为探讨春玉米不同生育期土壤呼吸速率对大气CO 2 浓度升高的响应,以黄土高原旱作春玉米为研究对象,通过改进的开顶式气室（OTC）模拟大气CO 2 浓度升高的环境,在田间条件下设置自然大气CO 2 浓度（CK）、OTC对照（OTC,CO 2 浓度同CK）与CO 2 浓度升高（OTC+CO 2 ,OTC系统自动控制CO 2 浓度700μmol/mol） 3种处理。研究了旱区覆膜高产栽培春玉米播前（V0）、六叶期（V6）、九叶期（V9）、吐丝期（R1）、乳熟期（R3）、蜡熟期（R5）及完熟期（R6）土壤呼吸速率对大气CO 2 浓度升高的响应特征,以及大气CO 2 浓度升高对土壤呼吸速率的温度与水分效应的影响。研究发现,OTC+CO 2 处理土壤呼吸速率,与CK相比,在R3和R5期分别增加43%、104%（P＜0.05）,与OTC相比,R3和R5期分别提升了63%、109%（P＜0.05）;OTC处理与CK相比,在整个生育期对土壤呼吸影响不显著;3种处理条件下,土壤温度和水分随生育期变化趋势基本一致,土壤呼吸速率与土壤温度和水分分别呈指数相关和抛物线型相关;结果表明:大气CO 2 浓度升高对土壤呼吸的影响因生育期而异,土壤温度和土壤水分是影响旱地农田土壤呼吸的重要因素,CO 2 浓度升高会使土壤呼吸温度效应值(Q 10 )降低,土壤呼吸对土壤水分响应的阈值提高。

植被恢复会对干旱半干旱区土壤固碳过程产生重要影响,探讨植被恢复对不同土壤颗粒碳含量的影响有利于进一步揭示荒漠土壤演变过程.选择毛乌素沙地东南缘人工植被恢复区的乔木林、灌木林、草地和流沙地为样地,对0-30 cm的土壤进行了分层取样分析.结果 表明:乔木、灌木和草地的恢复均会降低土壤粗颗粒(细砂粒、粗砂粒)含量,增加团聚体和粉黏粒含量;植被恢复后土壤有机碳(SOC)和无机碳(SIC)含量均显著增加,其中最大值均出现在乔木样地,分别达到流沙地的3.96倍和2.08倍;植被恢复对土壤有机碳密度(SOCD)的影响较土壤无机碳密度(SICD)更为明显;乔木有利于粗砂粒和细砂粒有机碳的累积,灌木更有利于粉黏粒和团聚体有机碳的累积;各粒级SOC含量在细砂粒中增幅最为明显;SIC含量在粉黏粒中增幅最为明显;粉黏粒有机碳对总有机碳的贡献率较为显著.总之,不同类型植被的恢复均会提高土壤有机和无机含量,从增加土壤固碳的角度出发,乔木为毛乌素沙地的最佳植被恢复类型.

干旱半干旱荒漠区是一个潜力巨大的碳汇,荒漠植被建设则进一步加速了其固碳过程.探究咸水滴灌条件下塔克拉玛干沙漠公路防护林土壤碳垂直分布特征及其影响因素,可为干旱荒漠区人工林碳储量的估算和可持续管理提供科学依据.选择沙漠公路沿线4.82～28.40 g/L的4个高矿化度地下水滴灌的人工防护林,采集并分析了0～5 m各层土壤有机碳(SOC)与无机碳(SIC)含量及碳密度的垂直分布特征及其与含水量、pH和土壤电导率(EC)间的相关关系.结果 表明,SOC与SIC随土层深度的增加分别呈现“减—增—减”与“增—减—增”趋势,并最终分别在2 m和3m以下土层趋于稳定;浅层(0～40 cm)土壤有机碳密度(SOCD)和无机碳密度(SICD)分别比流沙地增加了73％～346％和1.5％～14.0％,5 m深土层SOCD、SICD和总碳密度分别增加了8.3％～28％、5.4％～58％和8.3％～29.9％,其中SICD为SOCD的13.3倍;人工林SOC分布与含水量和EC呈正相关,SIC与含水量同样呈正相关,同时SOC与SIC间相关关系为正相关.总之,荒漠人工防护林建设显著提高了SOC与SIC储量,且灌溉水矿化度、土壤含水量和EC均对SOC和SIC储量及垂直分布产生不同程度的影响.

为探明大气CO2浓度升高对旱作玉米不同生育期土壤碳氮及其组分的影响,以旱作春玉米为研究对象,基于田间定位试验,利用改进的开顶式气室(OTC)模拟大气CO2浓度升高的环境,设置当前自然大气CO2浓度(CK)、CO2浓度升高(700 μmol/mol,OTC+ CO2)与OTC气室对照(OTC)3种处理,研究大气CO2浓度升高对玉米各生育期土壤有机碳、全氮、水溶性有机碳、水溶性氮、易氧化有机碳的影响.结果 表明:与OTC相比,大气CO2浓度升高(OTC+CO2)对土壤有机碳及组分、土壤全氮均无显著影响,使水溶性氮在12叶期(V12)降低18.17％,灌浆期(R3)升高108.56％ (P＜0.05).与CK相比,OTC+ CO2处理显著降低了各生育期土壤有机碳(收获期R6除外)和全氮(V12除外)含量,降幅分别为4.47％～14.42％和6.78％～12.48％ (P＜0.05),降低了苗期(V6)水溶性有机碳、V12期水溶性氮、抽雄吐丝期(R1)与R6期易氧化有机碳含量,升高了R3期水溶性有机碳含量(P＜0.05).因此,试验设置条件下,大气CO2浓度升高对土壤有机碳及组分、土壤全氮均无显著影响,对水溶性氮的影响因生育期而异.在利用OTC系统模拟大气CO2浓度升高进行相关研究时,OTC对试验结果的影响不可忽视.

The conversion of organic wastes into biochar via the pyrolysis technique could be used to produce soil amendments useful as a source of plant nutrients. In this study, we investigated the effects of fruit peels and milk tea waste-derived biochars on wheat growth, yield, root traits, soil enzyme activities and nutrient status. Eight amendment treatments were tested: no amendment (CK), chemical fertilizer (CF), banana peel biochar 1% (BB1 + CF), banana peel biochar 2% (BB2 + CF), orange peel biochar 1% (OB1 + CF), orange peel biochar 2% (OB2 + CF), milk tea waste biochar 1% (TB1 + CF) and milk tea waste biochar 2% (TB2 + CF). The results indicated that chlorophyll values, plant height, grain yield, dry weight of shoot and root were significantly (p < 0.05) increased for the TB2 + CF treatment as compared to other treatments. Similarly, higher contents of nutrients in grains, shoots and roots were observed for TB2 + CF: N (61.3, 23.3 and 7.6 g kg−1), P (9.2, 10.4 and 8.3 g kg−1) and K (9.1, 34.8 and 4.4 g kg−1). Compared to CK, the total root length (41.1%), surface area (56.5%), root volume (54.2%) and diameter (78.4%) were the greatest for TB2 + CF, followed by BB2 + CF, OB2 + CF, TB1 + CF, BB1 + CF, OB1 + CF and CF, respectively. However, BB + CF and OB + CF treatments increased β-glucosidase and dehydrogenase, but not urease activity, as compared to the TB + CF amendment, while all enzyme activity decreased with the increased biochar levels. We concluded that the conversion of fruit peels and milk tea waste into biochar products contribute the benefits of environmental and economic issues, and should be tested as soil amendments combined with chemical fertilizers for the improvement of wheat growth and grain yield as well as soil fertility status under field conditions.

Core Ideas In this study, switchgrass grew well on marginally saline soil with limited irrigation.The southern‐origin cultivars had greater biomass yield than the northern cultivars.Irrigation increased above and below ground biomass, but not soil C and N content.Switchgrass had the potential to sequester C into the soil. Limited information is available on switchgrass (Panicum virgatum L.) productivity in semiarid environments. A field experiment was conducted in semiarid Colorado, with the objectives were to determine: 1) aboveground biomass production of six upland switchgrass cultivars, and 2) soil organic carbon content of two switchgrass cultivars grown on a marginally saline soil under rainfed and minimal irrigation conditions. The experiment was a split plot design with rainfed vs. minimal irrigation treatment as the main plot and six cultivars [three southern cultivars (Blackwell, Pathfinder, and Trailblazer) and three northern cultivars (Sunburst, Forestburg, and Dacotah)] as subplot with three replications. Aboveground biomass for the six cultivars ranged from 1.1 to 7.8 Mg ha−1yr−1 in the establishment year, and 3.2–9.3 and 3.3–11.7 Mg ha−1yr−1 under rainfed and minimally irrigated conditions, respectively, during the following three stand years. Minimal irrigation (mean annual irrigation water of 21 cm) increased biomass yield compared to the rainfed control. Southern‐origin cultivars produced more biomass than the northern lines under both rainfed and minimal irrigation. Four years after establishment, within the top 0.6 m of soil, irrigation increased root biomass, with averages of 9.9 and 5.2 Mg ha−1 yr−1 for irrigation and rainfed treatments, respectively. Soil organic carbon accumulated rapidly at 0–20 cm soil depth in Blackwell and Pathfinder plots, at the rates of 1.07–1.36 Mg C ha−1 yr−1. Switchgrass growth in the semiarid environment was improved with limited supplemental irrigation and had the potential to sequester C into soil.

[目的]探讨人工樟子松林对毛乌素沙地土壤颗粒组成和固碳的长期影响,为综合评价沙地植被恢复的生态环境效应提供科学依据.[方法]选择毛乌素沙地东南缘人工栽植21,36和56 a的樟子松林和流沙地为采样地,对0-30 cm的土壤进行了分层取样分析,以探讨人工林建设对半干旱荒漠区土壤颗粒组成及不同粒级含碳量的长期影响.[结果]随着栽植年限的增加,土壤颗粒呈逐渐细化的趋势,且表层(0-5 cm)细颗粒含量均高于下层(5-30 cm).造林后土壤有机碳(SOC)和无机碳(SIC)含量均显著增加,最高值分别是流沙地的4.90倍和4.32倍;栽植年限对SOC含量和土壤有机碳密度(SOCD)的影响大于SIC含量和土壤无机碳密度(SICD).相对于流沙地,各粒级SOC,SIC含量均在栽植56 a样地增幅最大,且均在细砂粒组分中增幅最大.团聚体和粉黏粒有机碳含量与土壤总有机碳含量之间存在显著的线性相关关系(p＜0.01),粗砂粒和粉黏粒有机碳对总有机碳的贡献率和粉黏粒无机碳对总无机碳的贡献率较为显著(p＜0.05).[结论]随着樟子松栽植年限的增加,土壤团聚体、粉黏粒含量和土壤固碳能力均显著提高.

为探讨旱区覆膜玉米农田土壤酶活性对未来气候变化的响应,在田间条件下通过改进的开顶式气室(OTC)系统自动控制大气CO2浓度,设置自然大气CO2浓度(CK)、OTC对照(OTC)、OTC系统自动控制CO2浓度(700μmol·mol-1,OTC+CO2)3个处理,研究了旱区覆膜高产栽培春玉米播前、六叶期(V6)、十二叶期(V12)、吐丝期(R1)、乳熟期(R3)及完熟期(R6)土壤脲酶、碱性磷酸酶、蔗糖酶及过氧化氢酶活性对大气CO2浓度升高的响应特征.研究发现:OTC处理条件下,土壤碱性磷酸酶活性相比CK在V12期降低8.80％(P<0.05),而在R6期提高8.95％(P<0.05);蔗糖酶活性在播前、V6、R1期降低12.65％～21.43％(P<0.05),R3期升高17.50％(P<0.05);过氧化氢酶活性在V12、R1、R6期均显著降低.大气CO2浓度升高对玉米各生育期土壤脲酶活性均无显著影响;使R1、R6期碱性磷酸酶活性降低8.74％ 和6.39％(P<0.05);使V6、R3期蔗糖酶活性升高30.18％ 和18.37％(P<0.05);此外,增加了V12期过氧化氢酶活性,而降低了R3期过氧化氢酶活性.结果表明:当前旱作覆膜高产栽培模式下,大气CO2浓度升高对春玉米农田土壤酶活性的影响因作物生育期和酶种类不同而异;土壤酶活性对OTC及大气CO2浓度升高的响应程度不一,在当前试验条件下,OTC对土壤酶活性的影响较大气CO2浓度升高更为显著.

In order to improve the applicability and accuracy of Open-Top Chambers(OTCs)in simulating the effects of elevated CO2 on crop growth and yield under field conditions, the open-top area of the chamber was increased, the shape of the bottom was modified from oc-tagonal to square, a new material was used for the chamber walls, and fans were installed in the chamber to increase air circulation. These improved OTCs were used for simulating elevated CO2 concentration in spring maize farmland in 2015 and 2016. The chamber measured 4.0 m × 4.0 m × 3.0 m(length × width × height)and was equipped with an automated CO2 delivery system designed to maintain the CO2 con-centration at 700 μmol·mol-1 in the chamber. During the maize growth period, CO2 concentration, air temperature, and relative humidity were measured automatically every 10 minutes both inside and outside the OTCs. The CO2 concentration, air temperature, and relative hu-midity inside the OTCs were compared to those under natural conditions, and the simulation performance was analyzed. The results demon-strated that the CO2 concentration could be well controlled by the improved OTC system. The deviation from the targeted CO2 concentration ranged from-17.2μmol·mol-1 to 0.2μmol·mol-1 in 2015 and from-5.4μmol·mol-1 to 0.1μmol·mol-1 in 2016. The mean air temperature inside the OTCs was 0.8℃higher than that of the natural air during daytime in 2015(P<0.05), and no significant difference in such was observed for 2016. There was no significant difference in relative humidity between inside and outside of the chambers(P>0.05). Our re-sults indicated that the improved OTC has stable performance and high accuracy and can be used for future field simulation experiments.

Background, aim, and scope Biochar is a newly constructed scientific term which is defined as ‘‘a carbon(C)-rich and non-pollution product when biomass such as wood, manure or leaves is heated in a closed container with little or unavailable air’’. It has the properties of high internal surface area, microporosity, non-biological and biological stability. It has been widely proposed as a promising novel alternative of soil amendment to improve soil physical and chemical properties, to reduce the biological effectiveness of soil pollutant, as well as to reduce the emission of carbon dioxide and other greenhouse gases. However, to date, the effects of biochar addition on soil hydraulic properties, and the inlfuencing mechanism of biochar addition on water retention and holding capacity are still unclear.Materials and methods Effects of biochar with two sizes (1—2 mm and≤0.25 mm) and 4 doses (10 g?kg?1, 50 g?kg?1, 100 g?kg?1 and 150 g?kg?1) on wetting front, cumulative infiltration and retention curves of loessial soil were explored through simulated experiments in laboratory. The loessial soil was collected from the soil surface (0—20 cm) of a field without tillage in Ansai Ecological Experimental Station, Shaanxi Province innorthwest China. Experiment with biochar was charcoal-derived biochar and its carbon mass fraction was 85%. Results The results showed that (1) the infiltration capacity was obviously decreased and water holding capacity was significantly increased compared to the control due to the biochar addition in loessial soil. When the particle size was the same and within a certain infiltration time period, in addition to the≤0.25 mm treatment and the cumulative infiltration curve almost superposition under the 10 g?kg?1, 50 g?kg?1 and 100 g?kg?1 treatments, cumulative infiltration and wetting front moving rate tended to decrease with the increasing content of biochar, while water holding capacity tended to increase with the increasing content of biochar. Under the conditions of the same biochar addition dose, cumulative infiltration and wetting front moving rate tended to decrease with the particle size decreased within a certain infiltration period (40 minutes after infiltration start), while water holding capacity increased with the particle size decreased, but there was no significant effect on water holding capacity at the dose of 10 g?kg?1. 40 minutes after infiltration start, the wetting front moving rates for 1 — 2 mm treatment with 10 g?kg?1, 50 g?kg?1, 100 g?kg?1 and 150 g?kg?1 doses were decreased by 5.72%, 12.47%, 10.23% and 17.49%, respectively, compared with the control, cumulative infiltration were decreased by 11.17%, 24.48%, 22.07% and 31.10%, respectively; the wetting front moving rates of≤0.25 mm treatment with the addition doses of 10 g?kg?1, 50 g?kg?1, 100 g?kg?1 and 150 g?kg?1 were decreased by 13.49%, 14.79%, 22.79% and 36.28%, respectively, compared with the control, and cumulative infiltration were decreased most by 57.93% with the dose of 150 g?kg?1. The averaged wetting front moving rate and cumulative infiltration were decreased by 16.69% and 27.79% in loessial soil with the comparison to the control. Overall, biochar addition reduced the water infiltration capacity and increased the water holding capacity for loessial soil. (2) Variation of the wetting front with time demonstrated a power function relationship, the determination coefficient was 0.997—0.999. Kostiakov, Philip and Horton infiltration model were successively used to simulation the soil water infiltration process and Kostiakov infiltration model of which determination coefficient was 0.989—0.998 fitted best. (3) van Genuchten model was suitable for simulation the soil water holding process with biochar application, and the determination coefficient of it was 0.995—0.999.DiscussionThe results showed that the infiltration capacity was decreased and water holding capacity was increased with the biochar amendments to loessial soil. Biochar has high internal porosity and surface area and it creates a soil conditioning agent that can lower bulk density, increase the content of soil clay, affect pore size distribution and increase soil porosity. Therefore, it inhibited the infiltration capacity and improved water holding capacity of loessial soil. Conclusions The results showed that the loessial soil infiltration capacity tended to decrease with the increasing content of biochar, decreased with the particle size increased, while water holding capacity tended to increase with the increasing content of biochar, and the water holding capacity was best with the smallest particle size (≤0.25 mm) biochar addition in loessial soil. The results also showed that variation of the wetting front with time demonstrated a power function relationship, the determination coefficient was 0.997 — 0.999. Kostiakov, Philip, Horton infiltration model were successively used to simulation the soil water infiltration process and Kostiakov infiltration model fitted best. van Genuchten model was suitable for simulation the soil water holding process with biochar application.Recommendations and perspectives The data suggested that the use of biochar as soil amendment in loessialsoil plays an important role in increasing soil water holding capacity, and providing a scientific basis for the evaluation on the inlfuence of biochar application on soil hydrology in the Loess Plateau.

Shanxi-Shaanxi-Inner Monglia adjacent region is an important coal energy base, and also the most fragile ecological region in China. Recent years, the large-scale opencast mining has heavily destroyed the original landscape and ecosystem, and formed a large number of earth disposal sites. To guaranty the harmonious development of the local society, economy and ecosystem, the rapid artificial vegetation reconstruction in these sites is the key part of the local ecological restoration. To evaluate the effects of different vegetation measures in the process of land reclamation on the recovery of soil nutrient, the east earth disposal site in Heidaigou opencast coal mine located in Jungar Banner, Inner Mongolia was chosen as studying area, where the land reclamation was carried out with 7 different artificial vegetation configuration modes (Astragalus adsurgens, Stipa bungeana, Amorpha fruticosa, Robinia pseudoacacia, Hippophae rhamnoides, PoplarandPinus sylvestris var mongolica Litv) since 1996. The recovery degrees of soil total nitrogen (TN), soil organic carbon (SOC), NO3––N and NH4+–N within 0-40 cm were studied by comparing with the nearby natural soil under 2 vegetation types (natural Stipa bungeanaand natural Hippophae rhamnoides). The results showed that: 1) The content of TN, SOC, NO3––N and NH4+–N declined with the increase of the soil depth within 0-40 cm under different vegetation except thePinus sylvestris var mongolica Litv and Astragalus adsurgens. 2) Within 0-40 cm, the contents of TN and SOC of 7 artificial vegetation types were significantly lower than the 2 natural vegetation types, and there was no significant difference between 7 artificial vegetation types and 2 natural vegetation types in NH4+–N within 0-10 and 20-40 cm. Seven vegetation types improved soil quality at different levels, and the remediationdegree ofRobinia pseudoacacia vegetation was better than other vegetation patterns. Average TN, SOC, NO3––N and NH4+–N within 40 cm soil depth were recovered to 44.15%, 44.65%, 85.33% and 93.77% of naturalStipa bungeana site and 56.85%, 54.82%, 84.66% and 105.70% of naturalHippophae rhamnoides site after nearly 16 years’ recovery. And the remediationeffects ofPoplar andPinus sylvestris var mongolica Litv were no more than 40% of the 2 natural vegetation types. The remediationeffect of NH4+–N was relatively better under 7 vegetation patterns. Average NH4+–N within 40 cm soil depth was recovered to 79.50%-93.77% of naturalStipa bungeana site, and 89.47%-105.7% of naturalHippophae rhamnoides site. However, the remediationdegree of TN, SOC, and NO3––N were relatively lower than NH4+–N. Average TN, SOC, and NO3––N within 40 cm soil depth had recovered to 24.70%–44.15%, 25.09%–44.65%, 47.25%–85.33% of naturalStipa bungeana site, and 33.52%–56.85%, 32.83%–54.82%, 47.18%–84.66% of naturalHippophae rhamnoides site. Although soil nutrients of 7 artificial vegetation modes in land reclamation area have not reach the natural level completely after 16 years’ land reclamation, artificial vegetation is an effective measure to improve soil nutrients’ recovery.Fabaceous plantvegetation (mainlyRobinia pseudoacacia) was better than other vegetation patterns for soil nutrient recovery, soRobinia pseudoacacia, Hippophae rhamnoides andStipa bungeana could be the suitable vegetation for the land reclamation in this area. The research has evaluated the soil nutrient remediation degree of different vegetation measures in the process of land reclamation and provided the theoretical basis for the vegetation measure selection during ecological restoration and land reclamation in the opencast coal mine area.

Long-term information on switchgrass (Panicum virgatum L.) as a biomass energy crop grown on marginally saline soil and the associated impacts on soil carbon (C) and nitrogen (N) dynamics, greenhouse gas (GHG) emissions, and best management practices (BMPs) are limited. In this study, we employed the DAYCENT model, based on a 4-year switchgrass field experiment, to evaluate the long-term biomass yield potential and environmental impacts, and further to develop BMPs for switchgrass in a semi-arid region.The model showed that long-term (14-year) annual mean biomass yields were 9.6 and 5.2 Mg ha(-1) for irrigated and rainfed switchgrass systems, respectively. The simulated biomass yields correlated well with field-measured biomass with r(2) values of 0.99 and 0.89 for irrigated and rainfed systems, respectively. Soil organic carbon (SOC) and soil total nitrogen (STN) accumulated rapidly after switchgrass establishment, with mean accrual rates of 0.99-1.13 Mg C ha(-1) yr(-1) and 0.04-0.08 Mg N ha(-1) yr(-1), respectively. Based on the outputs of numerous long-term model simulations with variable irrigation water supplies and N rates, the irrigation regime and N rate with the highest yield to input ratio were chosen as BMPs. The DAYCENT model predicted-BMP was irrigating every 14 days at 70% potential evapotranspiration combined with an N rate of 67 kg ha(-1) yr(-1). Switchgrass established and produced biomass reasonably well in this semi-arid region; however, appropriate irrigation and N fertilization were needed for optimal biomass yield. Switchgrass had a great potential to sequester C into soils with low N2O emissions while supplying significant quantities of biomass for biofuel synthesis. (C) 2015 Elsevier Ltd. All rights reserved.

为探明降雨特别是酸雨对玉米冠层氮素淋失的影响,以盆栽试验春玉米为指示作物,采用自制人工降雨器进行模拟降雨,研究施氮与不施氮(对照)条件下玉米冠层NO3-N淋失动态、数量及随生育期和降雨酸度的变化规律.结果表明,中性和弱酸性降雨淋洗,NO3--N淋失量主要由冠层氮素含量决定,而强酸雨淋洗,NO3--N淋失量受降雨pH值和冠层氮素含量共同影响.各生育期玉米冠层NO3-N淋失量随降雨pH值降低变化规律不一,生育前期降雨pH值对冠层NO3--N淋失影响较生育后期显著,在研究降雨酸度对玉米冠层NO3--N淋失的影响时,必须考虑生育期.相同pH值模拟降雨条件下,玉米冠层NO3--N淋失量随生育期推进逐渐降低:11叶期＞吐丝期＞灌浆期,生育前期显著高于中后期.玉米冠层NO3--N淋失量不仅与介质施氮有关,同时受降雨pH值影响,2因素在不同生育期对NO3--N淋失贡献大小有所不同,但总体看,植物体氮素丰富程度是影响冠层NO3--N淋失的主要因素.各生育期玉米冠层均存在一定数量的NO3--N淋失,尤以生育前期为甚,说明在研究农田生态系统氮素流量和冠层氮素损失时,冠层氮素淋失应予以考虑.

为提高环境化学课程教学质量,针对当前环境化学教学中存在的普遍问题,进行课堂和实验教学改革,优化课程内容,增设学生自主讨论课和最新研究成果专题报告,并就实践效果进行分析,提出针对性的建议。

The teaching reform was investigated according to the problems existing the experimental teaching of environmental monitoring course. Aspects discussed included strengthening experimental teaching; adjusting the contents of the experiments; adding open experiments; enhancing the practice of computer and reforming the assessment method of experimental score, etc.

【Objective】 The objective of this paper was to study the effects of different levels of N and water supply on the accumulation and distribution of dry matter and N in maize leaf and straw-sheath. 【Method】 A pot experiment was therefore conducted during 2008-2009 to study the dry matter and N accumulation and distribution dynamics as affected by different levels of N supply and soil water availability. 【Result】 The results showed that N concentration of leaf and straw-sheath was significantly increased with application of N fertilizer except 11-leaf stage. Adequate water supply significantly enhanced the N concentration of leaf and straw-sheath in N application treatments,however,adequate water supply did not enhance but decreased the N concentration of leaf and straw-sheath in no N application treatments. Whether N were applied or not,the dry matter accumulation of leaf and straw -sheath showed a single-peak curve with maize growing under the condition of adequate water supply,but it showed a continuous increasing trend with growing under the condition of drought stress. The N accumulation of leaf and straw-sheath showed a single-peak curve with growing in all treatments except the one which were treated with not only drought stress but also no N application (in this treatment,no significant differences were observed in N content of leaf and straw -sheath among 3 stages). Whether N and water were supplied sufficiently or not,leaf was the main part of N distribution,but the distribution of dry matter varied with N application and growing stage. When no N fertilizer was applied,the cumulative amount of dry matter in straw-sheath was higher than in leaf from spinning to grain filling stage,however,it was lower than leaf at 11-leaf stage. When N fertilizer was sufficiently supplied,the cumulative amount of dry matter in straw-sheath was always higher than in leaf during the whole growing season.【Conclusion】 The accumulation of dry matter and N in leaf and straw-sheath were asynchronous,and the accumulation curves varied with different levels of water and N supply. Leaf was the main part of N accumulation,but the main part of dry matter accumulation varied with N application and growing stage. N application and irrigation both could significantly increase the dry matter and N content in maize canopy,and the interactive effects between irrigation and N application were significant,in addition,the effect of N application was higher than irrigation in present experiment.

N-Acetylglucosaminyltransferases Ⅴ(GnT-Ⅴ) plays a pivotal role in cancer progression and metastasis.In tumor,higher activity of GnT-Ⅴ was observed, and the product of GnT-Ⅴ,β1,6 GlcNAc branching was also increased.And β1,6 GlcNAc branching is a key structure associated with cancer metastasis.In this review,we demonstrated the research of GnT-Ⅴ,including GnT-Ⅴ catalyzes the formation of β1,6 GlcNac branches of N-glycans and plays a pivotal role in the processing of N-linked glycoproteins,also including structure and expression tissue specific of the GnT-Ⅴ gene,and regulation of GnT-Ⅴ is mediated by a transcription factor Ets-1.The most important part of the review is recently progress of molecular mechanism of GnT-Ⅴ in malignant transformations and cancer metastasis,including GnT-Ⅴ acts on adhesion molecular cadherin and integrin α5β1 and modification of EGF receptor and modify downstream signal transduction,and matriptase with β1,6 GlcNAc branching could increase invasion. Therefore,inhibiting the action of GnT-Ⅴ in terms of the above functions represents a reasonable strategy of new drug design for inhibiting tumor progression and metastasis.

The characteristics of community succession of M.sativa artificial grassland with ages from 1 to 30 years was studied using space for time method in Liudaogou catchment,in the north Loess Plateau in Shenmu County of Shaanxi Province.Results show that M.sativa productivity was low in general attributed to drought and poor soil fertility conditions.The highest fresh biomass was 4 000-5 000 kg/hm~2,but the flourishing duration was short no more than 6 years.Relevant managing measures,such as cultivation and fertilization that can ameliorate soil conditions and slow down competitive stress of M.sativa group,were suggested to be applied for the purpose of prolonging the life-span of artificial grasslands to some extent.The planting of M.sativa can significantly accelerate the succession process toward natural vegetations.M.sativa grassland can naturally succeed into the stage of stable prairie community-Stipa bungeana community in 10 years.Floristic species belonging to the three big families of Leguminocae,Compositae,and Gramineae played critical role in the degrading process of M.sativa grassland.The species number belonging to the three families occupied(54.5%)-78.6% of total numbers appeared in respective stage.As the main companion species of Stipa bungeana community in the studied area,Artemisia capillarys,Astraglus melilotoides and Lespedesa davurica reflected the arid climate condition and poor soil fertility.

Objective To obtain recombinant neural cell adhension molecule L1(L1) and to study its structure and biological activity.Methods The cDNA encoding the mature rat L1 was isolated using RT-PCR from total RNA extracted from newborn SD-rat hippocampus tissue.The expression plasmid pETL1 mutants of several extracellular domains of(L1) were constructed by inserting L1 and its mutants cDNA into plasmid pET-28a(+) containing T7 promoter and transformed into E.coli BL21(DE3). A series expression strain BLL1 mutants were selected.Recombinant L1 and its mutant proteins were expressed at levels about 18.5%～30% of total bacteria protein in form of inclusion body after the induction.By Ni~(2+) chelation affinity chromatography,up to 90% L1's mutant proteins were purified.The expressed plasmid pcDNA3-L1 were transfected into PC12 cells and constructed PC12-engineered cells which stably and highly expressed the L1.Results Purified and refolded IgI-FN5、Ig(Ⅰ-Ⅵ) and FN(1-5) fragments could significantly promote the neurite outgrowth of PC12-engineered cells;fragment Ig(Ⅴ-Ⅵ) also can promote the neurite outgrowth but not soobvious as the before;fragment FN(3-5) have no function to induce the neurite outgrowth of PC12-engineered cells.Conclusions These results suggested that there are at least two segments in extracellular domains of L1 Ig(Ⅰ-Ⅵ) and FN(1-5) fragments are critical for inducing the neurite outgrowth of PC12-L1 cells and the key amino acids for signaling transduction located in the segments of Ig(Ⅰ-Ⅵ) and FN(1-5);fragment Ig(Ⅴ-Ⅵ) is necessary but not crucial for promoting the neurite outgrowth;fragment FN(3-5) is not important for L1 biological function.