The impact of mowing as a management strategy for wet meadows on spider (Araneae) communities

Meadows are often managed by mowing to prevent succession and brushwood encroachment. This management practice is efficient to maintain plant diversity, but the effect on arthropod groups is less well known. We sampled spiders in the Grande Cariçaie (Switzerland), a site of nature conservation importance, in two types of wet meadows, an unmanaged site and one 2-years-old mown conditions. Numbers of individuals for the most abundant families, diversity measures, and indicator taxa were compared among vegetation and treatment types. The results indicate that the less mobile spiders and species linked to litter or dead reeds, including rare species, are reduced by mowing. Present management consists in triennial mowing of 2-4 ha non-contiguous sectors. We investigate the conflict between the need to mow the meadows to maintain them, and the negative effect of mowing on spider communities. We therefore propose a new management scheme aimed at maintain the vegetation while lessening its negative effects on spider communities by providing refuges.     

Effectiveness of biodiversity indicators varies with extent, grain, and region

The use of indicator taxa for conservation planning is common, despite inconsistent evidence regarding their effectiveness. These inconsistencies may be the result of differences among species and taxonomic groups studied, geographic location, or scale of analysis. The scale of analysis can be defined by grain and extent, which are often confounded. Grain is the size of each observational unit and extent is the size of the entire study area. Using species occurrence records compiled by NatureServe from survey data, range maps, and expert opinion, we examined correlations in species richness between each of seven taxa (amphibians, birds, butterflies, freshwater fish, mammals, freshwater mussels, and reptiles) and total richness of the remaining six taxa at varying grains and extents in two regions of the US (Mid-Atlantic and Pacific Northwest). We examined four different spatial units of interest: hexagon (∼649 km²), subecoregion (3800-34,000 km²), ecoregion (8300-79,000 km²), and geographic region (315,000-426,000 km²). We analyzed the correlations with varying extent of analysis (grain held constant at the hexagon) and varying grain (extent held constant at the region). The strength of correlation among taxa was context dependent, varying widely with grain, extent, region, and taxon. This suggests that (1) taxon, grain, extent, and study location explain, in part, inconsistent results of previous studies; (2) planning based on indicator relationships developed at other grains or extents should be undertaken cautiously; and (3) planning based on indicator relationships developed in other geographic locations is risky, even if planning occurs at an equivalent grain and extent.     

Indicators of biodiversity, what do they indicate? - Lessons for conservation of cryptogams in oak-rich forest

In the Nordic countries, sets of Indicator (Signal) species, predominantly cryptogams, have been used as one measure to find forest stands which may harbour Red List species. Such data could potentially also be used to prioritise among stands for protection as nature reserves. We studied if the number of Signal species indicates the number of Red List species in oak-rich mixed forest in south Sweden. We also explored if species richness of the investigated groups is correlated with the number of Red List or Signal species. In 25 stands, we surveyed epiphytic and epixylic bryophytes and lichens, ground-floor bryophytes, and wood-living fungi. We studied correlations for two datasets; (1) all forest species and (2) deciduous forest specialists. When relating the number of Signal species to the number of Red List species for each taxon and in total, a significant correlation was found for temperate deciduous forest lichens. The number of Signal species was further significantly correlated to total species richness for lichens (all forest species) and for wood-living fungi (both datasets). The number of Red List lichens was correlated to total lichen richness (deciduous forest species). Signal species seem not to be unequivocal in prioritising potential reserves among valuable oak-rich woodlands and surveys by Red List species experts may be needed. Signal species may be more useful for finding relatively valuable sites in a matrix of production forest. Moreover, Signal species seem to be useful surrogates for total cryptogam species richness.     

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.     

区域土地资源可持续利用评价指标体系的研究

从土地利用系统的角度,分析土地资源可持续利用的标准.构建了区域土地资源可持续利用指标体系的基本框架,其指标体系包括目标层、准则层、分目标层、指标层4个层次,并对各指标层进行说明。     

一种小鸡体液免疫应答能力指示系统的建立

本研究用兔、山羊、绵羊、黄牛、猪、鹅、鸭的红细胞(RBC)作为抗原,分别免疫小鸡,并用直接微量血球凝集(HA)试验测定鸡所产生的体液免疫应答。选用能刺激产生较高抗体水平的鹅红细胞(GRBC)作为指示系统,在7、14天龄分别接种试验鸡,检测(1)传染性囊病(IBD)病毒及疫苗,(2)马立克氏病(MD)病毒;(3)火鸡疱疹病毒(HVT)疫苗等接种1天龄小鸡后,对鸡体液免疫应答能力的影响。 结果表明,IBD—PBG_(98)毒株无免疫抑制作用;IBD—野毒株引起严重的免疫抑制效应;HVT疫苗和MD病毒对7天龄接种了GRBC的小鸡抗体产生有明显影响。同时对鸡的法氏囊进行组织学检查,取得相应的结果。然而,IBD中和抗体滴度并没有显出这种与法氏囊组织破坏呈正相关的关系。 试验证明本指示系统简便有效,易于推广应用。     

Bark beetle community structure under four ponderosa pine forest stand conditions in northern Arizona

We studied the bark beetle guild (Coleoptera: Scolytidae) in the ponderosa pine forests of northern Arizona to explore if the species assemblages and relative abundance differ between managed and unmanaged stands. Four stand conditions were assessed: (1) unmanaged stands with high tree density, (2) thinned stands, (3) thinned and burned (with prescribed fire) stands and (4) stands that had been burned by stand replacing wildfires. The study was conducted in the ponderosa pine forests of the Coconino Plateau, northern Arizona. For several decades this area has been relatively free of bark beetle outbreaks despite the current overstocked condition of many stands. We found that a similar species assemblage composed of Dendroctonus frontalis, D. brevicomis, D. valens, D. approximatus, D. ponderosae, and Ips pini occurred across all four stand conditions over 3 years of study. The population levels of all these species were endemic across all stand conditions. The non-aggressive D. approximatus and D. valens were indicator species for thinned and unmanaged stands, respectively, but this was not consistent among years. The ambrosia beetle Gnathotrichus sp. and the bark beetle predator Enoclerus sp. consistently indicated stands burned by wildfire. In addition to our field experiment, we analyzed the historical pattern of attacks of bark beetles in our area of study. Our findings suggest that the pattern of attack of D. brevicomis (the only Dendroctonus species for which attacks have been reported) and Ips spp. has been through scattered small infestations in groups of 1–10 trees. Whereas small infestations by Ips spp. are increasing, those for D. brevicomis are decreasing. Although we agree that the high density stands in northern Arizona are in an “unhealthy” condition, our results do not show that they were supporting large bark beetle outbreaks. Our results challenge the theoretical assumptions about the relationship between stand structure, tree resistance and bark beetle performance.     

柑桔花叶病毒的一种新的鉴别寄主─—枸头橙

在枸头橙上接种柑桔花叶病毒（ＣｉＭＶ），以后抽发的春梢幼嫩期表现黄化症状，随着春梢叶片的伸展产生花叶症状。而在枸头橙上接种类似病毒温州蜜柑萎缩病毒（ＳＤＶ），以后抽发的春梢表现正常。故认为枸头橙是ＣｉＭＶ的一种新的鉴别寄主，可以区分开ＣｉＭＶ和ＳＤＶ。     

食品安全与食品低温流通中的温度监控

食品的温度监控是一种有效的保证食品安全及保持冷藏链完整的手段,对冷冻冷藏食品在低温流通过程中实行温度监控是非常有必要的。目前,我国冷藏运输中的温度管理情况并不乐观,消费者获得的货物通常不能达到预计的要求。要解决这一问题,必须要借助于时间-温度指示器等来对其整个运输过程进行温度监控。本文对温度立法的必然性和前景,温度监控的重要性、原理以及在冷藏运输中的应用作了较详尽的介绍,并列举了几种国外时间-温度指示器的工作原理。     

Comparison of foliar composition of eucalyptus globulus and quercus agrifolia growing together

Foliage of each species was sampled at 26 paired locations in the San Francisco Bay area. Eucalyptus globulus had significantly higher concentrations of Mn, Ca and Na, but significantly lower concentrations of Cu, Fe, Zn, P, NO₃‐N and Kjeldahl‐N than did Quercus agrifolia. Concentrations of K and Mg did not differ between species. The relative concentration series for the species were similar: N>Ca>K>Mg>Na>P>Mn>Fe for Q. agrifolia and Ca>N>K> Mg>Na>Mn>P>Fe for E. globulus. Correlations between species were statistically significant for concentrations of Fe and Ca only. Thus, for these elements analysis of one species could be used as an indicator of the other.