Habitat fragmentation in an urban environment: large and small fragments support different arthropod assemblages

We investigated the effects of fragmentation due to urbanisation on the species composition and functional roles of ants, beetles, spiders, flies and wasps. The study was conducted in 21 fragments of heath and woodland in south-eastern Australia classed as either ‘small’ (? 4 km²) or ‘large’ (? 80 km²). Arthropods were pitfall-trapped and identified to family or genus and morphospecies and microhabitat characteristics were recorded. Large fragments did not support more species per unit area than small fragments for most arthropods, although there were more species of ants per sampling unit in small than large woodland fragments, mainly due to a higher frequency of generalist species in smaller fragments. Large and small habitat fragments contained different assemblages of spiders, wasps and ants, indicating that predators and parasitoids are affected more strongly than other trophic groups. Arthropod assemblages within larger fragments where grids were furthest apart were less similar than those within smaller fragments where grids were closer together in woodland, but not in heath. The responses of arthropods to fragmentation suggest that, in addition to effects of reduced area and proximity to the urban matrix, changes in fire regimes and the degradation of habitats resulting from urbanisation, may have a role in altering arthropod assemblages, particularly affecting those species belonging to higher trophic levels. Management goals for urban remnants should identify mechanisms for controlling fire and anthropogenic disturbance such that they closely resemble the levels of these factors in larger fragments.     

Tree Mortality,Needle Biomass Recovery and Growth Losses in Scots Pine Following Defoliation by Diprion pini (L.) and Subsequent Attack by Tomicus piniperda (L.)

Tree mortality and growth losses following insect defoliation are poorly documented in Scandinavia. In 1990-1991, Diprion pini (L.) caused extensive defoliation to Scots pine in Lauhanvuori national park and surrounding areas in south-western Finland. Most trees lost all their foliage in 1990. In 1991, the outbreak area was sprayed with diflubenzuron (Dimilin®), except in the national park, where trees were severely defoliated again. No further defoliation occurred in 1992. In spring 1993, sprayed trees had ca 30% foliage, whereas unsprayed trees on average carried less than 10% of full foliage. The latter trees were susceptible to attack by Tomicus piniperda (L.), whereas the former largely escaped beetle attack. Beetle attacks peaked in 1993, and depletion of suitable host trees probably terminated the beetle outbreak in the area. Two years of severe defoliation resulted in substantial tree mortality and growth losses. In spring 1997, these unsprayed stands had suffered a ca. 50% loss in basal area which was mainly because of mortality, and about half of the dead trees had been attacked by T. piniperda. Surviving trees had ca 50% of full foliage, and radial growth had still not recovered. Basal area growth was reduced by 40-70%, depending on the amount of foliage left after the second year of defoliation. In contrast, tree mortality and beetle attack in the sprayed stands were negligible, and these trees had recovered full foliage and radial growth by spring 1997. Thus, one year of total defoliation resulted in an estimated loss in basal area growth of approximately 30% during ca. 5 yrs. In conclusion, the spraying operation was economically justified, as it prevented substantial tree mortality and reduced growth losses.     

庞泉沟自然保护区周边农田甲虫群落调查

2006年6~8月,在山西庞泉沟国家自然保护区(111°22'~111°33'E,37°45'~37°55'N)周边的农田(海拔1 600~1 640m),包括玉米田、马铃薯田、莜麦田、胡麻田、大豆田、退耕还林地和荒地,利用巴氏罐诱法,并结合网筛、扫网等采集方法对甲虫群落进行了初步调查,共获标本1980号,隶属13科。优势类群为步甲科Carabi-dae,占总捕获量的74.04%。并结合该地区的农田耕作方式对不同功能类群的种类及数量分布进行分析。     

Abandonement of coffee agroforests increases insect abundance and diversity

Shade coffee including many tree species is known to support generally high biodiversity. Due to low coffee prices on the world market, many farmers have abandoned their farms, thereby creating a new ecosystem type, which has attracted increasing interest for biodiversity conservation. Here we used pyrethrum knockdown samples to compare the arthropod community on coffee plants of six traditionally managed coffee agroforests with those of six abandoned coffee agroforests in coastal Ecuador. We investigated eight randomly selected coffee shrubs per site, six of them inside and two at the edge. All arthropods were identified to orders and beetles to morphospecies. We additionally sampled the vegetation to test for vegetation-mediated effects on the arthropod community. The number of arthropod individuals was higher in abandoned than managed coffee, driven by the abundance of Arachnida, Blattaria, and Heteroptera, and higher in the edge than in the centre of the abandoned agroforests. Higher arthropod abundance appeared to be closely related to arthropod diversity, as shown for beetles (r = 0.79, n = 96). Contrary to expectations, predator-prey ratios in managed agroforests was as high as in the abandoned ones. In conclusion, abandonment of coffee agroforests greatly encourages arthropod communities, in particular in the habitat edges, and therefore, should be considered in landscape management for conservation.     

The influences of patch shape and boundary contrast on insect response to fragmentation in California grasslands

Landscape ecologists typically identify boundaries to demarcate habitatpatches. The boundary between two habitat types may be abrupt, such as thetransition between a grassland and a parking lot, or more gradual, such as theshift between successional forest stages. Two key aspects of landscapeboundaries, their shape and contrast, are predicted to influence movement ofmaterials, plants, and animals. Ecological theory suggests that a patchsperimeter-to-area ratio should strongly influence animal emigration when patchboundaries are relatively permeable, but not when boundaries are more severe.Weinvestigated the interactive effects of patch shape and boundary contrast onmovement of ground-dwelling beetles (Carabidae and Tenebrionidae) in nativegrassland habitat at Jepson Prairie, Solano County, California, USA. Weconducted a field experiment with two patch shape treatments, square andrectangle, that held patch area constant, and two boundary contrast treatmentscreated by mowing grass surrounding each plot at two different heights. Wemonitored the number of beetles leaving each patch over a three-week periodfollowing treatment establishment. We observed a significant effect of boundarycontrast on net movement of beetles, with low contrast boundaries exhibitingnetimmigration and high contrast boundaries experiencing net emigration. Moreover,the importance of patch shape appeared to be greater for low contrast versushigh contrast boundaries, consistent with theoretical expectations. Ourcombinedobservations indicate that these ground-dwelling beetles were more likely tomove into patches that were rectangular and surrounded by a low contrast matrixthan patches that were square or surrounded by a high contrast matrix. Weconclude that net movement of beetles across patch boundaries is stronglyinfluenced by boundary contrast and may be affected by patch shape whenboundarycontrast is low.This revised version was published online in May 2005 with corrections to the Cover Date.     

中国无分布记录的蒙古国天牛种类研究初报

天牛是一类重要的林木害虫,对我国林木业、果树业的发展有巨大的威胁。为阻止外来危险性天牛传入我国,对蒙古国的天牛种类进行了研究。本文记述了在蒙古国发生,而在我国无分布记录的天牛种类4亚科20属28种,并结合这些种类在蒙古国的生活环境和危害特点,分析了其对我国林木业、果树业可能造成的威胁,希望引起口岸检疫工作者的重视,以加强对相关检疫性种类的检验检疫。     

The Biology and Control of the Grasshopper Zonocerus variegatus

Abstract

The grasshopper Zonocerus variegatus (L.) is recognised as a pest of many crops in West Africa. Evidence that it is becoming an increasing problem in southern Nigeria prompted research into the biology, bionomics and control of this insect. Summaries of the main points in the biology, bionomics and recommended control are given. It is concluded that although a chronic pest it only periodically causes economical damage to cassava and community self help is the best level at which to effect control.     

Targets for maintenance of dead wood for biodiversity conservation based on extinction thresholds

Abstract

Forestry decreases the amount of dead wood, thereby threatening the persistence of many saproxylic (wood-living) organisms. This article discusses how targets for efforts to maintain and restore dead wood in managed forest landscapes should be defined. Several studies suggest extinction thresholds for saproxylic organisms. However, because the thresholds differ among species, the relationship between species richness and habitat amount at the local scale is probably described by a smoothly increasing curve without any distinct threshold. The most demanding species require amounts of dead wood that are virtually impossible to reach in managed forests. This means that unmanaged protected forests are needed. In managed forests, conservation efforts should focus on the landscape scale and on certain types of dead wood, but it is impossible to come up with any particular amount of dead wood that is desirable at the forest stand level.     

Saproxylic beetles in high stumps and residual downed wood on clear-cuts and in forest edges

Abstract

This study evaluates how the placement and the different possible outcomes of a spruce retention tree affected species richness and assemblages of spruce-associated saproxylic beetles. In a field experiment in the boreal zone of central Norway, high stumps were created and compared with residual wood pieces (i.e. top boles with branches), in clear-cuts versus in forest edges. Flight interception traps were mounted close to the substrate. The results were analysed using rarefaction techniques, ordination (DCA) and anova. It was found that the placement of retention trees of spruce does matter: beetle assemblages were significantly different in stumps in the four treatments. For all species pooled, the species richness was higher in stumps in clear-cuts than in stumps or boles in the forest edge. Four red-listed species were more abundant near stumps than boles, and two red-listed species were more abundant in clear-cuts than forest edge. To cater for the variety of habitat preferences among forest beetles in managed forest, managers should leave both standing spruce trees (many of which will end up as windthrown, downed boles) and some high stumps (to secure some upright dead wood), in both exposed clear-cut and semi-shaded forest edge.     

Effect of clear-cutting on the understory vegetation,soil and diversity of litter beetles in scots pine-dominated forest

Currently, the aim of modern forest management is not only timber production but also the protection of biodiversity. The initial effects of clear-cut logging on forest understory vegetation, soil and the diversity of litter beetles have been studied. We examined unstudied effects of clear-cutting disturbance on understory vascular plant species abundance, forest soils, and understory vegetation nutrients as well as beetle diversity one year after clear-cutting. Substantial changes in the prominence values and above-ground mass of forest-related vascular plant and moss species were detected. Clear-cuttings resulted in fast appearance of new light-loving plant species. The significant decrease in understory plant biomass influenced the reduction of nutrient pools in clear-cut areas after one year. The clear-cut logging negatively influenced the richness of species and the number of individuals of stenobiontic forest-related beetles in the forest litter. However, forest clear-cuttings were beneficial for eurytopic and open land species.