新疆艾比湖流域土壤有机质的空间分布特征及其影响因素

根据新疆艾比湖流域土壤有机质(SOM)数据,分析了土壤质地、植被群落类型和土壤剖面深度3个因素对SOM含量的影响,进一步研究了流域内有机质在不同土壤深度的空间分布特征及其沿土壤剖面深度垂直分布的空间异质性。结果表明:植被群落类型显著影响SOM含量,而土壤质地和深度对有机质总体分布水平影响不显著;随土壤深度变化有机质分布呈现不同的空间变异特征,流域内0—80 cm土壤有机质高含量区域与低含量区域斑块化分布呈现孔穴特征,但在80—120 cm土壤有机质含量变化较为连续,呈现流域东、西两端高而中间低的分布特征;有机质沿土壤深度垂直分布模式在流域内表现出分异特征,流域中部SOM随土壤深度增加而降低,SOM含量从0—20 cm浅层土壤的2.85 g/kg降至100—120 cm深层土壤的1.51 g/kg;但在流域东部和西部SOM随土壤深度增加呈升高趋势,流域西部SOM含量从0—20 cm土壤的1.80 g/kg大幅增加至100—120cm土壤的6.61 g/kg,流域东部SOM含量则从0—20 cm土壤的1.04 g/kg逐步增至100—120 cm土壤的2.86g/kg。艾比湖流域有机质在浅层和深层土壤不同的空间分布特征与干旱区绿洲生态景观斑块化分异特征和植被根际沉积特点密切相关,流域内土壤剖面成土演化的空间异质性对有机质沿土壤深度垂直分布的空间变异性有显著制约。     

华南亚热带山地土壤有机质更新特征及其影响因子

选择鼎湖山自然保护区及中国科学院华南植物研究所小良生态站6个土壤剖面,根据土壤有机质碳稳定同位素特征、^14C放射性水平、有机质含量、粒度特征,研究土壤有机质更新特征及其制约因素。结果表明,土壤有机质分解呈明显阶段性：有机质快速分解发生在0－100a之内,自地表向下,有机质含量急剧降低,因碳同位素分馏效应,有机质δ^13C值迅速增加;至170／240a,有机质δ^13C值达最大;自170／240－800／1400a,有机质分解速度变慢,有机质含量缓慢降低,因高δ^13C值组分分解,δ^13C值逐渐减小;约在1500a之后,有机质含量变化甚微,δ^13C值趋于稳定。对比研究表明,粘粒对有机质赋存状态及其更新有直接影响,粒度是制约土壤有机质动态的重要因子;地表植被类型及其发育特征直接影响土壤有机质更新,在植被类型相似情况下,植被覆盖史对土壤剖面有机质动态有明显影响。     

减少降雨对杉木幼林土壤有机质组分及稳定性的影响

由于土壤有机质(SOM)化学结构上的异质性,其对于全球气候变化的响应变得难以预测.随着分子水平技术逐渐应用于SOM结构、来源及分解状态的研究,长久以来关于SOM组分及稳定性的问题可能将被解决.本研究通过两年的减少降雨(50%)处理,运用生物标志物技术,对杉木幼林SOM组分及分解程度进行研究,以探究降水格局的改变对亚热带杉木幼林SOM稳定性的影响.结果表明: 减少降雨处理显著降低了土壤中游离脂质的含量,分别降低了短链烷酸的62.8%和萜类及固醇类含量的19.1%,而对其他脂类无显著影响.尽管短期减少降雨处理并未影响土壤中木质素总量,却显著降低了紫丁香基和香草基的酸醛比值.因此,随着降雨格局的改变,可能加快SOM易分解组分分解.尽管难分解组分(木质素)相对稳定,但从长远来看,其稳定性还需持续监测.     

一种青海湖流域消除植被光谱对土壤光谱影响的土壤有机质含量遥感估算方法

基于遥感技术手段快速测定区域尺度土壤有机质含量(SOM), 对气候、陆地生态系统和农业等领域具有重要的作用和意义。但现有的多光谱遥感影像因其波段宽度较窄, 包含的土壤有机质信息有限, 导致其估算结果的可靠性与精度较低。为此, 以青海湖流域为实证试验区, 将2016 年9 月底(此时, 青海湖流域牧草等植被停止生长, 土壤有机质积累达到全年最高)地面采集并测定的土壤有机质含量数据与同时期MODIS 黑空BRDF/Albedo 产品的宽、窄波段进行了对比与检验。发现: BRDF/Albedo 宽波段的相关性(近红外、短波波段相关系数分别为0.704 和 0.670)高于窄波段相关性(第2, 5, 6 波段的相关系数分别是0.583、0.631 和0.625), 证实了宽波段含有更加丰富、完整的土壤有机质含量信息。为了进一步提高SOM 估算的精度, 基于梯形方法构建了宽波段近红外反照率/植被覆盖度梯形特征空间,从宽波段近红外反照率(包含植被、土壤混合光谱)中成功分离出裸土反照率, 并分别构建了SOM 遥感估算模型。经验证,消除了植被对土壤光谱影响的裸土反照率模型精度(均方根误差为16.87、平均绝对百分比误差为30.0%, 希尔不等系数为0.22)高于宽波段近红外反照率模型精度(均方根误差为20.12、平均绝对百分比误差为31.0%, 希尔不等系数为0.27)。该方法简单易操作, 不仅有助于提高表层土壤有机质含量遥感估算的精度, 也可为土壤其他属性如N, P等元素含量的遥感估算提供了新思路。     

基于小波变换的土壤有机质含量高光谱估测术

利用统计分析方法选取了土壤N、P、K元素含量近似而有机质含量差异较大的样本60个,通过高光谱探测分析获得样本反射率对数的一阶导数光谱,采用Bior 1.3函数进行多层离散小波分解,剔除低频近似信号和高频噪声信号,得到反映土壤理化参数的特征光谱曲线;采用相关分析筛选土壤有机质含量的显著相关波段,基于显著相关波段和特征光谱曲线分别构建土壤有机质含量高光谱多元回归估测模型;通过比较分析,确定了提取土壤有机质特征光谱的最佳小波分解尺度并构建了最佳预测模型.结果表明:提取土壤有机质特征光谱的最佳小波分解层数是9层,其次是8层和10层;基于小波9层分解特征光谱曲线的有机质含量估测模型最佳,其决定系数(R2)为0.89,比基于显著相关波段构建模型的R2增加了0.31,比基于原始光谱所构建模型的R2增加了0.10.     

纳帕海高原湿地不同干扰强度下土壤真菌的分布格局

将无干扰的原生沼泽作为对照, 运用比较法研究了纳帕海高原湿地不同干扰强度下形成的湿地利用类型, 即沼泽(无干扰)、沼泽化草甸(轻度干扰)、草甸(中度干扰)和垦后湿地(重度干扰) 4个湿地利用类型的碳氮含量及其分布格局, 揭示干扰对纳帕海不同湿地利用类型碳氮及土壤真菌分布的影响。研究表明: (1) 4个湿地利用类型上下层土壤有机质(SOM)、全氮(TN)、碳氮比(C:N)和pH值均有显著的差异性(p < 0.01), 并且随着干扰强度的增大, SOM和TN含量逐渐减少。(2)土壤真菌经PDA培养基培养后计数, 在同一湿地类型上层的真菌数量大于下层, 随着干扰强度的增加, 真菌的数量逐渐增加。相关性分析表明: 真菌的数量与pH值、SOM和TN呈极显著负相关, 与C:N呈显著正相关。(3)系统发育研究表明: 纳帕海湿地分布有土壤真菌Ascomycota、Basidiomycota和Zygomycota, 其中Ascomycota是优势类群, 在高原湿地土壤碳氮分解等物质循环过程中Ascomycota处于主导地位。     

石灰和EM处理条件下土壤动物群落在落叶分解中的变化

2003年6月至2005年10月,用石灰和EM处理改变土壤微酸性特性和微生物活性,采用网袋分解法对大兴安岭地区土壤动物群落结构在落叶分解过程中的动态变化进行了研究。结果如下:(1) 土壤动物群落个体数、类群数和DG指数仍表现为季节波动性,气候因子是影响研究区土壤动物群落长期动态变化的重要因素,石灰和EM处理未改变这种规律。(2)处理条件下土壤动物在落叶分解过程中仍具有阶段性特征,且各类群集聚时间有所差异。(3) CCA排序分析表明,土壤pH值和有机质是影响土壤动物群落动态变化的重要因素,中气门亚目、前气门亚目、节跳虫科、甲螨亚目、绫跳虫科、山跳虫科、棘跳虫科、鳞跳虫科和石蜈蚣目对土壤pH值和有机质变化具有较强的适应能力。     

模拟N沉降下不同林龄马尾松林凋落叶分解-土壤C、N化学计量特征

模拟N沉降对森林生态系统的影响是当今全球变化生态学研究的一个热点问题,土壤碳库对N沉降比较敏感,N沉降增加了凋落叶分解过程中外源N含量,间接影响凋落叶分解的化学过程并改变凋落叶分解速率,因此,研究模拟N沉降下凋落叶分解-土壤C-N关系对预测森林C吸存有重要意义。利用原位分解袋法研究了模拟N沉降下三峡库区不同林龄马尾松林(Pinus massoniana)凋落叶分解过程中凋落叶-土壤C、N化学计量响应及其关系;N沉降水平分对照(CK,0 g m~(-2)a~(-1))、低氮(LN,5 g m~(-2)a~(-1))、中氮(MN,10 g m~(-2)a~(-1))和高氮(HN,15 g m~(-2)a~(-1))。结果表明:分解540 d后,N沉降促进20年生和30年生马尾松林凋落叶分解,46年生马尾松林中仅低氮处理促进凋落叶分解,4种处理均是30年生分解最快,说明同一树种起始N含量低的凋落叶对N沉降呈正响应,N沉降处理促进起始N含量低的凋落叶分解,起始N含量高的凋落叶分解过程中易达到"N饱和"。N沉降抑制20年生和46年生凋落叶C释放(低于对照0.62%—6.69%),促进30年生C释放(高于对照0.28%—5.55%);30年生和46年生林分N固持量均高于对照(高于对照0.15%—21.34%),20年生则低于对照(5.70%—13.87%),说明模拟N沉降处理促进起始C含量低的凋落叶C释放和起始N含量低的凋落叶N固持。N沉降处理下仅30年生马尾松林土壤有机碳较对照增加,且土壤有机质与凋落叶C、N和分解速率呈正相关,与凋落叶C/N比呈显著负相关;土壤总氮与凋落叶分解速率、凋落叶N含量呈正相关,土壤有机碳/总氮比与凋落叶C、N含量呈正相关;对照处理中凋落叶分解指标对土壤养分影响顺序是分解速率凋落物C含量凋落物C/N比凋落物N含量,低、中、高氮处理中则是凋落物C含量分解速率凋落物N含量凋落物C/N比。研究表明低土壤养分含量马尾松林对N沉降呈正响应,N沉降促进低土壤养分马尾松林凋落叶分解并提高土壤肥力;凋落叶质量和土壤养分含量低的生态系统土壤C对N沉降响应更显著。     

基于小波变换的土壤有机质含量高光谱估测

利用统计分析方法选取了土壤N、P、K元素含量近似而有机质含量差异较大的样本60个,通过高光谱探测分析获得样本反射率对数的一阶导数光谱,采用Bior 1.3函数进行多层离散小波分解,剔除低频近似信号和高频噪声信号,得到反映土壤理化参数的特征光谱曲线;采用相关分析筛选土壤有机质含量的显著相关波段,基于显著相关波段和特征光谱曲线分别构建土壤有机质含量高光谱多元回归估测模型;通过比较分析,确定了提取土壤有机质特征光谱的最佳小波分解尺度并构建了最佳预测模型.结果表明： 提取土壤有机质特征光谱的最佳小波分解层数是9层,其次是8层和10层;基于小波9层分解特征光谱曲线的有机质含量估测模型最佳,其决定系数（R²）为0.89,比基于显著相关波段构建模型的R²增加了0.31,比基于原始光谱所构建模型的R²增加了0.10.     

干湿交替条件下土壤氨基糖含量的动态变化

通过室内模拟培养试验,研究了恒湿和干湿交替条件下土壤中3种微生物来源氨基糖含量的动态变化,并且利用氨基葡萄糖和胞壁酸的比值分析了干湿交替条件下土壤真菌和细菌对土壤有机质转化的相对贡献.结果表明:恒湿条件下,细菌来源的胞壁酸在土壤中的分解速率大于真菌来源的氨基葡萄糖,氨基半乳糖在土壤中的分解速率较慢;干湿交替改变了土壤中3种氨基糖的分解特征,与恒湿处理相比,干湿交替培养前期以胞壁酸为代表的细菌残余物的分解速率高于以氨基葡萄糖为代表的真菌残余物,随着干湿交替频率的增大,以氨基葡萄糖为代表的真菌残余物分解速率高于以胞壁酸为代表的细菌残余物.可见,干湿交替条件改变了以氨基糖为代表的土壤氮素的微生物转化过程.     

Stabilization mechanisms of soil organic matter: Implications for C-saturation of soils

The relationship between soil structure and the ability of soil to stabilize soil organic matter (SOM) is a key element in soil C dynamics that has either been overlooked or treated in a cursory fashion when developing SOM models. The purpose of this paper is to review current knowledge of SOM dynamics within the framework of a newly proposed soil C saturation concept. Initially, we distinguish SOM that is protected against decomposition by various mechanisms from that which is not protected from decomposition. Methods of quantification and characteristics of three SOM pools defined as protected are discussed. Soil organic matter can be: (1) physically stabilized, or protected from decomposition, through microaggregation, or (2) intimate association with silt and clay particles, and (3) can be biochemically stabilized through the formation of recalcitrant SOM compounds. In addition to behavior of each SOM pool, we discuss implications of changes in land management on processes by which SOM compounds undergo protection and release. The characteristics and responses to changes in land use or land management are described for the light fraction (LF) and particulate organic matter (POM). We defined the LF and POM not occluded within microaggregates (53–250 m sized aggregates as unprotected. Our conclusions are illustrated in a new conceptual SOM model that differs from most SOM models in that the model state variables are measurable SOM pools. We suggest that physicochemical characteristics inherent to soils define the maximum protective capacity of these pools, which limits increases in SOM (i.e. C sequestration) with increased organic residue inputs.     

Priming effect and microbial diversity in ecosystem functioning and response to global change: a modeling approach using the SYMPHONY model

Integration of the priming effect (PE) in ecosystem models is crucial to better predict the consequences of global change on ecosystem carbon (C) dynamics and its feedbacks on climate. Over the last decade, many attempts have been made to model PE in soil. However, PE has not yet been incorporated into any ecosystem models. Here, we build plant/soil models to explore how PE and microbial diversity influence soil/plant interactions and ecosystem C and nitrogen (N) dynamics in response to global change (elevated CO₂ and atmospheric N depositions). Our results show that plant persistence, soil organic matter (SOM) accumulation, and low N leaching in undisturbed ecosystems relies on a fine adjustment of microbial N mineralization to plant N uptake. This adjustment can be modeled in the SYMPHONY model by considering the destruction of SOM through PE, and the interactions between two microbial functional groups: SOM decomposers and SOM builders. After estimation of parameters, SYMPHONY provided realistic predictions on forage production, soil C storage and N leaching for a permanent grassland. Consistent with recent observations, SYMPHONY predicted a CO₂‐induced modification of soil microbial communities leading to an intensification of SOM mineralization and a decrease in the soil C stock. SYMPHONY also indicated that atmospheric N deposition may promote SOM accumulation via changes in the structure and metabolic activities of microbial communities. Collectively, these results suggest that the PE and functional role of microbial diversity may be incorporated in ecosystem models with a few additional parameters, improving accuracy of predictions.     

The sources and distribution of carbon (DOC,POC, DIC) in a mangrove dominated estuary (French Guiana,South America)

Improved quantification of the factors controlling soil organic matter (SOM) stabilization at continental to global scales is needed to inform projections of the largest actively cycling terrestrial carbon pool on Earth, and its response to environmental change. Biogeochemical models rely almost exclusively on clay content to modify rates of SOM turnover and fluxes of climate-active CO₂ to the atmosphere. Emerging conceptual understanding, however, suggests other soil physicochemical properties may predict SOM stabilization better than clay content. We addressed this discrepancy by synthesizing data from over 5,500 soil profiles spanning continental scale environmental gradients. Here, we demonstrate that other physicochemical parameters are much stronger predictors of SOM content, with clay content having relatively little explanatory power. We show that exchangeable calcium strongly predicted SOM content in water-limited, alkaline soils, whereas with increasing moisture availability and acidity, iron- and aluminum-oxyhydroxides emerged as better predictors, demonstrating that the relative importance of SOM stabilization mechanisms scales with climate and acidity. These results highlight the urgent need to modify biogeochemical models to better reflect the role of soil physicochemical properties in SOM cycling.     

A Quantitative Model of Soil Organic Matter Accumulation During Floodplain Primary Succession

Texture is an important influence on organic matter (SOM) dynamics in upland soils but little is known about its role in riverine soils. We hypothesized that texture might be especially important to SOM accumulation in young alluvial soils. We combined the soil component of the CENTURY ecosystem model, which uses sand, silt, and clay concentration as primary variables, with a simple simulation model of fluvial deposition, and forest production to predict changes in soil carbon (C) and nitrogen (N) during primary succession on floodplains and terraces of the Queets River, Washington. Simulated soil C accumulated to a plateau of about 4000 g m⁻² at 110 years, closely matching observed patterns in an empirical chronosequence. Although direct fluvial OM deposition had only a small and short-lived influence on soil C, fluvial silt and clay deposition were an important influence on equilibrium C. The model underestimated soil N by about 35%, which appears to be due to failure of the model to account for N enrichment of an OM pool after its initial formation. These results suggest that basic influences on SOM retention in these young soils are not functionally different than those that apply to upland soils, but occur within highly dynamic physical contexts. Overbank deposition of silt and clay establishes a basic capacity for SOM retention. SOM, in turn, facilitates N retention. In this way, silt and clay are instrumental in propagating N forward from N-fixing red alder (Alnus rubra) stands to mature conifer forests that are frequently N-limited.     

Climate change effects on the stability and chemistry of soil organic carbon pools in a subalpine grassland

Mountain soils stock large quantities of carbon as particulate organic matter that may be highly vulnerable to climate change. To explore potential shifts in soil organic matter (SOM) form and stability under climate change (warming and reduced precipitations), we studied the dynamics of SOM pools of a mountain grassland in the Swiss Jura as part of a climate manipulation experiment. The climate manipulation (elevational soil transplantation) was set up in October 2009 and simulated two realistic climate change scenarios. After 4 years of manipulation, we performed SOM physical fractionation to extract SOM fractions corresponding to specific turnover rates, in winter and in summer. Soil organic matter fraction chemistry was studied with ultraviolet, 3D fluorescence, and mid-infrared spectroscopies. The most labile SOM fractions showed high intra-annual dynamics (amounts and chemistry) mediated via the seasonal changes of fresh plant debris inputs and confirming their high contribution to the microbial loop. Our climate change manipulation modified the chemical differences between free and intra-aggregate organic matter, suggesting a modification of soil macro-aggregates dynamics. Interestingly, the 4-year climate manipulation affected directly the SOM dynamics, with a decrease in organic C bulk soil content, resulting from significant C-losses in the mineral-associated SOM fraction (MAOM), the most stable form of SOM. This SOC decrease was associated with a decrease in clay content, above- and belowground plants biomass, soil microbial biomass and activity. The combination of these climate changes effects on the plant–soil system could have led to increase C-losses from the MAOM fraction through clay-SOM washing out and DOC leaching in this subalpine grassland.     

杉木人工林土壤有机质研究

土壤有机质在养分循环、土壤理化性质等方面具有重要作用,是陆地生态系统重要的碳库,对全球碳素循环的平衡起着重要作用．本文详细阐述了杉木林地土壤有机质的性质与组成。杉木连栽对土壤有机质含量、腐殖质结合形态的影响以及林分发育过程中土壤有机质的变化,炼山、整地、施肥等经营活动对杉木林地土壤有机质的影响．杉木纯林有机质含量和质量均低于混交林,且随栽植代数的增加有机质含量和质量呈下降趋势,林地土壤肥力下降．最后提出应加强对土壤有机质周转模型、有机质组分,尤其是活性有机质以及有机质与全球碳循环关系的研究．     

Soil organic matter dynamics after C3–C4 vegetation change of red soil in Southern, China: Evidence from natural 13C abundance

Soil samples from natural forests and adjacent farmland were analyzed to investigate the dynamics of soil organic matter of red soil in Southern, China. Based on the δ¹³C values and the content of soil organic matter, the data indicated that the turnover of soil organic matter under the virgin forest was slower than that under cultivation. Soil organic matter is fresh in coarse sand and oldest in fine silt and clay. Also, the soil light fraction contained the younger organic matter than soil heavy fraction and bulk soil. Deforestation has accelerated the decomposition rate of soil organic matter and reduced the proportion of active components in SOM and thus soil fertility.     

Endogeic earthworms shape bacterial functional communities and affect organic matter mineralization in a tropical soil

Priming effect (PE) is defined as a stimulation of the mineralization of soil organic matter (SOM) following a supply of fresh organic matter. This process can have important consequences on the fate of SOM and on the management of residues in agricultural soils, especially in tropical regions where soil fertility is essentially based on the management of organic matter. Earthworms are ecosystem engineers known to affect the dynamics of SOM. Endogeic earthworms ingest large amounts of soil and assimilate a part of organic matter it contains. During gut transit, microorganisms are transported to new substrates and their activity is stimulated by (i) the production of readily assimilable organic matter (mucus) and (ii) the possible presence of fresh organic residues in the ingested soil. The objective of our study was to see (i) whether earthworms impact the PE intensity when a fresh residue is added to a tropical soil and (ii) whether this impact is linked to a stimulation/inhibition of bacterial taxa, and which taxa are affected. A tropical soil from Madagascar was incubated in the laboratory, with a ¹³C wheat straw residue, in the presence or absence of a peregrine endogeic tropical earthworm, Pontoscolex corethrurus. Emissions of ¹²CO₂ and ¹³CO₂ were followed during 16 days. The coupling between DNA-SIP (stable isotope probing) and pyrosequencing showed that stimulation of both the mineralization of wheat residues and the PE can be linked to the stimulation of several groups especially belonging to the Bacteroidetes phylum.     

土壤活性有机质及其与土壤质量的关系

活性有机质是土壤的重要组成部分 ,主要包括溶解性有机碳、微生物生物量、轻组有机质。它在土壤中具有重要作用 :(1)可以表征土壤物质循环特征、评价土壤质量 ,可以作为土壤潜在生产力以及由土壤管理措施引起土壤有机质变化的早期指标 ;(2 )在养分周转中起重要作用 ,是植物的养分库 ,可以提供植物所需要的养分如氮、磷、硫等 ;(3)能稳定土壤结构 ,对维持团粒结构稳定性有重要作用。从土壤养分、土壤物理、化学性质方面讨论了活性有机质与土壤质量的关系。土壤中的溶解性有机碳、微生物生物量碳氮含量与土壤有机碳、全氮和碱解氮等物质的含量呈正相关。活性有机质受土壤质地、含水量、温度等因素影响 ,与土壤酸碱度、阳离子交换量等也有关。土壤微生物生物量碳和微生物量 C/有机碳比与土壤粘粒、粉粒含量呈正相关、与砂粒含量呈负相关