The impact of fragmentation and density regulation on forest succession in the Atlantic rain forest

The Atlantic Rain Forest, an important biodiversity hot spot, has faced severe habitat loss since the last century which has resulted in a highly fragmented landscape with a large number of small forest patches (<100 ha). For conservation planning it is essential to understand how current and future forest regeneration depends on ecological processes, fragment size and the connection to the regional seed pool. We have investigated the following questions by applying the forest growth simulation model FORMIND to the situation of the Atlantic Forest in the state of São Paulo, SE Brazil: (1) which set of parameters describing the local regeneration and level of density regulation can reproduce the biomass distribution and stem density of an old growth forest in a reserve? (2) Which additional processes apart from those describing the dynamics of an old growth forest, drive forest succession of small isolated fragments? (3) Which role does external seed input play during succession? Therefore, more than 300 tree species have been classified into nine plant functional types (PFTs), which are characterized by maximum potential height and shade tolerance. We differentiate between two seed dispersal modes: (i) local dispersal, i.e. all seedlings originated from fertile trees within the simulated area and (ii) external seed rain. Local seed dispersal has been parameterized following the pattern oriented approach, using biomass estimates of old growth forest. We have found that moderate density regulation is essential to achieve coexistence for a broad range of regeneration parameters. Considering the expected uncertainty and variability in the regeneration processes it is important that the forest dynamics are robust to variations in the regeneration parameters. Furthermore, edge effects such as increased mortality at the border and external seed rain have been necessary to reproduce the patterns for small isolated fragments. Overall, simulated biomass is much lower in the fragments compared to the continuous forest, whereas shade tolerant species are affected most strongly by fragmentation. Our simulations can supplement empirical studies by extrapolating local knowledge on edge effects of fragments to larger temporal and spatial scales. In particular our results show the importance of external seed rain and therefore highlight the importance of structural connectivity between regenerating fragments and mature forest stands.     

Modelling above-ground herbage mass for a wide range of grassland community types

Whereas it is recognized that management of plant diversity can be the key to reconciling production and environmental aims, most grassland models are tailored for high-value grass species. We proposed to adapt a mono-specific grass model to take into account specific features of species-rich permanent grasslands, especially over the reproductive phase. To this end, we used the concept of plant functional type (PFT), i.e. the grouping of plant species according to plant traits determined by the response of plant species to different management practices (land use and fertilization) and characterizing of agronomic properties of the corresponding species. In the model, weather and nutrient availability act upon rates of biophysical processes (radiation capture and use, plant senescence). These rates are modified over times due to PFT-specific parameters determined experimentally which represent the different strategies of plant species regarding growth. The integration of these parameters into the model made it possible to predict herbage biomass accumulation rate under different management practices for a wide range of plant communities differing in their PFT composition. The model was evaluated in two steps, first by analyzing separately the effects of PFT and an indicator of nutrient availability on herbage accumulation and then by conducting a sensitivity analysis. It was validated using two independent datasets; a cutting experiment running over the whole growing season to examine the consistency of the model outputs under different cutting regimes, and a monitoring of meadows and pastures in spring over a whole growth cycle to assess the model’s ability to reproduce growth curves. Although a good fit was observed between the simulated and observed data, the few discrepancies noticed between field data and predicted values were attributed mainly to the potential presence of non-grass species. More specifically, we noticed that nutrient (mainly nitrogen) availability is the main driver of plant growth rate, and that PFT determines the times at which this rate changes in relation to the phenological characteristics of species present. We concluded that integration of the PFT concept into the initial mono-specific growth model is especially suited to evaluating the consequences of management practices on species-rich permanent grasslands to meet feed production targets.     

天津城区道路雨水径流水质监测及污染特征分析

城市市区道路由于交通活动产生大量的重金属、无机阴离子、营养盐、有机污染物等,对受纳水体的水质造成很大破坏,并影响了水体的生态环境.通过对天津城区不同功能区(商业区、文教区和居住区)的道路降雨径流的30个水质指标进行监测分析,评估天津市区道路雨水径流的污染程度,进而分析天津市区降雨污染的基本特征.结果表明,不同功能区理化指标平均浓度的大小顺序为:商业区>居住区>文教区,天津市区道路雨水pH接近中性;金属离子中铅在3个功能区中均超标,在商业区、文教区和居住区中分别超标1.16、1.05和1.28倍,且天津市区重金属污染浓度与南京和澳门相近;无机阴离子并未超出地表水质量标准V类标准或集中式生活饮用水地表水源地补充项目标准限值.TN、TP、COD和BOD_5最大值分别严重超出国家地表水环境质量V类标准的2.5、2.0、10和50倍.挥发酚在3个功能区中均未超标,而阴离子表面活性剂在商业区、文教区和居住区分别超过地表水质量标准V类标准的37、17和6.3倍.     

Fhhh工程菌株降解PTA废水动力学研究

研究了工程菌株Fhhh降解精对苯二甲酸(PTA)石化废水的动力学.将测得的Fhhh降解废水的6项动力学参数值、废水自然参数值、废水排放标准控制值,输入环境生物技术信息学软件(Ebis)进行计算.结果表明,来源于3种保存方法的Fhhh菌株中,所需反应器的最小体积(V_min)为1309m³,比降解率(q_A)的最高数值为0.0136h^-1,是土著菌YZ1的4倍,高于国内外同类研究的4项数值,低于同类研究的2项数值.结果表明,Fhhh工程菌株具有降解PTA废水的显著优势.     

Comparative effects of different maize straw returning modes on soil humus composition and humic acid structural characteristics in Northeast China

In order to evaluate the effects of different maize straw returning modes on humus composition and humic acid (HA) structural, a field experiment was designed to have five treatments, i.e. Treatment CK (no straw returned), Treatment EIS (straw incorporated evenly into the soil using the crashing-ridging technique), Treatment SP (straw plowed into the soil), Treatment SM (straw returned as mulch) and Treatment SG (straw returned as pellets). Our results showed that Treatment EIS significantly increased the content of soil organic carbon (SOC), soil humus substances (HEC), soil humic acid carbon (HAC) and fulvic acid carbon (FAC) by 27.8%, 47.6%, 63.3% and 33.8%, respectively, as compared with CK. Among all the straw returning treatments, Treatment EIS was the most significant in effect of increasing the content of HEC, HAC and FAC. Moreover, Treatment EIS altered the composition of humus more significantly than all the other treatments, by increasing the proportion of alkyl C and the ratio of aliphatic C/aromatic C. These results suggest that straw returning accelerated the accumulation of soil organic C and various components of humus, significantly improved the structure of soil HA, with the practice of EIS in particular.     

气水比对A/O-BF处理低碳氮比农村生活污水脱氮的影响

为揭示好氧段气水比对缺氧/好氧生物滤池（Anoxic/Oxic Biofilter,A/O-BF）脱氮的影响机理,采用A/O-BF处理低碳氮比农村生活污水,结合实时荧光定量聚合酶链式反应技术,对比研究了好氧段气水比为4：1、2：1和1：1时A/O-BF的脱氮效能和微生物群落变化特征.结果表明：当气水比为4：1时,A/O-BF的氨氮（NH₄⁺-N）和总氮（TN）平均去除率分别为99.0%和75.9%;当气水比降至2：1时,NH₄⁺-N的平均去除率（99.5%）基本维持不变,而TN去除率有所提高（79.5%）;当气水比再降至1：1时,两者的平均去除率分别下降至92.0%和71.7%.气水比由4：1降至2：1时,好氧段中硝化菌脱氮功能基因amoA和Nitrospira 16S rDNA的拷贝数并无明显变化,为同一数量级,但缺氧段中4个反硝化菌脱氮功能基因（narG、nosZ、nirS和nirK）拷贝数却明显升高0~1个数量级;当气水比由2：1降至1：1时,好氧段中两个硝化菌脱氮功能基因拷贝数均下降1个数量级,但缺氧段中反硝化菌脱氮功能基因拷贝数无明显变化,除narG基因外均处于同一数量级.综上所述,2：1为A/O-BF处理低碳氮比农村生活污水脱氮的最佳气水比.     

真菌对磺胺二甲氧嘧啶降解过程的转录组分析及差异表达基因的功能分析

采用黄孢原毛平革菌降解磺胺二甲氧嘧啶（SDM）,4 d后SDM的去除率达74%,降解速率达3.24 mg·L^-1·d^-1.采用Illumina高通量测序平台对降解SDM后的菌株与对照组菌株进行测序,通过GO和KEGG富集分析,得到的差异表达基因能显著富集到与降解相关的“氧化还原酶活性”途径,及与应激反应有关的“ABC转运体”路径.通过对高表达高上调的差异表达基因的筛选与分析,得到了耐受和降解SDM的功能基因.水通道蛋白、ABC转运蛋白及甲基转运酶基因等在黄孢原毛平革菌对环境的耐受中起到重要的作用.乙醇氧化酶、细胞色素P450和糖苷水解酶等在黄孢原毛平革菌对SDM的降解中起着关键的作用.本文从转录组水平分析了SDM的降解机制,为黄孢原毛平革菌在环境修复中的应用提供一定的参考.     

铜尾矿坝及其周边土壤真菌群落结构与功能多样性

土壤真菌群落会因环境条件的变化而重新构建.为了探究山西省垣曲县十八河尾矿坝及其周边土壤中真菌群落的结构与功能多样性,本研究探讨了坝体草地、15 a杨树林、农田、10 a杨树林这4种土地利用方式下土壤真菌群落的结构组成和碳源利用功能多样性.结果表明,研究区15 a杨树林地中真菌群落丰度和多样性最高,坝体草地中最低;子囊菌门（Ascomycota）、担子菌门（Basidiomycota）和被孢霉门（Mortierellomycota）是研究区的优势真菌类群,其中,子囊菌门（Ascomycota）在所有样地中均有最大分布,其在坝体草地中的分布达到92.92%;15 a杨树林地中真菌群落碳源利用多样性最高,坝体草地中真菌群落碳源利用多样性显著高于农田和10 a杨树林地,坝体草地土壤真菌群落对糖苷类碳源的利用效率显著高于其余3种土地利用类型.相关分析表明,土壤真菌群落丰度与土壤总氮显著相关（P<0.05）,而与土壤重金属含量不相关.土壤真菌群落多样性指数与重金属Cd、As之间具有显著相关性,与其他重金属无显著相关性.本研究结果表明长期受重金属污染胁迫下,土壤中真菌群落更多受土壤肥力和土地利用方式影响,而与土壤重金属浓度不呈线性关系.本研究结果对土壤真菌群落在重金属污染区土壤修复中的应用具有重要意义.     

重金属钝化剂阻控生菜Cd吸收的功能稳定性和适用性

利用重金属钝化剂阻控蔬菜吸收重金属是治理中轻度重金属污染菜地和保障蔬菜安全生产的重要举措.以重金属固定细菌Bacillus megaterium N3（N3）、稻壳生物炭（BC）、羊粪有机肥（SM）、菌株N3联合生物炭（BC+N3）和菌株N3联合羊粪有机肥（SM+N3）为重金属钝化剂,采用盆栽试验连续种植生菜3次,而只在种植第1次时施重金属钝化剂,研究不同处理对生菜吸收Cd的影响及其功能的稳定性,并利用动态加权综合函数评估这几种钝化材料的综合适用性.结果表明,第1次种植生菜时,与对照相比,所有重金属钝化剂均能显著降低（61.2%~81%）生菜可食用部分Cd的含量.而在第3次种植生菜中,只有菌株N3联合羊粪有机肥的处理能显著降低生菜对Cd的吸收,这表明菌株N3联合羊粪有机肥阻控生菜Cd吸收的功能稳定性最好.利用动态加权综合函数,从新鲜生菜可食用部分Cd含量、土壤有效态Cd含量、每亩产量和每亩修复成本等4个方面进行综合评价.结果显示,菌株N3联合羊粪有机肥的综合适用性最好,其次是羊粪有机肥、菌株N3联合生物炭和生物炭,而菌株N3的综合评价效果最差.本研究结果为重金属污染菜地钝化修复提供理论依据和技术支撑.     

岩溶区稻田土壤真菌群落结构及功能类群特征

真菌是土壤生物地球化学循环的重要驱动者,然而岩溶区土壤真菌群落结构和功能类群具有怎样的特征还未见报道.以桂林毛村岩溶试验场稻田耕层土壤为研究对象,采用高通量测序技术,比较岩溶区和非岩溶（红壤）区（对照）水稻生长季土壤真菌群落结构,并用FUNGuild对真菌进行功能预测.结果表明,毛霉菌门（Mucoromycota）在岩溶区的平均相对丰度为4.87%,显著低于其在非岩溶区的平均相对丰度（29.92%）;被孢霉纲（Mortierellomycetes）在岩溶区的平均相对丰度为3.36%,显著低于其在非岩溶区的平均相对丰度（29.15%）,球囊菌纲（Glomeromycetes）、壶菌纲（Chytridiomycetes）和外担菌纲（Exobasidiomycetes）在岩溶区的平均相对丰度分别为0.91%、0.98%和0.23%,显著高于其在非岩溶区的平均相对丰度（0.47%、0.28%和0.04%）; Ramophialophora和翅孢壳菌属（Emericellopsis）在岩溶区的平均相对丰度分别为2.39%和1.25%,显著高于其在非岩溶区的平均相对丰度（0.05%和0.09%）,而被孢霉属（Mortierella）在岩溶区的平均相对丰度为3.04%,显著低于其在非岩溶区的平均相对丰度（28.34%）.岩溶区优势OTUs为OTU141、99和192等32个OTUs;在优势OTUs和土壤理化性质相关性网络图中,岩溶区的OTU69（Emericellopsis terricola）和OTU138（Westerdykella globosa）与阳离子交换量、交换性钙离子和总磷的连接度较高.共生营养型和病理-腐生过渡型在岩溶区平均丰度分别为1.29%和1.50%,显著高于其在非岩溶区的平均丰度（0.08%和0.09%）,而腐生-共生过渡型在岩溶区的平均丰度为10.81%,显著低于其在非岩溶区的平均丰度（63.69%）;岩溶区和非岩溶区最优势真菌分别是粪腐生-木质腐生菌和内生菌根-植物病原-未定义腐生菌,平均丰度分别占优势OTUs的9.73%和45.93%.以上研究表明,岩溶区稻田较高的阳离子交换量、交换性钙和总磷等土壤因子对优势真菌群落和功能类群的构建具有重要的作用.