不同人工恢复林对退化红壤团聚体组成及其有机碳的影响

研究土壤团聚体的组成及其有机碳的分布,有助于从微观角度理解土壤结构与功能的相互作用.采用于筛法和湿筛法,研究南方红壤退化地实施人工恢复30年后,马尾松与阔叶复层林(PB)、木荷+马尾松混交林(SP)和阔叶林(BF)3种典型林分在0～60 cm土层的团聚体组成及其有机碳分布特征,分析土壤团聚体有机碳与总有机碳相关关系.结果表明:各恢复林分土壤机械稳定性团聚体质量分数,以＞2 mm粒径所占比例最大(均在60％以上),而在水稳性团聚体中,以＜0.05 mm粒径占优势.不同林分土壤团聚体结构破坏率顺序依次为BF(53.38％～84.27％) ＞SP(52.22％ ～70.86％) ＞PB(22.70％ ～47.83％).机械稳定性和水稳性团聚体有机碳质量分数均以PB最高,随着土层深度的增加,各林分土壤团聚体有机碳质量分数呈下降趋势.水稳性大团聚体(＞0.25 mm粒径)有机碳质量分数总体高于相应土层的总有机碳质量分数,而微团聚体的(＜0.25 mm粒径)则低于后者,说明有机碳对于大团聚体的形成和水稳性具有积极作用.土壤团聚体有机碳与总有机碳的相关关系分析表明,土壤团聚体有机碳的增加,对总有机碳的积累具有正面影响.保留密度大、灌木(草)层盖度高的马尾松与阔叶复层林土壤团聚体的数量和质量更高;因此,在红壤侵蚀退化地森林恢复初期,可通过适当密植、增加林下灌草覆盖等措施,增加有机碳的输入,促进团聚体的形成和稳定,从而加速了退化土地的土壤结构改善和功能恢复.该研究可为南方严重红壤退化地生态恢复中的林分类型选择和优化配置提供科学依据.     

天保工程对东北和内蒙古重点国有林区保育土壤生态效益的影响

为了直观地反映天然林资源保护工程所带来的生态效益,体现重大生态工程的巨大作用,实现林业及生态的可持续发展,依据LY/T1721-2008《森林生态服务功能评估规范》,应用分布式测算方法,对东北和内蒙古重点国有林区天保工程保育土壤物质量及价值量进行评估.结果表明:1)截至2015年,9个优势树种固土和保肥总量分别为13.17亿t/a和8 203.72万t/a,比天保工程实施前分别增加2.36亿t/a和1 738.23万t/a;2)9个优势树种固土和保肥总价值分别为905.29和2 408.92亿元/a,比天保工程实施前分别增加455.44和699.69亿元/a;3)桦木林和阔叶混交林固土效益突出,而红松林和樟子松林固土效益不显著;落叶松林和阔叶混交林保肥效益均最好,樟子松林保肥效益较差;4)对森林实施保护,能有效改善其生态系统服务功能,使森林保育土壤生态效益得到相应的提升.研究为评估天保工程区森林的其他生态服务功能,以及后续天保工程的实施提供科学依据.     

无人机遥测技术在水土保持生态果园改造监测中的应用

以江西水土保持生态科技园为研究区,通过无人机遥测技术以及地理信息系统,对生态果园水土保持措施进行图斑化、信息化管理研究.结果表明:无人机遥测技术获取的不同阶段的航飞影像可用于生态果园改造的动态监测;利用Agisoft photoscan软件处理航飞影像可生成高分辨的数字正射影像(DOM)以及数字地表模型(DSM)数据;利用生成的DOM,结合地理信息系统,可获取生态果园水土保持措施的分布、数量、长度等信息,建立生态果园水土保持措施数据库,并输出报表和专题图.经与实际量测长度验证,基于DOM提取的长度平均精度为97.99％;与实测坡度验证,基于DSM数据提取的坡度平均精度为88.91％.无人机遥测技术能够快速、准确、自动获取地物的面积、长度、坡度等指标数据,可满足当前水土保信息化的要求,提升综合治理项目实施监测的信息化水平,提高施工监测的质量和效率.     

潮土小麦和玉米Olsen-P农学阈值及其差异分析

【目的】磷农学阈值是指导不同作物磷肥用量并获取最佳经济产量的重要依据,然而,不同地区不同的耕作制度、土壤类型、作物种类、pH、温湿度条件下,作物的磷农学阈值不同。明确小麦–玉米轮作体系下,典型潮土区小麦和玉米的磷农学阈值,并分析其差异。【方法】本研究基于“国家潮土土壤肥力与肥料效益长期监测站”25年的定位试验,选取氮、钾肥施用充足和磷肥用量不同的NK (不施磷肥)、NPK (施用氮磷钾化肥)、NPKM (氮磷钾化肥和有机肥配施)、1.5NPKM (高量氮磷钾化肥配施有机肥)、NPKS (氮磷钾化肥与玉米秸秆还田配施) 5个处理的试验数据,使用米切里西指数模型 (Mitscherlich exponential model) 拟合小麦和玉米的Olsen-P农学阈值,并通过对比不同土壤磷水平下两种作物的磷吸收利用特性,分析其阈值不同的原因。【结果】获得最大相对产量的95%时,潮土区小麦Olsen-P农学阈值为13.1 mg/kg,玉米Olsen-P农学阈值为7.5 mg/kg。玉米Olsen-P农学阈值低于小麦主要原因:1) 土壤磷水平较低时,小麦对磷缺乏更为敏感,而玉米可保持相对较强的吸磷能力,25年不施磷处理玉米吸磷量是小麦的1.4倍;2) 土壤Olsen-P含量达到玉米阈值,而未能达到小麦阈值时,可保障玉米籽粒、茎秆及小麦籽粒正常生长对磷的需求,但小麦茎秆磷浓度仅能达到相对最大磷浓度的68.9%,严重影响了小麦的正常生长和获取较高产量的能力;土壤Olsen-P含量提高到小麦阈值后,小麦茎秆磷浓度提高到相对最大磷浓度的80.5%以上,进而可保障小麦获得较高的产量;3) 土壤磷素养分充足时,小麦对磷的吸收量大于玉米,且主要是由于小麦茎秆磷浓度和吸磷量随土壤Olsen-P含量的增加而大幅度增加。【结论】小麦和玉米作为典型潮土区两种重要的粮食作物,Olsen-P农学阈值分别为13.1和7.5 mg/kg。由于两种作物的生理特性不同,小麦对磷素的吸收利用率较低,茎秆需要较高的土壤磷浓度维持正常生长,产量形成对磷养分需求更大。因此,小麦–玉米轮作体系下,小麦的磷农学阈值更高,小麦季所需土壤磷供应量大于玉米季。为增强磷肥利用效率,减少磷肥投入量和土壤中磷素的过量累积,玉米季磷肥使用量应适当小于小麦季。当土壤Olsen-P水平高于作物磷农学阈值后,减少或短时间停止施用磷肥并不会对作物产量有明显影响。     

Landscape,Soil, and Plant Analysis of Japanese Stiltgrass (Microstegium vimineum) Invasion in the Piedmont Region,SC

Japanese stiltgrass (Microstegium vimineum), an exotic invasive plant, is native to Southeast Asia. This study was conducted to determine the chemical composition of Japanese stiltgrass as well as soil and landscape characteristics that correlate with invasion of Japanese stiltgrass around Lake Issaqueena in the upper Piedmont of South Carolina. Geographic Information Systems (GISs) and Light Detection and Ranging (LiDAR) were used to determine the spatial pattern of invasion with respect to the aspect, slope, canopy cover, soils, and distance to roads and trails. Japanese stiltgrass was distributed on both sides of Lake Issaqueena in Pacolet and Madison soil map units (Fine, kaolinitic, thermic Typic Kanhapludults) on the average slopes of 21%, but it was particularly common on the eastern shore of the lake in low-lying wet and shaded areas (mean canopy cover 51%). In addition, invasion by Japanese stiltgrass was correlated with the proximity to roads and trails. Plant tissue analysis revealed many differences in the distribution of macronutrients, macrominerals, and micronutrients in the leaves, stems, and roots of Japanese stiltgrass, although those differences were not always statistically significant. Concentrations of nitrogen (N), phosphorus (P), and calcium (Ca) were the highest in leaves while zinc (Zn) concentrations were the highest in stems and concentrations of magnesium (Mg), copper (Cu), manganese (Mn), iron (Fe), and sodium (Na) tended to be higher in roots. Carbon (C), sulfur (S), and potassium (K) concentrations were generally higher in above-ground tissues versus roots. Soil chemical analysis revealed no statistical differences between control and invaded plots. Our findings suggest that watershed areas surrounding lakes may be particularly susceptible to the invasion of Japanese stiltgrass due to their microclimates, low-lying wet pathways for seed distribution and recreational uses.     

Site-Specific Nitrogen Management in Rice Using Remote Sensing and Geostatistics

Proper doses of nitrogenous fertilizer are most important for rice production system because a large part of the nitrogen may be lost if it is not applied judiciously. A study was conducted covering five blocks of Balasore and two blocks of Bhadrak districts. Soil samples were collected randomly, and field visit was conducted during peak vegetative stage of rice. Two approaches have been used in this study for estimating the site-specific nitrogen (N) requirement in the study area. In one approach, geostatisical analysis and kriging was used to develop the soil test–based N recommendation map by which a minimum of 72 kg N ha^?1 and maximum of 94 kg N ha^?1 were recommended. In a second approach, remote sensing was used and N recommendation map was developed using the moderate-resolution imaging spectroradiometer (MODIS) leaf area index (LAI) and normalized difference vegetation index (NDVI) satellite data, and a minimum requirement of 60 kg N ha^?1 and maximum of 120 kg N ha^?1 was estimated through this approach.     

Temporal variation of total and DTPA-extractable heavy metal contents as influenced by sewage sludge and perlite in a calcareous soil

Continuous application of sewage sludge (SS) as a source of organic matter, may increase available heavy metals (HMs) up to their critical levels. As a consequence their uptake by plants, risks of accumulation in food chain and groundwater pollution increases. To evaluate the effects of perlite and SS on total content and available fraction of iron (Fe), manganese (Mn), lead (Pb), copper (Cu), nickel (Ni), cadmium (Cd) and zinc (Zn) over 45 and 90 days a completely randomized pot experiment was conducted. Treatments consisted of SS (0, 2 and 4%) and combined SS and perlite levels (1:1, 1.5:0.5 and 0.5:1.5% SS:perlite). Mean available Fe, Ni, Cd, Mn and Zn fractions decreased over time by 7–27%, whereas, total contents did not change. Available HMs in SS-treated soils increased by 0.5–25%; whereas, only total Zn, Cu and Pb concentrations increased with SS application (although concentrations fall in the range of critical levels). The lowest (1.6 fold) and highest (22.1 fold) increases obtained for available Cu and Zn, respectively. Perlite could mitigate the adverse effect of high rate application of SS on amplification of HMs extractability. Therefore, their concomitant applications can be suggested considering the perlite durability and its positive effects on soil physical properties.     

水氮调控对设施土壤有机氮组分、全氮和矿质氮的影响

为探讨水氮调控对设施土壤有机氮组分、全氮和矿质氮的影响,通过膜下滴灌设施番茄田间定位试验,采用灌水下限(W_1、W_2、W_3)和施氮量(N_1、N_2、N_3)的两因素三水平随机区组设计,研究水氮调控对休耕期0—30cm土层土壤有机氮组分、全氮和矿质氮的影响。结果表明,不同水氮调控下,设施土壤有机氮主要是以酸解态氮为主,总体表现酸解态氮大于非酸解态氮含量。土壤有机氮组分在酸解态氮和非酸解态氮中分配比例差异明显。土壤有机氮各组分含量及占全氮比例的大小顺序为氨基酸氮/氨态氮未知氮氨基糖氮。除氨基糖氮,其余酸解态氮各组分和酸解总氮含量及其占全氮比例均随着土层深度的增加而降低,不同土层含量差异显著(P0.05)。土壤全氮、矿质氮和总有机氮含量随土层深度的增加也呈降低趋势,且含量差异达到极显著水平(P0.01)。除氨基糖氮,全氮与其他有机氮各组分、酸解总氮间均达到极显著正相关(P0.01);矿质氮仅与酸解氨态氮及酸解总氮的影响达到极显著(P0.01)和显著正相关(P0.05)。灌水下限、施氮量及水氮交互对设施土壤全氮、矿质氮和总有机氮及有机氮组分影响均达到极显著水平(P0.01)。因此,设施土壤氮素含量的变化与水氮管理模式紧密相关。氨态氮和氨基酸氮是设施土壤中最主要的有机氮形态,是土壤活性氮中的主要组分,亦是土壤供氮潜力的表征。考虑土壤供氮潜力,灌水下限35kPa、施氮量300kg/hm~2为该设施生产下最优的水氮管理措施。     

长期施肥对黄壤性水稻土有机碳矿化的影响

以贵州省农业科学院内黄壤性水稻土长期(22年)定位施肥试验为对象,采用室内模拟培养试验研究了不施肥(对照,CK)、施化肥(NPK)、低量有机无机肥配施(0.5MNPK)、施牛粪(M)和常量有机无机肥配施(MNPK)对土壤有机碳矿化的影响。结果表明:NPK处理土壤有机碳含量(21.6 g kg~(-1))与CK处理(22.8 g kg~(-1))基本相同,而0.5MNPK、M和MNPK处理的土壤有机碳含量较CK处理分别提高了30.6%、72.9%和62.2%,其中,M和MNPK处理差异达显著水平(p0.05)。模拟培养条件下,CO2产生速率在培养的第2天达到最大值,然后迅速下降,而后缓慢下降(第4~24天),后期(第24~30天)趋于稳定;各处理土壤有机碳矿化速率大小依次为:MMNPK0.5MNPKCKNPK,各处理土壤有机碳矿化速率随时间的动态变化均符合对数函数关系(p0.01)。培养结束(30 d)时,各处理土壤有机碳累积矿化量为1.23~2.37 g kg~(-1),以M处理和MNPK处理较高,较CK处理(1.46 g kg~(-1))分别增加了62.6%和44.2%(p0.05);各施肥处理土壤有机碳的累积矿化率(土壤有机碳累积矿化量/土壤有机碳含量)较CK处理(6.4%)均有所下降,以M处理和MNPK处理下降较多,降幅分别为1.2%和0.9%。土壤有机碳累积矿化量随培养天数的动态变化可以用一级动力学方程拟合(p0.01),模拟结果表明,CK处理土壤潜在可矿化有机碳量为1.55 g kg~(-1),与CK处理相比,NPK处理下降了11.6%,但差异不显著(p0.05),而有机肥处理(0.5MNPK、M和MNPK)有不同程度的提高(21.3%~73.6%),其中,M和MNPK处理提高幅度较大(p0.05);同时,MNPK处理能够提高土壤有机碳的周转速率,减少周转时间。上述结果指示黄壤性水稻土长期施用有机肥(0.5MNPK、M和MNPK)能够提高土壤有机碳的矿化速率,在促进土壤有机碳积累的同时降低其累积矿化率(单位有机碳矿化水平),增强土壤固碳能力。     

黑土区田块尺度土壤有机质含量遥感反演模型

为了对田块尺度土壤有机质进行空间反演并提高模型精度和稳定性,该文以黑龙江省黑土带41.3 hm~2田块为例,获取2016年5月中下旬两期(受限于拍摄周期和天气原因而选择不同卫星影像,2016年5月17日Landsat 8影像和5月25日Sentinel-2A影像)裸土时期遥感影像和4 m分辨率DEM数据;分析单期影像与土壤有机质(soil organic matter,SOM)的关系,两期影像所包含的土壤含水量变化信息与地形因素对SOM预测模型精度的影响,建立基于BP神经网络的SOM遥感反演模型。结果表明:该田块内SOM含量差异较大;利用单期影像预测SOM时,基于红波段和785~899 nm波段建立的预测模型精度(建模均方根误差RMSE 1.033,检验RMSE 1.079)和稳定性(建模决定系数R2 0.677,检验R20.644)较高;两期影像时,基于红波段和1 570~1 650 nm波段建立的预测模型精度(建模RMSE 0.855,检验RMSE 0.898)和稳定性(建模R2 0.792,检验R2 0.797)显著提高;在两期影像模型基础上,加入地形因子作为输入量,模型精度(建模RMSE 0.492,检验RMSE 0.499)和稳定性(建模R2 0.917,检验R2 0.928)进一步提高。研究成果可为土壤碳库估算和农田精准施肥提供理论与技术支持。