河岸带土壤溶解性有机质垂直分布特征及其性质研究

河岸带有机质（Soil organic matter,SOM）的迁移转化在有机碳从陆地生态系统向水域生态系统中迁移转化及污染物的迁移转化中起到了重要的作用。以崇明岛典型河岸带为研究对象,分析了不同区域河岸带土壤有机碳（Soil organic carbon,SOC）、土壤溶解性有机碳（Soil dissolved organic carbon,SDOC）垂直分布特征和三维荧光光谱（Excitation—Emission matrix,EEM）特征,探讨了河岸带对土壤溶解性有机质（Soil dissolved organic matter,SDOM）性质及其潜在环境影响。结果表明：表层土壤（0—30cm）SOC储量占采样深度土壤SOC的40％左右,SDOC占SOC的5％左右,从陆上区域到缓冲区域表层土壤SDOC呈累积效应。河岸带有机质主要来自河岸带植物残体及其代谢产物,地下水也可能是河岸带土壤DOM的另一来源,河岸带土壤中大部分类腐殖质被表层矿物质所吸附。在土壤系统中,综合应用荧光指纹指数[荧光指数（Fluorescence index,FI）,生源指数（The index of recent autochthonous contribution,BIX）和腐殖化指数（Humification index,HIX）]可以有效地揭示其来源和特性,但在土壤体系中单独应用指纹指数需审慎。     

National-scale estimation of methane emission from paddy fields in Japan: Database construction and upscaling using a process-based biogeochemistry model

We have estimated methane (CH₄) emission from total rice (Oryza sativa L.) paddies in Japan by means of a process-based biogeochemistry model, DeNitrification-DeComposition(DNDC)-Rice, combined with a geographic information system (GIS) database of climate, soil and farming practices. In the GIS database, 2 million ha of rice paddies were divided into 17,408 units according to 136 climate areas, 16 soil types, four classes of drainage rate and two classes of groundwater level, to simulate CH₄ flux from each of the units applying the DNDC-Rice model. As a result, the national-scale CH₄ emission in 1990 was estimated to be 216 Gg carbon (C), 13% lower than a previous inventory estimated by the Tier 2 method. By our Tier 3 approach, a relatively higher CH₄ flux was estimated from eastern regions than from western regions of Japan, presumably due to the differences in climate and water management. Sensitivity analysis and uncertainty assessment indicated that it is important to account for the heterogeneity in soil properties such as field water capacity, iron (Fe) concentration and drainage rate, in order to reduce the uncertainty in regional estimates.     

New method for the estimation of nitrous oxide emission rates from an agricultural watershed

Abstract

We developed a new and improved method, the ‘high-emission-incorporation (HEI) method’, for estimating soil nitrous oxide (N₂O) emission rates at a watershed level based on nitrogen (N) input (consisting of fertilizer, manure, slurry and excreta N) and N surplus (calculated by subtracting the amount of crop yield and consumed N from the N input) of different sites in a livestock farm located in a watershed. The main characteristic of this method is the inclusion of extremely high N₂O emission rates, ‘outlier’, which are normally excluded from estimation. High N₂O emission rates were estimated using the regression model obtained from the measured N₂O values and the amounts of N surplus; normal N₂O emission rates were estimated using the regression model obtained from the measured values and the amount of N input. The probability of occurrence of a high flux was used to incorporate calculated high and normal N₂O emissions into one. The annual N₂O emission rate from the livestock farm in the watershed (467?ha), estimated using the HEI method, was 1156?±?147?kg?N?year^?1 over a 5-year period. The annual N₂O emission rates calculated using the site-specific emission factor (EF?=?0.0789) and the emission factor of the Intergovernmental Panel on Climate Change (EF?=?0.01) were 1838?±?585?kg?N?year^?1 and 673 (522–1103) kg?N?year^?1, respectively. The estimated value using the measure-and-multiply method, in which each land-use area is multiplied by the representative emission rate for each land-use type, was 964 (509–1610) kg?N?year^?1. The N₂O emission rates estimated by our newly developed method were consistent with the values calculated by the measure-and-multiply method and offered improvement over this measure because the new measure can also predict future N₂O emission rates from the watershed.     

Availability of soil boron fractions to M.26 apple rootstock

The availability of various boron (B) fractions in soil to M.26 apple (Malus spp.) rootstock was examined. The study was carried out in a greenhouse on soils with diverse chemical and physical properties. The following B fractions were determined: (i) B in soil solution, (ii) B non‐specifically adsorbed on soil surface, (iii) B specifically adsorbed on soil colloid surfaces, (iv) B occluded in Mn oxyhydroxides, (v) B occluded in noncrystalline aluminum (Al) and iron (Fe) oxides, (vi) B occluded in crystalline Al and Fe oxides, (vii) B fixed with soil silicates, and (viii) total soil B. In the studied soils there were: 0.07–0.17 mg kg^‐1 B in soil solution, 0.01–0.03 mg kg^‐1 B non‐specifically adsorbed on soil surface, 0.04–0.08 mg kg^‐1 B specifically adsorbed on soil colloid surfaces, 0.28–0.67 mg kg^‐1 B occluded in manganese (Mn) oxides, 4.03–17.22 mg kg^‐1 B occluded in noncrystalline Al and Fe oxides, 8.93–50.62 mg kg^‐1 B occluded in crystalline Al and Fe oxides, 12.2–42.5 mg kg^‐1 B fixed with soil silicate, and 52.9–82.2 mg kg^‐1 total B. Simple correlation analysis showed positive correlation between B contents in M.26 apple rootstocks and amounts of B in soil solution (r=0.77), B non‐specifically adsorbed on soil colloid surfaces (r=0.65), B specifically adsorbed on soil surface (r=0.76) and B occluded in Mn oxyhydroxides (r=0.77). No relation was found between plant B contents and amounts of B occluded in non‐crystalline and crystalline Al and Fe oxides, B fixed with soil silicates and total B. The results indicated that extraction of B by 0.1 M NH₂OH HCl solution adequately represented amounts of B in soil solution, B non‐specifically and specifically adsorbed on soil compound surfaces and B occluded in Mn oxyhydroxides to assess availability of B to apple trees.     

MINERAL ELEMENT DISTRIBUTION AND ACCUMULATION PATTERNS WITHIN TWO BARLEY CULTIVARS

Growth stage effects on distribution of mineral nutrients or beneficial elements phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), chloride (Cl), iron (Fe), zinc (Zn), manganese (Mn), copper (Cu), molybdenum (Mo), sodium (Na), silicon (Si) and nickel (Ni), and the elements bromine (Br), rubidium (Rb), strontium (Sr), barium (Ba), lanthanum (La), cerium (Ce), and uranium (U) in two barley (Hordeum vulgare L.) cultivars and how the distribution of these elements changed were determined during the 2006–2007 growing season in a field experiment. Barley plants were sampled from the field at shooting, heading, soft dough, hard dough and harvest stages, and mineral nutrients and other elements concentrations of spike, flag leaf, old leaf, and stem samples were determined by polarized energy dispersive X-ray fluorescence (PEDXRF). Distribution patterns varied considerably from element to element. At the end of the season much of the Ca, Mg, S, Si, Fe, Mn, Cu, Ni, Sr, Ba, La, Ce, and U were located in the spikes. However, much of the P, K, Zn, Cl, Na, Br, and Rb remained in the old leaves or stem.     

Effect of rice straw application on CH4 emission from paddy fields

The effect of rice straw (RS) incorporated at the time of plowing in the previous cr–p season on CH₄ emission from rice paddies was investigated in a pot experiment. Rice straw that incorporated just before transplanting of rice seedlings (June) into a paddy field was collected after the harvest (October) and at the beginning of the next cropping period (May). Methane emission rates from the rice-planted pots with the application of fresh RS, RS collected in October. and RS collected in Mayas well as the pots without RS application were measured using the chamber method. The composition of organic constituents in the three kinds of RS was estimated by the proximate analysis. The cumulative amount of CH₄ emitted during the first 50–d period was lower in the order of the pots with RS collected in May, pots with RS collected in October, and pots with fresh RS. The cumulative amount of CH₄ emitted throughout the rice growth period from the pots with fresh RS and with RS collected in October was significantly larger while that from the pots with RS collected in May did not differ statistically compared with the total CH₄ emission from the pots without RS. These results suggested that there was an overall decrease in the amount of organic constituents in RS based on the large differences in T-C content and similar composition of organic constituents between the fresh RS and RS collected in May. Significant effect of RS continuously applied during the previous cropping period on the increase in CH₄ emission was discussed.     

施氮方式对玉米氮吸收及土壤养分、N2O排放的影响

通过3年定位试验,研究不施氮肥、农民传统施氮、比传统施氮减量20%、减氮20%配合秸秆还田、减氮20%施用包膜尿素处理对玉米年际产量、植株氮吸收、土壤养分变化及N2O排放的影响。结果表明:包膜尿素处理产量最高,比空白处理增产18.50%,比产量次高的秸秆还田处理仅增产0.51%,二个处理间产量差异不显著;包膜尿素处理和秸秆还田处理可增加植株氮的吸收固定;秸秆还田处理的肥料利用率和植株总氮积累量高于包膜尿素处理,但其氮收获指数最低,为0.606,从注重品质角度,包膜尿素处理的效果略好于秸秆还田处理;各施肥处理都比空白处理提高了土壤主要养分含量,但从有机质、全氮、有效磷和速效钾含量提升综合评价,包膜尿素处理和秸秆还田处理对土壤的培肥作用好于农民习惯施肥处理;秸秆还田处理的N2O-N季节排放总量和排放系数都最高,分别为N 1.50 kg·hm-2·季-1和0.27。因此,从保产稳产、培肥地力、提升品质、减少N2O排放综合考虑,建议推广比农民习惯施肥量减少氮量20%的包膜尿素一次性施入在玉米生产中的应用。     

Gross nitrogen transformations and N_2O emission sources in sandy loam and silt loam soils

The soil type is a key factor influencing N(nitrogen) cycling in soil; however, gross N transformations and N_2O emission sources are still poorly understood. In this study, a laboratory ~(15)N tracing experiment was carried out at 60% WHC(water holding capacity) and 25℃ to evaluate the gross N transformation rates and N_2O emission pathways in sandy loam and silt loam soils in a semi-arid region of Heilongjiang Province, China. The results showed that the gross rates of N mineralization, immobilization, and nitrification were 3.60, 1.90, and 5.63 mg N/(kg·d) in silt loam soil, respectively, which were 3.62, 4.26, and 3.13 times those in sandy loam soil, respectively. The ratios of the gross nitrification rate to the ammonium immobilization rate(n/ia) in sandy loam soil and silt loam soil were all higher than 1.00, whereas the n/ia in sandy loam soil(4.36) was significantly higher than that in silt loam soil(3.08). This result indicated that the ability of sandy loam soil to release and conserve the available N was relatively poor in comparison with silt loam soil, and the relatively strong nitrification rate compared to the immobilization rate may lead to N loss through NO_3~– leaching. Under aerobic conditions, both nitrification and denitrification made contributions to N_2O emissions. Nitrification was the dominant pathway leading to N_2O production in soils and was responsible for 82.0% of the total emitted N_2O in sandy loam soil, which was significantly higher than that in silt loam soil(71.7%). However, the average contribution of denitrification to total N_2O production in sandy loam soil was 17.9%, which was significantly lower than that in silt loam soil(28.3%). These results are valuable for developing reasonable fertilization management and proposing effective greenhouse gas mitigation strategies in different soil types in semiarid regions.     

新小黑麦1号光合速率及叶绿素荧光特性的研究

通过对新小黑麦1号光合速率及叶绿素荧光特性的研究,结果表明,光合速率（Pn）、基础荧光（Fo）随光强的变化呈相同的变化趋势;而光化学效率（Fv/Fm）、最大荧光（Fm）则相反,而在抽穗期与扬花期各参数的值基本相同,在蜡熟期下降较明显。随着生育期的延长,Pn、Fo、Fv/Fm和Fm均有所下降,但在蜡熟期仍有一定的光合作用,显示了小黑麦较好的抗逆性及丰产性。     

脲醛肥料对土壤N2O排放及氮素平衡的影响

【目的】研究脲醛肥料对土壤N_2O排放及氮素去向与平衡的影响,为脲醛肥料的应用提供理论依据。【方法】2013年9-12月,采用微型渗漏计-静态气箱法,在栽培3季不同叶菜(第1季小白菜、第2季菜心、第3季芥菜)的条件下,以不施氮肥为对照,设置3种脲醛肥料(UF1、UF2、UF3,其活性指数(AI)分别为50.8%,67.4%,83.3%)一次性施用、尿素一次性施用、尿素分次施用、脲醛肥料UF2与尿素混合一次性施用共6个处理,研究了脲醛肥料对N_2O排放、淋溶损失、土壤残留、植株吸收以及其他表观损失量的影响。【结果】与尿素一次性施用处理相比,无论脲醛肥料AI高低,脲醛肥料一次性施用、脲醛与尿素混合一次性施用和尿素分次施用均能够显著降低N_2O排放峰值和累积排放量,各处理N_2O气态氮素损失量依次为尿素一次性施用脲醛与尿素混合一次性施用尿素分次施用、AI高的UF3一次性施用AI中和低的UF2、UF1一次性施用,3种脲醛肥料处理的N_2O气态氮素损失量为2.32~4.40g/m2,仅为尿素一次性施用处理N_2O气态氮素损失量的33.1%~62.9%。脲醛肥料处理的土壤氮素残留量占总氮量的45%以上,较尿素处理提高了32.1%~34.0%。施用脲醛肥料后减少了氮素淋溶损失量和其他表观损失量,分别较尿素一次性施用处理减少32.6%~54.0%和52.4%~83.9%。脲醛肥料在一次性施用的情况下,植株氮素吸收量等同于尿素分次施用,显著大于尿素一次性施用。【结论】施用脲醛肥料能够明显改变氮素平衡,有利于氮素的植物吸收和土壤残留,而减少氮素的淋溶损失、气态损失及其他表观损失,不仅有利于环境保护,而且有利于提高肥料的利用率。