近期7则土壤科学研究进展|研究

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近期7则土壤科学研究进展。

来源：相关机构网站

在中国农田土壤有机碳时空变化及其驱动力分析方面取得重要进展

来源：土壤与农业可持续发展国家重点实验室网站（2018年4月19日）

土壤有机碳（SOC）作为土壤肥力形成的基础，不但影响土壤质量及功能，而且在全球气候变化中扮演重要角色。近30年来，中国农田施肥、耕作、秸秆还田等农业管理措施经历了巨大变化，然而，从国家尺度上来说，这些变化对中国农田SOC时空变化的影响及主要驱动因子的贡献仍不明晰。

针对这些问题，在中科院先导专项及国家自然科学基金等的资助下，南京土壤所联合中科院沈阳生态所、地理资源所、水保所、亚热带农业生态所、成都山地所等科研院所，以及南京农业大学、西南大学等高校，通过1980及2011年两个时段SOC实测数据及其对应点位管理措施实地调查数据的系统分析，发现中国农田表层SOC由1980年的28.56 t C/ha增加到了2011年的32.90 t C/ha，净增幅4.34 t C/ha，作物根系、秸秆及其它（主要是有机肥）碳输入变化对SOC增幅的贡献分别为30%、40%和30%，为中国农田土壤总体固碳提供了直接证据。

进一步从影响农业管理决策的经济和政策因素角度阐释了国家尺度农田SOC时空变化的驱动力，发现在中国农田相对较低初始SOC含量的背景下，2000年之前，作物增产经济效益驱动的化肥投入增加而导致的作物根系生物量增加是碳输入的主要影响因子，而2000年后，秸秆还田政策大规模推广导致的土壤碳输入增强则占支配地位，从而揭示了经济和政策驱动的碳输入增强是近30年来中国农田SOC累积的主要原因。并发现化学N肥过量输入及耕层变浅是未来可能限制中国农田土壤固碳的主要因子，为我国进一步优化农业管理措施、实现土壤固碳及肥力提升双赢战略提供了依据。

上述研究成果于2018年4月17日发表于美国国家科学院院刊PNAS.

Zhao YC, Wang MY, Hu SJ, Zhang XD, Ouyang Z, Zhang GL, Huang B, Zhao SW, Wu JS, Xie DT, Zhu B, Yu DS, Pan XZ, Xu SX, Shi XZ. Economics- and policy-driven organic carbon input enhancement dominates soil organic carbon accumulation in Chinese croplands. PNAS, doi: 10.1073/pnas.1700292114

Abstract

China’s croplands have experienced drastic changes in management practices, such as fertilization, tillage, and residue treatments, since the 1980s. There is an ongoing debate about the impact of these changes on soil organic carbon (SOC) and its implications. Here we report results from an extensive study that provided direct evidence of cropland SOC sequestration in China. Based on the soil sampling locations recorded by the Second National Soil Survey of China in 1980, we collected 4,060 soil samples in 2011 from 58 counties that represent the typical cropping systems across China. Our results showed that across the country, the average SOC stock in the topsoil (0–20 cm) increased from 28.6 Mg C ha−1 in 1980 to 32.9 Mg C ha−1 in 2011, representing a net increase of 140 kg C ha−1 year−1. However, the SOC change differed among the major agricultural regions: SOC increased in all major agronomic regions except in Northeast China. The SOC sequestration was largely attributed to increased organic inputs driven by economics and policy: while higher root biomass resulting from enhanced crop productivity by chemical fertilizers predominated before 2000, higher residue inputs following the large-scale implementation of crop straw/stover return policy took over thereafter. The SOC change was negatively related to N inputs in East China, suggesting that the excessive N inputs, plus the shallowness of plow layers, may constrain the future C sequestration in Chinese croplands. Our results indicate that cropland SOC sequestration can be achieved through effectively manipulating economic and policy incentives to farmers.

基于高级核磁共振技术对缺磷条件下潮土富里酸结构的响应研究取得进展

来源：土壤与农业可持续发展国家重点实验室网站（2018年4月18日）

土壤富里酸一般认为是土壤有机质中较为活性的腐殖质组分，其含量虽然不高但在土壤腐殖化过程中扮演着重要的角色。封丘的潮土有机质含量低，前期的研究表明缺磷对于提高土壤有机质含量和作物产量都有严重的影响，但目前尚不清楚缺磷条件下富里酸的结构如何响应变化。

为此，南京土壤所赵炳梓课题组利用封丘长期试验地平台借助高级核磁共振技术研究了23年长期平衡施肥和缺磷条件下富里酸的结构分异，并以土壤有机质含量较高的桃源水稻土作为对照。

结果表明潮土平衡施肥相比缺磷处理均增加了富里酸的分解程度和芳香度，暗示平衡施肥下富里酸的腐殖化程度更加明显；而水稻土富里酸的结构则差异较小，说明两种截然不同的气候环境和土壤中，富里酸结构对施肥的响应也有所区别。利用偶极相移技术研究还发现两种土壤富里酸中的芳香碳非质子化比例达到44-52%，施肥尤其是有机肥降低了该比例。非质子化的芳香碳相对难以被降解，从这个角度看富里酸并没有预期的高活性。

研究结果为富里酸结构提供了新的认识，并为提高土壤肥力提供了一定的理论依据。

Xu JS, Zhao BZ, Mao JD, Chu WY, Li DD, Ma L, Zhang JB, Wei WX. Does P-deficiency fertilization alter chemical compositions of fulvic acids? Insights from long-term field studies on two contrasting soils: A Fluvisol and an Anthrosol. Soil and Tillage Research, 2018, 178: 189-197

Abstract

Structural changes in fulvic acid (FA) in response to fertilization strategies, especially P-deficiency fertilization, have critical implications for soil carbon dynamics. This study examined how long-term fertilization influenced chemical compositions of soil FA and its humification degree. Advanced solid-state 13C nuclear magnetic resonance techniques were used to evaluate structural changes of FAs from two soils (a Fluvisol and an Anthrosol) under four fertilizer treatments: organic fertilizer combined with or without NPK fertilizer (OF and NPKOF), deficient in phosphorus only (NK) and Control. The greater aromaticity, hydrophobicity and alkyl/O-alkyl (A/O-A) ratios of FAs were observed in the Anthrosol than in the Fluvisol. The Anthrosol FAs contained more alkyl and aromatic C but fewer O-alkyls (mostly being protonated) than did the Fluvisol FAs. Both FAs comprised some nonprotonated aromatics, which decreased with applications of organic and NK fertilizers. This trend was less obvious for the Anthrosol than for the Fluvisol. Organic fertilizer treatments (OF and NPKOF) in the Fluvisol increased the A/O-A ratio and aromaticity compared with P-deficient soils (NK and Control), indicating organic fertilization promoted the humification degree of its FA. The NK treatment in the Fluvisol increased H/C ratio of FA. Compared with the Fluvisol FAs, the Anthrosol FAs displayed similar chemical natures, implying their formation followed similar processes with a similar humification degree. The findings suggest that long-term fertilization differently influenced the FAs from the Fluvisol and Anthrosol. Clearly, the Anthrosol FAs shared more common features among the treatments compared with the Fluvisol FAs, whereas P-deficiency rendered the Fluvisol FAs simpler.
 

基于可见-近红外光谱的稻田原状土壤样品属性预测的不同建模方法比较

来源：土壤与农业可持续发展国家重点实验室网站（2018年4月17日）

通过定期监测土壤养分状况并合理调控施肥，是实现作物高产优质且环境友好的重要保证，但土壤养分含量的快速测定一直是农业信息获取领域的难题。

近年来，随着高光谱遥感技术的发展，利用可见-近红外光谱技术（Vis-NIR）获取土壤养分信息已获得越来越广泛的关注。然而，传统Vis-NIR技术应用中土壤样品均需要经过烘干、研磨、过筛等预处理过程，很少采用无损的原状土壤样品；其次，土壤属性与高光谱之间的关系复杂，存在极大的随机性和非线性，不同建模方法所得模型的预测性能也存在着较大差异。

基于此，本课题组以江西省余江县148个无损原状水稻土样品为研究对象，通过高密度接触式反射探头获取原状土壤高光谱（图1），并采用传统线性建模方法（主成分回归PCR和偏最小二乘回归PLSR）与非线性建模方法（反向传播神经网络BPNN和支持矢量机回归SVMR）分别建立土壤有机质（SOM）、总氮 （TN）、总磷（TP）和总钾（TK）含量的高光谱反演模型，最终对其拟合效果进行对比，确定其最佳拟合模型。

交叉检验及独立验证结果表明，与2种线性模型相比，非线性建模方法（BPNN和SVMR）对四种土壤属性的预测精度均有较大程度地提高。其中，SVMR模型预测精度最高，其采用结构风险最小化原理，根据有限样本的信息，在模型复杂性和学习能力之间寻求最优折中，以使构建模型的泛化能力最强。四种土壤属性中，SVMR模型对SOM含量预测的独立验证相关系数和均方根误差分别为0.88和4.87 g/kg（图2）；对TN含量预测结果次之，其独立验证相关系数和均方根误差分别为0.86和0.31 g/kg。

图1. 原状土壤样品高光谱测量平台

图2. SOM含量预测模型的散点图：（a）PCR；（b）PLSR；（c）BPNN；（d）SVMR

秸秆黑炭长期介入下酸性红壤和碱性潮土的氨氧化微生物群落结构的响应研究取得进展

来源：土壤与农业可持续发展国家重点实验室网站（2018年4月16日）

硝化作用是决定作物氮素吸收、损失、土壤酸化、温室气体排放等过程的重要途径之一，是土壤氮转化的关键核心过程。近年来，黑炭已被作为农田固碳减排和改良土壤的潜力措施；前期关于黑炭介入下土壤硝化作用的响应的研究大多是通过黑炭-土壤的室内短期培养（<2年）来完成，目前尚缺乏关于长期黑炭介入下土壤硝化作用及氨氧化微生物的影响研究。

基于此，南京土壤所常熟站工作人员利用宜兴基地2011年建立的秸秆炭化还田土柱试验平台，对比分析了连续施加秸秆黑炭4年8季后酸性红壤和碱性潮土的硝化能力和氨氧化微生物群落结构的变化。结果表明，长期黑炭施加提高了酸性红壤pH值及营养元素含量，显著提高了其硝化潜力及氨氧化微生物的基因拷贝数；同时，氨氧化细菌AOB的优势物种Nitrosospira cluster 2逐渐向Nitrosospira cluster 3a /cluster 3b转化，且逐渐出现了与碱性潮土中相同的优势菌群，表明秸秆黑炭在修复红壤酸度和繁荣硝化微生物方面的作用。而长期黑炭施加对碱性潮土的硝化潜力及氨氧化微生物的群落组成并没有产生显著的影响。

本研究首次利用高通量测序手段比较揭示了长期种植作物和秸秆黑炭连续施用下红壤和潮土氨氧化微生物群落结构的不同响应，能加深黑炭施用对农田土壤硝化作用影响的认识，也可为长期黑炭介入下土壤氮素损失调控提供一定的理论支撑。

He LL, Bi YC, Zhao J, Cameron M. Pittelkow, Zhao X, Wang SQ, Xing GX. Population and community structure shifts of ammonia oxidizers after four-year successive biochar application to agricultural acidic and alkaline soils. Science of the Total Environment, 2018, 619-620: 1105-1115

Abstract

Long-term studies that advance our mechanistic understanding of biochar (BC)‑nitrogen (N) interactions in agricultural soils are lacking. In this study, soil potential nitrification rates (PNR), the abundance and composition of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) communities following 4-year of BC application were investigated using the shaken-slurry procedure and molecular sequencing techniques for an acidic Oxisol (QU) and an alkaline Cambisol (YU). Soils were obtained from an outdoor soil column experiment with straw-BC application rates of 0 (BC0), 2.25 (BC2.25) and 11.3 (BC11.3) Mg ha− 1 per cropping season for eight consecutive wheat/millet seasons. Quantitative polymerase chain reaction (qPCR) and 454 high-throughput pyrosequencing techniques were performed to quantify and sequence amoA gene copies and composition of AOA and AOB. Results showed that QU had lower PNR and a higher ratio of amoA gene copies of AOA to AOB than YU, PNR of QU with BC application was significantly associated with the amoA gene of AOB. Similar to previous short-term findings, BC application enhanced QU soil nitrification, which may be explained by the significant increase in AOB abundance and a shift in AOB community structure from Nitrosospira cluster 2 toward cluster 3, along with the disappearance of some obligate acidophile AOA groups, leading to the appearance of ammonia-oxidizers from neutral-alkaline soils in BC-amended acid soils. Canonical correspondence analysis (CCA) showed that soil pH was the most important factor driving shifts in ammonia-oxidizers composition. Although BC application did not have significant effects on PNR in YU, BC11.3 decreased AOA and AOB gene copies and influenced the relative abundance of community structure. Our findings represent the first investigation of long-term BC effects on AOA and AOB communities in agricultural soils using 454 high-throughput pyrosequencing, showing that BC application can alter soil characteristics and influence ammonia oxidizer community composition, abundance, especially in acid soils.

在微生物对红壤水稻土磷盈余响应的研究取得进展

来源：土壤与农业可持续发展国家重点实验室网站（2018年4月14日）

为了维持水稻稳产、高产，亚热带红壤区稻田磷肥投入水平一直较高。由于红壤富含铁铝，对磷的固定较为强烈，因此红壤水稻土磷盈余明显。磷的盈余一方面带来严重环境问题，另一方面深刻影响土壤生态过程。但是磷盈余如何影响红壤水稻土微生物多样性和群落组成目前仍不清楚。

南京土壤所李忠佩课题组针对亚热带红壤区典型水稻土，通过设置不同施磷梯度室内培育试验，结合高通量测序，研究了红壤水稻土细菌和真菌多样性以及群落组成对施磷水平的响应。

结果表明，不同施磷梯度对细菌α多样性和群落组成没有明显影响。过量施磷条件下，真菌丰富度指数和多样性指数显著降低。速效磷（P = 0.001）, 全磷 （P = 0.002）, 和微生物量磷（P = 0.005）是影响真菌群落组成的关键因素。53.6mg/kg是造成真菌群落变化的关键速效磷阈值，当红壤水稻土速效磷高于53.6mg/kg时，Penicillium和Trichocomaceae减少，但是Pseudogymnoascus和Geomyces 增加；过量施磷条件下，真菌在土壤有机质转化以及磷循环过程中可能起到关键作用。

Liu M, Liu J, Chen XF, Jiang CY, Wu M, Li ZP. Shifts in bacterial and fungal diversity in a paddy soil faced with phosphorus surplus. Biology and Fertility of Soils, 2018, 54(2): 259-267

Abstract

Abundant phosphorus (P) has been applied to paddy fields in the red soil region of subtropical China. Microbial communities play important roles in soil nutrient cycling; however, the effects of P surplus on soil microbial diversity and community composition are still unclear. Soils collected from paddy fields in subtropical China was incubated and subjected to four P treatments: 33 kg ha-1 (CK), 66 kg ha-1 (P1), 132 kg ha-1 (P2), and 264 kg ha-1 (P3). Changes in bacterial and fungal diversity and community composition were evaluated by high-throughput sequencing. The different P rates had no significant effect on bacterial diversity, whereas fungal richness and diversity indexes declined significantly by increasing P rates. Principle coordinate analysis (PCoA) also indicated a shift in fungal community composition when P rates were higher than 132 kg ha-1. Available P (AP) was the dominant factor affecting fungal community composition as evaluated by canonical correspondence analysis (CCA). Multivariate regression trees (MRT) revealed that the key threshold of 53.6 mg kg-1 of AP divided treatments into two distinct groups. Linear discriminant analysis effect size (LEfSe) showed that abundances of Pseudogymnoascus and Geomyces increased, but those of Penicillium and an unknown genus of Trichocomaceae decreased when AP was ≥ 53.6 mg kg-1.

细菌胞外聚合物在土壤表面的吸附机制

来源：土壤与农业可持续发展国家重点实验室网站（2018年4月13日）

土壤中细菌的生长与代谢过程伴随着胞外聚合物的产生，胞外聚合物含丰富的羧基、羟基、磷酸根等官能团，可在土壤表面发生吸附并影响土壤的电化学性质及土壤对养分的保持能力。但胞外聚合物在土壤表面的吸附能力受pH、离子强度等溶液条件的影响，已有研究大多采用纯矿物或合成的铁铝氧化物，对细菌保温聚合物在实际土壤中的吸附行为知之甚少。

南京土壤所徐仁扣课题组借助原位红外光谱技术(ATR-FTIR)结合电化学分析方法，研究了两种细菌胞外聚合物（EPS)在红壤和黄棕壤胶体表面的吸附容量及其结合机制。

研究发现黄棕壤吸附较多的EPS-C和EPS-N，而红壤对EPS-P具有更高的吸附容量。EPS-C、EPS-N和 EPS-P 在红壤和黄棕壤表面的吸附量均随着pH的增加而降低。随着离子强度的增加，EPS-C、EPS-N和 EPS-P 在红壤表面的吸附量持续降低，而在黄棕壤表面呈现先增加后维持稳定的趋势。ATR-FTIR分析表明EPS在红壤表面的饱和吸附量高于黄棕壤。红壤和黄棕壤粘土矿物组成特别是铁铝氧化物含量不同是两种土壤对EPS-C、EPS-N和 EPS-P吸附存在明显差异的主要原因。

研究发现静电作用对EPS吸附起着重要作用，此外，EPS中的蛋白质和磷酸基与土壤矿物之间的键合作用也对吸附有贡献。本研究可为解释细菌及其EPS对土壤养分保持与循环的影响提供理论依据。

Ren LY, Hong ZN, Qian W, Li JY, Xu RK. Adsorption mechanism of extracellular polymeric substances from two bacteria on Ultisol and Alfisol. Environmental Pollution, 2018, 237: 39-49

Abstract

The primary objective of this study was to identify the capacity and mechanism of extracellular polymeric substance (EPS) adsorption on soil colloids of Alfisol and Ultisol at different pH and ionic strengths. Two kinds of EPS were extracted from Bacillus subtilis and Pseudomonas fluorescens by centrifugation, and their adsorption on Ultisol and Alfisol was investigated using a batch adsorption experiment and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR). The average diameter of EPS from B. subtilis and P. fluorescens was 1825 and 1288 nm, respectively, and both the EPS were negatively charged. The zeta potentials of the two EPS became more negative with increasing solution pH from 3 to 8 and less negative with increasing ionic strength from 0 to 80 mM. The maximum adsorption capacity of EPS-C and EPS-N on Alfisol was higher than that on Ultisol, whereas the maximum adsorption capacity of EPS-P on Alfisol was lower than that on Ultisol. The adsorption of EPS-C, EPS-N, and EPS-P of both the EPS on Ultisol and Alfisol decreased with increasing solution pH from 3 to 8. Adsorption of EPS-C, EPS-N, and EPS-P of both the EPS on Alfisol significantly increased with increasing ionic strength from 0 to 10 mM, whereas it remained constant, slightly increased, or reduced, when the ionic strength was increased from 10 to 80 mM. The adsorption of EPS-C, EPS-N, and EPS-P on Ultisol slightly increased with increasing ionic strength from 0 to 80 mM. Saturation coverage determined by ATR-FTIR showed that adsorption of whole EPS on Ultisol was higher than that on Alfisol at pH 6 after 60 min. Thus, electrostatic force between EPS and soil colloids played an important role in EPS adsorption. Besides, proteins and phosphate groups in EPS also contributed to EPS adsorption on soil colloids.

揭示造林对干旱半干旱地区土壤碳氮储量的影响

来源：中国科学院网站（2018年4月16日）

全球约有27%的土壤有机碳储存在干旱半干旱地区，这些区域在全球碳循环中扮演着重要的角色。植树造林是该区域用来实现防风固沙和生态恢复的主要手段之一，然而其对土壤碳、氮储量的影响仍存在一定的争议，影响造林固碳和固氮效果的因素也尚不清晰。

针对上述问题，中国科学院新疆生态与地理研究所研究员李兰海团队通过收集过往发表文献中的数据，同时基于MetaWin平台对数据进行整合分析，评估了造林对全球干旱半干旱地区表层土（0~30 cm）有机碳和全氮储量的影响，分析了造林前土地利用类型、造林树种和造林后时间长度对土壤碳、氮的动态影响。

研究结果显示，干旱半干旱地区土壤有机碳和全氮储量在造林后分别显著提升了131%和88%。造林前土地利用类型是影响土壤碳、氮动态的最主要因素，其中荒地造林后土壤碳、氮储量的增幅要显著大于农田造林和草地造林。造林树种也会对碳、氮动态造成影响，栽植落叶阔叶树种后土壤碳、氮储量的增幅最大，且效果要显著优于栽植常绿阔叶树种，但与栽植针叶树种后土壤碳、氮储量的增幅相比无显著差异。相比之下，不同造林后时间长度下的土壤碳、氮动态并没有出现显著性差异。

上述结果表明，在干旱半干旱地区，在荒地上栽植落叶阔叶树种具有巨大的固碳和固氮潜力，且这种潜力能够在短期内就展现出来。研究结果可以为干旱半干旱地区土壤肥力的恢复与提升提供科学依据，同时对于制定有效的固碳减排措施以遏制全球变暖具有一定的参考价值。

相关研究以Dynamics of soil carbon and nitrogen stocks after afforestation in arid and semi-arid regions: A meta-analysis 为题发表于Science of The Total Environment。

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