硝化抑制剂与尿素配施对旱地土壤温室气体排放及硝化微生物的影响

为明确施肥措施对旱地土壤温室气体排放的综合效应及微生物机理,采集典型麦田土壤进行室内微宇宙培养,研究了双氰胺(DCD)和烯丙基硫脲(ATU)分别与尿素配施对旱地土壤氮素转化及N₂O、CO₂和CH₄排放的影响,同时监测了不同类型微生物群落的动态变化。结果表明氨氧化细菌(AOB)主导了施氮麦田土壤硝化过程及N₂O排放。单施尿素促进AOB迅速繁殖,使N₂O排放总量提高235%,同时促进了细菌生长,CO₂排放量增加18.5%。DCD与尿素配施极大程度抑制了AOB的生长,显著降低了N₂O排放(59.4%),但促进了细菌的生长并提高了CO₂的排放总量(50.6%)。而ATU与尿素配施同时抑制了真菌、细菌和AOB的生长,对反硝化细菌的影响则相反,使CO₂和N2O排放分别下降28.4%和35.2%。与不施肥相比,氮肥及与两种硝化抑制剂配施均显著降低了CH4的排放量。3种温室气体的综合温室效应在处理间差异显著...     

Soil carbon and nitrogen changes after 28 years of no-tillage management under Mediterranean conditions

Mouldboard ploughing is known to accelerate soil organic matter (SOM) mineralization rate in Mediterranean regions. Long-term reduced tillage intensity potentially diminishes soil organic carbon (SOC) and total nitrogen (STN) depletions. Here, we compared long-term no-tillage (NT) and conventional tillage (CT) impact on SOC and STN sequestration rates at different depths ranging from 0 to 30 cm. The long-term experiment started in 1986 on a Typic Xerofluvent soil in Central Italy using a randomized complete block design with four replications. Ten years after the experiment began, SOC and STN concentrations in the 0–30 cm soil layer were already higher under NT compared to CT. The shallow layer (0–10 cm) showed the highest SOC and STN concentration increments. However, no differences between tillage systems were observed in the deeper layers. After 28 years, continuous NT increased SOC and STN content in the 30 cm soil depth by 22% compared to initial values. In the same period, continuous CT decreased SOC and STN content by 3% and 5%, respectively. On average, the total SOC and STN gains under NT may be attributed to the shallow layer increments. In the 10–20 and 20–30 cm soil layers, SOC accumulation over time was negligible also under NT. In the whole profile (0–30 cm), the mean annual SOC variation was +0.40 Mg ha⁻¹ yr⁻¹ and −0.06 Mg ha⁻¹ yr⁻¹ under NT and CT, respectively. Under NT, SOC content increased rapidly in the first ten years (+0.75 Mg ha⁻¹yr⁻¹); later on, SOC increments were slower indicating the reaching of a new equilibrium. Data show that NT is a useful alternative management practice increasing carbon sequestration and soil health in Mediterranean conditions.     

土地整理工程对土壤碳排放的影响

土地整理的碳排放研究对优化土地利用格局、应对气候变化具有重要意义。以河北省邢台市巨鹿县、柏乡县土地整理项目为例,通过间接采样和随机采样方法,分析了土地整理前后玉米地土壤碳排放及其影响因子的变化情况。结果表明:(1)土地整理后,巨鹿县和柏乡县整理区玉米生长旺盛时期的土壤碳排放量增加,但均没有达到统计上的显著性水平,这说明在玉米生长旺盛时期,土地整理项目的开展暂未影响土地整理区土壤的碳排放。(2)在玉米生长旺盛时期,影响土壤碳排放变化的多个因子中,只有巨鹿县土地整理区的土壤碳氮比和柏乡县土地整理区的叶面积指数在土地整理前后发生了显著变化,其他因子虽然变化的大小和方向存在不一致,但是变化量均不显著。     

High carbon losses from established growing sites delay the carbon sequestration benefits of street tree plantings – A case study in Helsinki,Finland

We assessed the net carbon (C) sequestration dynamics of street tree plantings based on 10 years of measurements at two case study sites each with different tree species in Helsinki, Finland. We assessed C loss from tree soils and tree C accumulation, tested the applicability of pre-existing growth and biomass equations against observations, and estimated the time point for the beginning of net C sequestration for the studied street tree plantings. The tree woody biomass C accumulation in the first 10 years after planting was 18–32 kg per tree. At the same time the C loss from the growth media was at least 170 kg per growth media volume (25 m³) per tree. If this soil C loss was accounted for, the net C sequestration would begin, at best, approximately 30 years after planting. Biomass equations developed for traditional forests predicted more stem biomass and less leaf and branch biomass than measured for the species examined, but total aboveground biomass was generally well predicted.     

小麦分蘖与麦苗的碳氮同化及ATP含量的相关性研究

本文对不同分蘖的麦株做了几项生理指标测定.结果表明:分蘖多的植株较分蘖少的植株具有高的叶绿素含量和光合强度;对N0_3~--N吸收多,转化快;其心叶和根系的ATP含量也明显高于少蘖株,生长着的分蘖对整株(包括其他分蘖) 的生长发育及其成穗有明显的促进作用.此外,多分蘖植株的成穗率及穗部结实性状均优于少分蘖植株.     

Estimation of carbon losses by cultivation from soils of the Argentine Pampa using the Century Model

Abstract. The Century model was used for estimating soil carbon levels under grassland at the regional scale in the Pampean Region of Argentina. Predicted values were compared with observed soil carbon contents obtained from soil surveys and the differences considered to be the results of cropping on soil organic matter. The Pampean Region was divided into five major sub-regions and carbon in the top 20 cm of each estimated by Century using aggregated soil and climatic data. In four of the sub-regions small differences between predicted and observed carbon contents were obtained which suggested little land use effect on soils. In the Rolling Pampa, a northern portion of the Pampean Region, observed carbon content was about half of Century prediction. In this sub-region, the main agricultural area of the country, cropping intensity, rainfall and temperature are higher than in the rest of the Pampas. A degradation index constructed by a multiplicative approach, taking into account percentage of surface cropped, rainfall and temperature was 2–5 times higher in the Rolling Pampa than in the other pampean sub-region. The difference between predicted C and observed C in the Rolling Pampa was attributed to carbon losses by cropping in a warm and wet climate.     

Effects of CO2, temperature and their interaction on the growth, development and yield of cauliflower (Brassica oleracea L. botrytis)

Stands of summer cauliflower were grown within polyethylene-covered tunnels along which a temperature gradient was imposed. Two tunnels were maintained at either normal or elevated CO₂ concentrations. At the last harvest (88 days from transplanting) no interaction between CO₂ and temperature on total biomass was detected. The total dry weight of plants grown at 531 μmol mol⁻¹ CO₂ was 34% greater than those grown at 328 μmol mol⁻¹ CO₂, whereas a 1 °C rise reduced dry weight by 6%. From serial harvests the radiation conversion coefficient was 2.01 g MJ⁻¹ and 1.42 g MJ⁻¹ at 531 μmol mol⁻¹ CO₂and 328 μmol mol⁻¹ CO₂, respectively, but was not greatly affected by differences in temperature. No effect of either CO₂ or temperature on the canopy light extinction coefficient was detected. The rate of progress towards curd initiation increased to a maximum at 15.5 °C, and declined thereafter. Provided the effect of temperature was accounted for, CO₂ enrichment did not affect the time of curd initiation. From serial harvests after curd initiation, the logarithm of curd weight or diameter were negative linear functions of mean temperature from initiation. Increases in curd weight and diameter at 531 compared with 328 μmol mol⁻¹ CO₂ were greater at warmer temperatures (27% at 13 °C compared with 47% at 15 °C, 57 days after initiation). Effects of CO₂ on curd diameter were less than those on curd dry weight because the curd dry matter content was greater at 531 compared with 328 μmol mol⁻¹ CO₂. Thus, the effects of elevated CO₂ concentrations on fresh weight based yield parameters of cauliflower were less than the increase in total dry matter production.     

秸秆还田添加氮素调节碳氮比的研究

施用作物秸秆，常因碳氮比较宽，引起土壤微生物与作物苗期争夺土壤中无机氮的矛盾。本文采用盆栽试验方法，秸秆还田添加不同量的氮素，以冬小麦的产量、株高、分蘖数、叶片中叶　　　绿素含量以及植株对氮、磷、钾的吸收量为指标，找出适宜的碳氮比。结果表明，在冬小麦的各项　指标中，不同处理呈现Ｓ＋Ｎ３＞Ｓ＋Ｎ２＞Ｋ＞Ｓ＋Ｎ１＞Ｓ的规律，添加的氮量以碳氮比为２５：１为宜。     

Hepatoprotective effect of Paecilomyces tenuipes polysaccharides on carbon tetrachloride -induced liver injury

AIM:To investigate the protective effect of crude Paecilomyces tenuipes polysaccharides (cPtPs) and Paecilomyces tenuipes polysaccharides (PtPs) in a rat model of acute hepatic necrosis induced by carbon tetrachloride (CCl4). METHODS:Wistar rats were divided into four groups (control group, CCl4 group, cPtPs+CCl4 group and PtPs +CCl4 group), the four groups were given intragastrically with normal saline, cPtPs and PtPs for 15 d, respectively. In the last two days, these groups except control group were injected peritoneally with CCl4. Serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), direct bilirubin (DBIL) and indirect bilirubin (IBIL) were detected by automatic biochemistry analyzer. Pathological changes of hepatic tissue were assessed by hematoxylin-eosine (HE) staining. The levels of superoxide dismutase (SOD) and malondialdehyde (MDA) in liver homogenate were analyzed using xanthinoxidase and thio-barbituric acid, respectively. The concentration of Ca2+ in hepatocyte mitochondria was determined by colorimetric method. The expression of α-smooth muscle actin (α-SMA) was examined in hepatic tissue by immunohistochemical method. RESULTS:Compared with control group, serum levels of ALT, AST, TBIL, DBIL and IBIL in CCl4 group increased significantly, denaturation and necrosis implicated to the whole hepatic lobules. Compared with CCl4 group, serum levels of ALT, AST, TBIL, DBIL and IBIL in PtPs +CCl4 group decreased significantly, denaturation and necrosis located in the third region of hepatic lobules, the level of SOD increased and MDA decreased (P<0.05) in endochylema. Concentration of Ca2+ in mitochondria decreased in PtPs +CCl4 group and cPtPs +CCl4 group (P<0.05, P<0.01, respectively). Expression of α-SMA was found little in PtPs+CCl4 group. CONCLUSION:PtPs, the effect is better than cPtPs, lessens CCl4-induced hepatonecrosis significantly. The role may be related with anti-lipid peroxidation.