Influence of Residue and Nitrogen Fertilizer Additions on Carbon Mineralization in Soils with Different Texture and Cropping Histories

To improve our ability to predict SOC mineralization response to residue and N additions in soils with different inherent and dynamic organic matter properties, a 330-day incubation was conducted using samples from two long-term experiments (clay loam Mollisols in Iowa [IAsoil] and silt loam Ultisols in Maryland [MDsoil]) comparing conventional grain systems (Conv) amended with inorganic fertilizers with 3 yr (Med) and longer (Long), more diverse cropping systems amended with manure. A double exponential model was used to estimate the size (C _a, C _s) and decay rates (k _a, k _s) of active and slow C pools which we compared with total particulate organic matter (POM) and occluded-POM (OPOM). The high-SOC IAsoil containing highly active smectite clays maintained smaller labile pools and higher decay rates than the low-SOC MDsoil containing semi-active kaolinitic clays. Net SOC loss was greater (2.6 g kg⁻¹; 8.6%) from the IAsoil than the MDsoil (0.9 g kg⁻¹, 6.3%); fractions and coefficients suggest losses were principally from IAsoil’s resistant pool. Cropping history did not alter SOC pool size or decay rates in IAsoil where rotation-based differences in OPOM-C were small. In MDsoil, use of diversified rotations and manure increased k _a by 32% and k _s by 46% compared to Conv; differences mirrored in POM- and OPOM-C contents. Residue addition prompted greater increases in C _a (340% vs 230%) and C _s (38% vs 21%) and decreases in k _a (58% vs 9%) in IAsoil than MDsoil. Reduced losses of SOC from residue-amended MDsoil were associated with increased OPOM-C. Nitrogen addition dampened CO₂-C release. Clay type and C saturation dominated the IAsoil’s response to external inputs and made labile and stable fractions more vulnerable to decay. Trends in OPOM suggest aggregate protection influences C turnover in the low active MDsoil. Clay charge and OPOM-C contents were better predictors of soil C dynamics than clay or POM-C contents.     

不同熟化措施对黑土母质发育的新成土壤有机碳库的影响

基于8年田间定位试验,采用土壤团聚体分组和闭蓄态微团聚体分离技术,将土壤有机质分为总粗颗粒有机质(活性碳库)、总细颗粒有机质(慢性碳库)和总粉黏粒(惰性碳库) 3个组分,探讨不同熟化措施对黑土母质发育而成的新成土壤总有机碳库及不同活性有机碳库的影响,为黑土严重侵蚀地区母质表露后土壤肥力的快速恢复提供依据。试验设置自然恢复(NatF)、苜蓿种植(Alfa)、无肥(F0C0)、化肥(F1C0)、低量有机肥与化肥配施(F1C1)、高量有机肥与化肥配施(F1C2)等6个熟化处理。结果表明:黑土母质经过8年不同熟化处理后,土壤总有机碳和各组分有机碳含量均显著提高;与NatF相比,有机肥与化肥配施(F1C2和F1C1)对土壤总有机碳的提升作用最为明显,增幅分别为60.7%和41.2%;Alfa其次,增幅18. 2%;F0C0或F1C0处理土壤总有机碳与NatF间无显著差异;F1C2和F1C1处理土壤3个组分有机碳含量均显著高于其他熟化处理,与F1C1相比,F1C2处理对各组分有机碳提升作用更为明显;与NatF相比,Alfa处理土壤有机碳的增加主要表现为粉黏粒结合有机碳的增加;F1C0和F0C0处理土壤总细颗粒有机质和总粉黏粒中有机碳与NatF间无显著差异,总粗颗粒有机质中有机碳含量低于NatF。研究表明,在米豆轮作和传统耕作体系下,农田生态系统高量有机物料投入配施化肥能够加速黑土母质的熟化进程,快速提高土壤中活性碳库和惰性碳库的容量,是严重退化黑土有机质快速提升的有效措施。     

耕作方式对紫色水稻土轻组有机碳的影响

以位于西南大学实验农场的长期免耕试验田为研究对象,通过0—60cm分层采集土壤样品的方法,探讨了不同耕作方式———冬水田平作(DP)、水旱轮作(SH)、垄作免耕(LM)及垄作翻耕(LF)对土壤轻组有机碳的影响。结果表明,重组有机碳是土壤总有机碳的主体,约占土壤总有机碳的69.56%—95.66%,在土壤剖面上随土壤深度的增加其分配比例逐渐升高;其次是自由轻组有机碳,约占土壤总有机碳的5.03%—26.43%,从土壤表层向下,其分配比例迅速下降;闭合轻组有机碳最低,仅占土壤总有机碳的1.37%—4.93%,其分配比例随土壤深度的变化不明显。在0—60 cm土壤深度内,不同耕作方式下自由轻组有机碳的平均含量为LM(4.36 g/kg)>DP(2.11 g/kg)>LF(1.74 g/kg)>SH(1.46 g/kg),相应的有机碳分配比例分别为17.1%、14.0%、12.2%和11.3%;闭合轻组有机碳的平均含量为LM(0.82 g/kg)>DP(0.51 g/kg)>LF(0.36 g/kg)>SH(0.34g/kg),相应的有机碳分配比例分别为3.36%、3.45%、2.71%和3.00%。因此,在西南地区紫色水稻土上实行垄作免耕能提高轻组有机碳的含量及其分配比例,从而改善土壤有机碳质量。另外,与土壤总有机碳、重组有机碳及闭合轻组有机碳相比,自由轻组有机碳对耕作方式的变化最敏感,是指示土壤有机碳变化的良好指标。     

亚热带典型森林地上和地下凋落物输入对土壤新老有机碳动态平衡的影响

凋落物是森林土壤有机碳(SOC)形成、稳定和周转的重要影响因子。目前针对亚热带不同类型森林地上和地下凋落物对新SOC累积和老SOC输出动态平衡的影响仍不清楚。本研究以中亚热带常绿阔叶天然林、马尾松人工林和杉木人工林为对象,基于C3/C4植物-土壤置换试验,利用稳定同位素¹³C示踪方法开展3年野外定位试验,分析了森林地上、地下凋落物输入对SOC周转的影响。结果表明: 森林类型、凋落物处理和时间均能显著影响SOC含量、土壤δ¹³C值、新SOC和老SOC含量,且存在显著的森林类型×凋落物处理交互效应。地上和地下凋落物输入均能显著提高SOC含量和净增量,与杉木人工林相比,天然林SOC对凋落物输入的响应更敏感。凋落物输入显著降低了土壤δ¹³C值,且天然林、马尾松人工林土壤δ¹³C显著低于杉木人工林。在马尾松人工林,地下凋落物处理的新SOC含量显著高于地上凋落物;在天然林和马尾松人工林,地下凋落物输入处理的老SOC含量显著低于地上凋落物处理。此外,地上凋落物归还量和地下根生物量与SOC含量和净增量呈显著正相关,而地下根凋落物量和C/N与新SOC含量呈显著正相关。森林地下凋落物比地上凋落物输入对SOC周转的影响更重要,且不同森林凋落物输入对SOC的影响存在差异性。本研究可为揭示亚热带典型森林土壤有机碳库的形成和可持续管理提供依据。     

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     

不同植茶年限土壤团聚体及其有机碳分布特征

作为土壤结构的基本单元和土壤肥力的重要组成部分,土壤团聚体对土壤的物理、化学和生物特性均有重要影响。试验选取了雅安市名山区中峰乡生态茶园区12—15a、20—22a、30—33a和50a的茶园,研究其土壤团聚体及其有机碳总量、储量和活性组分的分布特征,探究植茶年限对土壤团聚体及其有机碳分布的影响。结果表明:(1)研究区土壤以2 mm粒级团聚体为主,约为70%—80%,且在0—20 cm土层植茶20—22a土壤团聚体含量最高;(2)茶园土壤团聚体有机碳含量随团聚体粒级的减小而增加,最大值出现在0.25 mm粒级团聚体,且在植茶50a时达最高值,0—20 cm土层团聚体有机碳含量均高于20—40 cm,土壤团聚体水溶性有机碳和微生物生物量碳随植茶年限的延长呈先增加后降低的变化趋势,植茶30—33a时含量最高,且小粒级团聚体水溶性有机碳含量较高而微生物量碳较低;(3)土壤团聚体对有机碳的贡献率约有70%来自2 mm粒级团聚体,团聚体有机碳储量随植茶年限延长呈增加的趋势,不同植茶年限0—20 cm土层各粒级团聚体有机碳储量均高于20—40 cm土层,且以0.25 mm粒级团聚体有机碳储量最高。研究结果在一定程度上揭示了不同植茶年限土壤团聚体及其有机碳的分布特征,可为改善区域土壤质量及实施退耕还茶工程提供理论指导。     

Soil Organic Carbon Pools and Stocks in Permafrost-Affected Soils on the Tibetan Plateau

The Tibetan Plateau reacts particularly sensitively to possible effects of climate change. Approximately two thirds of the total area is affected by permafrost. To get a better understanding of the role of permafrost on soil organic carbon pools and stocks, investigations were carried out including both discontinuous (site Huashixia, HUA) and continuous permafrost (site Wudaoliang, WUD). Three organic carbon fractions were isolated using density separation combined with ultrasonic dispersion: the light fractions (<1.6 g cm⁻³) of free particulate organic matter (FPOM) and occluded particulate organic matter (OPOM), plus a heavy fraction (>1.6 g cm⁻³) of mineral associated organic matter (MOM). The fractions were analyzed for C, N, and their portion of organic C. FPOM contained an average SOC content of 252 g kg⁻¹. Higher SOC contents (320 g kg⁻¹) were found in OPOM while MOM had the lowest SOC contents (29 g kg⁻¹). Due to their lower density the easily decomposable fractions FPOM and OPOM contribute 27% (HUA) and 22% (WUD) to the total SOC stocks. In HUA mean SOC stocks (0–30 cm depth) account for 10.4 kg m⁻², compared to 3.4 kg m⁻² in WUD. 53% of the SOC is stored in the upper 10 cm in WUD, in HUA only 39%. Highest POM values of 36% occurred in profiles with high soil moisture content. SOC stocks, soil moisture and active layer thickness correlated strongly in discontinuous permafrost while no correlation between SOC stocks and active layer thickness and only a weak relation between soil moisture and SOC stocks could be found in continuous permafrost. Consequently, permafrost-affected soils in discontinuous permafrost environments are susceptible to soil moisture changes due to alterations in quantity and seasonal distribution of precipitation, increasing temperature and therefore evaporation.     

Simulation of management and soil interactions impacting SOC dynamics in sugarcane using the CENTURY Model

Newer methods of management and harvesting of sugarcane are being considered to improve soil and water conservation in Brazil. Our aim in this study was to evaluate soil C dynamics under sugarcane cultivation as influenced by the use of conservation management, using measurements from four different management systems and land use histories, i.e. conventional management with preharvest burning, no burning with residue retention and two systems without burning plus additional organic amendments. Field sites also differed in terms of soil texture. We compared field measurements of soil C stocks, ¹³C and microbial biomass with simulated results from the Century ecosystem model for each of the sites and management histories. We also did long-term simulations of the management treatments and sites to approximate steady-state SOC levels, to explore potential management-induced differences in SOC stocks and interactions with soil texture. The model accurately represented treatment and site differences for total SOC stocks, in which SOC stocks were strongly affected by both rates of organic matter input to soil and soil clay content. However, the model tended to underestimate the relative contribution of sugarcane-derived C to total SOC for sites with high residue and external organic matter amendments. Measured microbial biomass C across the sites was closely aligned with relative amounts of organic matter input but did not appear to be strongly affected by soil texture, whereas the model predicted that both texture and organic matter input rate would impact microbial biomass C. Long-term simulations of the conservation management alternatives suggested that SOC stocks could be maintained at or above levels in the original native Cerradão vegetation, whereas conventional practices using residue burning would result in a reduction of SOC to ca. 60% of native levels. Our results support the use of the CENTURY model as an aid to assess the impacts of different soil management practices on SOC stocks under sugarcane in Brazil.     

温度对不同粘粒含量稻田土壤有机碳矿化的影响

模拟了亚热带地区3种不同粘粒含量的水稻土(砂壤土、壤粘土、粉粘土)在5种温度(10、15、20、25和30℃)下的有机碳(SOC)矿化特征,分析SOC矿化对温度变化的响应.结果表明:在160d的培养期内,温度对3种水稻土SOC矿化量的影响有一定差异,30℃时砂壤土、壤粘土和粉粘土SOC矿化量分别是10℃时的3.5、5.2和4.7倍.在较低温度(≤20℃)下,SOC矿化速度较低且相对稳定;在较高温度(≥25℃)下,前期SOC矿化速度较高,随着培养时间的延长逐渐降低,并趋于稳定.3种水稻土SOC矿化的温度系数(Q10)随培养时间出现波动,砂壤土的Q10平均值最低,为1.92,壤粘土和粉粘土的Q10平均值较接近,分别为2.37和2.32;3种土壤矿化速率常数(k)与温度呈极显著的指数相关(P<0.01).3种水稻土有机碳矿化对温度变化的响应敏感度依次为壤粘土>粉粘土>砂壤土.     

黑土坡耕地有机碳及其组分累积-损耗格局对耕作侵蚀与水蚀的响应

耕作与水蚀是黑土区坡耕地碳库退化的主导因素,为进一步探究土壤有机碳(SOC)及其组分对不同侵蚀驱动力(耕作、水力)的响应格局,基于该区耕作侵蚀与水蚀模型,在定量表达耕作侵蚀-沉积量与水蚀量的基础上,利用地统计学的方法,分析了东北黑土区典型漫岗地形坡面尺度SOC及其3种组分的空间分布特征.结果表明: 耕作侵蚀与沉积速率分别表现为坡上>坡下>坡中>坡脚和坡脚>坡下>坡中>坡上;水蚀速率表现为坡下>坡脚>坡中>坡上;坡下陡坡位置耕作侵蚀与水蚀协同引起严重的土壤流失.虽然耕作侵蚀速率(0.02～7.02 t·hm^-2·a^-1)远小于水蚀速率(5.96～101.17 t·hm^-2·a^-1),但耕作侵蚀在全坡面范围均可对SOC产生不同程度的影响,而水蚀则主要在坡下径流汇集区显著影响SOC的累积-损耗.受水蚀与耕作侵蚀-沉积作用影响,SOC、颗粒有机碳、水溶性有机碳在侵蚀点含量低于沉积点,而微生物生物量碳变化趋势相反;耕作侵蚀通过影响颗粒有机碳参与SOC的积累-损耗过程.     

红壤和风沙土添加不同化学结构有机碳对外源碳去向及累积贡献的影响

植物凋落物碳输入显著影响陆地生态系统土壤CO₂排放和有机碳(SOC)形成,然而,针对不同质地土壤添加不同化学结构外源碳去向依然不清楚。本研究将¹³C标记的葡萄糖、淀粉和纤维素添加至红壤和风沙土,比较2种质地土壤添加不同化学结构外源碳在土壤释放的CO₂、SOC、可溶性有机碳(DOC)和微生物生物量碳(MBC)库的净累积量、回收率及贡献比例上的差异。结果表明: 添加外源有机碳显著提高了CO₂、SOC、DOC和MBC的δ¹³C值,且随着外源有机碳化学结构复杂性的增加,CO₂的δ¹³C峰值依次延迟出现;外源有机碳种类、土壤类型和培养时间均显著改变外源碳去向及其在各碳库的贡献比例;在风沙土中,外源有机碳更多被矿化为CO₂,且CO₂库的外源碳净累积量和回收率大小依次为葡萄糖>淀粉>纤维素;红壤添加外源碳转变为SOC的累积量和回收率显著高于风沙土,且红壤SOC库的外源碳净累积量和回收率大小顺序也为葡萄糖>淀粉>纤维素。可见,外源有机碳化学结构和土壤质地共同调控外源碳去向及累积贡献。     

Mechanisms of Carbon Sequestration in Soil Aggregates

Soil and crop management practices have a profound impact on carbon (C) sequestration, but the mechanisms of interaction between soil structure and soil organic C (SOC) dynamics are not well understood. Understanding how an aggregate stores and protects SOC is essential to developing proper management practices to enhance SOC sequestration. The objectives of this article are to: (1) describe the importance of plants and soil functions on SOC sequestration, (2) review the mechanisms of SOC sequestration within aggregates under different vegetation and soil management practices, (3) explain methods of assessing distribution of SOC within aggregates, and (4) identify knowledge gaps with regards to SOC and soil structural dynamics. The quality and quantity of plant residues define the amount of organic matter and thus the SOC pool in aggregates. The nature of plant debris (C:N ratio, lignin content, and phenolic compound content) affects the rate of SOC sequestration. Mechanisms of interaction of aggregate dynamics with SOC are complex and embrace a range of spatial and temporal processes within macro- ( > 250 μ m e.c.d.) and microaggregates ( < 250 μ m e.c.d.). A relevant mechanism for SOC sequestration within aggregates is the confinement of plant debris in the core of the microaggregates. The C-rich young plant residues form and stabilize macroaggregates, whereas the old organic C is occluded in the microaggregates. Interactions of clay minerals with C rich humic compounds in correlation with clay mineralogy determine the protection and storage of SOC. Principal techniques used to assess the C distribution in aggregates include the determination of total organic C in different aggregate size fractions, isotopic methods to assess the turnover and storage of organic C in aggregates, and computed tomography and X-ray scattering to determine the internal porosity and inter-aggregate attributes. The literature is replete with studies on soil and crop management influences on total organic C and soil aggregation. However, research reports on the interactions of SOC within aggregates for C sequestration are scanty. Questions still remain on how SOC interacts physically and chemically with aggregates, and research is needed to understand the mechanisms responsible for the dynamics of aggregate formation and stability in relation to C sequestration.     

黄土高原不同土壤质地农田土壤碳、氮、磷及团聚体分布特征

结合野外观测和室内分析,研究了黄土高原不同土壤质地农田土壤碳、氮、磷含量及其生态计量学特征,以及土壤团聚体分布状况,以揭示土壤质地对区域农田土壤肥力的影响,以及土壤团聚体对肥力的调控作用.结果表明: 黄土高原农田土壤大团聚体含量、主要养分含量及其生态计量比值均随土壤质地由细变粗(壤质黏土→黏壤土→砂质壤土)逐渐降低;土壤pH值和微团聚体含量则呈现出相反的变化趋势. 随土壤黏粒含量增加,大团聚体含量、有机碳、全氮和全磷含量,以及C/P和N/P显著增加,土壤pH和微团聚体含量显著降低. 土壤有机碳、全氮和全磷含量,以及C/P和N/P随大团聚体含量的增加显著增加.表明区域尺度上农田土壤肥力状况取决于土壤质地,并受土壤大团聚体的调节.     

耕作方式对紫色水稻土有机碳和微生物生物量碳的影响

以位于西南大学的农业部紫色土生态环境重点野外科学观测试验站始于1990年的长期定位试验田为对象,研究了冬水田平作(DP)、水旱轮作(SH)、垄作免耕(LM)及垄作翻耕(LF)等4种耕作方式对紫色水稻土有机碳(SOC)和微生物生物量碳(SMBC)的影响。结果表明,4种耕作方式下SOC和SMBC均呈现出在土壤剖面垂直递减趋势,翻耕栽培下其降低较均匀,而免耕栽培下其富集在表层土壤中。同一土层不同耕作方式间SOC和SMBC的差异在表层最大,随着土壤深度的增加,各处理之间的差异逐渐减小。在0—60 cm剖面中,SOC含量依次为:LM(17.6 g/kg)>DP(13.9 g/kg)>LF(12.5 g/kg)>SH(11.3 g/kg),SOC储量也依次为:LM(158.52 Mg C/hm2)>DP(106.74 Mg C/hm2)>LF(93.11 Mg C/hm2)>SH(88.59 Mg C/hm2),而SMBC含量则依次为:LM(259 mg/kg)>SH(213 mg/kg)>LF(160 mg/kg)>DP(144 mg/kg)。与其它3种耕作方式比较,LM处理显著提高SOC含量和储量以及SMBC含量。对土壤微生物商(SMBC/SOC)进行分析发现,耕作方式对SOC和SMBC的影响程度并不一致。SMBC与SOC、全氮、全磷、全硫、碱解氮、有效磷均呈现极显著正相关(P<0.01),与有效硫呈显著正相关(P<0.05);表明SMBC可以作为表征紫色水稻土土壤肥力的敏感因子。     

草原土壤有机碳含量的控制因素

基于374个高寒草原和温带草原土壤样品的测试结果,运用多元逐步回归分析模型定量评估了土壤环境因子对土壤有机碳(SOC)含量的影响.结果表明:高寒草原土壤有机碳含量(20.18 kg C/m2)高于温带草原(9.23 kg C/m2).土壤理化生物学因子对高寒草原和温带草原SOC含量(10 cm)变化的贡献分别是87.84％和75.00％.其中,土壤总氮含量和根系对高寒草原SOC含量变化的贡献均大于对温带草原SOC含量变化的相应贡献.土壤水分是温带草原SOC含量变化的主要限制性因素,其对SOC含量变化的贡献达33.27％.高寒草原土壤C/N比显著高于温带草原土壤的相应值,揭示了青藏高原高寒草原较高的SOC含量是由于较低的土壤微生物活性所导致.     

连续免耕对不同质地稻田土壤理化性质的影响

以我国南方地区典型的单季水稻生产大田为研究对象,按土壤质地分为壤质和粘质两个系列,探讨不同质地稻田土壤理化性质变化对连续免耕的响应规律。结果表明,在无秸秆覆盖条件下,随着免耕年限的增加,壤质和粘质稻田土壤的耕层均有紧实度提高的趋势,特别是粘质土壤,导致耕层变浅。与常年翻耕土壤相比,免耕6a后壤质水稻土0—20 cm土层的紧实度值平均增加了32%,而粘质的平均增加了90%。在相同免耕年限条件下粘质稻田土壤容重的增加也比壤质土壤的明显。壤质土壤0—10 cm土层有机质和碱解氮含量随免耕年限延长而提高,而在粘质土壤则显著降低。无论是壤质还是粘质土壤,连续免耕多年后土壤速效磷均在耕层(0—20 cm)富集,而速效钾则相反。总体而言,壤质水稻土对免耕的适宜性要优于粘质土壤;应根据土壤质地的不同选择性地实施免耕技术,并结合秸秆覆盖,以实现免耕稻田土壤的可持续利用。     

长白山阔叶红松林和杨桦次生林土壤有机碳氮的协同积累特征

次生演替是森林土壤有机碳、氮库变化的重要驱动因素.本研究以长白山原始阔叶红松林和杨桦次生林为例,通过成对样地途径,研究了森林土壤有机碳、氮的数量分布及其协同积累特征,探讨了次生演替导致的温带森林土壤碳库和碳汇效应变化及其碳氮耦合机制.结果表明: 杨桦次生林比原始阔叶红松林在土壤表层和亚表层(0～20 cm)积累了更多的有机碳和氮,其土壤C/N值也显著低于阔叶红松林;相对于阔叶红松林,杨桦次生林土壤(0～20 cm)有机碳储量平均增加了14.7 t·hm^-2,相当于29.4 g·m^-2·a^-1的土壤碳汇增益.土壤有机碳和全氮在不同林型的不同土层中均表现为极显著正相关,二者具有明显的协同积累特征.与阔叶红松林生态系统相比,相对富氮的杨桦次生林生态系统的上部土层中氮对有机碳的决定系数明显高于阔叶红松林,说明杨桦次生林土壤有机碳的积累在更大程度上依赖含氮有机质积累.在有机质最丰富的表层(0～10 cm),两种林型间轻组有机碳、氮储量无显著差异,但杨桦次生林重组有机碳、氮的含量、储量及分配比例均显著高于阔叶红松林,其中,重组有机碳储量平均增加了8.5 t·hm^-2,表明次生演替过程中土壤有机碳、氮库的增加主要在于矿物质结合态稳定性土壤有机碳、氮库的增容.凋落物分解和稳定性土壤有机质形成中的碳氮耦合机制是次生演替过程中土壤有机碳、氮库变化的重要驱动机制.     

长期不同植被覆盖对黑土团聚体内有机碳组分的影响

为探究黑土团聚体内土壤有机碳(SOC)的“分馏”特征, 揭示不同植被覆盖下土壤团聚体的固碳机制, 该文以中国科学院海伦农业生态系统国家野外综合研究站内不同植被覆盖(草地、农田和裸地)长期定位实验的土样为研究对象, 利用团聚体湿筛分组、有机碳物理和化学分组相结合的方法, 研究了黑土团聚体及其内部的碳密度和腐殖质组分的碳分配特征。研究发现, 黑土经过不同植被覆盖31年后, 长期草地覆盖使土壤表层SOC、全氮(TN)含量显著增加, 农田和无植被覆盖的裸地SOC含量减少, 且在裸地显著降低。3种处理中, 2-0.25 mm (含2 mm, 下同)粒级团聚体均为优粒级。土壤团聚体的稳定性顺序为草地>农田>裸地。草地覆盖使土壤大团聚体的比例和有机碳库增加, 微团聚体和粉黏粒所占比例和碳库均减少, 说明草地覆盖促进了土壤大团聚体形成, 土壤固碳能力显著增强。而农田和裸地因外源碳投入少, 有机碳含量均是微团聚体>大团聚体>粉黏粒, SOC主要分布在微团聚体中。不同植被覆盖处理对土壤团聚体内密度组分和腐殖质各组分碳的富集“分馏”作用很明显, 与农田和裸地相比, 长期草地植被覆盖处理>2 mm和2-0.25 mm粒级团聚体中轻组碳含量富集的较多, 2-0.25 mm粒级团聚体中富里酸、胡敏酸和胡敏素的碳富集均最高, 而农田和裸地促进了微团聚体内腐殖质碳的富集。草地覆盖显著增加了大团聚体内活性有机碳组分, 来源于植物的碳首先进入到大粒径的团聚体中, 使土壤团聚结构显著改善, 农田和无植被覆盖的裸地土壤中轻组碳含量显著降低, 团聚体内有机碳以重组碳和胡敏素为主, 稳定化程度更高。     

Daycent模型模拟不同农作管理措施下华北地区土壤有机碳的变化

基于华北地区3个长期定位试验站点（河南郑州、山东禹城和河北曲周）的试验数据,用站点实测作物产量和土壤有机碳（SOC）双标准对Daycent模型进行校验和验证.结果表明： 模型参数组合对作物产量和SOC的长期变化动态拟合效果良好,表明Daycent模型可较好地模拟作物产量和SOC的动态变化.用校验和验证了的模型对3个站点在气候情景RCP 4.5下4种不同管理措施（单施化肥NPK、化肥+有机肥MNPK、秸秆还田SNPK、免耕+秸秆NT）下SOC的变化动态进行模拟.结果表明： 郑州站点NPK、MNPK、SNPK处理中,MNPK处理的SOC相对年平均增幅最高,2001—2050年间的SOC年增幅达1.7%,其次为SNPK处理（年均增幅为1.3%）和NPK处理（年均增幅为0.8%）,从长远角度看,增施有机肥对灌溉轻壤土有机碳的增加有明显效果.在禹城站点,研究期间,MNPK处理的SOC年均增幅（0.4%）高于NPK处理（0.3%）,由于该站点土壤有轻度盐化特征,因此各措施下SOC的增幅较低.在曲周站点,NT处理更有利于SOC的增加,研究期间的SOC年均增幅达1.3%,远高于SNPK处理（0.7%）和NPK处理（0.4%）.华北地区气温适宜、灌溉条件好、具备秸秆还田及免耕机械条件,免耕+秸秆还田是该地区增加SOC的较好农作管理措施.     

盐渍化条件下土壤团聚体及其有机碳研究进展

土壤团聚体是土壤结构的基本单元,对改善土壤结构和增加土壤固碳具有重要作用.盐渍化导致的特殊土壤性质,如高盐分离子(主要为Na+)浓度、低有机质含量和较差的微生物条件等因素,对团聚体的形成和稳定产生障碍作用,因此探讨盐渍化土壤团聚体特征更具有重要性和特殊性.滨海湿地和内陆盐渍化沼泽湿地是盐渍化生态系统的重要组成部分.本文...