Driving forces of soil organic matter change in Jiangsu Province of China

Soil organic matter (SOM) is a key property determining soil functions and a major form of carbon stored in soil. Understanding the spatial and temporal variability of SOM and the driving forces responsible for spatial and temporal changes is important to assess regional soil quality and carbon sequestration potential and, particularly, to establish better practices for land use and management. We evaluated the spatio‐temporal change in SOM content from 1979–1982 to 2006 and its driving forces in Jiangsu Province, East China, using geostatistics. The results showed that mean SOM content increased from 16.60 ± 8.50 to 18.31 ± 8.32 g/kg over a 26‐yr period. The maps of SOM generated by ordinary kriging represented the increasing trend from north to south across the province in the two periods. The level of SOM in 1979–1982 affected the pattern of change: the SOM increasing in areas initially with a small content while decreasing in areas having a large content. The map of SOM change showed that the rate of increase decreased from north to south within the province. Increased fertilizer application promoted crop production with more residual biomass being retained in the soil, which resulted in increased SOM content. Land use changes to paddy, upland or forest improved SOM content, whereas abandoning land reduced SOM content.     

北京市平谷区农用地土壤有机质空间变异特征

采用传统统计、地统计及地理信息系统(GIS)相结合的方法,初步研究了北京市平谷区农田土壤有机质(SOM)含量的空间分布规律及其影响因素.传统统计分析结果表明,研究区土壤样本呈对数正态分布,平均值为15.36 g·kg-1,变异系数为0.32,属中等变异程度.方差分析表明,高程和土地利用类型均对研究区SOM含量的分布有显著影响.地统计分析表明,研究区SOM含量空间变异具有一阶趋势和各向异性特征;由空间自相关部分和随机部分引起的空间变异性程度大体相当,具有中等的空间相关性.结合普通Kriging插值方法,获得了研究区SOM含量的空间分布图,比较分析表明研究区农用地SOM含量的空间分布是自然和人为利用因素共同作用的结果.     

江苏省土壤有机质含量时空变异特征及驱动力研究

土壤有机质(SOM)含量是估算土壤碳储量、评价土壤肥力的重要指标,研究SOM时空演变对评估区域土壤固碳潜力,实现土壤可持续利用具有重要意义。以江苏省为例,利用全国第二次土壤普查资料和2006年采样数据,基于地统计学方法和GIS技术,对比研究了1980 - 2006年全省范围内表层(0 ~ 20 cm)SOM含量的时空变异特征及其驱动因子。结果表明：1980年和2006年江苏省SOM平均含量分别为16.55 ± 8.50 g kg^-1和18.31 ± 8.32 g kg^-1,变异系数分别为51.36%和45.44%。两个时期SOM的变异函数均符合指数模型,块金系数由51.85%增加为56.52%,变程由71.55 km减少至37.83 km,SOM含量的空间自相关性减弱,自相关距离减小。1980-2006年,SOM含量空间分布呈现出北增南减,沿江平原增,宁镇丘陵减,滨海平原基本持平的空间格局,增加幅度由北向南逐渐减小。SOM含量的初始值影响其空间格局的演变,总体上呈现初始SOM含量的高值降低、低值增加的趋势。肥料的大量使用在提高粮食产量的同时也增加了作物残茬和根系的生物量;秸秆还田的大力推行,使得大量的有机物质进入土壤,促进了SOM的累积。不同的土地利用变化对SOM含量变化的作用不同,土地利用方式转变成水田、旱地和林地促进了SOM的增加,而转变成荒地后导致SOM含量下降。     

南方花岗岩红壤典型区土壤有机质的空间变异特征

 通过野外实地调查与室内试验,以长汀县为研究区,在GIS的支持下,运用地统计学方法分析南方花岗岩红壤典型区表层土壤有机质的空间变异特征。结果表明:研究区土壤有机质质量分数总体水平中等并具有中等的空间相关性,平均为2.73%;变异系数为72.73%,属中等变异;由空间自相关部分引起的空间变异性程度较大,C0/(C0+C)值为47.13%,变程为21.48km;在空间分布上呈现四周高中间低的分布特征,在中部地区形成连片的低值区,西部有机质质量分数整体较高,存在最高值。研究成果可为南方花岗岩红壤侵蚀退化地的生态恢复与重建提供参考。     

Managing soil organic matter – implications for soil structure on organic farms

Abstract. This paper reviews current understanding of soil structure, the role of soil organic matter (SOM) in soil structure and evidence for or against better soil physical condition under organic farming. It also includes new data from farm case studies in the UK. Young SOM is especially important for soil structural development, improving ephemeral stability through fungal hyphae, extracellular polysaccharides, etc. Thus, to achieve aggregate stability and the advantages that this conveys, frequent input of fresh organic matter is required. Practices that add organic material are routinely a feature of organically farmed soils and the literature generally shows that, comparing like with like, organic farms had at least as good and sometimes better soil structure than conventionally managed farms. Our case studies confirmed this. In the reviewed papers, SOM was generally larger on the biodynamic/organic farms because of the organic additions and/or leys in the rotation. We can therefore hypothesize that, because it is especially the light fraction of SOM that is involved in soil structural development, soil structure will improve in a soil to which fresh organic residues are added regularly. Thus, we argue it is not the farming system per se that is important in promoting better physical condition, but the amount and quality of organic matter returned to a soil.     

基于多元地统计的土壤有机质含量空间格局反演

为了提高土壤有机质含量的空间预测精度,该文采用了一种多元地统计方法来构建遥感定量反演模型。考虑到回归误差在空间上具有一定程度的聚类,该文提出了基于局部变化均值的普通克里金方法,然后用其构建土壤有机质含量遥感定量反演模型。对四川省西南部土壤有机质含量进行空间预测试验,并与普通克里金、普通遥感定量反演、基于回归克里金的遥感定量反演等方法相比较。结果表明:该文提出方法的空间预测结果最优,其原因为该方法通过空间统计来建立采样数据与地表反射率间的联系,充分考虑了数据间的空间相关性,因此可以更精确地获得土壤有机质含量的遥感反演模型;相比基于回归克里金的遥感定量反演方法,基于局部变化均值的普通克里金假设回归误差在局部邻域内的均值也不一定为零,更符合实际情况。该方法为农田养分管理及区域农业的可持续发展提供科学依据。     

中国地带性土壤有机质含量与酸碱度的关系

利用中国第二次土壤普查确定的886个典型地带性土种剖面资料,通过统计分析研究了全国及6个地理区域(华东、华南、西南、东北、华北和西北)地带性土壤表层有机质含量与pH的关系。结果表明,土壤表层有机质含量和pH在不同地理区域间有明显差异;土壤有机质含量有随pH升高而降低的趋势,二者间呈极显著的负相关关系(r=-0.332～-0.530,p<0.001),在控制温度、降雨和海拔条件下,二者间的偏相关关系也均达到1%的显著水平(r偏=-0.217～-0.322);指数方程(SOM=aebpH,a和b为常数)可以较好地描述土壤表层有机质含量与pH的关系,土壤pH变异可以分别解释有机质含量总变异的12.2%～22.9%。     

沙地土壤有机质与土壤水动力学参数的关系

试验测定了不同有机质含量的沙地土壤饱和导水率、水分特征曲线及一些水分常数,研究分析了沙地土壤有机质含量与水动力学参数的关系以及有机质影响沙地土壤水分运动的机理。结果表明沙地土壤有机质含量与几个水分常数均呈极显著线性相关,土壤水吸力相同时有机质含量越高,土壤含水量也越大;土壤有机质含量和<0.01mm物理性粘粒与土壤饱和导水率呈极显著线性负相关,沙地土壤有机质是影响水分动力学参数最重要的因子之一。     

Temporal variation of soil organic matter content and potential determinants in Tibet, China

Understanding temporal variations in soil organic matter (SOM) is important because SOM improves soil, sustains soil productivity, and sequesters carbon. The Tibetan Plateau plays a critical role in climate change at both regional and global scales. Thus, the main objective of this study was to investigate temporal variations in SOM content in Tibetan soils as an important indicator of climate change. SOM content data were obtained from soil surveys conducted in the 1980s and resampled in the 2000s. In this study, SOM content data from the A horizon of the soil profile were compared over time, and a paired t-test was conducted to verify differences between the two datasets. The results reveal that SOM content in the A horizon decreased significantly. To determine the causes of SOM content decreases in the A horizon, soil samples were grouped into ten soil types, four land-use types, and seven physiogeographical units. SOM content in four soil types (felty soils, cambisols in the World Reference Base (WRB) for soil resources; cold calcic soils, cambisols in the WRB; bog soils, gleysols in the WRB; and meadow soils, umbric gleysols/haplic phaeozem in the WRB), pasture, and broad valleys and basins of the south Tibetan zone of montane shrubby steppe decreased significantly in the A horizon. Based on the analysis of some known realities, this change should be attributed to pasture degradation resulting from overgrazing and climate warming.     

大别山区江子河流域土壤有机质的空间变异

土壤有机质(Soil organic matter,SOM)是土壤的重要组成部分,是反映土壤肥力的重要指标,是全球碳循环的重要源和汇,目前已成为土壤学和环境学的研究热点之一[1]。土壤空间异质性是系统的某种属性在空间上的复杂性和变异性,是土壤重     

东北黑土有机质组分与结构的研究进展

在全球气候变化背景下研究土壤有机质的转化过程对于评价陆地生态系统碳截获潜力具有重要意义,而土壤有机质的循环特征及其稳定性与土壤有机质的组成和结构密切相关.东北黑土区是我国重要的商品粮基地,近年来,黑土有机质含量呈显著下降趋势,造成黑土肥力和质量的严重退化.本文通过文献资料的整理,总结了不同农田管理措施下黑土土壤有机质的消长动态、组分变化以及结构特征的研究现状,并探讨了研究中存在的问题.开垦和耕作导致土壤有机质总量、活性组分以及腐殖物质含量的显著降低,而平衡施用化肥和有机肥是维持和提升土壤有机质数量和质量的有效途径,长期有机无机配施使土壤有机质结构趋于简单化,有利于土壤肥力的保持.黑土有机质组分化学结构变化的驱动机制是值得人们长期探索的问题.     

The quality of exogenous organic matter: short-term effects on soil physical properties and soil organic matter fractions

We examined the short-term effect of five organic amendments and compared them to plots fertilized with inorganic fertilizer and unfertilized plots on aggregate stability and hydraulic conductivity, and on the OC and ON distribution in physically separated SOM fractions. After less than 1 year, the addition of organic amendments significantly increased ( P  <   0.01) the aggregate stability and hydraulic conductivity. The stability index ranged between 0.97 and 1.76 and the hydraulic conductivity between 1.23 and 2.80 × 10⁻³ m/s for the plots receiving organic amendments, compared with 0.34–0.43, and 0.42–0.64 × 10⁻³ m/s, respectively, for the unamended plots. There were significant differences between the organic amendments (P <  0.01), although these results were not unequivocal for both soil physical parameters. The total OC and ON content were significantly increased ( P  <   0.05) by only two applications of organic fertilizers: between 1.10 and 1.51% OC for the amended plots versus 0.98–1.08% for the unamended and between 0.092 and 0.131% ON versus 0.092–0.098% respectively. The amount of OC and ON in the free particulate organic matter fraction was also significantly increased ( P  <   0.05), but there were no significant differences ( P  <   0.05) in the OC and ON content in the POM occluded in micro-aggregates and in the silt + clay-sized organic matter fraction. The results showed that even in less than 1 year pronounced effects on soil physical properties and on the distribution of OC and ON in the SOM fractions occurred.     

江苏省外生菌根真菌资源调查

A total of 1400 soil samples from the plow layer （0-20 cm） at an approximate interval of 5 km were collected in the autumn of 2002 over the entire black soil arable crops region to determine the spatial variability of seven variables, such as total organic matter content （OMC）, total N, total P, total K, alkali-dissolvable N （AN）, available P （AP） and available K （AK）, with classical statistics and geostatistical analysis across the entire black soil area in Northeast China. In nonsampled areas ordinary kriging was utilized for interpolation of estimated nutrient determinations. Classical statistics revealed highly significant （P ≤ 0.01） correlations with all seven of the soil properties, except for OMC with AP and total K with AK. In addition, using coefficients of variation, all soil properties, except for total K, were moderately variable. A geostatistical analysis indicated that structural factors, such as parent material, terrain, and water table, were the main causes of the spatial correlations. Strong spatial correlations were noted with OMC, total N, total P, AN, and AP, while they were moderate for total K and AK. The effective spatial autocorrelation of OMC, total N, total P, and AN ranged from 1 037 to 1353 km, whereas the ranges of total K, AP, and AK were only from 6 to 138 km. The fit of the experimental scmi-variograms to the theoretical models indicated that except for AN, kriging could successfully interpolate other six variables. Thns, the geostatistical method used on a large scale could accurately evaluate the spatial variability of most black soil nutrient properties in Northeast China.     

土壤含水量对反射光谱法预测红壤土壤有机质的影响研究

研究土壤含水量对有机质预测的影响,可为野外红壤有机质快速测定提供理论依据。本文在实验室条件下测量了不同含水量红壤的可见光-近红外光谱反射率,运用偏最小二乘回归(PLSR)建立不同含水量的土壤有机质预测模型。结果显示,随土壤含水量的增加,有机质与一阶微分光谱的相关性先增加后下降,含水量为100～150 g/kg时相关系数最大。分380～2 400、380～1 300、1 300～2 400 nm三个波段建立不同含水量的有机质预测模型,模型预测精度均随土壤含水量增加而呈现先增加后下降的趋势。利用1 300～2 400 nm建立有机质预测模型可以有效避开氧化铁影响,建立的模型预测精度最高。本研究认为,当土壤含水量小于200 g/kg时,可以利用在室内控制条件下测定的土壤反射率,建立1 300～2 400 nm波段的PLSR模型,进行红壤土壤有机质含量预测。     

冀西北栗钙土有机质分解及土壤速效养分变化的研究

采用尼龙网袋法研究栗钙土有机质分解及土壤速效养分的变化结果表明,不同有机物(肥)料在前3个月分解较快,最初30d坡梁栗钙土和旱滩草甸栗钙土分解率分别为32.68％和30.32％。新施入有机物(肥)料可明显提高土壤有机质活性系数,平均提高16％左右,腐殖质活性顺序依次为牛粪>莜麦秸>豌豆秸。有机物(肥)料腐解周年后土壤有机碳及速效氮、速效磷、速效钾明显增加。2类土壤有机碳分别为106.67％～135.00％和53.33％～58.18％,速效氮、速效磷、速效钾分别提高34.62％～52.31％和21.10％～50.37％、18.20％～207.60％和34.20％～210.05％、64.92％～143.12％和28.75％～102.49％。     

荒漠土壤有机质含量高光谱估算模型

为解决荒漠土壤有机质含量高光谱估算存在的困难,提高土壤有机质含量估算的精准性,该文对准噶尔盆地东部荒漠土壤进行采样、化验分析和光谱测量、处理,分析土壤光谱与有机质含量的相关性,确定敏感光谱波段,建立荒漠土壤有机质含量多种高光谱估算模型,旨在通过模型精度的比较,确定最优模型。结果表明：反射率、倒数对数光谱与荒漠土壤有机质含量相关性低,而经过一阶微分、二阶微分变换后,相关系数有所提高,部分波段的相关系数通过0.01显著水平的检验,可以用来荒漠土壤有机质含量的估算;一元线性回归建立的估算模型的精度低,不适用荒漠土壤有机质含量高光谱的估算。荒漠土壤有机质多元逐步回归模型的二阶微分、倒数对数二阶微分修正决定系数得到了较大提高,分别提高了0.22和0.31,均方根误差下降了0.66和0.80,建模精度高于一元线性回归模型。荒漠土壤有机质一阶微分、二阶微分光谱的最小偏二乘回归模型的决定系数比其多元逐步回归模型提高了0.07、0.04,一阶微分、二阶微分均方根误差都下降了0.11,二阶微分偏最小二乘法回归模型是该研究所建12个模型的最优估算模型。在多元逐步、偏最小二乘回归模型中,最优估算模型是二阶微分模型,因而用偏最小二乘法回归估算荒漠土壤有机质含量是个可行的方法。该研究的成果为荒漠土壤有机质高光谱遥感分析提供了支撑,实现荒漠土壤有机质监测的时效性、准确性,为区域生态环境的修复提供依据。     

基于高光谱特征的土壤有机质含量估测研究

在室内条件下,利用ASD2500高光谱仪测定了潮土和水稻土自然风干土壤样品的光谱。通过系统分析两种不同类型土壤的高光谱特征差异及其有机质含量的敏感波段区位,建立了土壤有机质含量的光谱估测模型。结果表明,具有相同有机质含量的两种类型土壤整体光谱变化趋势无明显差别,但反射率表现出明显差异,一阶导数变换能较好地显现谱图中的肩峰。潮土和水稻土有机质的敏感波段集中在相同区域,原始反射率在685 nm处相关性最高,而一阶导数光谱在554 nm处相关性最高。通过对整体样本的多元逐步回归分析,筛选出两种土壤有机质相同的敏感波段为800 nm、1 398 nm和546 nm。进一步以一阶导数为自变量,基于1 400nm和554 nm两个波段构建了土壤有机质差值指数SOMDI及估测模型,即Y=4.19 12.85×(R_FD554 R_FD1 400)。利用独立的样本对建立的光谱模型进行了检验,预测决定系数均达0.79以上。上述结果表明,利用高光谱技术可实现土壤有机质的快速监测与诊断。     

县域土壤有机质动态变化及其影响因素分析

本文以河北省曲周县为例, 采用 1980 年和 1999 年两次全县的土壤肥力监测以及农户调查数据和统计数据, 系统分析了过去 20 年中土壤有机质的动态及其与之相关的农作管理方式的变化。 结果显示, 在过去的近 20 年 间, 曲周县土壤表层的有机质含量呈现增长的趋势, 导致这种变化的农作管理方式有化肥施用量的大幅度提升、秸 秆还田量的增加、盐碱地的开垦利用、灌溉面积和复种指数的提高以及主要种植模式和种植作物的土壤有机质处 于正平衡状态。 然而当前的生产管理方式尽管有利于土壤有机质积累, 但是也带来了一系列的生态环境问题。 实 施保护性耕作、降低化肥用量、提高秸秆还田量和有机肥的用量成为今后农业生产管理方式调整的主要方向。     

基于高光谱特征指数的土壤有机质含量建模

以江苏中部的水稻土和潮土为研究对象,采集178个表层土壤(0～20 cm)样品,并测定了土壤有机质含量(Soil Organic Matter,SOM).运用ASD FieldSpec 3光谱仪测量了土壤的高光谱曲线,首先对原始光谱进行倒数对数和去包络线变换,分析了不同SOM含量梯度和土壤类型的高光谱特征.其次,基于原...     

Testing a practical indicator for changing soil organic matter

Long-term changes in soil organic carbon (SOC) resulting from management change are documented for many experimental situations, and corresponding trends in the field have been observed by national survey. Since these changes are relevant to atmospheric carbon balance a practical measure to confirm the impact of recent management decisions at any location, without resorting to repeated sampling, is highly attractive but none has previously been tested. This study assessed intra-aggregate C to fulfil the role, based on a temporary deviation from its predictable contribution to total SOC under stable management. A total of 166 surface soil samples (0–15 cm) were analyzed for intra-aggregate C using an established physical fractionation protocol or compatible scaled-up procedure. Soils were arable (or ley-arable) managed by conventional or minimum-tillage, or permanent grassland, and assigned ‘stable’ or ‘changing’ status on the basis of a verbal account of management history. Log-normal populations of intra-aggregate C were compared for soils of stable and changing status using F-tests. Intra-aggregate C shows promise as an indicator of changing SOC in arable soils up to 30% clay content, particularly soils <20% clay. A larger dataset is required to establish its utility in grassland soils. It is not certain that intra-aggregate C is capable of confirming direction of change or trajectory (endpoint), and functions to indicate change, rather than confirm stable status. Supplementary information on the history of soil use and management is therefore essential in the interpretation of such measurements.