植被恢复对黄土高原矿区重构土壤理化性质、酶活性以及真菌群落的影响

[目的]研究黄土高原矿区重构土壤植被恢复对土壤理化性质、酶活性以及真菌群落的影响,准确评价植被恢复对该地区的土壤生态恢复效果。[方法]在内蒙古自治区准格尔旗选择3种典型植被恢复类型(灌木、乔木、草地)和未复垦地采集0—20 cm土壤样品,采用扩增子测序技术分析了土壤真菌多样性和群落组成,同时结合土壤理化性质探讨了不同植被恢复类型影响真菌群落多样性的重要因素。[结果]①与未复垦地相比,3种典型植被恢复类型不仅对土壤理化性质和酶活性均有明显提升,还提高了土壤真菌可操作分类单元(OUTs)和多样性指数,且差异显著,以灌木的效果最好。②真菌主要菌门相对丰度在各样地变化趋势为子囊菌门(Ascomycota)担子菌门(Basidiomycota)球囊菌门(Glomeromycota),相对丰度之和已超过50%,土壤真菌群落结构在4个样地之间保持了一定的稳定性。③土壤含水量为影响真菌群落结构的最主要因素。[结论]植被恢复影响土壤理化性质、酶活性及真菌群落多样性,黄土高原矿区生态恢复是一个漫长的过程,在生态恢复过程中,宜种植灌木来改善重构土壤的生态环境。     

生态工程背景下黄土高原植被变化时空特征及其驱动力

[目的]分析1990—2015年黄土高原植被的时空演变规律,并从气候变化和人类活动两个方面分析该地区植被变化的驱动力,以期为生态环境保护相关政策的制定和区域可持续发展提供理论依据。[方法]基于GIMMS NDVI和MODIS NDVI建立长时间序列NDVI数据集,采用线性趋势分析、多元线性回归和改进的人类残差等分析方法,以NDVI为指标,辅助土地利用数据,对黄土高原地区1990—2015年期间植被时空变化特征及其影响因素进行了定量分析。[结果]①在1990到2015年期间,黄土高原地区植被的NDVI总体表现为上升趋势,且变化趋势较明显的分为两个时期,其中2000年以后NDVI上升速率较快;②2000年以后,黄土高原植被NDVI迅速上升,上升区域面积达到总面积的91.90%,其中NDVI显著上升面积比为65.78%;③黄土高原地区植被面积总体表现为增加,且主要来自于耕地的转入;④人类活动促使的植被恢复区域占黄土高原总面积的21.74%,主要分布在内蒙古的东部和北部、甘肃和宁夏的南部,以及陕西和山西的中部地区。[结论]随着退耕还林还草政策的实施,黄土高原地区植被面积持续增加,且植被生长状况持续变好,黄土高原植被恢复的原因主要是气候和人类共同影响,其中人类影响的程度较大。     

一株苏云金亚种的发酵产物对柳蚜3种保护酶活性的影响

为探究苏云金杆菌(Bacillus thuringiensis Bt)对蚜虫的生物活性影响及作用方式,以苏云金亚种(Bacillus thuringiensis subsp.thuringiensis)为目的菌株,以发酵产物为材料。利用5种不同浓度的菌液分别喷雾处理柳蚜,72h校正死亡率为29.74%～78.88%,其浓度与及死亡率呈正相关关系。苏云金杆菌亚种发酵液和发酵液滤液处理柳蚜后,12～24h柳蚜超氧化物歧化酶(SOD)比活力均被抑制,其抑制率分别为21.06%～38.11%和4.69%～36.79%,其中18h、24h对SOD比活力的抑制达显著水平(p<0.05)。发酵液和滤液处理组18h前对柳蚜过氧化氢酶(CAT)比活力的影响总体呈激活趋势,其中发酵液和滤液处理组分别在18h、12h对柳蚜CAT的激活率最高,其CAT比活力分别为对照的1.8890倍和2.9463倍。滤液处理组对柳蚜POD比活力总体呈激活作用,其激活率为14.78%～57.39%;发酵液处理组6h和18hPOD比活力显著高于对照,其他时间点POD比活力与对照无显著差异。     

1-MCP和壳聚糖处理保持红枣贮藏品质及其机理研究

以新疆灰枣为试材,研究纸片型1-甲基环丙烯（1-methylcyclopropene,1-MCP）与壳聚糖（chitosan,COS）处理在（0±1）℃条件下对灰枣品质及相关酶活性的影响。结果表明：至贮藏90 d时,与对照（CK）相比,1-MCP＋COS的腐烂率、失质量率分别降低53.4%、51.2%,可溶性固形物（total soluble solid, TSS）含量高出18.6%。抗氧化酶系统中的超氧化物歧化酶（superoxide dismutase, SOD）峰值水平提高58.2%,过氧化氢酶（catalase, CAT）峰值高出34.8%;贮藏结束时过氧化物酶（peroxidase, POD）活性是CK的1.98倍,抗坏血酸过氧化物酶（ascorbate peroxidase, APX）活性高出51.7%,差异显著（P＜0.05）。1-MCP、COS及1-MCP+COS处理均可不同程度地降低果实腐烂率、失质量率,保持较高的果实硬度和TSS含量,推迟呼吸高峰和乙烯释放速率高峰的到来并抑制丙二醛（malondialdehyde, MDA）的积累,抑制脂氧合酶（lipoxygenase, LOX）和多酚氧化酶（polyphenol oxidase, PPO）活性,显著提高抗氧化酶系统活性。其中1.50 μL/L纸片型1-MCP与1% COS复合处理对保持果实贮藏品质、延缓果实衰老、延长货架期最有利。     

滨海沙地不同固氮树种叶片氮、磷重吸收与生物固氮的耦合关系

福建滨海沙地氮磷养分匮乏,季节性干旱严重。养分重吸收可以减弱植物对土壤养分供应的依赖,从而增强植物适应逆境的能力。以福州市滨海后沿沙地人工营造的木麻黄、肯氏相思和纹荚相思人工林为研究对象,进行不同叶龄(成熟叶、衰老叶)叶片N、P浓度及稳定氮同位素丰度值(δ15 N)的测定,通过统计手段研究叶片N、P重吸收效率(NRE、PRE)、重吸收度(NRP、PRP)及其与生物固氮率的关系。结果表明:(1)滨海沙地不同固氮树种叶片NRE表现为纹荚相思(52.80%)>肯氏相思(28.27%)>木麻黄(24.63%),纹荚相思叶片NRE显著高于肯氏相思和木麻黄,但后两者间无显著差异;PRE表现为肯氏相思(74.08%)>纹荚相思(63.99%)>木麻黄(40.47%),且相互之间差异显著。(2)滨海沙地不同固氮树种生物固氮率表现为肯氏相思(69.45%)>纹荚相思(69.15%)>木麻黄(34.59%),2种相思树种生物固氮率无显著差异,但显著高于木麻黄99.88%～100.77%。(3)滨海沙地不同固氮树种生物固氮率与NRE、PRE和NRP呈负相关关系,与叶片PRP呈正相关关系。因而,滨海沙地不同固氮树种生物固氮与叶片的氮、磷重吸收存在耦合关系,并显著影响氮、磷重吸收效率和重吸收度。研究结果为揭示滨海沙地不同固氮树种对贫瘠土壤和季节性干旱的适应机制提供依据,也为滨海沙地营林管理提供参考。     

警惕危险害虫庭园象甲入侵我国

庭园象甲(Phlyctinus callosus)是一种能对水果、观赏植物造成严重危害的害虫,原产南非,现已传播到新西兰和澳大利亚等地,我国尚无分布记录.庭院象甲寄主广,适应性强,为害具有较高的隐蔽性,有较大的入侵风险.本文对庭园象甲的分类地位、寄主、分布、形态特征、为害特点、生物学特性、防控措施等进行了详细介绍,为口...     

Response of an agricultural soil to pentachlorophenol (PCP) contamination and the addition of compost or dissolved organic matter

The response of a fresh, agricultural soil when contaminated with pentachlorophenol (PCP) and supplemented with compost (C) or dissolved organic matter (DOM) was studied in the laboratory. The concentration of PCP and the changes in various functionally related properties (i.e. microbial biomass, basal respiration, soil hydrolase and oxidoreductase activity) were measured over 150 d. Variations in the main physical and chemical properties of the soils were also monitored. Two different doses of compost (C1 = 0.27% and C2 = 0.83%, corresponding to 10 and 30 t ha⁻¹, respectively) or DOM (D1 = 0.07% and D2 = 0.2%) equivalent to the carbon content of the two compost doses C1 and C2 were used and the following five systems were investigated: soil (S), soil–compost (S-C1 and S-C2) and soil–DOM (S-D1 and S-D2). PCP concentrations declined progressively and significantly with time. This effect was most pronounced for the soils amended with the lower compost dose C1 (S-C1) and with the two DOM (S-D1 and S-D2) amounts. Significantly reduced amounts of PCP were extracted after its 500-d residence in the various systems. Higher amounts of the residual PCP were extracted from the humic acids (HA), fulvic acids (FA) and humin–mineral (HU) fractions of the 500 d aged samples than from the same unfractionated samples, indicating that the residual PCP preferentially accumulated in the organic fractions of soil. The soil showed an endogenous microbial activity as indicated by basal respiration, microbial biomass and all the enzymatic activities tested (dehydrogenase, glucosidase, phosphatase, arylsulphatase and urease). Addition of the PCP severely depressed some of the tested biochemical properties suggesting an inhibitory effect on microbial activity. Conversely, higher basal respiration, and similar β-glucosidase and phosphatase activities were measured in comparison with the controls. No significant effects were observed following the addition of two doses of the compost or the DOM. Fungal colonies belonging to the taxonomic group of Ascomycetes and identified as Byssochlamys fulva developed with time in all the PCP-contaminated samples. Growth of B. fulva in vitro in the presence of PCP showed that the isolate was tolerant to 12.5 and 25 mg l⁻¹ PCP and degraded 20% of its initial concentration in 8 d. Overall, the results indicate that many complex processes occurred in the contaminated soil and combinations of these determined the response to PCP contamination. The sorption of PCP to the soil matrix (which increased with time) and its degradation/transformation by indigenous soil microbial activity were likely involved. Both the processes appeared to be favoured by the presence of dissolved organic matter.     

土壤结构性质和磷脂剖面的联合保存: 三种干燥技术的比较

There is a need to simultaneously preserve evidence of interactions between the biological community and soil structural properties of a soil in as near an intact （natural） state as possible. Three dehydration techniques were implemented and assessed for their ability to minimise disruption of both biological and physical properties of the same arable soil sample. Dehydration techniques applied until samples were at constant weight were i） air-drying at 20℃ （AD）; ii） -80 ℃ freeze for 24 h, followed by freeze-drying （-80FD）; and iii） liquid nitrogen snap freeze, followed by freeze-drying （LNPD） and were compared to a moist control. Physical structure was determined and quantified in three dimensions using X-ray computed tomography and microbial phenotypic community composition was assessed using phospholipid fatty acid （PLPA） profiling. This study confirms that any form of dehydration, when preparing soil for simultaneous biological and physical analysis, will alter the soil physical properties, and cause some change in apparent community structure. Freeze-drying （both the LNFD and -80FD treatments） was found to minimise disruption （when compared to the moist control soil） to both the soil physical properties and the community structure and is a preferable technique to air-drying which markedly alters the size and character of the pore network, as well as the phenotypic profile. The LNFD was the preferred treatment over the -80FD treatment as samples show low variability between replicates and a fast turn-around time between samples. Therefore snap freezing in liquid nitrogen, followed by freeze drying is the most appropriate form of dehydration when two sets of data, both physical and biological, need to be preserved simultaneously from a soil core.