广州城市道路分车带绿化调查

通过调查广州12条主要道路中央及两侧分车绿化带的树种选择、植物群落配置、景观营造、色彩搭配、绿化功能的合理性等,得出:1)每条道路平均配置5.5种植物,其中乔木2.17种,灌木2.5种,草本0.92种,平均乔灌比0.87;2)配置模式主要是乔木+灌木+地被、乔木+灌木绿篱、乔木+地被和灌木+地被4种形式。     

磷酸、膦酸酯类农药的质谱裂解规律研究

在对23种磷酸、膦酸酯类农药及其氧化物的质谱数据进行归纳整理的基础上,明确了这类农药质谱裂解规律。结果表明:电子轰击离子化条件下,磷酸、膦酸酯类农药分子极易裂解,且分子离子峰较弱。发现C_2H_6O_3P~+(m/z109)是其最具代表性的特征碎片离子。磷酸酯类农药裂解规律是二甲氧基磷酸酯P-0键易发生a断裂,生成m/z 109特征碎片离子。二乙氧基磷酸酯易脱去中性碎片C_2H_4,形成m/z81的特征离子。R'含有烯烃结构,易产生m/z127的特征碎片离子。膦酸酯类农药裂解规律与磷酸酯类似,特征性弱,膦键容易发生a断裂。选定了磷酸、膦酸酯类农药在质谱分析中常见的碎片离子,为农药残留筛查、确证分析提供参考。     

The combined effects of cover crops and symbiotic microbes on phosphatase gene and organic phosphorus hydrolysis in subtropical orchard soils

P deficiency is a major obstacle for crop production in subtropical red soils in South China, and the hydrolysis of organic P (Po) is of great significance in these soils due to the immobilization of P by Fe and Al. Cover cropping in orchards and symbiotic microbial inoculation are considered to improve soil quality, including P status, however, their effects on the hydrolysis of Po is little known. In this study, five soil managements were established in a guava orchard in South China for two and a half years, including clean culture (CC), cover cropping with Paspalum natatu (PN), PN with arbuscular mycorrhizal fungal inoculation (PNA), cover cropping with Stylosanthes guianensis (SG), SG with rhizobial inoculation (SGR). Soil chemical, biochemical and microbial properties were analyzed. Results indicate that soil pH and SOM content tended to increase following cover cropping alone or with microbial inoculation. Po content was significantly elevated in PNA. Po fractionation revealed that cover cropping alone or with microbial inoculation significantly affected the contents of moderately labile Po (MLPo) and moderately resistant Po (FAPo). Enzyme assay indicated that cover cropping with microbial inoculation increased the activities of acidic phosphomonoesterase (ACP), neutral phosphomonoesterase (NP) and alkaline phosphomonoesterase (ALP), with ALP the most sensitive, although ACP activity dominated in red soils. Correlation analysis suggested a significantly positive relationship between ALP activity and MLPo or FAPo. PCR-DGGE profile of the alp-harboring bacterial community showed that cover cropping with S. guianensis and mycorrhizal inoculation to P. natatu promoted the bacterial diversity and/or species richness. For almost all the measured parameters, PN and SG were comparable, however, PNA was superior to SGR, indicating the stronger additive effect of arbuscular mycorrhizal fungus than that of rhizobia. Cat-PCA indicated that MLPo was the most influential factor on phosphomonoesterase. In general, this study suggests that, in subtropical orchards with red soil, cover cropping with microbial inoculation can improve the Po hydrolysis via the promoted alp-harboring bacterial community and then ALP activity. Our results also suggest that the combination of P. natatu and arbuscular mycorrhizal fungus is better than S. guianensis and rhizobia, which possesses practical significance for sustainable production in these orchards.     

Influence of summer legume residue recycling and varietal diversification on productivity,energetics, and nutrient dynamics in basmati rice–wheat cropping system of western Indo-Gangetic Plains

A field experiment was conducted on summer mungbean residue recycling (SMBRR) and basmati rice–wheat cropping system (BRWCS) at New Delhi, India. The SMBRR enhanced the system productivity and net returns by ～19.1% and 22.1% compared to summer fallow (SF) with highest magnitude under genotypic sequence of P 2511/HD 2967. Two genotypes each in basmati rice (PB 1 and P 2511) and wheat (HD 2967 and HD 2733) responded well to SMBRR with respect to grain yield efficiency index (GYEI) ≥ 1.0. SMBRR also registered ～13.5% higher microbial biomass carbon (MBC) than SF. Soil organic carbon (SOC) storage also increased by ～6.8% in 0–30 cm soil layer. The rice–wheat–summer mungbean system produced significantly highest energy efficiency compared to the rice–wheat–summer fallow system with highest values under genotypic sequence of P 2511/HD 2967 as a result of better yield expression. Overall, SMBRR with suitable genotypic sequence improved the system productivity, profitability, and nutrient dynamics in BRWCS, which are vital for long-term sustainability of this system.     

宁夏东部荒漠草原猪毛蒿光合特征和水分利用效率对降水变化的响应

荒漠草原植物的生长和生存受降水影响很大,本研究以宁夏东部荒漠草原猪毛蒿种群为研究对象,2017-2020年连续4年监测了降水改变条件下土壤水分特征,测定了猪毛蒿净光合速率、蒸腾速率、气孔导度和胞间CO₂浓度等光合特征,并对其内禀水分利用效率和瞬时水分利用效率进行了分析。研究表明：4年中无效降水事件（<5 mm）发生次数较多,占当年降水频次的60.00%~82.54%;大雨（≥25 mm且≤49.9 mm）和暴雨等级（≥50 mm）降水事件较少,平均单次降水事件的降水量仅为3.3~6.5 mm·次^-1。不同处理各土层的土壤含水量存在较大差异,表层（10 cm）土壤含水量较次表层（20 cm）和深层（60 cm）的变幅大;次表层（20 cm）土壤平均含水量低于表层,与小降水事件发生频次较高无法入渗补给以及植物吸收消耗有关;深层（60 cm）土壤含水量变化小,较稳定。净光合速率随着光合有效辐射的增加而增大,当光合有效辐射在400~1600 μmol·m^-2·s^-1时,增雨处理提高了猪毛蒿的净光合速率;在光合有效辐射>1600 μmol·m^-2·s^-1时,猪毛蒿净光合速率有下降趋势,且增雨处理下降幅度最大。光合有效辐射在>400 μmol·m^-2·s^-1时,胞间CO₂浓度呈直线下降,达到1600 μmol·m^-2·s^-1时,胞间CO₂浓度最小。蒸腾速率和气孔导度随着光照强度的增加未有显著变化,但增雨处理下猪毛蒿的蒸腾速率和气孔导度均大于其他处理。气孔限制值随着光合有效辐射的增加呈上升趋势,同时降水的增加减小了气孔限制值。猪毛蒿的内禀水分利用效率和瞬时水分利用效率均在较低的光照强度时（<400 μmol·m^-2·s^-1）随着光强的增加而迅速增大,之后增速减缓。各处理中猪毛蒿最大内禀水分利用效率和最大瞬时水分利用效率在1600~2000 μmol·m^-2·s^-1时达到最大。随着干旱程度的增加,猪毛蒿最大水分利用效率对应的光照强度由2000减小至1600 μmol·m^-2·s^-1。在荒漠草原,当光照强度>400 μmol·m^-2·s^-1时,适度干旱提高了猪毛蒿的水分利用效率。     

Regional patterns of microsatellite diversity in Ethiopian tetraploid wheat accessions

This study was conducted to assess regional patterns of diversity of Ethiopian tetraploid wheat accessions and to identify areas of diversity that can be used as source of new germplasm for developing high yielding and stable varieties. A collection of 133 Ethiopian tetraploid wheat accessions and eight introduced cultivars was analysed using 29 wheat microsatellite markers. A total of 383 alleles were detected with an average value of 13.14 alleles per locus. Relatively more alleles were observed in the B genome than in the A genome. Gene diversity indices ranged from 0.08 to 0.95, with a mean value of 0.72. Accessions collected from the same region were pooled and the number of alleles and gene diversity were calculated over the 29 simple sequence repeats for each region. Higher numbers of alleles were detected in the Shewa region (8.72), followed by Tigray (5.86) and Hararghe (5.76). The highest average gene diversity value was found in Shewa (0.65), followed by Gondar (0.64). No significant correlation was observed between geographic distance and genetic distance. Out of 383 different alleles detected, 93 (24.4%) were observed to be region‐specific. Region‐specific alleles were found across all chromosomes except for Xgwm752, Xgwm155 and Xgwm148. Genetic similarity coefficients were estimated for all the possible 55 pairs of regional comparisons and they ranged from 0.16 to 0.52, with a mean value of 0.50. All provinces were differentiated in the UPGMA cluster diagram.     

4种微生物菌剂对多年连作甜瓜土壤真菌群落的影响

为了探究微生物菌剂对土壤真菌群落及成员的影响,利用4种微生物菌剂(A.谷乐丰聚谷氨酸微生物菌剂,B.启高系列生物菌剂,C.施特葆系列菌剂,D.新型菌剂NBmelon)对土壤进行处理,样品经DNA抽提、PCR扩增和真菌ITS测序,进行分析制图。结果显示,处理B和A的Shannon指数、Simpson指数高于CK,处理D、C的Simpson指数高于CK,表明菌剂处理后,土壤真菌群落均匀度得到提高,真菌多样性优于CK。优势种群相对丰度在不同处理间存在差异,处理A、B、D与CK相比分布在不同象限,且图中距离较远,表明菌剂处理后土壤样品的物种构成发生了变化。处理D(新型菌剂NBmelon)具有降低镰刀菌属相对丰度的效果,能减少镰刀菌属群落数量,可供后续开发利用。因此,施用微生物菌剂具有改变土壤真菌群落结构、提高土壤真菌多样性、降低有害菌镰刀菌属相对丰度、改良土壤的作用。     

Alley cropping and mulching withErythrina poeppigiana (Walp.) O. F. Cook andGliricidia sepium (Jacq.) Walp.: effects on maize/weed competition

The potential of allye cropping systems to sustain a high productivity with low external inputs and the reduction of maize/weed competition through weed suppression in different alley cropping and sole-cropped mulched systems was studied in Costa Rica at CATIE. Data were recorded eight years after establishment of the experiment. Plant residues ofErythrina poeppigiana trees (10 t/ha dry matter) planted at 6 by 3 m reduced weed biomass by 52%, whileGliricidia sepium trees (12 t/ha dry matter) planted at 6 by 0.5 m reduced weed biomass by 28%, in comparison to controls.Erythrina had a considerable impact on grass weeds, whileGliricidia reduced the incidence of some dicot weeds. Weed competition significantly reduced maize yield in all systems. Nevertheless weed suppression contributed to the higher maize grain yield underErythrina andGliricidia alley cropping of 3.8 t per hectare as opposed to the unmulched control yield of 2.0 t per hectare.     

A study of the potential of hedgerow intercropping in semi-arid India using a two-way systematic design

The potential of hedgerow intecrropping with Leucaena leucocephala was explored on vertic Inceptisols over 4 years at ICRISAT Center, Patancheru, India. The study was conducted using a systematic layout involving different alley widths ranging from 1.35 to 4.95 m and with varying distances between hedge and crops. The alleys were cropped with alternate rows of sorghum and pigeonpea. Hedges composed double Leucaena hedgerows 60 cm apart were periodically harvested for fodder. Sole crops of all components and a sorghum/pigeonpea intercrop were included in all four replications of the study.Starting in the second year, Leucaena was progressively more competitive to annual crops, causing substantial yield reduction. Competition (primarily for moisture) was most severe in narrow alleys and was greatest on pigeonpea.The growth of Leucaena was not sufficient to compensate for reduced crop yields. Land equivalent ratios (LERs) calculated on the basis of grain yield of crops and Leucaena fodder yields showed that hedgerow intercropping (HI) was advantageous over sole crops only during the first two years using wide alleys, but disadvantegeous in the last two years. LERs calculated on the basis of total dry matter indicated only a small advantage for HI (13–17 percent) over sole crops in wider (>4 m) alleys. Average returns per year from HI exceeded those of the most productive annual crop system (sorghum/pigeonpea intercropping) by 8 percent in 4.05 m alleys, and by 16 percent in 4.95 m alleys. Fodder production during the dry season was 40 percent of the annual total in these alley widths. Thus hedgerow intercropping at 4–5 m alley width is not very attractive for farmers in semi-arid India, which has 600–700 mm of annual rainfall. There is a need to examine the potential of HI in wider alleys. The merits and limitations of the systematic design are discussed.     

Acacia cyanophylla for forage and fuelwood in North Africa

Forage and wood yield of Acacia cyanophylla, also known as Acacia saligna, was studied in a 300–400 mm precipitation zone in Tunisia. Yields were measured during and after drought. This short (2–8 m) evergreen leguminous tree is used as a forage drought reserve in frost free regions where mean annual precipitation exceeds 250 mm. The standing crop of leafy forage builds up year after year for at least four years or until the tree is cut. It rapidly regrows after cutting from coppice shoots. The leaves provide high protein forage for sheep and goats during the long dry summer season typical of the Mediterranean climate as well as emergency forage during drought. The tree is used to stabilize moving sand dunes, and as a windbreak to protect cropland. It also provides fuelwood and increasaes soil nitrogen by fixation. The need for supplemental irrigation during establishment is a major constraint. Research in the 350 mm precipitation zone of Tunisia found 3.2 year old trees to yield over 1400 kg of forage standing crop per hectare after a severe drought. Trees harvested at 2.5 years of age in May, during the worst drought in over 30 years, yielded a standing forage crop of 724 kg per hectare. Forage regrowth 8 months after cutting and 4 months after rains returned was 700 kg/ha. The forage standing crop for trees harvested only once during the 3.2 year period was double the amount of forage regrowth from trees harvested the previous year, but mean annual forage yield similar. This demonstrates that it is possible for forage to be conserved as a living forage reserve for later use during drought. Total wood yield was only 1621 kg/ha for trees cut twice compared to 3683 kg/ha for trees cut only once. Annual cutting will substantially reduce the amount of forage available during drought and reduce the production of fuelwood. It may also reduce the vigor, productivity and life of the tree. Acacia cyanophylla alley cropped on cereal farmland can protect the soil from erosion, protect the associated crop from wind damage, fix nitrogen, provide fuelwood and provide a reserve of high quality forage for use during drought. This work was supported by the Government of Tunisia and the U.S.A.I.D. Tunisia Range Development and Management Project (664-0312.8).