贵州雷公山土壤发生学性状的垂直变化特征研究

为了解我国亚热带山地土壤发生学性状随海拔的垂直变化特点,选择位于亚热带常湿润气候区的贵州省雷公山作为研究对象,调查与采样分析了不同海拔高度的17个土壤剖面的理化性状及其与海拔的关系。结果表明,雷公山土壤的众多发生学性状与海拔高度存在显著的相关,随着海拔的升高,呈现土壤矿物质风化减弱而有机质和养分积累增强的变化趋势。表土层厚度、砾石、有机质、全氮和全磷含量、腐殖质的H/F比,土壤粉砂含量、粉黏比、CEC、ba值、氧化铁活化度、黏粒Sa值、黏粒矿物中蛭石和云母相对比例均随海拔的升高而增加;而土体厚度、表土胡敏酸E4/E6比值、土壤黏粒含量、游离氧化铁含量、氧化铁游离度和黏粒矿物中高岭石相对比例则随海拔升高而下降。研究土壤酸化明显,pH和盐基饱和度普遍较低,随海拔升高的变化趋势不明显。研究认为,雷公山地区土壤发生学性状主要受现代成土环境影响,随海拔变化的温度可能是控制这一地区土壤空间变异的主要因素。区内土壤主要发生学性状随海拔升高呈波动状变化,多数发生学性状具有协同变化的特征;不同地理发生学分类土壤带间发生学性状存在一定的差异。根据中国土壤系统分类,研究区土壤类型主要为淋溶土和雏形土,二者也不存在海拔上的明显分界,而呈现复合分布。     

鼎湖山土壤有机质深度分布的剖面演化机制

根据鼎湖山森林植被带(SL)、灌丛—草甸过渡带土壤剖面(GC)有机质含量,有机质Δ14C、δ13C值,土壤粘粒含量及孢粉分析结果,研究华南亚热带山地土壤有机质深度分布特征的成因机制。结果表明土壤有机质的深度分布特征与土壤剖面的发育过程密切相关,随深度增大,有机质的来源数量不断减少,而成土时间增加,分解作用导致的有机质含量降低幅度增大,有机质含量不断减少。土壤有机质14C表观年龄随深度增加,土壤有机质δ13C值与有机质含量的深度变化具有明显对应关系,这些都是土壤剖面发育过程中有机质不同更新周期组分呈规律性分解的结果。粘粒的深度分布反映土壤剖面淋滤淀积的特点,表明土壤剖面经受了长期成土风化。土壤剖面的上述特征均为剖面发育过程中不断沉积、不断成土的结果,表明土壤剖面成土演化对于有机质深度分布具有显著制约。     

华北山地土壤CaCO_3含量/石灰反应垂直分布特征及其发生学解释

为了探究华北山地土壤CaCO_3含量/石灰反应垂直分布特征及其发生学解释,对北京市、山西省257个山地土壤剖面的机械组成、CaCO_3含量和石灰反应进行统计分析。结果表明:华北山地表土的机械组成以粉砂为主,与黄土相似,说明黄土降尘是土壤矿物质的重要来源;海拔1 500m的中山和高山地区的剖面,由于CaCO_3淋洗强,造成无论何种成土母质,CaCO_3被淋洗出土体,土壤通体无石灰反应;海拔介于500~1 500 m的中山地区和低山地区的剖面,CaCO_3淋洗弱,土壤普遍具有石灰反应,成土母质对土壤中CaCO_3含量/石灰反应起主导作用,生物气候条件的影响居于次要地位;海拔500 m的低山丘陵地区的剖面,各土层的CaCO_3含量/石灰反应无明显分布规律。结论:黄土降尘为华北山地表土输入了碳酸钙,但由于不同海拔高度地区土壤湿度存在差异,导致土壤CaCO_3淋溶程度和含量差异明显。淋溶过程强弱导致的土壤CaCO_3含量/石灰反应垂直分布特征是华北山地土壤的典型发生学特征之一,不同海拔高度起主导作用的因素有所不同。研究成果可为华北山地土壤调查、发生与分类研究提供参考。     

不同种植年限设施菜地土壤有机质组成与结构变化

试验采集不同种植年限设施菜地土壤样品,测定土壤有机质(SOM)、可溶性有机碳(DOC)、胡敏酸(HA)、富里酸(FA)、微生物量碳(MBC)、微生物商(C_(mic)-to-C_(org))、C矿化和E4/E6值等指标,结合傅立叶变换红外光谱技术解析不同种植年限土壤有机质组成与结构变化的规律。结果显示,随着种植年限的增加,SOM、DOC、HA、HA/FA、MBC、C_(mic)-to-C_(org)、E4/E6值、C矿化率和CO_2释放速率均出现明显下降趋势,其中MBC、C_(mic)-to-C_(org)、C矿化率、CO_2释放速率和HA/FA在种植6 a时下降最明显,之后变化缓慢。与露天农田土壤(CK)相比,设施菜地呈现较高的SOM、DOC、Humus、HA、FA、HA/FA和E4/E6。胡敏酸红外光谱图谱显示设施菜地种植20 a处理土壤芳构化程度高,结构稳定,难以降解,其他三种种植年限(3 a、6 a和10 a)的芳构化程度相对较低,脂肪族成分相对较高。综上可知,设施菜地土壤有机质组成与结构随着种植年限的增加具有规律性变化,结果加深了对设施菜地土壤有机质演变规律的认知。     

黄土高原区137Cs与土壤颗粒及有机质的关系研究

研究了黄土高原地区土壤颗粒及有机质对137Cs分布的影响以及137Cs与有机质的关系.结果表明,137Cs与土壤颗粒的剖面分布趋势并不一致,而只是与某一粒级在某一深度上表现出一致性.137Cs与有机质的剖面分布则因不同的利用方式而有所差异.对于非耕作土壤,137Cs与有机质主要分布在土壤剖面的表层;而对于耕作土壤,由于人为的耕作作用,137Cs与有机质都均匀分布在耕作层中.土壤中的137Cs含量与有机碳含量的相关分析表明,两者之间呈显著相关,相关系数为0.791.     

大围山花岗岩风化物发育土壤抗蚀性垂直分异

为了研究花岗岩风化物发育土壤抗蚀性垂直分异特征,以湖南省浏阳市大围山花岗岩风化物发育而成的山地土壤为例,选取了土壤的有机质、团聚状况、团聚度、分散率、0.25mm水稳性团粒含量五项抗蚀性指标以及采用EPIC模型计算出土壤的可蚀性K值,对土壤抗蚀性垂直分异特征进行了研究。结果表明:大围山花岗岩风化物发育土壤团聚状况和团聚度随海拔高度的升高呈现递减的趋势,趋势较为显著;土壤分辨率随海拔高度的升高而增大,趋势不显著;有机质含量和0.25mm水稳性团粒含量与海拔相关性很小;土壤可蚀性K值随海拔高度的升高而增大,趋势较显著。大围山花岗岩风化物发育的土壤抗侵蚀能力弱,容易被侵蚀,但因土壤所处地貌部位、山地土壤类型以及植被覆盖情况的不同而产生差异。总体上随海拔高度的升高土壤抗蚀性呈现递减的趋势,但趋势不显著。     

不同海拔蔗区土壤有机质、全氮含量和pH值特征

为明确海拔高度对云南省山地甘蔗土壤有机质、全氮及p H的变化影响,研究了云南省甘蔗种植面积最大的地级市——临沧市甘蔗生产区1 740份土壤样品的有机质、全氮含量和p H值的差异。结果表明:土壤有机质和海拔呈极显著相关关系(γ=0.156**,p0.01),随海拔升高而增加;土壤全氮含量、p H值与海拔无显著相关关系,不随海拔升高而增加。临沧市蔗地土壤有机质含量平均为25.6 g·kg~(-1),变幅为0.3 g·kg~(-1)~79.1 g·kg~(-1),变异系数为41%;土壤全氮平均含量为0.120 g·kg~(-1),变幅0.117 g·kg~(-1)~0.122 g·kg~(-1),变异系数为44%;土壤p H值平均5.3,变幅3.6~8.6,变异系数15%。     

不同母质发育土壤的中红外吸收光谱特征

选取湘东丘陵区四种典型母质发育土壤(酸性紫色土、花岗岩红壤、板岩红壤和第四纪红土红壤),采集剖面(深至母岩/母质层)样品,应用傅里叶变换红外光谱仪研究灼烧去除有机质处理、土层深度和母质类型对土壤中红外吸收光谱特征的影响,分析吸收光谱与土壤理化性质的关系。结果表明,去除有机质后,特征区的中红外吸收值升高,反映矿物质对红外吸收谱线的强烈影响。在剖面上,底土(60~80 cm或100~120 cm)的中红外吸收值高于表土(0~20 cm),与土壤有机质含量的剖面分布相反。四种土壤的中红外光谱均属典型的高岭石图谱。砂粒、粘粒含量与红外吸收值的相关性最好,砂粒含量的最大相关系数(0.51)出现在3700、913和720~540 cm~(-1)附近,粘粒含量的最大相关系数(0.54)出现在1100~694 cm~(-1);本研究表明,原土的中红外吸收光谱特征主要受矿物质的支配,可以很好地反映土壤质地的状况,指示土壤质量变化。     

不同海拔高度下梵净山土壤碳、氮、磷分布特征

为探明梵净山地区海拔高度与土壤性质间的关系,在不同海拔高度采集不同深度土层土样,测定土壤有机质、全氮、全磷、碱解氮、有效磷含量。结果表明:在不同采样深度下,随着土层深度的增加,土壤有机质、全氮、全磷、碱解氮、有效磷以及碳氮比、碳磷比和氮磷比均逐渐下降。在不同海拔高度下,受气候、生物和地形等因素的影响,0—20cm层土壤中有机质、碱解氮含量与海拔高度显著相关,有机质含量随海拔的增加呈先增加后下降的趋势,在海拔1 450m达到最大值,碱解氮含量随海拔的增加而增加;20—40cm层土壤各项指标与海拔高度相关度不紧密;40—60cm层土壤中,有机质、全氮含量、碳磷比、氮磷比与海拔高度显著相关,均随海拔的增加而增加。     

秦岭火地塘林区不同海拔森林土壤理化性质

为了探究海拔高度与土壤理化性质之间的关系,对秦岭火地塘林区不同海拔高度土壤理化性质进行研究。在不同海拔高度设置样地,对土壤进行分层取样,室内测定土壤pH值、有机质、全氮、全磷、全钾、有效氮、有效磷和有效钾含量。结果表明：（1）在不同采样深度下,随着土壤深度增加,除土壤pH值逐渐升高外,有机质、全氮、有效磷和有效钾的含量逐渐降低,其他指标无明显变化规律;（2）土壤pH值、有机质、全氮和有效磷含量与海拔之间有显著的相关关系,土壤pH值随海拔升高先逐渐升高,最高点出现在海拔1 800～2 000m,后随海拔升高逐渐降低;有机质、全氮含量随着海拔升高而升高;有效磷含量随海拔升高而下降;有效氮、全磷、全钾和有效钾的含量和海拔之间不存在明显的相关关系。该林区应结合当地森林植被类型状况,针对不同海拔林地土壤的特点,调整林分模式,改善林地土壤性质,以维护该区林地的可持续发展。     

贵州中部山区植烟土壤有机质含量与海拔和成土母质之间的关系

土壤有机质含量影响着烤烟的产量和品质,与成土母质类型关系密切。本文在贵州中部山区7个烤烟主产县共采集了42个典型烟田耕层多点混合农化样品和来自剖面的165个发生层样品。对土壤有机质含量分析结果表明,贵州中部山区植烟土壤有机质含量的平均值为27.7 g/kg,变幅为24.3~31.6 g/kg,变异系数为9.48%,土壤有机质含量总体处于全国第二次土壤普查肥力评价标准中的三级水平(20~30 g/kg),总体处于植烟适宜水平;贵州中部山区植烟土壤有机质含量与海拔高度呈极显著正相关关系;沟谷堆积物母质发育的土壤有机质含量显著高于第四纪红土和岩类风化残积-坡积物母质发育的土壤;在剖面垂直分布上,土壤有机质含量均表现出较强的表聚性,表现出较明显的从上往下依次递减的规律,不同成土母质发育形成的土壤在相同土层上有机质含量由高到低依次是沟谷堆积物第四纪红土岩类风化残积-坡积物。     

Relation of soil organic matter concentration to climate and altitude in zonal soils of China

With a total of 886 data sets distributed in different regions of China, the relation of soil organic matter (SOM) concentration to climate and altitude was investigated. These data sets were obtained from the 2nd National Soil Survey of China that was completed in early 1980s. According to climate gradient and vegetation community succession, six geographical regions, including eastern, southern, northern, northeastern, northwestern and southwestern China, were divided to identify the key factors regulating surface SOM concentration in different geographical regions. Correlation analysis indicates that surface SOM concentration is in general negatively correlated with annual mean temperature (T) and positively correlated with annual mean precipitation (P) and altitude (H). A further investigation suggested that multiple regression models with different combination of T, P and H could explain 41.5%–56.2% of the variability in surface SOM concentration for different geographical regions, while the driving variables are different. Variables of T and P determined surface SOM concentration in northern, northeastern and northwestern China. In eastern and southern China, variables of P and H are key factors regulating surface SOM concentration. Surface SOM concentration in southwestern China is determined by a linear combination of T, P and H.     

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%。     

Evaluation of Soil Organic Matter Content under Topographic Influences in Agroforestry Ecosystems: a Study in Central Vietnam

Eurasian Soil Science - We investigate the key predictors that influence the soil organic matter (SOM) content in higher altitude plantations. This is to study the potential of carbon sequestration...     

Differences in chemical composition of soil organic matter in natural ecosystems from different climatic regions - A pyrolysis-GC/MS study

Soil organic matter (SOM) is a key factor in ecosystem dynamics. A better understanding of the global relationship between environmental characteristics, ecosystems and SOM chemistry is vital in order to assess its specific influence on carbon cycles. This study compared the composition of extracted SOM in 18 topsoil samples taken under tundra, taiga, steppe, temperate forest and tropical forest using pyrolysis-GC/MS. Results indicate that SOM from cold climates (tundra, taiga) still resembles the composition of litter, evidenced by high quantities of levosugars and long alkanes relative to N-compounds and a clear odd-over-even dominance of the longer alkanes. Under temperate conditions, increased microbial degradation generally results in a more altered SOM chemistry. SOM formed under temperate coniferous forests shows an accumulation of aromatic and aliphatic moieties, probably induced by substrate limitations. Tropical SOM was characterized by an SOM composition rich in N-compounds and low in lignins, without any accumulation of recalcitrant fractions (i.e. aliphatic and aromatic compounds). Lignin composition moreover varies according to vegetation type. Results were validated against 13 new samples. The humic signature of topsoil organic matter formed under different biomes indicates a dominating effect of (i) SOM input composition related to vegetation, and (ii) SOM breakdown reflecting both climate and input quality. No evidence was found for a chemically stabilized SOM fraction under favorable decomposition conditions (temperate or warm climate with broadleaved vegetation).     

Long-term effects of fallow, tillage and manure application on soil organic matter and nitrogen fractions and on sorghum yield under Sudano-Sahelian conditions

Abstract. Soil organic matter (SOM) controls the physical, chemical and biological properties of soil and is a key factor in soil productivity. Data on SOM quantity and quality are therefore important for agricultural sustainability. In 1990, an experiment was set up at Saria, Burkina Faso on a sandy loam Lixisol to evaluate long-term effects of tillage (hand hoeing or oxen ploughing) with or without 10 t ha⁻¹ yr⁻¹ of manure and fallowing on SOM and N concentrations and their distribution in particle size fractions. The field was sown annually to sorghum ( Sorghum bicolor [L.] Moench). Ten years later, total organic C and total N, SOM fractions and their N concentrations, and sorghum yield were determined. Continuous sorghum cultivation without organic inputs caused significant losses of C and N in the hoed and ploughed plots. However, addition of manure to hoed plots was effective in maintaining similar levels of C and N to fallow plots. Without manure, SOM was mainly stored in the size-fraction <0.053 mm (fine organic matter, FOM). SOM was mainly stored in the size-fraction between 0.053 and 2 mm (particulate organic matter, POM). In plots with manure and in fallow plots, the addition of manure more than doubled POM concentrations, with levels in tilled plots exceeding those of the fallow plots, and the highest levels in manually hoed plots. Nitrogen associated with POM (POM-N) followed a similar trend to POM. Hoeing and ploughing led to a decline in sorghum grain yield. Manure application increased yields by 56% in the hoed plots and 70% in the ploughed plots. Grain yield was not correlated with total SOM but was positively correlated with total POM. This study indicated that POM was greatly affected by long-term soil management options.     

Landscape and Land‐Use Effects on the Spatial Variation of Soil Chemical Properties

The current study addressed the spatial variation of soil organic matter (SOM), total nitrogen (TN), extractable phosphorus (EP), and extractable potassium (EK) in agricultural soils of a representative region, northeast China. Soil cation exchange capacity (CEC) and the effects of landscape attributes and land use were also investigated. The techniques used included conventional statistics, geostatistics, and geographic information systems (GIS). Our study demonstrated that EP had the greatest coefficient of variation (CV), and CEC had the least CV. The experimental semivariograms of the five soil chemical properties included in this study were all fitted with exponential models. The five soil variables all showed moderate spatial dependence. The SOM, EK, and CEC decreased with increasing altitude. Significant negative relationships were found between the slope gradient and EP, EK, and CEC. Relatively steeper slopes might result in greater soil erosion, which leads to a decline in soil nutrients. Soil types had significant impacts on all soil chemical properties, which reflect the effect of the parent soil material. In general, the mean values of soil variables for vegetable land were statistically greater than those for upland and paddy fields. After being divided into two parts along the Yinma River, soil samples of the western part have statistically greater SOM, EP, EK, and CEC values than those collected from the eastern part.     

Effects of cropping systems on soil organic matter in a pair of conventional and biodynamic mixed cropping farms in Canterbury, New Zealand

Effects of cropping systems on soil organic matter (SOM) in a pair of conventional and biodynamic mixed cropping farms were investigated. Soil samples (0–75 and 75–150-mm depths) were analysed for total carbon (TC), total nitrogen (TN), microbial biomass C (BC) and microbial biomass N (BN), and sequentially extracted for labile and stable SOM using cold water, hot water, acid mixtures and alkalis. In the biodynamic farm, TC and TN decreased with increasing period of cropping but the reverse occurred under pastures. These were not shown in soils from the conventional farm, probably due to N fertilizer additions. Under pastures, increases in SOM were attributed to greater biological N₂ fixation and the return of plant residues and excreta from grazing animals. Overall, sensitive SOM quality indicators found for labile SOM were BN, BN:TN and HC:TC, and for stable SOM were HCl/HFC, HCl/HFC:TC, humin C, humin N, humin C:TC and humin N:TN. The BN and BN:TN were better indicators than BC and BC:TC. The humin fraction was strongly related to both labile and stable SOM fractions suggesting that humin contained non-extractable strongly complexed SOM components with mineral matter and also non-extractable plant and microbial residual components. Received: 10 October 1996     

How do earthworms influence organic matter quantity and quality in tropical soils?

Earthworms are important regulators of soil structure and soil organic matter (SOM) dynamics; however, quantifying their influence on SOM cycling in tropical ecosystems remains little studied. Simulated rainfall was used to disrupt casts produced by Amynthas khami and their surrounding soil (control) into a range of small sized aggregates (50-250, 250-500, 500-2000 and 2000-5000 μm). To gain insight into how earthworms influence SOM biogeochemical composition in the aggregates, we carried out elemental and stable isotope analysis, and analytical pyrolysis (Py GC/MS). We also characterized their lignin component after oxidation with cupric oxide (CuO).The C content of smaller size fractions (<500 μm) in the control soil was higher than in the larger fractions. Our study therefore suggests that the aggregate hierarchy concept, which is used to understand soil aggregates and SOM dynamics in temperate soils, may not be applicable to the tropical Acrisol studied here. Earthworms modified SOM organization in soil aggregates. Although the isotope analyses were useful for highlighting SOM enrichment in the earthworm casts, aggregate fractions could not be classified according to particle size. Molecular analyses were necessary to indicate that SOM in all size fractions of casts consisted of relatively undecomposed material. Protection of the most labile SOM structures occurred in the smallest aggregate size fraction (50-250 μm). Py GC/MS showed that earthworm casts and control aggregates <2000 μm could be clearly distinguished according to the molecular properties of their SOM. Aggregates larger than 2000 μm, however, were most probably composed of all fractions and were not different. As a consequence, our results indicate that studies to determine the impact of earthworms on SOM turnover in soil are spatially dependant on the scale of observation.     

Chemical composition of young and old carbon pools throughout Cambisol and Luvisol profiles under forests

The long-term storage of soil organic matter (SOM) in forest soils is still poorly understood. In this study, particle size fractionation in combination with accelerator mass spectroscopy (AMS) and solid state ¹³C nuclear magnetic resonance (NMR) spectroscopy was applied to investigate organic carbon (OC) stabilisation in Cambisol and Luvisol profiles under spruce (Picea abies) and beech (Fagus sylvatica L.) forests. In most samples, OC was preferentially associated with <2 μm fractions. Throughout soil profiles the contribution of OC in the clay fraction to the total OC increased from 27%-53% in A horizons to 44-86% in E, B and EB horizons. The 200-2000 μm fractions from all sites and all depths showed a percentage of modern C (pmC)>100. They were enriched in ¹⁴C owing to high inputs of recent material from leaves and roots. Clearly less active material was associated with <2 and 2-20 μm fractions. This demonstrated that the particle size fractionation procedure applied to our study was capable to isolate a young OC fraction in all samples. The pmC values were strongly decreasing with depth but the decrease was much more pronounced in the fine fractions. The <2 and 2-20 μm fractions of B, E and EB horizons revealed radiocarbon ages between 512 and 4745 years before present which indicated that the SOM in those horizons was little affected by the recent vegetation. The major components of labile and stable SOM pools in topsoils and subsoils were always O/N-alkyl C (28-53%) and alkyl C (14-48%) compounds. NMR spectra of bulk soils and particle size fractions indicated that high alkyl C and O/N-alkyl C proportions throughout the soil profile are typical of Cambisols and Luvisols which were not subjected to regular burning. A relation between radiocarbon age and chemical composition throughout soil profiles was not observed. This suggests that the long-term stabilisation of SOM is mainly controlled by the existence of various mechanisms of protection offered by the soil matrix and soil minerals but not by the chemical structure of SOM itself.