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。     

Soil organic matter composition and soil lightness

Relationships between soil lightness, soil organic matter (SOM) composition, content of organic C, CaCO₃, and texture were studied using 42 top‐soil horizons from different soil types located in southern Germany. SOM composition was determined by CPMAS ¹³C NMR spectroscopy, soil color was measured by diffuse‐reflectance spectrophotometry and given in the CIE L*a*b* color coordination system (Commission Internationale de l'Eclairage, 1978). Multiple‐regression analysis showed, that soil lightness of top‐soil horizons is principally determined by OC concentration, but CaCO₃ and soil texture are also major variables. Soil lightness decreased with increasing OC content. Carbonate content had an important effect on soil lightness even at low concentrations due to its lightening property. Regressions between soil lightness and organic C content were strongly linear, when the soils were differentiated according to texture and CaCO₃ content. The aryl‐C content was the only SOM component which correlated significantly with soil lightness (r_S = –0.87). In the linear regressions carried out on the different soil groups, soil aryl‐C content was a more significant predictor for soil lightness than total OC content.     

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。     

Assessing land degradation in the Monduli District,northern Tanzania

One of the many contentious issues facing the appropriate and accurate assessment of land degradation is the varying emphasis placed on vegetation degradation and soil degradation processes. This has led to the compartmentalization of land degradation assessment methods, depending on the particular perspective adopted. The land degradation assessment method presented here attempts to take into account both vegetation and soil degradation. This methodology is applied to the southern part of the Monduli District of northeast Tanzania, an area typifying the so‐called ‘affected drylands’ of Africa. Three sets of land cover maps synchronized against long‐term rainfall data (1960s, 1991 and 1999) were used to assess land degradation in the area. Utilizing these three sets of land cover maps as a basis for change detection, it is possible to distinguish areas that experienced changes in vegetation due to rainfall variability from those areas that were subject to changes consequent upon anthropological factors. All areas that displayed overall depletion of natural and semi‐natural vegetation due to human factors were deemed to have undergone land degradation, whereas areas that experienced inter‐annual land cover changes due to rainfall variability were classified as experiencing cover change due to ecosystem dynamics. This method provides a complete and appropriate assessment of land degradation in the study area and can be used to improve degradation assessment in other semiarid areas. Copyright © 2006 John Wiley & Sons, Ltd.     

黑土典型区土壤有机质遥感反演

土壤有机质（SOM）含量时空变异规律研究对于土壤肥力评价、土壤碳库估算、土壤资源利用与保护具有重要意义,而地貌、成土母质、土壤类型等差异、高光谱卫星影像较少等因素制约了区域尺度的SOM含量遥感反演方法研究的开展。该文以黑龙江省黑土带典型区为例,采集区域土壤样本,获取Landsat TM遥感影像,基于有机质含量与土壤反射率的定量关系,建立区域SOM遥感预测模型。结果表明：黑土区SOM含量高,一般大于2%,决定了有机质对土壤反射光谱特性的主要作用,而且该区SOM空间变异性显著,且耕作方式、气候等因素决定了裸土时间长,因而该区适于SOM含量遥感反演;有机质与TM各波段反射率均显著相关,最大相关系数在第3波段（0.63～0.69 μm）,为-0.710,其次为4波段（0.76～0.90 μm）,与实验室基于高光谱反射率数据分析的结果一致;基于TM影像2、3、4波段的SOM指数模型最优,预测精度高、稳定性好,可以用于揭示黑土典型区SOM含量的空间分布特征。该研究将为改进土壤理化参数遥感反演、土地质量评价、土壤碳库估算等工作方法提供理论与技术支持。     

Storage and stability of organic matter and fossil carbon in a Luvisol and Phaeozem with continuous maize cropping: A synthesis

Quantitative information about the amount and stability of organic carbon (OC) in different soil organic‐matter (OM) fractions and in specific organic compounds and compound‐classes is needed to improve our understanding of organic‐matter sequestration in soils. In the present paper, we summarize and integrate results performed on two different arable soils with continuous maize cropping (a) Stagnic Luvisol with maize cropping for 24 y, b) Luvic Phaeozem with maize cropping for 39 y) to identify (1) the storage of OC in different soil organic‐matter fractions, (2) the function of these fractions with respect to soil‐OC stabilization, (3) the importance and partitioning of fossil‐C deposits, and (4) the rates of soil‐OC stabilization as assessed by compound‐specific isotope analyses. The fractionation procedures included particle‐size fractionation, density fractionation, aggregate fractionation, acid hydrolysis, different oxidation procedures, isolation of extractable lipids and phospholipid fatty acids, pyrolysis, and the determination of black C. Stability of OC was determined by ¹³C and ¹⁴C analyses. The main inputs of OC were plant litter (both sites) and deposition of fossil C likely from coal combustion and lignite dust (only Phaeozem).     

沱江流域中游土壤有机质的空间变异特点及其影响因素

土壤有机质(SOM)是陆地生态系统中碳循环的重要源与汇[1-3]。其不仅能提高土壤肥力和生产力,且其对碳的固定也是人类应对大气CO2浓度升高的重要途径[4-5]。在区域尺度上,土壤有机质主要受气候、土地利用方式、地理因素如海拔高度、坡度和质地等差异的影响[6-9]。且不同自然地理条件和社会经济发展水平的区域,其土壤有机质的主要影响因素及其影响程度也会有所差异[10-12]。     

Soil organic matter and sorption capacity under different soil management practices in a productive vineyard

The effect of soil organic matter (SOM) on sorptive parameters under different soil management practices in Rendzic Leptosol was studied. In 2006, an experiment of different management practices in a productive vineyard was established in the locality of Nitra-Dra?ovce (Slovakia). The following treatments were established: (1) control (grass without fertilization), (2) T (tillage), (3) T + FYM (tillage + farmyard manure), (4) G + NPK3 (grass + 3rd intensity of fertilization for vineyards), (5) G + NPK1 (grass + 1st intensity of fertilization for vineyards). Soil samples were collected every month during the year 2010. Obtained results showed increased hydrolytic acidity (by 23%), sum of basic cations (by 37%) and decreased total cation exchange capacity (CEC) (by 36%) with higher doses of fertilization in comparison to control. Application of farmyard manure had a positive effect on the increase in the SOM cation sorption capacity. Positive correlations between pH and sum of basic cations (SBC) (r = 0.493, p ≤ 0.001), CEC (r = 0.498, p ≤ 0.001) and cation sorption capacity of SOM (r = 0.391, p ≤ 0.01) were observed. Higher values of labile carbon:potentially mineralizable nitrogen (C_L:N_pot) ratio corresponded with lesser CEC, SBC and base saturation values in the soil. With increased humus quality (higher values of humic acid:fulvic acid (C_HA:C_FA) ratio), cation sorption capacity of SOM significantly increased (r = 0.329, p ≤ 0.01). The results of this study proved that the application of farmyard manure had a positive effect on the increase of SOM sorption capacity, but higher doses of mineral fertilizers added to soil had a negative effect.     

C and N NMR spectroscopy as a tool in soil organic matter studies

Nuclear magnetic resonance (NMR) is a valuable tool for the characterization of soil organic matter and humification processes in soils. This review highlights soil organic matter studies based mainly on solid-state ¹³C and ¹⁵N NMR spectroscopy and some emerging applications, that may provide significant progress in our knowledge on soil organic matter. A major advantage of Nmr spectroscopy is that it can be used as a non-invasive method for solid soil samples or soil fractions. Although resolution is limited, one can obtain an overview on the organic matter structures present in the soil sample. Application of ¹³C and ¹⁵N NMR to soils has, for a long time, been confined to the study of bulk soils or humic extracts for structural characterization. The transformations of soil organic C and N are now being investigated after addition of ¹³C- and ¹⁵N-labelled parent materials to the soil and following their evolution in different C and N pools. With labelling techniques it is also possible to study the interaction of organic pollutants with soil organic matter. Contamination of a soil with man-made additives, such as soot or brown coal dust, can also be detected in soils or individual soil fractions.     

Labile and stable pools of organic matter in soil amended with sewage sludge biochar

One of the main advantages of using biochar for agricultural purposes is its ability to store carbon (C) in soil for a long-term. Studies of labile and stable fractions of soil organic matter (SOM) may be a good indicator of the dynamics of biochar in soils. This study evaluated the effects of applying sewage sludge biochar (SSB) in combination with mineral fertilizer on fractions of SOM. To conduct this evaluation, 15 Mg ha^?1 of SSB combined or not with mineral fertilizer (NPK) was applied to the soil in two cropping seasons. Apart from total organic C (TOC), the labile and stable fractions of SOM were also determined. The combined use of SSB and NPK resulted in higher TOC, a 22% to 40% increase compared to the control and to the NPK treatments, respectively. The SSB produced at a lower temperature increased the labile fractions of SOM, especially the microbial biomass C, showing its capacity to supply nutrients in the short-term. The stable pools of SOM are increased after adding SSB produced at a higher temperature. It was concluded that pyrolysis temperature is a key-factor that determines the potential of SSB to accumulate C in labile and stable fractions of SOM.     

土壤有机质空间变异与农用地自然质量关系研究

该文以广州市花都区赤坭镇为试验区,根据典型农用地类型的土壤采样基于Cokriging方法进行土壤有机质精确插值与空间变异分析,并将结果与农用地分等成果进行相关分析。结果表明,以土壤有机质和农用地类型为协因子的球状模型Cokriging总体插值精度最高,试验区内土壤有机质分布格局是四周丘陵和水库区含量较低,巴江河两岸的平原地区、西南角的山前冲积平原含量较高,这也是灌溉水田密集的区域;试验区内土壤有机质含量菜地分布比较均匀、空间相关性很强,而水浇地分布差异较大、空间变异性较高;土壤有机质分布在南北、东北-西南两个方向相关性较强具有各向同性特征,在东南-西北、东西方向具有各向异性特征,受到随机因素的影响变异性较大。土壤有机质Cokriging插值结果与试验区内农用地自然质量等指数的相关性很显著,菜地与农用地自然质量等指数相关性最强,灌溉水田其次,旱地最差。     

Soil organic matter content and chemical composition under two rotation management systems in a Mediterranean climate

The crop rotation system in organic farming is a determinant factor to accumulate and preserve soil organic matter (SOM), and in depth knowledge on its effects is still lacking. Tillage intensity in particular is crucial to maintain soil aggregates and protect SOM from degradation. The evolution of SOM was tested in two adjacent fields under two different rotation cropping systems (low-intensity tillage and high-intensity tillage), and the effect of a further cultivation of legume in both fields was evaluated using ¹³carbon (C)-nuclear magnetic resonance (NMR) and elemental analysis of samples isolated through combined aggregate size and density fractionation. The two adjacent fields had been managed using the following organic farming methods for 13 seasons since 1998: i) alfalfa-based, with nitrogen (N) enrichment and low-frequency tillage with alfalfa (Medicago sativa) (9 seasons), winter wheat (Triticum durum) (3 seasons), and broad bean (Vicia faba) (1 season) and ii) cereal-based, with N depletion and annual tillage with barley (Hordeum vulgare) (7 seasons), sunflower (Helianthus annuus) (2 seasons), broad bean (Vicia faba) (3 seasons), and bare fallow (1 season). Soil sampling was carried out at the end of the 13-year rotation (T0, November 2011) and after winter wheat and chickpea cultivation in both fields over two subsequent years (T1, July 2013). Bulk organic C was significantly higher in the alfalfa-based system than in the cereal-based system at both T0 and T1, with SOM occluded in soil aggregates and associated with mineral particles. In terms of the macroaggregates heavy fraction at T0, the alfalfa-based field contained twice the organic C of that in the cereal-based field, as well as three times the organic C in the occluded particulate organic matter (POM). The occluded POM (oPOM) had a lower aryl/O-alkyl C ratio in the alfalfa-based system than in the cereal-based system, suggesting that oPOM undergoes a lower degree of decomposition during low-intensity management. The aryl/O-alkyl C ratios of the macro-and microaggregate oPOM decreased from T0 to T1 in the cereal-based system, suggesting increased protection of these fractions by soil aggregates. Thus, including legumes in crop rotation appears to positively affect the accumulation of SOM associated with mineral particles and within soil aggregates.     

Near‐infrared spectroscopy can predict the composition of organic matter in soil and litter

The usefulness and limitations of near‐infrared reflectance spectroscopy (NIRS) for the assessment of several soil characteristics are still not sufficiently explored. The objective of this study was to evaluate the ability of visible and near‐infrared reflectance (VIS‐NIR) spectroscopy to predict the composition of organic matter in soils and litter. Reflectance spectra of the VIS‐NIR region (400–2500 nm) were recorded for 56 soil and litter samples from agricultural and forest sites. Spectra were used to predict general and biological characteristics of the samples as well as the C composition which was measured by ¹³C‐CPMAS‐NMR spectroscopy. A modified partial least‐square method and cross‐validation were used to develop equations for the different constituents over the whole spectrum (1st to 3rd derivation). Near‐infrared spectroscopy predicted well the C : N ratios, the percentages of O‐alkyl C and alkyl C, the ratio of alkyl C to O‐alkyl C, and the sum of phenolic oxidation products: the ratios of standard deviation of the laboratory results to standard error of cross‐validation (RSC) were greater than 2, the regression coefficients (a) of a linear regression (measured against predicted values) ranged from 0.9 to 1.1, and the correlation coefficients (r) were greater than 0.9. Satisfactorily (0.8 ≤ a ≤ 1.2, r ≥ 0.8, and 1.4 ≤ RSC ≤ 2.0) assessed were the contents of C, N, and production of DOC, the percentages of carbonyl C and aromatic C and the ratio of alkyl C to aromatic C. However, the N‐mineralization rate and the microbial biomass were predicted unsatisfactorily (RSC < 1.4). The good and satisfactory predictions reported above indicate a marked usefulness of NIRS in the assessment of biological and chemical characteristics of soils and litter.     

Colluvisols under cultivation in Schleswig-Holstein. 3. Soil organic matter transformation after translocation

‘Colluvisols’ (Colluvi-cumulic Anthrosols) are an important soil unit in North Germany. In the landscape of loamy till these soils are associated with eroded Luvisols. The soil organic matter (SOM) of top layers of both soils was compared by using approaches of wet chemistry, CPMAS ¹³C-NMR and pyrolysis field-ionization mass spectrometry (Py-FIMS). The Luvisols are sources of SOM transfer due to a continuous erosion process. The annual input of straw and plant residues induces the dominance of litter compounds like proteins, polysaccharides and lignin in the SOM. The Colluvisols are sinks of SOM transfer with a predominance of humic compounds. Lignin is degraded forming humic compounds with an alkylic and aromatic structure. In these soils selected compounds with higher mass signals were detected by Py-FIMS, which may indicate the existence of typical “SOM markers” in the colluvic materials.     

基于HJ卫星的棉田土壤有机质空间分布格局反演

以北疆绿洲区棉田表层土壤为研究对象,利用国产HJ-1A/1B卫星CCD多光谱数据对裸土有机质空间分布格局进行研究。通过分析多光谱数据不同波段的光谱反射率及其变换形式与实地采样得到的土壤有机质含量的相关性,探寻适合绿洲区棉田表层土壤有机质含量快速反演的敏感波段及参数,并针对不同参数分别建立一元线性、二次、三次、对数、倒数、幂函数、生长型、S型回归模型,以及多元回归模型;对生成的模型进行综合对比分析,获取北疆绿洲区棉田表层土壤有机质含量的最佳反演模型,从而实现整个研究区土壤有机质空间格局的遥感反演。结果表明:HJ卫星多光谱数据4个波段的反射率均与土壤有机质含量存在显著的相关性,第3波段的倒数与土壤有机质含量相关性最为显著;且以第3波段光谱反射率作为因变量得到的三次线性回归模型对土壤有机质含量进行反演的效果最佳;通过空间布局反演得到研究区土壤有机质空间分布整体呈现南北两端有机质含量较高,中部有机质含量较低的格局。该研究表明虽然与黑土有机质含量具有差别,但是遥感技术仍能够作为绿洲区土壤有机质含量空间布局反演的方法,为遥感技术在土壤参数监测中更好的发挥作用提供理论支持,同时也为新疆棉田生产管理和农田可持续利用提供科学依据。     

Soil organic matter dynamics in lands continuously cultivated with maize and soybean in Heilongjiang Province,Northeast China: Estimation from natural 13C abundance

Abstract

Northeast China is the main production area of maize and soybean in China. In the present study, the rates of decomposition and replacement of soil organic carbon (SOC) were estimated using the soil inventory collected since 1991 from long-term maize and soybean cultivation plots in Heilongjiang Province, Northeast China, to evaluate the sustainability of the present cultivation system. The total carbon (C) content in soil was stable without any significant changes in the plots (approximately 28.5 g C kg^?1). The δ¹³C value of soil organic matter under continuous maize cultivation increased linearly with an annual increment of 0.07 from ?23.9 in 1991, which indicated that approximately 13% of the initial SOC was decomposed during the 13-year period of maize cultivation, with a half-life of 65 years. Slow decomposition of SOC was considered to result from the low annual mean temperature (1.5°C) and long freezing period (170–180 days year^?1) in the study area. In contrast, the amount of organic C derived from maize increased in the soil with a very slow annual increment of 0.17 g C kg^?1, probably because of the removal of all the plant residues from the plots. Based on the soil organic matter dynamics observed in the study plots, intentional recycling/maintenance of plant residues was proposed as a way of increasing soil fertility in maize or soybean cultivation.     

Soil development on restored opencast coal sites with particular reference to organic matter and aggregate stability

Abstract. Organic indices and aggregate stability were measured in soils of similar texture on two restored opencast coal sites and on adjacent, undisturbed land in South Wales, UK. The aim was to assess rates of soil change over time, to relate these changes to conditions in undisturbed land and to evaluate organic-aggregation relationships across these range of soils. Several management factors were included in the comparisons.
Organic matter accumulated at the surface (0–7.5 cm) of restored soils, contents being greater than undisturbed soils after 21 years. However, this increase in total organic matter did not result in proportionate increases in carbohydrates and microbial biomass, nor did aggregate stability increase to the degree expected. Between 7.5 and 15 cm depth, rates of change were slower. Microbial metabolic quotient and respiration relative to total soil C were highest in recently (9 years) restored soils, intermediate in 21 year old restored soils and least for undisturbed soils.
Sewage (100t/ha) applied at reinstatement improved clay stability but had little effect on other parameters when measured 9 years later. Drainage of soils restored in 1972 reduced total organic content but its influence on other organic indices was more complex. Carbohydrate contents had the closest association with aggregate stability and microbial biomass.
Although the productivity of restored land may recover more quickly, findings suggest that rehabilitation of normal soil processes following surface mining may take much longer than the normal five year aftercare period.     

稻田垄作免耕对土壤团聚体和有机质的影响

该文以1990年建立的耕作制定位试验田紫色水稻土为研究对象,分析了冬水田（FPF）、水旱轮作（CR）和垄作免耕（RNT）3种耕作方式对土壤团聚体组成和有机质的影响。结果表明,垄作免耕减少了对土壤大团聚体的破坏,在0～10 cm土层,垄作免耕大团聚体含量分别是冬水田和水旱轮作的1.48和1.32倍,微团聚体含量则显著降低;在 ＞10～20 cm土层有相同的趋势。3种耕作条件下,有机碳和氮在团聚体中的分布模式类似,均有向大团聚体富集的趋势,但垄作免耕条件下土壤有机碳和氮质量分数显著高于冬水田和水旱轮作。对土壤颗粒有机质（POM）的分析结果表明,垄作免耕0～10 cm土层轻质组分（LF）的质量分数（1.92 g/kg）与水旱轮作（1.70 g/kg）差异不显著,但显著高于冬水田（1.42 g/kg）。冬水田、水旱轮作和垄作免耕的0～10 cm土层,团聚体内总颗粒有机质（total iPOM）质量分数分别为0.96,1.12,2.14 g/kg;垄作免耕土壤团聚体内细颗粒有机质（fine iPOM）分别为冬水田和水旱轮作土壤的3.02和2.46倍,占总POM差异的57%和66%。垄作免耕土壤团聚体内粗颗粒有机质（coarse iPOM）分别为冬水田和水旱轮作土壤的1.56和1.40倍,占总POM差异的18%和19%。在＞10～20 cm土层有相似的趋势,但在＞10～20 cm层土壤粗iPOM的差异对总POM差异的贡献较0～10 cm层大。垄作免耕减少了对大团聚体的破坏并促进微团聚体向大团聚体团聚;降低了团聚体的周转速率,促进了细iPOM的固定,利于紫色水稻土对碳的固定和积累。