power frequency magnetic field health effects. If these fields are biologically active, failure to detect them could compromise exposure assessments associated with epidemiologic studies.     

Red spruce forest regeneration dynamics across a gradient from Acadian forest to old field in Greenwich,Prince Edward Island National Park,Canada

Red spruce forests have declined considerably throughout their range in the past decades. As agricultural fields are abandoned and land becomes available for reforestation, the possibility arises for red spruce forests to expand onto them. This study addresses the potential for red spruce forests to expand onto adjacent old fields in Greenwich, Prince Edward Island National Park, Canada. We examined red spruce distribution and abundance, plant species diversity and changes in community composition along a gradient from the interior of red spruce forests out towards the centre of adjacent old fields. Examining the patterns of red spruce distribution and abundance revealed that, where cultivation and logging have been abandoned recently in the fields and forests, regeneration is limited to the forest stands, but in the sites with older fields and forests, regeneration extends into and is more vigorous in the fields. Although species diversity varied from forest to field only for the tree and shrub layers, important changes occurred in the ground species composition. There is no evidence yet that the herbaceous species present in the forest stands will colonise the old fields. The results suggest that both environmental differences among sites and length of time since the fields were abandoned explain red spruce regeneration patterns. In order to more accurately assess the potential for red spruce regeneration in old fields, long-term monitoring of the production, dispersal and viability of red spruce seeds from adjacent forests and of the constraints to seedling establishment and survival in old fields will be needed.