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91.
It is assumed that the abundance of Agriotes wireworms (Coleoptera: Elateridae) is affected by agro-ecological factors such as climatic and edaphic factors and the crop/previous crop grown at the sites investigated. The aim of this study, conducted in three different geographic counties in Croatia from 2007 to 2009, was to determine the factors that influence the abundance of adult click beetle of the species Agriotes brevis Cand., Agriotes lineatus (L.), Agriotes obscurus (L.), Agriotes sputator (L.), and Agriotes ustulatus Schall. The mean annual air temperature, total rainfall, percentage of coarse and fine sand, coarse and fine silt and clay, the soil pH, and humus were investigated as potential factors that may influence abundance. Adult click beetle emergence was monitored using sex pheromone traps (YATLORf and VARb3). Exploratory data analysis was preformed via regression tree models and regional differences in Agriotes species’ abundance were predicted based on the agro-ecological factors measured. It was found that the best overall predictor of A. brevis abundance was the previous crop grown. Conversely, the best predictor of A. lineatus abundance was the current crop being grown and the percentage of humus. The best predictor of A. obscurus abundance was soil pH in KCl. The best predictor of A. sputator abundance was rainfall. Finally, the best predictors of A. ustulatus abundance were soil pH in KCl and humus. These results may be useful in regional pest control programs or for predicting future outbreaks of these species.  相似文献   
92.
该项研究调查了山东省内三个北美红花槭实生苗木繁育试验点;通过对高度、地径、通直度、叶色、叶形、主裂、分枝、落叶和叶面积等性状的调查,确实出该树种在山东生长较为适应,生长量没有太大的波动,实生苗的叶片的变异非常丰富,各项性状的变异系数CV均大于0.2以上。性状的多样性指数(Simpson指数和Shannon—Wirner指数)值都较大,分别介于25—32和5—6之间,充分反映出各个群体都具有较广的多样性丰富度。苗木群体本身就是一个很好的基因库,这为今后的育种,培育不同观赏品种提供了一个良好的物质基础。  相似文献   
93.
Effects of oceanic-climate changes on the abundance of Pacific saury (Cololabis saira) in the northwestern Pacific during the last half century were investigated. Abundance indices of both large and medium size groups exhibit interannual–decadal variations, but their patterns were different. The large and medium size groups of saury are corresponding to the recruitments of winter- and spring-cohort, respectively. The abundance of large size group saury was significantly correlated with the winter sea surface temperature (SST) in the Kuroshio region, whereas the medium size group saury showed high correlations with SST in the Kuroshio–Oyashio transition zone and the Oyashio region, indicating that the two size groups are affected by subtropical and subarctic environment, respectively. Significant negative correlation between the abundance index and the southern oscillation index (SOI) suggested that El Niño-southern oscillation (ENSO) events have marked impacts on the large size group saury. Subtropical high pressure index and far east zonal index also show high correlations with the abundance of both large and medium size group saury, indicating a linkage between large-scale atmospheric circulation and the abundance of saury. These correlations demonstrate that the abundance of Pacific saury is directly affected by the SST fields through large-scale atmosphere–ocean interactions from the equatorial Pacific to mid- and high-latitude areas such as El Niño events.  相似文献   
94.
Field experiments were conducted to investigate the mechanism of the underlying patterns (abundance, species richness, diversity and similarity) of rove beetles in transgenic Bt (MON810) and in near isogenic maize stands in Hungary. During the three-year (2001–2003) survey, 1538 individuals and 21 species were sampled with pitfall traps. The Cry1Ab protein expressed by the MON810 maize hybrid did not influence the overall community structure. After grouping staphylinids into guilds we found no significant differences for non-aphidophagous predators and parasitoids, whereas there were significantly and marginally significantly higher abundances for predators with aphids in their diet in isogenic maize stands in 2002 and 2003 respectively. The abundance of the prey Rhopalosiphum padi (L.) showed a high fluctuation between stands and years and was numerically higher only in isogenic stands in the second half of the maize-growing season. The abundance of predatory guilds including aphids in their diet did not correlate with the total annual number of R. padi in the same year, but there was a linear correlation in successive years.  相似文献   
95.
Voles and shrews are key species in northern forest ecosystems. Thus, it is important to quantify to what extent new forestry practices such as planting of non-native tree species impact these small mammals. In northern Norway stands of coastal subarctic birch forests have increasingly been converted to non-native spruce stands during the last century. This leads to changes in the forest floor vegetation and soil conditions that can be expected to negatively impact the community of ground-dwelling small mammals. In this 10-year trapping study we contrasted seasonal small mammal population abundances in spruce plantations with four birch forest varieties. Six different small mammal species were trapped (in descending order of abundance; common shrew Sorex araneus, red vole Myodes rutilus, field vole Microtus agrestis, grey-sided vole M. rufocanus, pygmy shrew S. minutus and water shrew Neomys fodiens). None of the voles appeared to exhibit temporal dynamics resembling population cycles. The three most numerous species were clearly less abundant in the spruce plantations compared to the other forest types. Autumn abundances were most impacted by spruce plantations, indicating that growth rates in the reproductive season were more influenced than winter declines. Species associated with productive forest habitats (i.e. field vole and common shrew) were most impacted by tree species conversion. Still young spruce plantations inter-mixed with birch trees and the ecotone habitat, sustained small mammal abundances comparable to the native birch forests. This implies that managing spruce plantations to maintain a mix of different tree species and high spatial heterogeneity (i.e. more ecotones), will reduce the negative impacts on the small mammal community. On the contrary, if young spruce plantations, as they age become spruce monocultures covering larger parts of the landscapes than they do presently, the negative effects on small mammal communities may be larger than observed in the present study.  相似文献   
96.
西双版纳热带雨林树种多度与丰富度空间分布特征   总被引:1,自引:0,他引:1  
兰国玉  朱华  曹敏 《热带作物学报》2011,32(6):1086-1092
基于西双版纳20 hm2森林动态监测样地内直径≥1cm的树种资料,分析该样地树种多度(个体数)和丰富度(物种数)及其方差与变异系数在7个取样尺度(5 m×5 m,10 m×10 m,20 m×20 m,25 m×25 m,50 m×50 m,100 m×100 m,200 m×250 m)的变化规律。结果显示:(1)西双版纳热带雨林样地环境异质性较大,多度和丰富度随着尺度的增加均表现非线性增加。(2)多度的方差随尺度增加而线性增加;丰富度的方差与尺度都表现出非线性的关系。丰富度的方差在尺度100 m×100 m上最大。(3)多度、丰富度和多样性指数的方差、变异系数均大于随机分布模型拟合的数值,表明树种在样地内分布不是随机分布。总之,在生物多样性的保护和管理中要特别注意,尽管多度具有可加性,只有当环境异质性不大时用小尺度多度估计大尺度多度才比较可靠;丰富度的非线性变化使得一个尺度上生物多样性"热点",在另一个取样尺度上却可能为"冷点"。  相似文献   
97.
庞绪贵  祝德成  代杰瑞  郭瑞朋  张帆  董健  陈磊 《安徽农业科学》2013,(28):11363-11365,11367
(目的]研究山东半岛蓝色经济区土壤中元素的分布与富集。[方法]按1km^2采集1件袁层土壤样品,4km^2组合成1件分析样品,4km^2采集1件深层土壤样品,16km^2组合成1件分析样品,测试Ag、As、Au、B、Ba、Be、Bi、Hr、C等54项指标。[结果]山东半岛蓝色经济区土壤地球化学调查是研究这些指标在表层、深层土壤中的分布规律,认为表层、深层土壤中除与金及多金属成矿作用有关的Ag、Au、Hg、Mo、S、Sb等元素和Cl、Br、I等卤族元素空间变异性大外,大部分元素分布均匀,且表层、深层土壤元素分布具有相似性。[结论]对比区内表层、深层土壤元素地球化学含量值的变化,可以看出大部分指标在表层土壤中的含量继承了土壤母质,后期人类活动对其影响较小;但是,表层土壤中SOC、N、Hg、P、S、Se等指标的富集和pH明显降低,表明表生作用和人类活动等因素已对这些指标的分布分配产生明显影响.  相似文献   
98.
Fungal abundance and diversity in earthworm casts and in uningested soil   总被引:1,自引:0,他引:1  
Earthworm casts and adjacent uningested soil from 30 different locations were compared to determine the abundance and diversity of fungal species. The casts contained larger fungal populations (g-1 dry soil weight) and numbers of fungal species than the soil. Variations in these parameters between casts and soil were statistically significant (P=0.05). Fungal populations and the number of fungal species in casts and soil also varied significantly (P=0.05) between samples from different locations. A total of 27 fungal species were recorded from the casts and soil. Indices of dominance (0.084 casts; 0.14 soil) and general diversity (2.53 casts; 2.02 soil) demonstrated that the casts displayed more diverse fungal flora than the soil. The diversity of fungal species increased in earthworm casts after passing through the earthworm gut.  相似文献   
99.
Land cover change, predominantly habitat conversion to agricultural use and urbanization, has recently been recognized as the primary cause of biodiversity loss in terrestrial ecosystems. We evaluated the relative effects of urban and agricultural landscapes on anuran species richness and the abundance of six anuran species found at breeding ponds in and around the cities of Ottawa, Ontario and Gatineau, Quebec. We performed six call surveys at 29 permanent focal ponds surrounded by one of three landscape contexts: primarily urban, primarily agricultural, and primarily forested. We also measured three local pond variables to control for the effects of local habitat quality in our analyses. We found that anuran species richness was significantly lower in breeding ponds in urban landscapes compared to forested and agricultural landscapes, which exhibited no significant difference in species richness. The abundances of individual anuran species were also consistently lower in urban landscapes for all species except one, which exhibited no response to landscape type. Three species had their highest abundances in ponds in forested landscapes, whereas two species had their highest abundances in ponds in agricultural landscapes. We conclude that ponds embedded in urban landscapes support lower biodiversity than ponds in agricultural settings. We suggest that landscapes composed of a mosaic of forest and open habitats surrounding wetlands would hold the highest biodiversity of these species.  相似文献   
100.
2015年春季(5月)、夏季(7月)和秋季(9月)在渤海湾近岸海域进行浮游纤毛虫丰度和生物量的调查。浮游纤毛虫丰度、生物量及种类组成均表现出明显的季节变化。春、夏和秋季纤毛虫的平均丰度分别为(1016±868)、(2011±1327)和(2456±1776)ind./L,平均生物量分别为(1.91±2.53)、(5.78±4.45)和(3.11±2.40)μg?C/L。3个季节砂壳纤毛虫占纤毛虫丰度的比例平均为(26.7±23.3)%,夏季最高,为(43.4±25.1)%,秋季最低,为(12.3±8.1)%。无壳纤毛虫和砂壳纤毛虫丰度和生物量的水平分布特点不同,无壳纤毛虫在3个季节中没有表现出明显的分布规律,在近岸和远岸都有丰度和生物量高值的出现;砂壳纤毛虫丰度和生物量则一般在近岸较高。3个季节共鉴定出砂壳纤毛虫8属25种,其中,拟铃虫属(Tintinnopsis)种类最多。春季砂壳纤毛虫优势种为波罗的拟铃虫(Tintinnopsis baltica)、百乐拟铃虫(Tintinnopsis beroidea)和原始筒壳虫(Tintinnidium primitivum);夏季砂壳纤毛虫优势种为妥肯丁拟铃虫(Tintinnopsis tocantinensis)、原始筒壳虫和厦门拟铃虫(Tintinnopsis amoyensis);秋季砂壳纤毛虫优势种为原始筒壳虫。春季砂壳纤毛虫群落口径较小,为(31.5±2.5)μm,夏季和秋季较大,分别为(35.9±8.2)和(34.8±5.2)μm。夏季砂壳纤毛虫群落Shannon指数及Pielou指数均较春季和秋季大。本研究可为该海区浮游纤毛虫分布的长期变化、浮游生态系统的研究及渔业资源的发展提供基础数据。  相似文献   
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