植草带宽度对蜘蛛和步甲群落动态及比邻玉米田害虫发生的影响

农田边界植草带是农田系统各斑块间生物物种迁移和群落演替、物质和能量交换的主要区域,对维持农业生物多样性及提高农田生产力具有重要意义。基于作物-害虫-天敌互作有机整体对植草带宽度的响应,选取不同宽度植草带(2 m、4 m、6 m)及其比邻农田并以对应宽度作物边界作为对照,采用地表陷阱法对蜘蛛和步甲进行取样调查,探究植草带宽度对蜘蛛和步甲种群结构、迁移扩散规律以及对农田害虫控制潜力的影响。结果表明:植草带内蜘蛛和步甲个体数均显著高于对照条带,4 m、6 m植草带的蜘蛛和步甲多度显著高于2 m植草带,且物种丰富度和多度显著高于其对照条带。此外,不同宽度植草带蜘蛛和步甲群落存在较高的异质性,蜘蛛和步甲群落结构差异显著;在4 m和6 m植草带及其比邻玉米田内,蜘蛛和步甲多度在植草带和植草带与比邻玉米田交界处显著高于农田内部,且随距离的增加,蜘蛛物种多度呈显著降低趋势,植草带宽度和距离共同决定蜘蛛和步甲的空间分布;Monte Carlo检验结果表明,植草带宽度、植被Margalef指数对农田中蜘蛛和步甲群落结构的影响均达到显著水平,蜘蛛主要优势科和步甲主要优势种主要分布在6 m植草带比邻玉米田内;4 m、6 m植草带比邻的玉米田中蜘蛛和步甲对玉米害虫的益害比显著高于2 m植草带比邻的玉米田,且4 m、6 m植草带显著增加了玉米籽粒的百粒重及比邻农田的玉米总产量。本研究对植草带涵养捕食性天敌预防害虫发生的最适宽度进行探索,综合考虑植草带耕地占用、天敌涵养和生物控害潜力等因素,确定4 m宽度植草带是具有推广价值的农田边界模式。     

Tasmanian high altitude grassy vegetation: its distribution,community composition and conservation status

Grassy woodland, grassy shrubland, grassy sedgeland, tussock grassland and grassland are extensive on basalt, limestone and fine-textured Quaternary deposits, are occasional on dolerite, granite and fine-grained sedimentary rocks, but are absent from the siliceous mountains of Tasmania. With the exception of limestone lithosols, the grassy communities are confined to relatively deep soils with a low surface rock cover. Much of the area of the grassy communities below the climatic treeline has clearly been forest in the recent past, although some of the higher subalpine plains seem likely to have been grassy at least since the peak of the Last Glacial. The first axis of an ordination of floristic data from 190 quadrats had at one extreme the grassy communities which most resembled in their species composition the sedgelands and sclerophyll shrub woodlands of the west of Tasmania, and at the other extreme the grassy woodlands on relatively fertile, well drained sites in the centre and east of Tasmania. The second axis was correlated with altitude, probably inversely reflecting the growing season. The third axis was related most closely to a soil drainage index. Many of the 15 communities recognized from a polythetic divisive classification of the quadrats have highly local distributions. Six of the communities are totally unreserved and four are poorly reserved. An iterative method is used to develop a minimum reservation strategy involving seven areas.     

Effects of burning and rainfall on former agricultural land with remnant grassy woodland flora

Grassy woodlands have been extensively cleared for agricultural land uses; land managers need to know whether restoration of biodiversity on such sites requires further interventions beyond simply stopping agricultural land use. Cumberland Plain Woodland occurs on shale‐derived soils in western Sydney; former Cumberland Plain Woodland sites can range from grasslands cleared for agricultural use to regenerated woodlands. An experiment was established in Scheyville National Park to determine what effect repeated burning would have in this system. Four blocks were established (three in grassy areas, one in woodland) and plots in each block were either burnt in 2001 and 2005 or left unburnt. Native plant species richness was initially lower in the grassy blocks than in the woodland, and this ranking remained on unburnt plots over time. The first fire increased species richness of both natives and exotics on the grassy blocks, with the largest increases observed for native and exotic forbs, and lesser increases for grasses (native only), gramminoids and shrubs. Native species richness changed very little with burning in the woodland. Fire effects on species richness were still apparent 3 years later on the grassy blocks; the difference between the grassy blocks and the woodland was not significant on burnt plots at this stage. Changes in native species richness were far less after the second fire on the grassy blocks, with grasses and gramminoids showing increases; native species richness remained higher in the burnt treatment. The first fire reduced the initial differences in native species richness between the grassy blocks and the woodland, and the second fire maintained the benefit through time. Fire also increased exotic species richness; the proportion of total species as natives was not altered by the two fires. On unburnt grassy plots, native species richness and prior cumulative rainfall were positively related; a decline in native species richness on unburnt plots corresponded to increasingly drier conditions over the study.     

Differentiation of spring carabid beetle assemblages between semi‐natural habitats and adjoining winter wheat

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Movement of carabids from grassy strips to crop land in organic agriculture

The colonisation process of carabid beetles from field margins to crop fields under organic agriculture was investigated in 2010 and 2011 in northern Germany in order to find the supporting effects of grassy strips in the agricultural landscape. Displacement and speed of Pterostichus melanarius, Carabus auratus and Poecilus spp. were higher in the crops than in the grassy strips, except for the speed of C. auratus. Among the four species C. auratus, P. melanarius, Pterostichus niger, and Poecilus spp., C. auratus revealed the highest displacement and speed, whereas no significant differences were found between the other three species. P. melanarius showed higher displacement and speed in wheat than in red-clover or pumpkin. Speed and displacement of P. melanarius differed between spring and autumn generations in wheat or red-clover. When they were released at a junction of arable crop and field strips, C. auratus moved indifferently to either arable field or field margins/strips, whereas P. melanarius moved directly to crop centres. At the field margin, Poecilus spp. preferred to move along a grassy strip, while it moved irrespective from the grassy strips in a central site. C. nemoralis and P. niger preferred to move within the grassy strips. Our studies reveal that grassy strips do not affect the dispersal of typical arable field species; however, the species demanding grass vegetation can only overcome the barriers of arable fields either by grassy strips alone or by grassy strips with an adjacent hedge.     

Can burning restrict eucalypt invasion on grassy balds?

Abstract: Eucalyptus tereticornis seedlings occurring on the edges of grassy balds on the Bunya Mountains were burnt by four separate fires. From the results, a logistic model demonstrated that lignotuber size was positively related and fire temperature negatively related to survivorship. While mortality was high for young seedlings there was no mortality of 5‐year old survivors from these trials subject to repeat burning. The model predicted that burning every 2 years will not substantially limit seedling establishment. This prediction was strengthened by results verifying that management fires on the grassy balds are generally of low intensity. Fire intensity is weakly related to a Fire Danger Index, indicating that the timing of burning in relation to weather conditions will not substantially enhance opportunities for more intense fires. Thus, even with biennial burning under optimal conditions eucalypt forest will replace grassy balds where they adjoin. Regular burning by aborigines may have maintained grassy bald‐rainforest boundaries, but not boundaries with eucalypt forest. Seed dispersal and migration barriers may have limited the expansion of eucalypt forest. It is concluded that under current conditions the long‐term preservation of the grassy balds is only possible where they are entirely surrounded by rainforest and are regularly burnt.     

Logs and Fern Patches as Recruitment Sites in a Tropical Pasture

Forest recovery in degraded pastures is often highly variable, possibly due to variation in the availability of adequate recruitment sites. In an actively grazed pasture in northeastern Costa Rica, this study examines how recruitment of woody species in patches of the fern Nephrolepsis sp. and near logs compares with recruitment in grassy areas. Fern patches and logs had five and eight times higher densities of woody recruits, respectively, as grassy areas. They also had more than twice the species richness and growth as grassy areas. Grass apparently presents a competitive barrier against invading woody recruits, and also attracts cattle that may trample and/or consume recruits. Both logs and patches of fern appeared to provide superior conditions for establishment and growth of woody species, and they did not attract cattle. This study suggests that fern patches and logs can be managed to accelerate forest succession.     

Giant noctule bats face conflicting constraints between roosting and foraging in a fragmented and heterogeneous landscape

Noting that some ground-dwelling passerine birds have remarkably long claws, reflected in such names as longclaw (Motacillidae) and longspur (Emberizidae), this comparative study assessed whether these features might aid movement over grassy ground vegetation. Using measurements of museum specimens, we found that, corrected for body size, larks (Alaudidae) living in grassy habitats ( n =31) had significantly longer toes and claws and hence larger footspans than species dwelling on bare substrates ( n =25). Using phylogenetically corrected contrasts, the claw result remained strongly significant, and the footspan result marginally significant, while there was no significant difference between the toes of the two groups. Among 15 matched pairs of other ground-dwelling passerines, where one member of the pair inhabits vegetated ground and the other inhabits bare ground, the former had significantly longer toes and claws and hence larger footspans. We conclude that ground-dwelling passerines living on vegetated, typically grassy ground, have larger feet, due to both longer toes and claws. This probably facilitates movement over uneven and unstable vegetation.     

Energy budget changes caused by varying solar angles,cloud scenarios,and air temperatures in contrasting landscapes

The combination of two physically-based models of solar radiationcloud attenuation and a steady state surface energy budget made possible the systematic examination of the causal effects of varying solar altitudes, selected cloud types and amounts, and air temperatures on the resultant energy budget components extant in two contrasting (grassy and barren) landscapes. The grassy landscape reacted more conservatively to the forcing by changing solar angles, cloud, and air temperature regimes. The results are considered as universal and they are assumed to encompass many possible extremes encountered in the continuum formed by real world landscapes.     

Spatial and temporal distribution of endemic entomopathogenic nematodes in a heterogeneous vegetable production landscape

Entomopathogenic nematodes within the families Steinernematidae and Heterorhabditidae (Order: Rhabditida) are potential biological control agents for many soil-dwelling vegetable pests. However, their low persistence and efficacy after field releases have resulted in limited use in pest management programs. Understanding the factors regulating natural populations of entomopathogenic nematodes may provide insight into practices to conserve populations within production systems. A series of investigations were conducted within a vegetable production area in Willard, Ohio during 2000–2003 to gain insight into the population ecology of endemic populations of entomopathogenic nematodes. A total of 440 sites across four habitats associated with the production landscape were sampled to ascertain the natural occurrence of these beneficial nematodes. Habitats included cultivated areas, grassy banks adjacent to cultivated areas, undisturbed shrub lands and forests. Twelve sites along grassy banks were monitored over a growing season to estimate associations between abiotic and biotic factors and endemic populations. Entomopathogenic nematodes were only detected along grassy banks adjacent to the cultivated areas; nematodes were recovered from 15 to 30% of sites sampled in 2001 and 2002, respectively. Two species of nematodes were isolated, Heterorhabditis bacteriophora Poinar and Steinernema feltiae Filipjev. H. bacteriophora was the most prevalent nematode species and was recovered from 60% of positive samples. Nematode populations varied temporally and spatially along grassy banks; mean population density over the growing period was 1313 infective juveniles/m². Neither macro- nor microarthropod communities nor soil temperature differed between sites at which nematodes were detected and those at which nematodes were not detected. Soil moisture, however, was associated with the occurrence and persistence of nematodes along grassy banks; mean soil moisture at sites at which nematodes were detected and those sites at which nematodes were not detected was 37.3 and 26.8%, respectively. Water management is an important component of vegetable production and our results suggest that soil moisture manipulation would be important in the establishment and sustained presence of entomopathogenic nematode populations within cultivated areas over the growing season.     

Asymmetric response of forest and grassy biomes to climate variability across the African Humid Period: influenced by anthropogenic disturbance?

A comprehensive understanding of the relationship between land cover, climate change and disturbance dynamics is needed to inform scenarios of vegetation change on the African continent. Although significant advances have been made, large uncertainties exist in projections of future biodiversity and ecosystem change for the world's largest tropical landmass. To better illustrate the effects of climate–disturbance–ecosystem interactions on continental-scale vegetation change, we apply a novel statistical multivariate envelope approach to subfossil pollen data and climate model outputs (TraCE-21ka). We target paleoenvironmental records across continental Africa, from the African Humid Period (AHP: ca 14 700–5500 yr BP) – an interval of spatially and temporally variable hydroclimatic conditions – until recent times, to improve our understanding of overarching vegetation trends and to compare changes between forest and grassy biomes (savanna and grassland). Our results suggest that although climate variability was the dominant driver of change, forest and grassy biomes responded asymmetrically: 1) the climatic envelope of grassy biomes expanded, or persisted in increasingly diverse climatic conditions, during the second half of the AHP whilst that of forest did not; 2) forest retreat occurred much more slowly during the mid to late Holocene compared to the early AHP forest expansion; and 3) as forest and grassy biomes diverged during the second half of the AHP, their ecological relationship (envelope overlap) fundamentally changed. Based on these asymmetries and associated changes in human land use, we propose and discuss three hypotheses about the influence of anthropogenic disturbance on continental-scale vegetation change.     

陕北天然草场的类型研究

对陕北天然草场的植物种类组成,地域分布和群体生产力进行了调查和分析,将本区草场资源划分为6个类型,干草原草场,草甸草原草场,草本半灌木草场,灌木草丛草场,低湿地草甸草场及农林隙地杂类草草场,根据各类草场利用中存在的问题,提出了合理开发和改良的措施。     

Restoring grassy ecosystems – Feasible or fiction? An inquisitive Australian's experience in the USA

Many small‐scale projects in Australia suggest that ground‐layer elements of ecosystems can be restored, but scaling up of grassland and grassy understorey restoration has not occurred to date. Paul Gibson‐Roy recently travelled through the USA, where well‐developed markets for restoration have created a large, financially viable native‐herbaceous seed production and restoration sector. Here, he shares his observations, which show how much about the USA situation can be a model and inspiration for Australian grassy ecosystem restoration.     

Restoring grassy woodland diversity through direct seeding: Insights from six ‘best‐practice’ case studies in southern Australia

Ecological restoration of grassy woodland ecosystems is now a significant landscape‐scale conservation objective throughout southern Australia. Technological improvements in direct seeding are now sufficiently well‐advanced to examine whether cost‐effective restoration of grassy woodlands is feasible. Consideration of six ‘best practice case studies shows substantial evidence of success. Further refinement of direct seeding techniques, in combination with native seed production systems, however, will be required into the future to meet the scale of woodland conservation targets and restore ecological function.     

Variations in Diversity and Richness of Gut Bacterial Communities of Termites (Reticulitermes flavipes) Fed with Grassy and Woody Plant Substrates

Diets shape the animal gut microbiota, although the relationships between diets and the structure of the gut microbial community are not yet well understood. The gut bacterial communities of Reticulitermes flavipes termites fed on four individual plant biomasses with different degrees of recalcitrance to biodegradation were investigated by 16S rRNA pyrosequencing analysis. The termite gut bacterial communities could be differentiated between grassy and woody diets, and among grassy diets (corn stover vs. sorghum). The majority of bacterial taxa were shared across all diets, but each diet significantly enriched some taxa. Interestingly, the diet of corn stover reduced gut bacterial richness and diversity compared to other diets, and this may be related to the lower recalcitrance of this biomass to degradation.     

Fire frequency influences composition and structure of the shrub layer in an Australian subcoastal temperate grassy woodland

Little is known about the relationship between fire regimes and plant diversity in Australia's temperate grassy woodlands. The effect of fire frequency on shrubs in grassy woodland remnants across Western Sydney's Cumberland Plain was examined. Shrub species richness and composition were compared in sites that had experienced a high, moderate or low frequency of fire over the previous 20 years. Nine sites were surveyed, three in each fire frequency category; most sites, including all low‐fire‐frequency sites, had burnt 9–36 months prior to sampling. Fire frequency had a profound effect on the composition and structure of the shrub layer. Per cent frequency and density of the prickly shrub Bursaria spinosa (Pittosporaceae) was considerably higher in low‐fire‐frequency sites than where fires had occurred at least once a decade. In sites where fire had been absent for decades prior to a recent fire, this species dominated the landscape, while elsewhere it occurred as clumps in a grassy matrix. Per cent frequency of other native shrubs, particularly obligate seeders, was greatest at moderate fire frequencies. Exotic shrubs were recorded most often where fire had been rare. While ordination clearly separated out the low‐fire‐frequency sites, complete separation between high‐ and moderate‐fire‐frequency blocks was not achieved. The increase in Bursaria in the absence of fire mirrors the encroachment of woody plants into a range of grassy ecosystems around the world. The sensitivity of obligate seeder species, many of them short‐lived legumes with fire‐cued seeds, to both very frequent and very infrequent fire shows the vulnerability of these species to extreme fire regimes, despite the safeguards conferred by hard‐seededness. Competition from Bursaria, as well as loss of viable seed in the soil, may have contributed to the low frequency of these species after a long inter‐fire interval.     

植被边界带对相邻麦田地表步甲和蜘蛛分布及蚜虫发生的影响

通过管理半自然生境提高农田中天敌多样性及农田害虫的生物控制效率是当前生态农业研究的基本问题之一。为探讨不同类型半自然植被边界带对相邻麦田地表天敌的发生以及对小麦蚜虫生物控制潜力的影响,在北京顺义区赵全营镇采用陷阱法调查了不同类型植被边界带（人工林地、人工种植草带、自然演替草带）相邻的小麦田中,距离边界0,15 m和30 m处步甲和蜘蛛两类重要地表天敌的多度分布及小麦田蚜虫发生情况,同时分析了边界带植被群落结构对步甲和蜘蛛群落分布的影响。结果表明：人工林地相邻的小麦田中维持了显著较高的步甲、蜘蛛和蚜虫发生密度;不同类型植被边界带相邻小麦田中步甲和蜘蛛群落组成显著不同,植被边界带宽度以及乔木层盖度是影响相邻麦田步甲和蜘蛛群落分布的主要因子;距离植被边界带不同取样界面处,不同迁移方向的步甲和蜘蛛的活动密度无显著性差异;与林地相邻的麦田中,蜘蛛活动密度从农田边界向农田内部处依次降低,与人工种植草带以及自然演替草带相邻的麦田中,农田边界处蜘蛛的活动密度显著高于农田内部。研究显示,半自然植被边界带与麦田交界处维持了较高的蜘蛛活动密度,并具有向农田内部扩散的趋势,然而,并非高天敌密度就意味着低害虫发生率,深入研究天敌群落与害虫发生关系及其影响因素是未来天敌保护和害虫生物防治的重要方面。同时,因为不同类型植被边界带维持的天敌群落具有高度异质性,未来的研究需要充分考虑不同类型植被边界带对天敌维持的作用,以及不同类型生境界面地表天敌的活动规律。     

Unionid growth patterns in rivers of differing riparian vegetation

1. Growth rates were examined as potential controlling agents of unionid distributions.
2. Analyses of long-term growth in unionid shells revealed two distinct patterns. Species which dominate rivers with forested riparian vegetation (e.g. Elliptio dilatata ) show slow growth throughout life, whereas species which dominate grassy rivers (e.g. Pyganodon grandis ) show rapid growth during early life and achieve a smaller maximum size at a younger age.
3.  Pyganodon grandis , which occurs in both river types but is much more abundant in grassy habitats, demonstrates a single growth pattern in both basin types. In contrast, Lasmigona complanata (Barnes, 1823), which occurs equally in both basin types, demonstrates two growth patterns which differ depending upon which river is inhabited. In forested rivers, L . complanata grow slow and steady, whereas in grassy rivers, these unionids grow faster and achieve maximum size earlier.
4. Short-term transplant studies of P . grandis and E . dilatata confirmed this pattern of growth for specialist species.     

The antiquity of Madagascar’s grasslands and the rise of C4 grassy biomes

Aim Grasslands and savannas, which make up > 75% of Madagascar’s land area, have long been viewed as anthropogenically derived after people settled on the island c. 2 ka. We investigated this hypothesis and an alternative – that the grasslands are an insular example of the post‐Miocene spread of C₄ grassy biomes world‐wide. Location Madagascar, southern Africa, East Africa. Methods We compared the number of C₄ grass genera in Madagascar with that in southern and south‐central African floras. If the grasslands are recent we would expect to find fewer species and genera in Madagascar relative to Africa and for these species and genera to have very wide distribution ranges in Madagascar. Secondly, we searched Madagascan floras for the presence of endemic plant species or genera restricted to grasslands. We also searched for evidence of a grassland specialist fauna with species endemic to Madagascar. Plant and animal species endemic to C₄ grassy biomes would not be expected if these are of recent origin. Results Madagascar has c. 88 C₄ grass genera, including six endemic genera. Excluding African genera with only one or two species, Madagascar has 86.6% of southern Africa’s and 89.4% of south‐central Africa’s grass genera. C₄ grass species make up c. 4% of the flora of both Madagascar and southern Africa and species : genus ratios are similar (4.3 and 5.1, respectively). Turnover of grasses along geographical gradients follows similar patterns to those in South Africa, with Andropogoneae dominating in mesic biomes and Chlorideae in semi‐arid grassy biomes. At least 16 monocot genera have grassland members, many of which are endemic to Madagascar. Woody species in frequently burnt savannas include both Madagascan endemics and African species. A different woody flora, mostly endemic, occurs in less frequently burnt grasslands in the central highlands, filling a similar successional niche to montane C₄ grasslands in Africa. Diverse vertebrate and invertebrate lineages have grassland specialists, including many endemic to Madagascar (e.g. termites, ants, lizards, snakes, birds and mammals). Grassland use of the extinct fauna is poorly known but carbon isotope analysis indicates that a hippo, two giant tortoises and one extinct lemur ate C₄ or CAM (crassulacean acid metabolism) plants. Main conclusions The diversity of C₄ grass lineages in Madagascar relative to that in Africa, and the presence of plant and animal species endemic to Madagascan grassy biomes, does not fit the view that these grasslands are anthropogenically derived. We suggest that grasslands invaded Madagascar after the late Miocene, part of the world‐wide expansion of C₄ grassy biomes. Madagascar provides an interesting test case for biogeographical analysis of how these novel biomes assembled, and the sources of the flora and fauna that now occupy them. A necessary part of such an analysis would be to establish the pre‐settlement extent of the C₄ grassy biomes. Carbon isotope analysis of soil organic matter would be a feasible method for doing this.     

Ecological features of cenofloras of subarctic tundras of Siberia

The cenofloras of moss tundras, dryas tundras, and cryophytic grassy bogs of Subarctic Yamal, Taimyr, and Yakutia have been compared in such parameters as activity and species richness of their ecological groups. Comparison of the three cenofloras of subarctic tundras in conditions of heat and moisture has shown that the habitats of Yamal noticeably differ from the habitats of Taimyr and Yakutia. In Yamal, the conditions are warmer in all the habitats except grassy bogs in the zone of typical tundras. Most habitats in Yamal are drier. The hydrothermal conditions of Taimyr and Yakutia are similar. The differences arise as the climate becomes increasingly more continental from west to east.