喀斯特洞穴小型土壤节肢动物多样性

研究洞穴土壤节肢动物,有助于了解土壤节肢动物对特殊环境的响应,对于深入认识喀斯特生态过程具有重要意义。以喀斯特洞穴生态系统小型土壤节肢动物为研究对象,采用主成分分析、重复测量方差分析、相关性分析和冗余分析等方法探讨了小型土壤节肢动物与环境因子的相互作用关系。调查共获得小型土壤节肢动物2399个,隶属7纲15目121科。其中,自然林优势类群为等节跳科(Isotomidae),洞穴优势类群为奥甲螨科(Oppiidae)。PCA分析显示,洞穴与自然林小型土壤节肢动物群落组成差异明显。洞穴小型土壤节肢动物类群数、密度和Shannon-Wiener指数(H′)显著低于自然林(P<0.05),自然林小型土壤节肢动物类群数、密度和Shannon-Wiener指数(H′)季节差异显著(P<0.05),洞穴类群数、密度和Shannon-Wiener指数(H′)季节差异不明显。相关性分析结果表明,小型土壤节肢动物类群数和Shannon-Wiener指数(H′)与pH值、全磷和光照强度显著相关(P<0.05),密度与pH值、全磷、有机质和光照强度显著相关(P<0.05)。RDA分析表...     

干旱与半干旱区灌丛微生境中红砂枯落物分解特征及中小型节肢动物的作用

在干旱区(内蒙古乌拉特后旗)和半干旱区(宁夏盐池)荒漠草原区,选择柠条灌丛内外微生境为研究样地,以红砂枯落物为研究对象,利用2种规格网孔分解袋(30目和250目网孔),探索中小型节肢动物在红砂枯落物分解过程中的作用规律,研究灌丛微生境中红砂枯落物质量损失变化特征及节肢动物群落的贡献。结果表明：(1)在干旱与半干旱区,红砂枯落物分解常数K均表现为灌丛内外微生境间无显著差异,且有无节肢动物参与对K的影响均较小。(2)分解至12个月时,无节肢动物参与的情况下,干旱与半干旱区红砂枯落物残留率均表现为裸地显著低于灌丛;但有节肢动物参与时,枯落物残留率则表现为灌丛内外微生境间无显著差异。分解至44个月时,无节肢动物参与的情况下,仅在干旱区枯落物残留率表现为裸地显著高于灌丛;而有节肢动物参与时,干旱与半干旱区枯落物残留率均表现为灌丛内外微生境间无显著差异。(3)节肢动物对红砂枯落物质量损失的贡献率呈现单峰值现象,且在分解至24个月时达到峰值。枯落物分解至12个月时,仅半干旱区节肢动物对红砂枯落物分解的贡献率表现为裸地显著低于灌丛;分解至44个月时,仅干旱区节肢动物对红砂枯落物分解的贡献率表现为裸地显...     

Soil fertility shapes belowground food webs across a regional climate gradient

Changes in soil fertility during pedogenesis affect the quantity and quality of resources entering the belowground subsystem. Climate governs pedogenesis, yet how climate modulates responses of soil food webs to soil ageing remains unexplored because of the paucity of appropriate model systems. We characterised soil food webs along each of four retrogressive soil chronosequences situated across a strong regional climate gradient to show that belowground communities are predominantly shaped by changes in fertility rather than climate. Basal consumers showed hump‐shaped responses to soil ageing, which were propagated to higher‐order consumers. There was a shift in dominance from bacterial to fungal energy channels with increasing soil age, while the root energy channel was most important in intermediate‐aged soils. Our study highlights the overarching importance of soil fertility in regulating soil food webs, and indicates that belowground food webs will respond more strongly to shifts in soil resources than climate change.     

Microarthropod community structures (Oribatei and Collembola) in Tam Dao National Park, Vietnam

A study on the microarthropod community with special reference to species diversity of Oribatid and Collembola communities (Microarthropoda: Oribatei and Collembola) in Tam Dao National Park of Vietnam, a subtropical evergreen broad leaf alpine forest, was undertaken with the aim to explain how they are related to forest decline, and whether they can be used as bioindicators of forest plant succession. The results have shown that microarthropod community structures, particularly species diversity of oribatid and collembolan communities, are related to forest decline. Therefore they can be used as bioindicators of forest plant succession. In Tam Dao National Park, there was an inverse relation between species diversity of the oribatid and collembola communities. The species diversity of the oribatid community gradually decreased with forest decline whereas the species diversity of the collembola community gradually increased.     

小型表栖节肢动物群落对高寒湿地退化的响应

为查明小型表栖节肢动物群落对高寒湿地退化的响应,2014年7月和9月利用吸虫器法对若尔盖高寒湿地的沼泽草甸、草原草甸、中度退化草甸3种生境的小型表栖节肢动物群落进行调查。结果为:共采集到小型表栖节肢动物18661只,隶属于3纲15目85类(科或属),优势类群为球圆跳属(Sphaeridia)、长跳属(Entomobrya)和莓螨科(Rhagidiidae),其中长跳属仅出现在草原草甸。小型表栖节肢动物群落结构在不同生境间差异明显,主成分分析(PCA)结果表明影响群落结构的主要类群是长跳属(Entomobrya)、球圆跳属(Sphaeridia)、齿步甲螨属(Odontocepheus)、瘤蚜科(Pemphigidae)和叶蝉科(Jassidae),但不同月份间存在差异。小型表栖节肢动物的群落密度及类群数均以草原草甸最高,中度退化草甸最低,3种生境间有显著差异(P0.01)。3种生境的小型表栖节肢动物群落密度均是7月显著低于9月(P0.01),Shannon-Wiener指数和Simpson优势度指数则是7月显著高于9月(P0.01);类群数在沼泽草甸中7月显著低于9月(P0.05),在草原草甸和中度退化草甸则是7月显著高于9月(P0.05)。典范对应分析(CCA)及多元回归分析结果表明植物种类、生物量、土壤有机质含量是影响小型表栖节肢动物群落组成结构、密度及多样性的主要因子。研究结果表明高寒湿地退化能够显著影响小型表栖节肢动物群落的组成结构、密度和多样性及其季节动态。     

Influence of urea and superphosphate fertilizers on microarthropod numbers and fungal activity during a short-term incubation of material from aPinus radiata D. Don forest floor

Urea and superphosphate dramatically increased the concentrations of exchangeable ammonium-N and water-soluble P in incubated forest floor samples. Urea also increased absolute but not relative nitrate production. Superphosphate depressed pH while urea elevated it. Microarthropod numbers and fungal activity were depressed by fertilizer addition. Mites were more sensitive to urea than were collembola, which were more sensitive to superphosphate. Both groups were more adversely effected by superphosphate than urea. In contrast, fungal activity was more retarded by urea than superphosphate. It is uncertain whether the observed changes resulted from increased osmotic potentials, pH or pH induced toxicities.     

Survival Studies with the Fire Blight Pathogen Erwinia amylovora in Soil and in a Soil-inhabiting Insect

The survival of Erwinia amylovora in soil and in the soil-inhabiting insect Folsomia candida was investigated. Although E. amylovora is an air-borne pathogen, it may reach the soil with rain and other dissemination events. The pathogen was selected on agar plates with two antibiotics and identified by its characteristic colony morphology on minimal agar with copper ions and confirmed by polymerase chain reaction assays. Rates of bacterial decline were much higher in non-sterile than in sterile soil, where the number of living bacteria was stable over 11 weeks. It declined rapidly in untreated soil from a field, and the pathogen was no longer detected 5 weeks after inoculation. Soil-living microarthropods such as F. candida (Collembola) contain large amounts of bacteria in their gut. When fed with gfp -labelled E. amylovora , the pathogen was digested in the gut within a few days, contributing to the decrease of the bacterial population in the soil and thus preventing bacterial distribution by insects.