【作者】 罗斌；

【导师】 葛滢； 常杰；

【作者基本信息】 浙江大学 ， 生态学， 2020， 博士

【摘要】 生物多样性与生态系统功能(BEF)关系在近几十年来一直是生态学的前沿问题。近来,越来越多的工作深入到外部干扰(如加氮和增温)对BEF关系的影响。碳纳米管等工程纳米材料的应用和生产不断增加,废弃纳米材料进入生态系统后影响生物有机体和生态系统过程及功能,已成为生态系统的一类新型干扰。然而,已有的研究主要关注碳纳米管对植物单种(特别是作物)的影响,缺少关注碳纳米管对野生植物和多种共存生态系统的结构及植物多样性-生态系统功能的影响。人工湿地是一种广泛应用的污水处理系统,因其条件可控,已经成为BEF研究的良好平台。进入污水中的许多废弃碳纳米管最初汇集于湿地生态系统。因此,人工湿地是探究碳纳米管这类新兴干扰对BEF关系影响的理想实验平台。本研究设置了包含108个独立人工湿地微宇宙的植物多样性控制实验系统。这些微宇宙均分为两组,一组为碳纳米管处理组,另一组作为对照组。两组微宇宙设置相同的植物多样性配置,选择4种野外常见的湿地植物,设置3个丰富度梯度(1,3,4),9个植物物种组合。本研究旨在探究碳纳米管干扰对植物种生物量生产、种间竞争、物种多样性与生态系统生产力关系以及与氮过程和功能之间关系的影响。主要结果和结论有:(1)碳纳米管干扰对不同植物种的生物量生产造成了不对称影响。在单种植物的微宇宙系统中,碳纳米管使干扰前最高产物种芦苇的生物量生产降低26%,但不影响其他三个物种;在混种系统中碳纳米管的影响逆转:不影响芦苇的生物量生产,反而使菖蒲、皇冠草和梭鱼草的生物量生产分别降低了15%、24%和17%。物种间生物量生产的不对称响应改变了种间竞争能力,碳纳米管干扰后原有的竞争最优种芦苇的竞争优势(相对产量)增强,而其他三个种的竞争能力减弱。这些变化加剧了种间竞争的不对称性,无干扰时群落中存在芦苇和梭鱼草两个竞争优势种,而碳纳米管干扰后只剩芦苇一个竞争优势种。(2)碳纳米管干扰使人工湿地生态系统生产力平均降低了12%,但是干扰下植物物种丰富度对生态系统生产力的促进作用保持不变。碳纳米管干扰降低了植物种间互补效应,但是高产物种芦苇在混种系统的竞争优势增强,减缓了混种系统生产力的降低。最终,碳纳米管干扰下单种和混种生产力的下降程度相当,丰富度与整合各物种生物量的生态系统生产力的关系保持不变。(3)碳纳米管干扰改变了人工湿地生态系统的氮过程。干扰使植物氮吸收降低11%,同时使反硝化增强50%(氮的质量平衡分析和氮同位素分析共同证明了反硝化作用的增强),不影响基质氮存留。无碳纳米管干扰时物种丰富度降低生态系统反硝化作用,但干扰后混种系统的反硝化作用的增加程度(72%)高于单种系统的增加程度(29%),导致物种丰富度与反硝化的负相关变平缓。不同的是碳纳米管干扰不改变物种丰富度与植物氮吸收的正相关关系。(4)碳纳米管干扰使人工湿地微宇宙的氮去除速率增加4%,并且触发物种多样性对人工湿地氮去除的促进作用。在无纳米管干扰时,物种丰富度不影响总无机氮去除,而干扰后提高物种丰富度变得增加总无机氮去除。碳纳米管干扰后,人工湿地混种系统中反硝化作用的增强导致硝态氮去除的增加,是混种系统总无机氮去除增加的原因。此外,碳纳米管干扰后,芦苇×菖蒲×皇冠草混种组合中出现了“超去除效应”,即该组合的总无机氮去除比去除率最高的单种系统还高3%。(5)碳纳米管干扰改变了物种丰富度与人工湿地氨挥发的关系。无碳纳米管干扰时物种丰富度通过生物量的级联作用而降低氨挥发;而干扰后,物种丰富度变得不影响氨挥发。这是因为碳纳米管对氨排放有直接且强大的抑制作用,使高多样性和低多样性系统的氨排放都降低至相同的低水平。这说明了碳纳米管干扰影响BEF关系的另一种模式,即碳纳米管对氨的减排作用足够大,使得物种丰富度与氨挥发及其健康损害的负相关关系解偶联。(6)碳纳米管对人工湿地的氧化亚氮排放没有显著影响;碳纳米管干扰下,提高物种丰富度保持对氧化亚氮排放的抑制作用,这与干扰下物种丰富度与生物量生产的正相关关系保持不变有关。然而,碳纳米管干扰改变了物种丰富度与单位反硝化的氧化亚氮排放的关系,因为碳纳米管干扰后单种系统的单位反硝化的氧化亚氮排放不变,而混种系统的单位反硝化的氧化亚氮排放降低。此外,碳纳米管干扰后,物种丰富度从不影响甲烷排放变为降低甲烷排放。碳纳米管干扰下,物种丰富度对整合了氧化亚氮和甲烷排放的温室气体的健康损害的减缓作用保持不变;同时,物种丰富度对单位氮去除的健康损害的减缓作用也不受碳纳米管干扰的影响。说明碳纳米管干扰在引发植物多样性对氮去除的促进作用的同时,不影响植物多样性降低气态污染物的健康损害的作用。本研究首次发现了碳纳米管这类新型干扰对生态系统中植物种间关系的改变和对生物多样性-生态系统过程和功能的影响。本研究一方面将生态系统干扰类型拓展到工程纳米材料,另一方面将工程纳米材料的毒性和安全风险研究拓展到对生态系统的结构和结构-功能关系的影响上。碳纳米管干扰改变了植物的种间关系,改变生物多样性对于生态系统功能维持或增强的作用。本研究为理解工程纳米材料这类新型干扰下生态系统结构和功能的变化提供新的见解。应对新型人源污染物干扰时,需要进一步进行生态系统尺度甚至区域尺度的研究。更多还原

【Abstract】 The relationship between biodiversity and ecosystem functioning(BEF)has been a frontier issue in ecology in recent decades.Recently,increasing attention has been paid to the effects of disturbances(e.g.,nitrogen addition and warming)on the BEF relationship.With the increasing use and disposal of engineering nanomaterials(e.g.,carbon nanotubes,CNTs),the wasted nanomaterials have become a new kind of disturbance to the ecosystem by affecting organisms and ecosystem processes and functions.However,the existing studies mainly focused on the effect(toxicity)of CNTs on the performance of single species,especially crops.How the CNTs affect wild plants,structure,and BEF relationship in ecosystems with multiple coexisting species remains unknown.Constructed wetlands(CWs)is a kind of widely used wastewater treatment systems.Due to their controllable experiment conditions,CWs have become a good platform for the BEF study.The wasted CNTs entering the wastewaters initially sink in the wetland ecosystems.Therefore,CWs are an ideal experimental platform to explore the effect of emerging disturbance of CNTs on BEF relationship.This study set up a biodiversity control experimental system including 108 independent CW microcosms.These microcosms were divided into two groups,in which one was treated with CNTs and the other was the control.Four common wetland plants were selected to set up three richness gradients(1,3,4)and 9 species combinations.This study aims to explore the effects of CNTs disturbance on plant biomass production and interspecific competition,the relationship between species diversity and ecosystem productivity,nitrogen processes,and nitrogen functions.The main results and conclusions are as follows.(1)The disturbance of CNTs induced an asymmetric effect on biomass production among different plant species.In monocultures,CNTs decreased the biomass production of Phragmites australis by 26% compared with the controls but did not affect those of the other three species.In mixtures,the effect of carbon nanotubes was reversed.CNTs did not affect the biomass production of P.australis,but decreased the biomass production of Acorus calamus,Echinodorus amazonicus,and Pontederia cordata in mixtures by 15%,24%,and 17%,respectively.The asymmetric response of species changed the interspecific competition.After the disturbance of CNTs,the competitive advantage(relative yield)of the original superior competitor,P.australis,was enhanced,while the competitive abilities of the other three species were weakened.These exacerbated the asymmetry of interspecific competition.In ecosystems without CNTs,there were two superior competitors,P.australis and P.cordata,while only one superior competitor(P.australis)left after the disturbance of CNTs.(2)The disturbance of CNTs reduced the productivity of CW ecosystem by 12% on average.However,the positive effect of plant species richness on ecosystem productivity remained unchanged under the disturbance.The CNTs intensified competition and reduced the complementarity effect,but the increased competitive advantage of the most productive species slowed down the decline of productivity in mixtures.Finally,the decline of productivity in monocultures and mixtures were similar,and the relationship between species richness and productivity was robust to CNT disturbance.(3)CNTs disturbance altered the nitrogen processes in CW ecosystems.CNTs reduced plant nitrogen uptake by 11% but enhanced denitrification by 50%(proved by the mass balance analysis and stable isotope analysis).In ecosystems without CNTs,increasing plant species richness reduced denitrification,while the negative relationship between species richness and denitrification was flattened after CNTs disturbance.It is due to the increase in denitrification of mixtures(72%)was higher than that of monocultures(29%).However,the positive correlation between species richness and plant nitrogen uptake kept unchanged under CNTs disturbance.(4)CNTs disturbance increased nitrogen removal rate by 4% and triggered a positive species diversity effect on nitrogen removal in CWs.Species richness did not affect the total inorganic nitrogen removal in ecosystems without disturbance,and became increase total inorganic nitrogen removal after CNTs disturbance.The enhancement of denitrification in mixtures led to the increase in nitrate and total inorganic nitrogen removal in mixtures.In addition,an "over-removal effect" appeared in the combination of P.australis × A.calamus × E.amazonicus after the disturbance,that is to say,the total inorganic nitrogen removal rate of the combination was 3%higher than that of the monoculture with the highest removal rate.(5)CNTs disturbance altered the relationship between species richness and ammonia volatilization in CWs.In CWs without disturbance,species richness decreased ammonia volatilization by a cascading effect through increasing plant biomass production.However,species richness did not affect ammonia volatilization after CNTs disturbance.This was because the inhibitory effect of CNTs was so effective that the ammonia volatilization of monocultures and mixtures decreased to the same low level.This indicated another pattern of CNTs disturbance on the BEF relationship.That is to say,the CNTs had a large enough effect on ammonia volatilization reduction to uncouple the negative relationship between species richness and ammonia volatilization.(6)CNTs disturbance did not affect nitrous oxide emission of CWs.Species richness kept a negative effect on nitrous oxide emission under disturbance,due to the unchanged positive diversity-productivity relationship.However,CNTs disturbance triggered a negative relationship between species richness and nitrous oxide emission per unit of denitrification.It was because that nitrous oxide emission per unit of denitrification remained unchanged in monocultures,but decreased in mixtures.In addition,the species richness also triggered a negative diversity effect on methane emission.The negative effect of species richness on the health damage cost integrated with nitrous oxide and methane emissions remains unchanged under the disturbance of CNTs;at the same time,the mitigation effect of species richness on the health damage cost per unit of nitrogen removal was not affected by disturbance.It is indicated that CNTs not only triggered a positive effect of plant diversity on nitrogen removal,but also did not affect the mitigation effect of diversity on health damage cost of gaseous pollutants in CWs.This study firstly reported that CNTs,as a new type of disturbance,altered the interspecies relationship and biodiversity-ecosystem process and functioning relationship.In this study,on the one hand,the types of ecosystem disturbances were extended to engineering nanomaterials;on the other hand,the toxicity and safety risk of engineering nanomaterials were extended to their effects on the ecosystem structure and structure-function relationship.CNTs intensified interspecific competition and reshaped the role of biodiversity in maintaining or enhancing ecosystem functioning.This work provides new insights into understanding the changes in ecosystem structure and function under the emerging disturbance of engineering nanomaterials.To deal with the disturbance of emerging anthropogenic pollutants,further study on the ecosystem and regional scale is needed.更多还原