【作者】 高旭；

【导师】 李晓琼；

【作者基本信息】 广西大学 ， 生态学， 2022， 硕士

【摘要】 空间上相互分离的地上和地下植食性生物通过共同的寄主植物发生复杂的相互作用,不同的互作类型可能会对土壤养分及微生物群落结构产生不同影响。我们选用乌桕2种食叶害虫(专食性癞皮夜蛾、广食性斜纹夜蛾)和南方根结线虫作为研究对象,通过室内生测实验,比较南方根结线虫侵染对不同食性害虫寄主选择和幼虫发育的影响;进而通过同质园实验探究在两种食叶害虫反复取食下,对根结数及土壤养分和微生物群落结构影响的差异。主要结果如下:1.南方根结线虫侵染对两种食叶害虫表现的影响因害虫的食性广度和龄期而异。非选择性和选择性产卵实验中,南方根结线虫使癞皮夜蛾产卵量分别减少了30.5%和40.8%,反之,选择性产卵实验中,南方根结线虫侵染增加了斜纹夜蛾52.7%的产卵量。南方根结线虫胁迫下,癞皮夜蛾5龄、6龄幼虫体质量,5龄幼虫相对生长率,6龄幼虫取食量,4龄、5龄幼虫近似消化率均显著减少,而斜纹夜蛾3龄幼虫的相对生长速度显著增加了43.1%,2龄、3龄幼虫的发育历期则显著减少了34.2%和29.9%。此外,受南方根结线虫侵染的乌桕叶片对癞皮夜蛾3龄幼虫有一定的吸引作用,而对斜纹夜蛾4龄、5龄幼虫具明显驱避作用。2.两种食叶害虫对南方根结线虫的影响也显著不同。癞皮夜蛾取食危害下南方根结线虫的根结数显著增加了51.4%,而斜纹夜蛾为害未对南方根结线虫形成显著影响。3.癞皮夜蛾和南方根结线虫的单独胁迫均对土壤养分和微生物生物量碳产生不利影响,但二者协同作用往往有利于乌桕根际土壤养分和微生物生物量碳水平的维持与提高,这种互作效应在斜纹夜蛾中并不显著。癞皮夜蛾单独取食下,乌桕根际土壤有机碳、速效钾及微生物生物量碳含量与无取食植株相比分别减少了51.8%、18.5%和68.4%;南方根结线虫的单独胁迫则分别降低了乌桕根际土壤43.6%的全氮、27,6%的全磷及46.8%的微生物生物量碳含量;斜纹夜蛾未对土壤养分形成显著影响。而南方根结线虫与癞皮夜蛾的协同作用下,乌桕根际土壤有机碳、全氮、全磷及微生物生物量碳含量与对照组相比差异不显著,微生物生物量碳氮比则显著提高了252.81%。此外,南方根结线虫与两种食叶害虫互作下乌桕根际土壤的速效钾、碳氮比及碳磷比均显著高于癞皮夜蛾或斜纹夜蛾单独胁迫。4.两种食叶害虫的单独取食及其与南方根结线虫互作均未对土壤PLFAs含量和相对丰度形成显著影响,而南方根结线虫侵染下,乌桕根际土壤的细菌/真菌以及细菌、革兰氏阴性菌及原核生物的相对丰度分别显著降低了5.8%、1.7%、4.8%和13.9%,革兰氏阳性菌/革兰氏阴性菌则显著提高了6.0%。主成分分析表明,食叶害虫对土壤微生物群落结构的影响较小,南方根结线虫则显著改变了乌桕根际土壤中的微生物群落结构。冗余分析表明,土壤全氮和氮磷比是驱动乌桕根际土壤微生物群落发生变化的最主要环境因子。以上结果表明:南方根结线虫与两种食叶害虫的互作因植食性昆虫的食性广度而异。地上-地下不同植食性生物互作会对土壤养分造成不同影响。与食叶害虫相比,南方根结线虫对乌桕根际土壤微生物群落结构的影响更大。本文研究结果有助于丰富地上-地下生物互作理论,了解地上-地下植食性生物间的互作关系及其所引发的一系列后续效应,对地上-地下植食性生物互作下的土壤生态过程变化及其对植物地上部的反馈研究具有重要意义。更多还原

【Abstract】 The complex interactions can occur between the herbivorous organisms that are spatially separated aboveground and belowground through common host plants,and the soil nutrients and microbial community structure may vary among different interactions.Here,we chose two kinds of defoliators(the specialist Gadirtha fusca,the generalist Spodoptera litura)and Meloidogyne incognita of Triadica sebifera as the research objects.Under the M.incognita stress,the host selection and larval development of defoliators with different diet breadth were compared through laboratory bioassay.Furthermore,the effects of two defoliators on the root-knot number and the impact of their interactions on soil nutrients and microbial community structure were explored by a commongarden experiment.The main results were summarized as follows:1.Effects of the M.incognita infection on the performance of two kinds of defoliators varied with their diet breadths and instars.In non-selective and selective ovigerous bioassay,with the M.incognita infection,the egg-laying of G.fusca decreased by 30.5% and 40.8%,while in selective ovigerous bioassay,the egg-laying of S.litura.increased by 52.7%.After M.incognita infection,the larval biomass of 5th and 6th larvae,the relative growth rate of 5th larvae,the food consumption of 6th larvae,and the approximate digestibility of 4th and 5th larvae of G.fusca all significantly decreased compared with the control group,while the relative growth rate of 3rd larvae of S.litura significantly increased 43.1%,the developmental duration of 2nd and 3rd larvae significantly decreased 34.2% and 29.9%.Furthermore,The 3rd larvae of G.fusca were attracted by the leaves of T.sebifera that were infected by M.incognita,while the 4th and 5th larvae of S.litura were repellent.2.The effects of the two defoliators on M.incognita were also significantly different.With G.fusca,the root-knot number of M.incognita was significantly increased by 51.4%,while M.incognita were not considerably affected by S.litura.3.The soil nutrients and microbial biomass carbon were negatively affected by the single stress of G.fusca or M.incognita.Still,their synergistic effects were often conducive to the maintenance and the improvement of the soil nutrients and microbial biomass carbon levels in the rhizosphere of T.sebifera.However,this interactive pattern was not found between M.incognita and S.litura.Compared with the plants without herbivores,the contents of soil organic carbon,available potassium and microbial biomass carbon of rhizosphere soil of T.sebifera with G.fusca increased by 51.8%、18.5% and 68.4% respectively,the 43.6% soil total nitrogen,27.6% total phosphorus and 46.8% microbial biomass carbon of T.sebifera with M.incognita decreased.There was no significant difference in the soil nutrients of rhizosphere soil of T.sebifera with S.litura.When the T.sebifera was used by M.incognita and G.fusca,compared with the control,there was no significant differences in the soil organic carbon,total nitrogen,total phosphorus,the ratio of microbial biomass C/N,and the soil microbial biomass carbon increased 252.8%.In addition,compared with the stress of G.fusca or S.litura,the available potassium,the ratio of C/N and C/P in rhizosphere soil of T.sebifera with the co-stress of M.incognita and two defoliators were significantly higher.4.The soil PLFAs contents and the relative abundance of PLFAs were not affected by two defoliators or the interactions between defoliators and M.incognita.While,with the M.incognita infection,the ratio of bacteria/fungi and the relative abundance of bacteria,gram-negative bacteria and prokaryotes significantly decreased 5.8%,1.7%,4.8% and 13.9% respectively,but the ratio of gram-positive bacteria/gram-negative bacteria significantly increased 6.0%.The results of the principal component analysis showed that there was no significant effects on the soil microbial community structure with two defoliators or the interactions between defoliators and M.incognita.In contrast,M.incognita significantly changed the soil microbial community structure.Determined by redundancy analysis,the soil total nitrogen and the ratio of N/P were the most critical environmental factors driving changes in soil microbial community structure.These results indicate that the interaction between M.incognita and two defoliators varies with the diet breadths,and the effects of the different above-belowground herbivore interactions on soil nutrients are different.Compared with the defoliators,the effects of M.incognita on soil microbial community structure of the rhizosphere soil of T.sebifera are more significant.These results are helpful to enrich the theory of above-belowground herbivore interactions,understand the interactive patterns between aboveground and belowground herbivores and their series of subsequent effects,and are significant to the study of soil ecological process changes under the above-belowground herbivore interactions and its feedback to the aboveground.更多还原