Microbial characteristics in anaerobic membrane bioreactor treating domestic sewage: Effects of HRT and process performance

Two anaerobic membrane bioreactors (AnMBRs) equipped with different membrane pore size (0.4 or 0.05μm) were operated at 25℃ and fed with domestic wastewater.The hydraulic retention time (HRT) of the reactors was shortened.The microbial communities of the two AnMBRs were investigated by 16S rRNA gene amplicon sequencing to see the effects of HRT.The predominant Archaea was an aceticlastic methanogen Methanosaeta.The composition of hydrogenotrophic methanogens changed with the HRTs:the population ...     

红壤区退化林地表土真菌群落结构对土壤改良措施的响应

真菌群落结构和多样性对于土壤改良效果具有高敏感性.研究南方红壤区侵蚀退化林表土真菌群落对有机肥、生物炭和石灰+微生物肥的响应,以明晰不同改土措施的作用.结果表明：(1)3种土壤改良措施均降低了表土真菌丰富度,其中石灰+微生物肥降低作用最大,3种土壤改良措施对表土真菌多样性也有影响,但影响不显著;(2)表土中优势真菌门为子囊菌门(Ascomycota, 31.29%～46.55%)、担子菌门(Basidiomycota, 30.07%～70.71%),优势真菌属为阿太菌属(Amphinema)和单形古根菌属(Archaeorhizomyces),3种土壤改良措施对表土真菌群落结构的影响不同,有机肥提高了子囊菌门和单形古根菌属的相对丰度,生物炭提高了担子菌门和阿太菌属的相对丰度,而石灰+微生物肥则提高了担子菌门和单形古根菌属的相对丰度;(3)土壤pH是影响表土真菌丰富度的关键因子,而表土真菌群落结构则受pH、全氮和有机碳的影响.研究结果为南方红壤区侵蚀退化林地土壤改良,林下植被生态恢复提供科学指导.     

底泥疏浚对太湖内源及底栖生物恢复的影响

底泥疏浚对湖泊内源削减具有重要的作用,是富营养化湖泊内源治理的重要技术之一.以太湖疏浚区为对象,估算了近十余年疏浚对内源负荷的削减量,并评估了太湖北部竺山湖和梅梁湖的底泥疏浚效果.结果表明,太湖累计疏浚的4 200万m³底泥,共计清除了底泥中氮约6.26万t,总磷约1.83万t,有机质约117万t,相当于清除了蓄积于底泥中二十余年的外源污染物输入量.对于外源控制较好的梅梁湖,底泥疏浚后5 a内水质改善明显,随后出现反弹,但仍有效削减了表层底泥总氮和总磷含量.相反,对于外源输入仍较大的竺山湖,疏浚十余年后,底泥内源又回复到浚前水平.对竺山湖疏浚区开展了长达6 a的底栖生物群落跟踪评估,发现疏浚初期对底栖生物群落具有一定的影响,但浚后2 a,底栖生物密度与生物量等指标已接近浚前水平. 6 a后,疏浚区与未疏浚区的底栖生物群落多样性指数已无差别.结果也表明,底泥疏浚对湖体内源具有较好的控制效果,且疏浚效果维持程度与外源输入强度密切相关.此外,长期来看,疏浚区底栖生物群落依靠自恢复能力可达到浚前水平,疏浚不会对底栖生物群落结构造成影响.     

生物炭和秸秆还田对微咸水滴灌棉田土壤真菌群落结构多样性的影响

微咸水灌溉增加土壤盐分,改变土壤环境,进而影响土壤真菌的结构和多样性.在长期微咸水灌溉的基础上,分别添加生物炭和秸秆（采用等碳量设计,分别为3.7 t·hm^-2和6 t·hm^-2）,探究生物炭和秸秆对土壤理化性质和真菌群落结构多样性的影响.结果表明：与不施生物炭和秸秆（对照）相比,生物炭施用显著增加土壤的pH、全碳、速效钾和速效磷含量,但显著降低土壤电导率,降低幅度为20.71%;秸秆处理显著增加土壤的速效钾和速效磷含量,但显著降低土壤容重和电导率,降低幅度为4.17%和64.50%.生物炭和秸秆处理对真菌群落Chao1指数和ACE指数有增加趋势,对Shannon指数和Simpson指数有降低趋势.土壤优势真菌门类为子囊菌门、被孢霉门、担子菌门、壶菌门和球囊菌门;优势真菌属为毛壳菌属、赤霉菌属、镰刀菌属、Idriella和被孢霉属.施加生物炭和秸秆提高子囊菌门、被孢霉门、担子菌门、球囊菌门和毛壳菌属的相对丰度;但降低壶菌门、赤霉菌属和Idriella的相对丰度.LEfSe分析表明,施用生物炭和秸秆还田降低真菌群落潜在生物标志物数量.RDA结果显示,土壤真菌群落结构与EC_1：5和TN显著相关.微咸水灌溉给土壤带来了不利影响,其中EC_1：5和TN是驱动土壤真菌群落结构变化的主要因子,土壤真菌群落通过生物炭和秸秆对土壤的改良作用来适应盐胁迫环境.     

Cultivating hybrid collectives: research methods for enacting community food economies in Australia and the Philippines

Across the globe, groups are experimenting with initiatives to create alternatives to the dominant food system. What role might research play in helping to strengthen and multiply these initiatives? In this paper we discuss two research projects in Australia and the Philippines in which we have cultivated hybrid collectives of academic researchers, lay researchers and various non-human others with the intention of enacting community food economies. We feature three critical interactions in the “hybrid collective research method”: gathering, which brings together those who share concerns about community food economies; reassembling, in which material gathered is deliberatively rebundled to amplify particular insights; and translating, by which reassembled ideas are taken up by other collectives so they may continue to “do work”. We argue that in a climate-changing world, the hybrid collective research method fosters opportunities for a range of human and non-human participants to act in concert to build community food economies.     

Radical,reformist, and garden-variety neoliberal: coming to terms with urban agriculture's contradictions

For many activists and scholars, urban agriculture in the Global North has become synonymous with sustainable food systems, standing in opposition to the dominant industrial agri-food system. At the same time, critical social scientists increasingly argue that urban agriculture programmes, by filling the void left by the “rolling back” of the social safety net, underwrite neoliberalisation. I argue that such contradictions are central to urban agriculture. Drawing on existing literature and fieldwork in Oakland, CA, I explain how urban agriculture arises from a protective counter-movement, while at the same time entrenching the neoliberal organisation of contemporary urban political economies through its entanglement with multiple processes of neoliberalisation. By focusing on one function or the other, however, rather than understanding such contradictions as internal and inherent, we risk undermining urban agriculture's transformative potential. Coming to terms with its internal contradictions can help activists, policy-makers and practitioners better position urban agriculture within coordinated efforts for structural change, one of many means to an end rather than an end unto itself.     

Bumblebee Vulnerability: Common Correlates of Winners and Losers across Three Continents

Abstract:  It is widely agreed that in many parts of the world some bumblebee ( Bombus ) species have declined, and that this has often been driven by land-use changes that cause reductions in the abundance of food plants. There is much less agreement about how changes in food plants affect some bumblebee species more than others. We sought to identify which species' characteristics are generally associated with the relative winners and losers by comparing the 3 independent bumblebee faunas from parts of Britain, Canada, and China. Using available survey data, we assessed species characteristics, including competition with congeners, climatic specialization, proximity to climatic range edge, food specialization, phenology, body size, and range size. Results of our meta-analysis of correlations showed support for the hypotheses that decline susceptibility is generally greater for species that have greater climatic specialization, for species in areas where they occur closest to the edges of their climatic ranges, and for species that have queens that become active later in the year. The latter characteristic may render a species at a particular disadvantage when they have long colony cycles if there are losses of food plants in mid to late colony development.     

Lichen Conservation in Heavily Managed Boreal Forests

Lichens are an important component of the boreal forest, where they are long lived, tend to accumulate in older stands, and are a major food source for the threatened woodland caribou (Rangifer tarandus caribou). To be fully sustainable, silvicultural practices in the boreal forest must include the conservation of ecological integrity. Dominant forest management practices, however, have short‐term negative effects on lichen diversity, particularly the application of herbicides. To better understand the long‐term effects of forest management, we examined lichen regeneration in 35 mixed black spruce (Picea mariana) and jack pine (Pinus banksiana) forest stands across northern Ontario to determine recovery following logging and postharvest silvicultural practices. Our forest stands were 25–40 years old and had undergone 3 common sivilcultural treatments that included harvested and planted; harvested, planted, and treated with N‐[phosphonomethyl] glycine (glyphosate); and harvested, planted, and treated with 2,4‐dichlorophenoxyacetic acid (2,4‐D). Forest stands with herbicide treatments had lower lichen biomass and higher beta and gamma diversity than planted stands that were not treated chemically or control stands. In northwestern Ontario, planted stands that were not treated chemically had significantly greater (p < 0.05) alpha diversity than stands treated with herbicides or control stands. Our results show that common silvicultural practices do not emulate natural disturbances caused by wildfires in the boreal forest for the lichen community. We suggest a reduction in the amount of chemical application be considered in areas where lichen biomass is likely to be high and where the recovery of woodland caribou is an objective. Conservación de Líquenes en Bosques Boreales Manejados Intensivamente     

Understanding Trait‐Dependent Community Disassembly: Dung Beetles,Density Functions,and Forest Fragmentation

Abstract: Anthropogenic disturbances such as fragmentation are rapidly altering biodiversity, yet a lack of attention to species traits and abundance patterns has made the results of most studies difficult to generalize. We determined traits of extinction‐prone species and present a novel strategy for classifying species according to their population‐level response to a gradient of disturbance intensity. We examined the effects of forest fragmentation on dung beetle communities in an archipelago of 33 islands recently created by flooding in Venezuela. Species richness, density, and biomass all declined sharply with decreasing island area and increasing island isolation. Species richness was highly nested, indicating that local extinctions occurred nonrandomly. The most sensitive dung beetle species appeared to require at least 85 ha of forest, more than many large vertebrates. Extinction‐prone species were either large‐bodied, forest specialists, or uncommon. These explanatory variables were unrelated, suggesting at least 3 underlying causes of extirpation. Large species showed high wing loading (body mass/wing area) and a distinct flight strategy that may increase their area requirements. Although forest specificity made most species sensitive to fragmentation, a few persistent habitat generalists dispersed across the matrix. Density functions classified species into 4 response groups on the basis of their change in density with decreasing species richness. Sensitive and persistent species both declined with increasing fragmentation intensity, but persistent species occurred on more islands, which may be due to their higher baseline densities. Compensatory species increased in abundance following the initial loss of sensitive species, but rapidly declined with increasing fragmentation. Supertramp species (widespread habitat generalists) may be poor competitors but strong dispersers; their abundance peaked following the decline of the other 3 groups. Nevertheless, even the least sensitive species were extirpated or rare on the smallest and most isolated islands.     

Nitrogen deposition alters soil chemical properties and bacterial communities in the Inner Mongolia grassland

Nitrogen deposition has dramatically altered biodiversity and ecosystem functioning on the earth; however, its effects on soil bacterial community and the underlying mechanisms of these effects have not been thoroughly examined. Changes in ecosystems caused by nitrogen deposition have traditionally been attributed to increased nitrogen content. In fact, nitrogen deposition not only leads to increased soil total N content, but also changes in the NH₄⁺-N content, NO₃^--N content and pH, as well as changes in the heterogeneity of the four indexes. The soil indexes for these four factors, their heterogeneity and even the plant community might be routes through which nitrogen deposition alters the bacterial community. Here, we describe a 6-year nitrogen addition experiment conducted in a typical steppe ecosystem to investigate the ecological mechanism by which nitrogen deposition alters bacterial abundance, diversity and composition. We found that various characteristics of the bacterial community were explained by different environmental factors. Nitrogen deposition decreased bacterial abundance that is positively related to soil pH value. In addition, nitrogen addition decreased bacterial diversity, which is negatively related to soil total N content and positively related to soil NO₃^--N heterogeneity. Finally, nitrogen addition altered bacterial composition that is significantly related to soil NH₄⁺-N content. Although nitrogen deposition significantly altered plant biomass, diversity and composition, these characteristics of plant community did not have a significant impact on processes of nitrogen deposition that led to alterations in bacterial abundance, diversity and composition. Therefore, more sensitive molecular technologies should be adopted to detect the subtle shifts of microbial community structure induced by the changes of plant community upon nitrogen deposition.