Evaluation of cold resistance of ornamental species for planting as urban rooftop greening

Rooftop gardening or green roof establishment, one of the methods of afforestation for urban greening, has many benefits for the environment, the economy and urban landscapes. Various environmental stresses including heat, strong wind, sunshine and cold prevent most plants from growing well in extensive green roof systems. For the establishment of urban rooftop gardening in Beijing, we evaluated 13 ornamental plant species [Berberis thunbergii ‘Atropurea Nana’, Euonymus fortune (Turcz.) Hand., Viburnum dilatatum Thunb., Cotinus coggygria Scop., Swida alba Opiz., Weigela florida (Bunge.) A. DC., Jasminum nudiflorum Lindl., Euonymus japonicus Thunb., Euonymus japonicus ‘Cuzhi’, Buddleja davidii Franch., Pyracantha fortuneana (Maxim.) Li., Ligustrum lucidum Ait. and Spiraea salicifolia L.] for greening of flat rooftops. We obtained three indices concerning cold resistance, i.e., electrical conductivity of leaves, amounts of soluble sugars and amounts of free proline, providing a theoretical basis for selection of plants fit for roof and balcony greening. The results show that the six species P. fortuneana (Maxim.) Li., B. thunbergii ‘Atropurea Nana’, J. nudiflorum Lindl., E. fortune (Turcz.) Hand., E. japonicus Thunb. and E. japonicus ‘Cuzhi’ are excellent plants for rooftop gardening, judging from their strong ability in cold resistance. Plants such as L. lucidum Ait., C. coggygria Scop. and W. florida (Bunge) A. DC. showed a medium ability in cold resistance. However, these species can be used in roof and balcony greening after intensive management or acclimatization of variety. The ability to resist cold of plants such as W. florida (Bunge) A. DC., S. salicifolia L., V. rhytidophyllum and S. alba Opiz. (Cornus alba L.) was found to be rather weak. Therefore, cold-proof measures are recommended when using these species.     

干粉PAM溶解时间对土壤饱和导水率的动态影响

本试验选取两种质地土壤(黏壤土和砂壤土),采用3种干粉PAM施用水平(0、22.5 kg/hm~2和45 kg/hm~2),测定土样在10.25 mm/h入渗速度下的土壤饱和导水率(KS),然后根据土样团聚体含量和稳定性及团聚结构的微观图片,分析干粉PAM影响下土壤结构的变化特征,进而说明干粉PAM溶解时间对KS的影响机理。结果表明:施用PAM后,KS随干粉PAM在水中溶解时间的延长而逐渐减小,最终趋于稳定;干粉PAM溶解时间较短时,PAM处理的KS高于对照,其中PAM施用水平45 kg/hm~2时砂壤土KS提高幅度最大,较对照提高26.87%,但不同PAM施用量处理间的KS差异不显著。干粉PAM溶解时间足够长时,PAM处理的KS均显著低于对照,其中PAM施用水平45 kg/hm~2时黏壤土KS降低幅度最大,较对照降低10.86%,但是不同施用量处理间KS差异不显著。从影响机理上分析,PAM主要是通过增加土壤团聚体含量及稳定性来提高KS;而干粉PAM溶解时间足够长时,由于PAM易吸附土壤颗粒,水解后的PAM分子链不断伸张延长,堵塞了土壤孔隙,加上PAM本身的黏滞特性,从而降低了KS。研究干粉PAM溶解时间对KS的动态影响,可以为PAM在改善土壤导水能力方面的应用提供理论依据。     

基于磁感式土壤表观电导率空间变异性的插值方法比较

针对目前黄河三角洲地区存在的土壤盐渍障碍问题，以该地区典型地块为研究对象，运用磁感大地电导率仪(EM38)，结合GIS与地统计学研究了不同样点密度下土壤表观电导率的空间变异特征，确定了最佳的空间插值模式，并采用偏差指数对各分布图层的空间相似性进行了评价。结果表明：不同样点密度下的土壤表观电导率均呈中等变异强度，并服从对数正态分布；各样点密度下的土壤表观电导率均表现为强空间相关性，其空间变异主要表现在小于10 m的田间尺度上，且对于预测精度，泛克立格>普通克立格>反距离权重>局部多项式。偏差指数法分析表明，各插值方法分布图的空间相似性均随样点密度的降低而下降；对于相同的样点密度减小比例下的空间信息保留度，泛克立格>普通克立格>反距离权重>局部多项式，采用泛克立格法可以在保证预测精度的基础上合理降低样点密度。该研究为黄河三角洲地区盐渍土地磁感式田间数据采集的合理密度确定以及优化空间插值模式选取提供了理论依据与技术参考。     

太湖地区水稻土中的β-葡糖苷酶活性

The electrical conductivity （EC） of 1：5 soil-water extract （EC1：5） was studied utilizing path coefficient analysis. The study focused on revealing the main chemical factors contributing to EC of soil extracts and their relative importance. Results showed that the most important factors influencing the EC1：5 of coastal salt-affected soils were the concentration of salt in 1：5 soil-water extract （So）, Cl^-, and the sodium adsorption ratio （SAR）, while effects of pH, CO3^2-, HCO3^, soluble sodium percentage （SSP）, and sodium dianion ratio （SDR） were very weak. Though the direct path coefficients between EC1：5 and SO4^2- , Ca^2＋, Mg^2＋, K^＋, or Na^＋ were not high, influence of other chemical factors caused the coefficients to increase, making the summation of their direct and indirect path coefficients relatively high. Evidences showed that multiple regression relations between EC1：5 and most of the primary factors （So, Cl^-, and SAR） had sound reliability and very good accuracy.     

重复添加植物残体后土壤微生物活性和生物量对盐度的响应特征

Microbial adaptation to salinity can be achieved through synthesis of organic osmolytes,which requires high amounts of energy;however,a single addition of plant residues can only temporarily improve energy supply to soil microbes.Therefore,a laboratory incubation experiment was conducted to evaluate the responses of soil microbes to increasing salinity with repeated additions of plant residues using a loamy sand soil with an electrical conductivity in saturated paste extract（EC_e） of 0.6 dS m^-1.The soil was kept non-saline or salinized by adding different amounts of NaCl to achieve EC_e of 12.5,25.0 and 50.0 dS m^-1.The non-saline soil and the saline soils were amended with finely ground pea residues at two rates equivalent to 3.9 and 7.8 g C kg^-1 soil on days 0,15 and29.The soils receiving no residues were included as a control.Cumulative respiration per g C added over 2 weeks after each residue addition was always greater at 3.9 than 7.8 g C kg^-1 soil and higher in the non-saline soil than in the saline soils.In the saline soils,the cumulative respiration per g C added was higher after the second and third additions than after the first addition except with3.9 g C kg^-1 at EC_e of 50 dS m^₁.Though with the same amount of C added(7.8 g C kg^-1),salinity reduced soil respiration to a lesser extent when 3.9 g C kg^-1 was added twice compared to a single addition of 7.8 g C kg^-1.After the third residue addition,the microbial biomass C concentration was significantly lower in the soils with EC_e of 25 and 50 dS m^₁ than in the non-saline soil at3.9 g C kg^-1,but only in the soil with EC_e of 50 dS m^-1 at 7.8 g C kg^-1.We concluded that repeated residue additions increased the adaptation of soil microbial community to salinity,which was likely due to high C availability providing microbes with the energy needed for synthesis of organic osmolytes.     

重庆市四面山不同土地利用类型饱和导水率

[目的]探讨不同土地利用类型和土壤理化性质对饱对导水率的影响。[方法]采用定水头法测定四面山不同土地利用类型的饱和导水率,并运用回归分析,相关分析和主成分分析法分析其与土壤物理因子和有机质的关系,以及影响饱和导水率的主导因子。[结果]各土地利用类型的平均饱和导水率均高于荒地,其顺序为:林地农地草地,林地中天然林饱和导水率大于人工林;饱和导水率随土层深度的增加呈负指数递减规律;饱和导水率与容重呈幂函数关系,与孔隙度呈正相关,与黏粒含量呈负相关;有机质含量的提高对饱和导水率有积极的促进作用。[结论]影响饱和导水率的主导因子是容重、有机质、非毛管孔隙度和毛管孔隙度,其次,土壤机械组成对其也有一定影响。     

Effect of soil compaction on hydraulic properties of two loess soils in China

Soil compaction affects hydraulic properties, and thus can lead to soil degradation and other adverse effects on environmental quality. This study evaluates the effects of three levels of compaction on the hydraulic properties of two silty loam soils from the Loess Plateau, China. Undisturbed soil cores were collected from the surface (0–5 cm) and subsurface (10–15 cm) layers at sites in Mizhi and Heyang in Shaanxi Province. The three levels of soil compaction were set by increasing soil bulk density by 0% (C0), 10% (C1) and 20% (C2) through compression and hammering in the laboratory. Soil water retention curves were then determined, and both saturated hydraulic conductivity (K_s) and unsaturated hydraulic conductivity were estimated for all of the samples using standard suction apparatus, a constant head method and the hot-air method, respectively. The high level of compaction (C2) significantly changed the water retention curves of both the surface and subsurface layers of the Heyang soil, and both levels of compaction (C1 and C2) changed the curves of the two layers from the Mizhi site. However, the effects of compaction on the two soils were only pronounced below water tensions of 100 kPa. Saturated hydraulic conductivities (K_s) were significantly reduced by the highest compaction level for both sampled layers of the Heyang soil, but no difference was observed in this respect between the C0 and C1 treatments. K_s values decreased with increasing soil compaction for both layers of the Mizhi soil. Unsaturated hydraulic conductivities were not affected by soil compaction levels in the measured water volume ratio range, and the values obtained were two to five orders of magnitude higher for the Mizhi soil than for the Heyang soil. The results indicate that soil compaction could strongly influence, in different ways, the hydraulic properties of the two soils.     

基于混合高斯模型渗灌复合材料导水特性分析

为了定量研究由蒙脱土和聚丙烯酰胺制备而成的渗灌复合材料导水特性与其组分之间及土壤湿度的关系,该文利用混合高斯模型模拟求解渗灌复合材料的平衡导水率、材料组分比例及土壤湿度之间的关系。设置9组组分比例不同(蒙脱土与聚丙烯酰胺质量比5~25)的渗灌复合材料在8个土壤湿度(土壤质量含水率3%~17%)下进行建模,另外2组((蒙脱土与聚丙烯酰胺质量比8和18)不同的组分制备而成复合材料在2组不同土壤湿度(土壤质量含水率4%和14%)下进行验证。结果表明:建立的渗灌复合材料平衡导水率与材料组分的关系函数,相应模拟值与实测值之间的均方根误差(root mean squared error,RMSE)≤25.87 g/h,误差平方和(sum of squares of error,SSE)≤160,决定系数(coefficient of multiple determination,R2)≥0.8933,利用混合高斯模型模拟平衡导水率、材料组分关系函数的相关参数与土壤湿度之间的关系,相应模拟值与实测值之间的RMSE≤195 g/h,SSE≤98350,决定系数R2≥0.6868,说明利用混合高斯模型拟合渗灌复合材料的平衡导水率、材料组分比例及土壤湿度之间的关系函数具有很好的稳定性、可行性及精确性;经验证,平衡导水率、材料组分比例及土壤湿度关系函数的模拟值与实测值之间的最大相对误差为14.14%,表明用该函数模拟渗灌复合材料H-C-M之间关系的可靠性。该研究对于后续的渗灌材料的研制及应用具有指导意义。     

施用生物炭对紫色土坡耕地耕层土壤水力学性质的影响

该研究通过野外坡耕地小区施用1%秸秆生物炭1年后的对比试验,揭示生物炭对川中丘陵区紫色土耕作层土壤水力学参数、大孔隙度及其对饱和导水率的贡献率所产生的影响。试验设对照区与施用生物炭区2个处理,各处理有3个平行小区,耕作层土壤分为表层和亚表层(2~7和7~12 cm)。比较2个处理小区试验结果,可以发现:1)施用生物炭导致植物难以利用的土壤滞留水和易流失的结构性孔隙水的含量(θstr)下降,而基质性孔隙中植物有效水含量显著提高(P0.05),由(0.058±0.003)cm3/cm3增加至(0.085±0.002)cm3/cm3;2)表层和亚表层土壤中对产流起主要贡献的半径125μm的总有效孔隙度分别平均增加54%和8%,其中孔径500μm的孔隙增加最为明显,高达110%和355%;3)表层和亚表层土壤的饱和导水率分别平均增加45%和35%。研究证明,施用生物炭,一方面,能增加土壤有效水的持水量,有利于植物抗旱;另一方面,提高土壤导水率,有利于水分入渗,从而减少地表径流及土壤侵蚀的发生。     

低温胁迫对油麦菜幼苗抗寒性生理生化指标的影响

[目的]探明低温胁迫对油麦菜抗寒性相关生理生化指标的变化规律。[方法]分别在4、8℃低温条件下对油麦菜幼苗叶片内过氧化物酶活性、电解质外渗率和丙二醛含量的变化进行了研究。[结果]低温胁迫初期油麦菜幼苗叶片内电解质外渗率和丙二醛含量均呈上升趋势,胁迫后期呈下降趋势,抗低温能力增强。与对照组相比,4、8℃低温胁迫时油麦菜幼苗叶片内过氧化物酶活性均升高。[结论]低温胁迫时油麦菜幼苗叶片内过氧化物酶活性的升高,有助于提高它的抗寒性。