USLE在我国的应用和发展

美国的通用土壤流失方程USLE是当今世界上应用最为广泛的水蚀模型。 2 0世纪 70年代中期以来 ,我国在引进、消化、应用USLE方面取得了突破性的进展 ,统一了方程中R、K、S、L、C、P的算法 ,将六大因子的计算完全基于GIS和RS ,提高了监测预报的精度和速度 ,已成功地在国内一些地区得到应用。介绍了USLE的发展过程和在我国的应用与发展     

USLE/RUSLE中水土保持措施因子研究进展

通用土壤流失方程(USLE)及修正通用土壤流失方程(RUSLE)是目前世界上应用最为广泛的土壤侵蚀预报模型,水土保持措施因子(P)是USLE/RUSLE方程中的重要参数之一。依据国内外研究成果,归纳总结了5种估算P因子值的方法,包括小区和小流域资料法、美国农业部手册查询法、基于RS和GIS提取法、USLE/RUSLE方程反求法、经验模型方程法。分析了各种方法的优缺点,并对P因子的研究提出展望。     

黄土高原向阳沟流域水土保持措施效益分析

在ArcGIS软件的辅助下,根据不同坡度的土地利用对土壤侵蚀的影响,将向阳沟流域划分了5个坡度等级单元,利用通用土壤流失方程(USLE)对流域现有水土保持措施下不同坡度等级单元侵蚀量进行了估算,并与治理前土壤侵蚀量进行对比分析。结果表明,实施水土保持措施后,水土流失有了极大的改善,水保效益较为可观,但区域仍属中度侵蚀,25°～35°坡度等级单元对流域土壤侵蚀量的贡献最大,其次为15°～25°和＞35°等级单元。根据不同坡度等级单元的水土流失侵蚀模数估算结果分析,结合现有水土保持措施,提出了今后进一步治理的的几点建议。     

长江上游定量遥感监测模型地形因子应用研究

以长江上游商南县为研究区,利用GIS软件平台建立研究区数字高程模型(DEM),选用水土流失定量监测模型(QRSM),用水土流失地形像元SL因子算法专用软件计算像元坡度与坡长因子值,对数字高程模型(DEM)进行了差错与精度评价,并对地形因子计算过程中水体边界坡度、坡度因子、坡长、坡长因子和凹点、回流问题等关键技术进行了处理。结果表明,15°~25°坡度面积为530.51km2,占总面积的22.93%,25°~45°坡度面积为1 083.32km2,占总面积的46.82%。15°~45°坡度面积合计接近70%,是造成商南县严重水土流失的主要区域,监测结果符合研究区实际现状。该研究将监测模型推广应用到长江流域上游地区,对逐步实现长江流域水土流失的监测预报具有前瞻性,并对其他小流域也有一定的理论和实践价值。     

基于DEM通用土壤流失方程地形因子的算法设计与优化

论述了通用土壤流失方程在区域尺度应用时,基于数字高程模型计算其地形因子的算法及其流程,并在ArcGIS的GRID平台上开发实现.实践证明,采用最大坡降坡度法和累积坡长法求取坡度和坡长,进而计算通用土壤流失方程地形因子的算法合理可信.通过水系数据的叠加优化,一方面提高了程序的计算效率,同时也减少了不合理累积坡长值出现的机率.     

中国USLE/RUSLE因子研究

USLE/RUSLE是土壤侵蚀监测与预报的核心工具,方程中各因子赋值的合理性决定了方程应用结果的准确度。然而,由于我国地形条件的复杂性等原因,方程在我国范围内的应用受到限制。因此,为明晰土壤流失方程各因子计算中需把握的关键因素,以及当前我国研究中存在的主要问题,采用文献综合对比研究的方法,通过CNKI中国学术期刊全文数据库和Web of Science数据库,搜集了土壤流失方程因子相关文献共373篇。文献综合分析结果表明：各因子的研究普遍存在缺乏估算公式选用和估算结果的精度检验,坡长坡度因子存在公式误用的情况,作物覆盖与管理因子、水土保持措施因子缺少系统性定量计算的方法,土壤可蚀性因子计算的背景条件差异大,难以进行横向比较。为此,提出两条提高模型使用精度的建议,一是通过建设标准化的地面监测系统,系统观测和建立土壤侵蚀因子定量方法,二是明确此类模型应用边界,在较为适合的环境应用。     

基于GIS、RS和RUSLE的林区土壤侵蚀定量研究--以大兴安岭呼中地区为例

USLE是美国农业部(USDA)土壤保持局建立的以大量试验数据为基础的经验性方程,主要应用于农业区域的土壤侵蚀的监测,现已被广泛应用.RUSLE是USLE的改进方程,尽管它们的表达式相同,但RUSLE从技术性和确定因子的两方面进行了改进,具有更广泛的应用范围和更高的精度.以地理信息系统(GIS)、遥感(RS)和修正的通用土壤流失方程(RUSLE)为核心,根据呼中地区1990年遥感影像解译数据、统计资料和实地考察得到地貌、植被、降雨量,林业采伐,火烧迹地等资料,确定方程中各因子,并介绍林区各因子确定的方法,对大兴安岭呼中地区土壤流失量进行了定量化分析,评价该区森林采伐和火烧对土壤流失的影响,进行水土流失的定量评价.结果表明呼中地区总水土流失量为427 537.5 t/a,大部分地区小于3.5 t/(hm2·a),低于水利部1984年颁布的允许流失量标准(2～10 t/hm2·a),总体水土保持良好.但是研究区内水土流失严重地区十分集中,主要分布在坡度较陡处和火烧、采伐迹地.在无人类和火烧干扰的情况下坡度对水土流失影响最显著.     

聚丙烯酰胺对凹凸型坡土壤侵蚀影响的室内试验

通过室内人工模拟降雨试验,研究了聚丙烯酰胺(polyacrylamide,PAM)施用量(0、0.5、1.0和2.0 g/m2)对凸型坡(上、下坡坡度分别为5°、10°、15°和20°、25°)和凹型坡(上、下坡坡度分别为20°、25°和5°、10°、15°)土壤侵蚀规律的影响。结果显示,无PAM应用时,凹型坡或小坡度凸型坡(上坡坡度为5°)径流含沙量随降雨历时逐渐减小,而大坡度凸型坡(上坡坡度≥10°)径流含沙量在降雨过程中会急剧增大。凸型坡平均土壤流失量是凹型坡的8.4倍。PAM应用显著增大了凹型坡和小坡度凸型坡径流含沙量和土壤流失量(P0.05),但减小了大坡度凸型坡土壤流失量。PAM应用后,土壤流失量与坡度大小无明显关系,此时凸型坡平均土壤流失量为凹型坡的1.2倍。在生产实践中PAM可用于控制较陡(≥10°)凸型坡的土壤流失。     

福建省水土流失现状分析

[目的]运用遥感技术监测福建省水土流失状况,为研究区的水土保持工作提供一定的科学依据。[方法]利用2014年Landsat-8OLI等遥感数据,基于通用土壤流失方程(USLE)定量计算得到研究区的土壤侵蚀量,并运用GIS空间分析和数理统计的方法分析水土流失在地理空间上分布特征。[结果]福建省2014年的水土流失总面积为10 939.8km2,总流失率为8.93%,其中以轻度流失为主,占总流失面积的82.3%,境内流失等级为强度及以上的区域主要集中在北部的宁德和南平、南部的漳州和西部的龙岩一带;其中22个水土流失重点县流失面积为4 786.65km2,占全省流失总面积的43.76%,平均流失率为10.54%。[结论]水土流失主要发生在海拔高程为200~1 000m的区域,流失面积有8 954.35km2,占流失总面积的81.85%;坡度与水土流失关系密切,水土流失主要发生在坡度为8°~25°的区域,流失面积有69 871.71km2,占总流失面积的57.23%;容易发生水土流失的土地利用类型是裸地和林地,流失比例分别达到30.99%和9.47%。     

GIS技术在通用土壤流失方程中的应用研究

通用土壤流失方程(USLE)在我国应用,重要的是要对各相关因子值进行科学的确定。结合遥感与地理信息系统(GIS)技术,可以实现以USLE为平台的区域土壤流失遥感监测。本研究介绍了USLE中因子的GIS生成以及土壤流失量的GIS生成过程,其研究成果可作为水行政部门决策与执法的依据,也可作为研究区域基础地理信息资料进行储存备份与延伸应用。     

Accumulation of copper in soils and leaves of tomato plants in greenhouses in Turkey

Copper (Cu)‐containing fertilizers, fungicides, and bactericides has been used extensively in the greenhouses in the Antalya province in recent decades with the use of such materials tending to increase year by year. The level of DTPA‐extractable Cu was determined in 210 soils (0–20 and 20–40 cm depth) and 105 leaf samples obtained from 105 tomato greenhouses. The DTPA‐extractable Cu contents of the soils taken from the 0–20 depth ranged between 0.76 and 88.03 mg kg^‐1 (mean 7.79 mg kg^‐1). The percentage of soils containing DTPA‐extractable Cu greater than the critical toxicity level (20 mg kg^‐1) was 8.1. The Cu content of tomato leaf samples ranged between 2.4 and 1,490 mg kg^‐1 (mean 166.5 mg kg^‐1). The Cu concentration in leaf samples was very high due to the intensive use of foliar applied Cu‐containing chemicals. As a consequence, 24.8% of the leaf tomato samples analyzed contained over 200 mg Cu kg^‐1, the maximum accepted tolerance level. Therefore, it may be necessary to reduce the use of Cu‐containing pesticides and fertilizers, or at least reduce the amount of Cu‐containing fertilizers being used in those greenhouses where Cu‐containing pesticides have been or are being used.     

Role of selenium in mitigation of cadmium toxicity in pepper grown in hydroponic condition

Selenium (Se) is an essential element for humans but is not considered as essential for plants. However, its beneficial role in improving plant growth and stress tolerances is well established. In order to study the role of Se in cadmium (Cd) toxicity in pepper (Capsicum frutescens cv. Suryankhi Cluster), this experiment was carried out in greenhouse conditions. Treatments comprised Cd [0, 0.25, and 0.5 mM cadmium chloride (CdCl₂)] and Se [0, 3, and 7 µM sodium selenite (Na₂SeO₃)] with three replications. The result showed that Cd decreased chlorophyll a, chlorophyll b, and carotenoids, whereas Se supplementation diminished Cd toxicity on photosynthetic pigment. Selenium at 7 µM significantly increased the leaf area in the plants grown at 0.25 mM Cd. The application of Se at 3 µM with 0.25 mM Cd and Se at 3 µM and Se at 7 µM with 0.5 mM Cd increased the activity of catalase (CAT). Selenium at 7 µM decreased the proline content of pepper leaves exposed to Cd at 0.5 mM (30%). Selenium significantly enhanced the antioxidant activity of leaves, which was diminished by Cd toxicity. In general, Se has a beneficial effect on plant growth and is an antioxidant enzyme of pepper cv. Suryankhi Cluster under Cd stress and non-stress conditions.     

Occurrence of Sexual Hormones in Sediments of Mangrove in Brazil

The presence of sexual hormones (female estrogens) was assessed in sediments of a mangrove located in the urban region of southern Brazil. The estrogens are involved in human sexual reproduction. They act as the chemical messengers, and they are classified as natural and synthetic. The estrogens inputs in the environment are from treated and untreated sewage. The presence of estrogens in sewage is excretion from the female due to natural production and use of contraceptives (synthetic estrogens). With the indiscriminate release of sewage into the environment, estrogens can be found in rivers, lakes, and even in oceans. In this work, the presence of estrone (E1), 17-??-estradiol (E2), and 17-??-ethynilestradiol (EE2) in eight sedimentary stations in Itacorubi mangrove located on Santa Catarina Island, south Brazil, was investigated. Historically, the Itacorubi mangrove has been impacted by anthropogenic activities because the mangrove is inserted in the urban area of the Florianopolis. The estrogen EE2, used as contraceptive, had the highest concentration in mangrove sediment, 129.75?±?3.89 ng/g. E2 was also found, with its concentration ranging from 0.90?±?0.03 to 39.77?±?1.19 ng/g. Following the mechanism, under aerobic or anaerobic conditions, E2 will first be oxidized to E1, which is further oxidized to unknown metabolites and finally to CO₂ and water (mineralized). EE2 is oxidized to unknown metabolites and also finally mineralized. Theoretically, under anaerobic conditions, EE2 can be reduced to E1 even in environments such as mangrove which is essentially anaerobic.     

红壤区不同肥力水稻土根际硝化作用特征

通过根际培养箱(三室)——速冻切片技术研究了红壤地区高、低两种肥力下水稻苗期根表、根际和土体土壤矿质态氮含量和硝化强度,以及水稻生长、氮素积累的差异。结果表明,肥力水平对水稻根表和根际土壤铵态氮(NH4+-N)含量无显著影响,但高肥力显著提高土体土壤NH4+-N含量,以及根表、根际和土体土壤硝态氮(NO3--N)含量及硝化强度。两种肥力水稻土硝化强度最大值均出现在距根表2 mm处,分别为0.20和0.31μmol kg-1 h-1。土体土壤硝化强度随距根表距离增加而降低,低肥力土壤在距根表10～40mm处时硝化强度接近本底值,而高肥力土壤在距根表20～40 mm处时接近本底值。与不种水稻的CK相比,种植水稻显著提高根际土壤硝化强度。高肥力能显著改善水稻生长,增加植株氮素积累量,尤其显著促进根系生长及通气组织发育。由于红壤稻田肥力水平的差异造成水稻根际硝化强度以及水稻吸收NO3-的差异,导致高肥条件下水稻显示出更强的生长势和氮素吸收利用能力。因此,合理提高红壤稻田肥力水平对改善红壤区水稻根际土壤硝化作用及水稻氮素营养具有重要意义。     

自由基在鸡肾病发生中的作用研究

肾病即急性肾小管坏死.鸡肾病在养鸡生产中极为常见,尤其近年来,鸡肾病的发生日益增多,由于其发生机制不清楚,临床治疗鸡肾病的依据不足,致使治疗效果不佳,为此,提出本研究以探讨鸡肾病的发生机制,为本病防治提供理论依据.     

Effect of iron-quercetin complex on reduction of nitrite in in vitro and in vivo systems

This study investigated whether reducing agents such as quercetin and iron(II) facilitate formation of nitric oxide (NO) gas from orally ingested nitrite in an vivo study. When 3 mg/kg Na (15)NO2 was orally administered to rats with or without iron(II) or quercetin, Hb (15)NO, which is indicative of systemic (15)NO, was detected in the blood, with the maximum blood concentration of Hb (15)NO at 15 min after nitrite or nitrite plus quercetin treatment, whereas after administration of nitrite plus iron(II) or nitrite plus iron(II) and quercetin, the time was shortened to 10 min. Interestingly, iron(II), quercetin, or iron(II) plus quercetin did not affect the total amount of Hb (15)NO generated from orally administered Na (15)NO2. However, the systemic nitrite concentration was significantly decreased in the presence of iron(II) or iron(II) plus quercetin. These results may indicate that iron(II) is critical to the generation of NO gas from nitrite, whereas quercetin contributed little under the in vivo experimental conditions.     

旱地果园水肥管理模式研究进展

分析了旱地果园水肥管理模式的研究进展和存在问题,指出水肥胁迫尤其是水钾已成为旱区果树高产稳产优质化的主要限制因子。在系统探讨旱地果园水分管理、养分管理、综合管理以及果树叶营养综合诊断施肥标准的基础上,提出了旱地果园的高效水肥管理模式。     

Meta-analysis in the Selection of Groups in Varieties of Citrus

Brazil is the largest producer of oranges (Citrus sinensis) in the world. The nutrient management of tree orchards is designed from experiments with a limited number of varieties. This knowledge is transferred to other varieties by diagnosing tissue nutrient composition and tree demand. Compositional data analysis has been first applied to tissue analysis of agricultural crops using centered log ratios with compositional nutrient diagnosis (CND-clr). The isometric log ratio (ilr) transformation is a new approach based on binary nutrient ratios and the principle of orthogonality (CND-ilr). We analyzed eleven nutrients: nitrogen (N), sulfur (S), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), boron (B), copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) in leaf tissue samples across 108 commercial plots (thirty-one grow Valencia, twenty-two Hamlim, twenty Pera, and thirty-five Natal). Nutrients were partitioned between macro- and micronutrients as well as anionic and cationic species. The effect size of varieties over Valencia was quantified by the mean and standard deviation of ilr values across ilr coordinates. Specific varietal nutrient profiles and ilr norms were defined. The nutrient profile of orange varieties could be classified into homogeneous groups to take advantage of fertilizer trials conducted on varieties of the same group. The Aitchison distance and a perturbation vector could be instrumental for diagnostic purposes and nutrient management.     

Role of aldehyde oxidase in the hepatic in vitro metabolism of 3-methylindole in pigs

The metabolism of 3-hydroxy-3-methylindolenine (HMI), a recently discovered metabolite of 3-methylindole (3MI, skatole) produced by porcine liver microsomes, was investigated in vitro using porcine liver cytosol. HMI was rapidly metabolized to a single product, 3-hydroxy-3-methyloxindole (HMOI), by porcine cytosol. By the use of the selective inhibitors menadione and quinacrine, it was shown that the enzyme responsible for the oxidation of HMI into HMOI was aldehyde oxidase (AO; aldehyde:oxygen oxidoreductase, EC 1.2.3.1). The activity of AO in the conversion of HMI to HMOI was measured in a population of pigs (n = 30) with a wide range of 3MI levels in back fat (0.07-0.30 mg/kg). AO activity was found to be negatively correlated (r = -0.70; P < 0.001) with the level of 3MI in fat. The results of the present study suggest that AO plays an important role in the metabolism of 3MI in the pig and that its catalytic activity is related to an adequate 3MI clearance.     

Role of hydrocolloids in the creaming of oil in water emulsions

The influence of guar gum and xanthan gum on the creaming of 10% oil in water emulsions has been investigated. The presence of very low concentrations of the polysaccharides (typically < approximately 0.075%) was found to induce depletion flocculation of the emulsion droplets and increased the rate of creaming. However, at higher polysaccharide concentrations (typically > approximately 0.1%) the creaming rate was reduced due to the increased viscosity of the aqueous phase. For most systems a delay period was noted before creaming started, which was found to be dependent on the zero shear viscosity of the continuous phase and independent of polysaccharide type. The delay period increased significantly at zero shear viscosities approaching 1 Pa s. A mathematical model has been used to fit the creaming rate profiles and a simple exponential relationship obtained between delay time and polysaccharide concentration.