干湿交替对武夷山不同海拔土壤碳矿化的影响

干湿交替(DW)对土壤有机碳矿化作用、养分循环和微生物生长代谢有着重要的影响。本文选择武夷山不同海拔0~10 cm的表层土壤作为研究对象,分别在5、15和25℃温度下培养,模拟DW循环,并设置恒湿处理(CW)作为对照,研究干湿循环对不同海拔土壤碳矿化作用的影响。结果表明:与CW处理相比,土壤变干时显著减少土壤有机碳矿化速率。重新变湿后,土壤有机碳的脉冲效应被观察,且变湿的脉冲效应随着DW数的增加而逐渐降低。重复的DW处理土壤累积碳矿化量显著低于CW处理,表明湿润引起的激发碳矿化量不足以抵消干旱期间减少量。DW处理的温度敏感性Q10显著低于CW处理。在DW循环中,湿度敏感性k值随海拔的升高而增加,表明高海拔土壤矿化更强的水分依赖性。DW处理微生物生物量碳含量高于CW处理,而冷水和热水浸提的可溶性有机碳含量则低于CW处理。     

常绿阔叶林与杉木林的土壤碳矿化潜力及其对土壤活性有机碳的影响

采用室内土壤培养法,比较分析了湖南省会同地区常绿阔叶林、杉木纯林土壤有机碳的矿化速率和累计矿化量,分析了有机碳矿化量与土壤活性有机碳初始含量的关系。结果表明:常绿阔叶林土壤有机碳矿化速率和累计矿化量均显著高于杉木纯林。在培养的第21天,在培养温度为9℃和28℃条件下,常绿阔叶林0～10和10～20cm土层的土壤有机碳累计矿化量为杉木纯林的1.7～2.7倍。常绿阔叶林土壤有机碳矿化释放的CO2-C分配比例高于杉木纯林。林地土壤有机碳矿化量受土壤微生物碳、可溶性有机碳初始含量的影响(P<0.01)。土壤有机碳矿化使土壤微生物碳增加而可溶性有机碳下降,但变化幅度均不大。温度从9℃升高到28℃后,林地土壤有机碳矿化速率提高3.1～4.5倍;2林地有机碳矿化对温度的敏感性无显著差异。     

川西高寒山地灌丛草甸不同海拔土壤有机碳矿化的季节动态

为探明高寒山地灌丛草甸不同海拔土壤碳矿化潜力,选取折多山3800 m、4000 m、4200 m 3个海拔梯度的灌丛草甸,采用室内培养法测定不同季节土壤累积矿化量和矿化速率,运用一级动力学方程对土壤碳矿化过程进行拟合,并分析不同海拔土壤活性碳组分季节变化及累积矿化量与土壤环境因子的关系。结果表明:土壤累积矿化量及活性碳组分均呈现出0—20 cm土层显著高于20—40 cm土层,且夏季最高的季节变化,而海拔变化趋势不一致,但大体呈现出3800 m灰化土最大。土壤碳矿化速率随着培养时间的推移逐渐降低慢慢趋于平缓,且前21 d降低幅度显著高于后21 d。各海拔C_0和C_0/SOC均夏季最高,表明高寒灌丛草甸夏季土壤固碳能力最低,且3800 m灰化土固碳能力最低。土壤碳矿化与土壤全氮、有机碳、活性碳显著相关,且微生物量碳更能直接影响土壤碳矿化。土壤碳矿化季节性变化受土壤理化性质和环境因素综合影响,这些因子共同作用使得土壤有机碳库各组分发生复杂变化,所以对于高寒灌丛草甸地区植被多样性的保护及夏季牧场的合理控制至关重要。     

模拟增温对武夷山不同海拔森林表层土壤碳氮及酶活性的影响

为了解亚热带森林土壤碳氮及酶活性对气候变暖的响应,以武夷山不同海拔的三种典型森林群落土壤为研究对象,采用把高海拔土柱置换到低海拔的方式模拟增温,探究模拟增温对土壤碳、氮、磷循环相关酶活性及土壤理化性质的影响。结果表明:土柱置换后海拔梯度上土壤温度平均增加2℃。土柱置换模拟增温导致高海拔(1400 m)土壤有机碳下降幅度最大;不同海拔土壤铵态氮、硝态氮、微生物生物量碳均呈下降趋势,仅高海拔达到显著水平。土柱置换对各海拔土壤水解酶活性影响较大,而对氧化酶活性没有显著影响。相反,土柱置换增温增加了各海拔土壤归一化酶活性,且高海拔土壤归一化酶活性对增温的响应程度比低海拔更大。冗余分析结果发现,土壤有机碳、可溶性有机碳、土壤温度和含水率是影响土壤酶活性变化最重要的因子。本研究表明模拟增温对高海拔土壤碳氮循环过程影响较大,其机制主要是通过提高微生物活性和分泌酶的能力来影响土壤碳氮循环过程。     

江西官山常绿阔叶林土壤有机碳组分沿海拔的变化

对江西官山国家级自然保护区不同海拔(400、600、800、1000、1200 m)常绿阔叶林土壤总有机碳、惰性有机碳和活性有机碳进行分析,研究土壤有机碳的海拔分布特征。结果表明: 土壤总有机碳、惰性有机碳及活性有机碳含量在土壤表层最高,随土层加深而逐渐下降。随海拔升高,土壤总有机碳、惰性有机碳、易氧化有机碳、微生物生物量碳及0～20 cm土层土壤颗粒有机碳含量均出现先增后降的趋势, 且在海拔1000 m达到峰值,而土壤水溶性有机碳及20～40 cm土层土壤颗粒有机碳含量无明显变化。在0～10 cm土层,土壤惰性有机碳占总有机碳的比例在海拔800和1200 m显著高于海拔400和1000 m,而土壤活性有机碳占总有机碳的比例在海拔400 m最高;土壤惰性有机碳和活性有机碳占总有机碳的比例在10～40 cm土层随海拔的增加均呈先增加后降低的趋势,峰值分别在1000和600 m处。各组分有机碳与土壤湿度、微生物生物量氮、可溶性有机氮均呈显著正相关,而且活性有机碳与铵态氮呈显著正相关。海拔显著影响常绿阔叶林土壤有机碳组分的分布,惰性有机碳、易氧化有机碳和微生物生物量碳对海拔变化的响应更敏感。高海拔土壤惰性有机碳和活性有机碳在水分和氮素充足条件下易发生分解与转化,降低土壤碳库的稳定性。在全球气温持续升高背景下,要加强高海拔地区森林土壤有机碳的动态变化研究。     

黄土高原土壤有机碳矿化及其与土壤理化性质的关系

土壤有机碳矿化与陆地生态系统碳循环和全球气候变化密切相关。采集98个共7类黄土高原土样,通过密闭培养法对有机碳矿化动态进行分析,探讨了土壤理化性质对有机碳矿化的影响。结果表明,黄土高原地区主要土壤有机碳在培养初期日均矿化量较高,之后逐渐降低。土壤类型对黄土高原土壤有机碳矿化影响较大,不同土壤有机碳的日均矿化量、累积矿化量和矿化率具有显著或极显著的差异。褐土有机碳总矿化量最高,CO2-C达到0.252g.kg-1,风沙土最低,CO2-C仅为0.095g.kg-1。下层土壤的有机碳矿化量较上层的有所下降,但土层深度对有机碳矿化大体上无明显影响。一级动力学方程能很好模拟黄土高原土壤有机碳矿化特征。供试土壤有机碳矿化潜力(Cp)和矿化速率常数(k)值均较低,分别为0.329-0.116g.kg-1和4.55-8.57×10-5d-1。不同土壤的Cp值变异较大,而k和Cp/SOC值无明显的变异。土壤Cp与土壤总有机碳、全氮、全磷、速效钾、粘粒和粉粒含量均呈极显著的正相关,而与k、pH值和砂粒含量呈显著的负相关。研究结果对黄土高原土壤有机碳循环和土壤碳库研究具有重要的科学价值。     

城市不同地表覆盖类型下土壤有机碳矿化的差异

土壤有机碳(SOC)矿化是陆地生态系统碳循环的重要过程。因受到强烈的人为干扰,城市土壤生态服务功能严重退化,进而对城市土壤地球化学循环尤其是碳循环产生深刻的影响。以北京市奥林匹克森林公园的5种典型地表覆盖类型(草坪、灌木、行道树、植草砖、硬化地表)下土壤为研究对象,研究了城市不同地表覆盖类型下土壤有机碳矿化过程及固碳能力的差异。结果表明,城市5种地表覆盖类型下的土壤有机碳矿化趋势与自然生态系统中的土壤基本一致,都表现为前期矿化较为快速,后期明显减慢并且趋于平稳;不同地表覆盖类型下土壤的有机碳矿化作用有显著差异,灌木、行道树、植草砖覆盖下土壤有机碳矿化能力较强,硬化地表和草坪较弱,与土壤有机碳含量特征类似;一级动力学方程对各土样有机碳矿化过程的模拟结果较好,结果显示草坪覆盖下土壤固碳能力较强,灌木覆盖下次之,行道树、植草砖和硬化地表覆盖下较弱;土壤固碳能力的高低并不对应着土壤有机碳含量的高低,城市人为干扰和外源有机碳的输入对土壤有机碳储量影响较大;硬化地表下不同土层有机碳矿化作用无明显差异,而其他地表覆盖类型下的土壤有机碳矿化作用随土层加深显著减弱,特别是植草砖和行道树特征最为明显;各地表覆盖类型下土壤固碳能力随土层深度变化的规律不显著。城市土壤有机碳矿化的最主要限制因子是土壤有机碳的含量,土壤p H值、养分含量、粘粒含量等性质也通过影响土壤有机碳含量及微生物活动等对土壤有机碳矿化过程产生影响。     

季节性冻融期间川西亚高山/高山森林土壤净氮矿化特征

气候变暖情景下季节性冻融格局的改变可能显著影响高寒森林土壤氮素矿化过程.本文采用原状土壤移位培养的方法,以海拔梯度形成的温度差异模拟气候变暖,研究了川西亚高山/高山森林在生长季节和季节性冻融期间土壤的净氮矿化量和净氮矿化速率.结果表明： 在川西亚高山/高山森林,土壤铵态氮和硝态氮含量均表现为从生长季节至冻结初期明显下降,完全冻结期明显增加,而在融化初期明显降低的变化过程.季节性冻融期土壤的净氮矿化量和净氮矿化速率显著低于生长季节,并且出现明显的氮素固持现象.与低海拔相比,中海拔森林土壤的氮素固持作用相对较大,高海拔相对较小,可能与不同海拔梯度土壤温度变化及引起的冻融循环密切相关.在生长季节,土壤净氮矿化量和矿化速率均随海拔的降低呈明显增加趋势,尤其在低海拔处土壤的氮素矿化作用最为强烈.在气候变暖背景下,温度的增加明显促进了生长季节土壤氮素矿化,并且通过提高冻融循环频次、缩短冻结时间来影响土壤氮素矿化速率.这一过程可能受到微环境的影响.     

不同培养温度下严重侵蚀红壤的有机碳矿化特征

研究侵蚀土壤有机质矿化及其温度敏感性(Q₁₀)对深入认识水土流失地区土壤有机碳动态变化具有重要意义。该文以福建省长汀县河田镇严重侵蚀区的裸露红壤为研究对象, 通过测定不同培养温度(10 ℃、20 ℃和30 ℃)下的土壤有机碳矿化速率、培养过程中微生物生物量碳(MBC)和可溶性有机碳(DOC)含量的变化, 探讨了温度对严重侵蚀红壤有机碳矿化特征的影响及其Q₁₀。结果表明: 温度对严重侵蚀红壤有机碳矿化具有显著影响, 温度越高土壤有机碳矿化速率和矿化率越高; 培养过程中土壤有机碳累积矿化量与MBC显著正相关, 与DOC极显著负相关, 说明微生物生物量和可利用碳含量显著影响土壤有机碳的矿化。尽管严重侵蚀红壤有机碳含量仅为1.54 g·kg^-1, 但培养180天的土壤有机碳的累积矿化率高达22.2%-33.3%, 表明侵蚀红壤有机碳容易被矿化。严重侵蚀红壤在10-20 ℃时的Q₁₀值为1.41, 20-30 ℃时Q₁₀值下降到1.06, 土壤有机碳质量低是导致Q₁₀值较低的重要原因, 而严重侵蚀区的红壤长期裸露使微生物对高温产生适应性是高温时Q₁₀值接近1的重要原因。因此, 在未来气候变暖的趋势下, 恢复植被覆盖对减少严重侵蚀红壤有机碳矿化损失具有重要意义。     

马尾松人工林土壤和团聚体有机碳矿化对穿透雨减少的响应

为研究气候变化背景下降水格局对森林土壤碳排放机制的影响,在南亚热带马尾松人工林中模拟穿透雨减少50%,采用室内恒温培养法研究减水处理对土壤和不同粒级团聚体有机碳矿化的影响.结果表明: 1～2 mm团聚体有机碳累积矿化量高于其他粒级团聚体.干湿季减雨样地表层土壤含水量分别是对照样地的82.1%和82.7%,而其0.106～0.25 mm土壤团聚体质量分数分别比对照增加1.8%和4.2%.与对照相比,穿透雨减少显著降低了干季土壤和微团聚体易矿化碳库的矿化速率(k₁),增加了土壤和<1 mm团聚体难分解碳库的分解速率(k₂),但对土壤有机碳累积矿化量无显著影响.相关分析表明,土壤和微团聚体k₁呈显著正相关,土壤和0.25～1 mm团聚体k₂呈显著正相关.受团聚体结构、水分条件和土壤有机碳含量的影响,穿透雨减少对干季土壤易矿化和难分解有机碳的矿化分别起抑制和促进作用.     

水分对武夷山草甸土壤有机碳激发效应的影响

水分是影响土壤有机碳激发效应的重要因子,但水分如何影响山地草甸土有机碳激发效应尚不清楚.本试验以武夷山高海拔(2130 m)山地草甸土为研究对象,通过室内添加13C标记的葡萄糖结合控制土壤水分(30％FWC和60％ FWC,FWC为田间持水量),进行为期126 d的室内培养试验,定期测定CO2浓度和13C-CO2丰度值...     

长白山不同海拔梯度森林土壤中性糖分布特征

2010年7月,采集长白山北坡5个典型植被带(阔叶红松林、明针叶林、暗针叶林、岳桦林和高山苔原)林下土壤,研究了不同海拔梯度下森林土壤的中性单糖分布、数量及其影响因素,并结合中性糖来源差异探讨土壤有机质的生物化学积累机制.结果表明: 在长白山不同海拔梯度下,森林土壤的中性糖差异显著,中性糖来源碳在土壤有机碳(SOC)中的相对含量为80.55～170.63 mg·g^-1,并且随海拔升高呈递增的趋势.采用多元线性拟合分析发现,生长季平均气温是影响土壤中性糖相对含量的主要因素,低温有助于中性糖的积累.土壤中(半乳糖+甘露糖)/(阿拉伯糖+木糖)为1.62～2.28,且随海拔升高呈增加趋势,说明土壤中微生物来源中性糖的贡献随海拔升高逐渐增加.微生物熵随海拔升高而降低,说明低温条件下微生物活性下降而对外源碳的利用效率提高,植物残体被微生物分解转化后,以微生物同化物的形式固存于土壤中,从而增加了微生物来源中性糖的比例.     

Microbial characteristics of soils on a latitudinal transect in Siberia

Soil microbial properties were studied from localities on a transect along the Yenisei River, Central Siberia. The 1000 km‐long transect, from 56°N to 68°N, passed through tundra, taiga and pine forest characteristic of Northern Russia. Soil microbial properties were characterized by dehydrogenase activity, microbial biomass, composition of microbial community (PLFAs), respiration rates, denitrification and N mineralization rates. Relationships between vegetation, latitude, soil quality (pH, texture), soil organic carbon (SOC) and the microbial properties were examined using multivariate analysis. In addition, the temperature responses of microbial growth (net growth rate) and activity (soil respiration rate) were tested by laboratory experiments. The major conclusions of the study are as follows: 1. Multivariate analysis of the data revealed significant differences in microbial activity. SOC clay content was positively related to clay content. Soil texture and SOC exhibited the dominant effect on soil microbial parameters, while the vegetation and climatic effects (expressed as a function of latitude) were weaker but still significant. The effect of vegetation cover is linked to SOC quality, which can control soil microbial activity. 2. When compared to fine‐textured soils, coarse‐textured soils have (i) proportionally more SOC bound in microbial biomass, which might result in higher susceptibility of SOC transformation to fluctuation of environmental factors, and (ii) low mineralization potential, but with a substantial part of the consumed C being transformed to microbial products. 3. The soil microbial community from the northernmost study region located within the permafrost zone appears to be adapted to cold conditions. As a result, microbial net growth rate became negative when temperature rose above 5 °C and C mineralization then exceeded C accumulation.     

Carbon sequestration potential of soils in southeast Germany derived from stable soil organic carbon saturation

Sequestration of atmospheric carbon (C) in soils through improved management of forest and agricultural land is considered to have high potential for global CO₂ mitigation. However, the potential of soils to sequester soil organic carbon (SOC) in a stable form, which is limited by the stabilization of SOC against microbial mineralization, is largely unknown. In this study, we estimated the C sequestration potential of soils in southeast Germany by calculating the potential SOC saturation of silt and clay particles according to Hassink [Plant and Soil 191 (1997) 77] on the basis of 516 soil profiles. The determination of the current SOC content of silt and clay fractions for major soil units and land uses allowed an estimation of the C saturation deficit corresponding to the long‐term C sequestration potential. The results showed that cropland soils have a low level of C saturation of around 50% and could store considerable amounts of additional SOC. A relatively high C sequestration potential was also determined for grassland soils. In contrast, forest soils had a low C sequestration potential as they were almost C saturated. A high proportion of sites with a high degree of apparent oversaturation revealed that in acidic, coarse‐textured soils the relation to silt and clay is not suitable to estimate the stable C saturation. A strong correlation of the C saturation deficit with temperature and precipitation allowed a spatial estimation of the C sequestration potential for Bavaria. In total, about 395 Mt CO₂‐equivalents could theoretically be stored in A horizons of cultivated soils – four times the annual emission of greenhouse gases in Bavaria. Although achieving the entire estimated C storage capacity is unrealistic, improved management of cultivated land could contribute significantly to CO₂ mitigation. Moreover, increasing SOC stocks have additional benefits with respect to enhanced soil fertility and agricultural productivity.     

Carbon Sequestration in Reclaimed Minesoils

Minesoils are drastically influenced by anthropogenic activities. They are characterized by low soil organic matter (SOM) content, low fertility, and poor physicochemical and biological properties, limiting their quality, capability, and functions. Reclamation of these soils has potential for resequestering some of the C lost and mitigating CO₂ emissions. Soil organic carbon (SOC) sequestration rates in minesoils are high in the first 20 to 30 years after reclamation in the top 15 cm soil depth. In general, higher rates of SOC sequestration are observed for minesoils under pasture and grassland management than under forest land use. Observed rates of SOC sequestration are 0.3 to 1.85 Mg C ha^{? 1} yr^{? 1} for pastures and rangelands, and 0.2 to 1.64 Mg C ha^{? 1} yr^{? 1} for forest land use. Proper reclamation and postreclamation management may enhance SOC sequestration and add to the economic value of the mined sites. Management practices that may enhance SOC sequestration include increasing vegetative cover by deep-rooted perennial vegetation and afforestation, improving soil fertility, and alleviation of physical, chemical and biological limitations by fertilizers and soil amendments such as biosolids, manure, coal combustion by-products, and mulches. Soil and water conservation are important to SOC sequestration. The potential of SOC sequestration in minesoils of the US is estimated to be 1.28 Tg C yr^?1, compared to the emissions from coal combustion of 506 Tg C yr^{? 1}.     

武夷山不同海拔高度土壤活性有机碳变化

采用连续熏蒸 培养法,测定了福建武夷山自然保护区不同海拔高度具有代表性的中亚热带常绿阔叶林、针叶林、亚高山矮林以及高山草甸土壤中有效碳含量,分析了土壤有效碳（LOC）与微生物量碳（MBC）、土壤总有机碳（TOC）、细根生物量（FRB）和土壤全氮（TN）之间的关系.结果表明：土壤有效碳占总有机碳的3.40%～7.46%;微生物量碳只是土壤有效碳中的一部分,占土壤有效碳26.87%～80.38%; 不同林分土壤有效碳含量随海拔增高而显著增大,随土层深度的增加而降低;土壤有效碳与微生物量碳、土壤总有机碳、细根生物量、土壤全氮之间呈极显著的相关关系.高海拔土壤有效碳含量显著高于低海拔土壤.     

火烧对森林土壤有机碳的影响研究进展

对国内外火烧影响森林土壤有机碳动态的研究成果进行了综合述评。较多研究表明低强度火烧不会造成土壤有机碳贮量的明显变化,但火烧非常强烈而彻底,土壤有机碳明显减少。有限研究表明火烧对森林土壤呼吸的影响结果有增加、降低或无影响,因火烧强度、火后观测时间、森林类型、火烧迹地上植被恢复进程和气候条件等而异。同时,火烧对土壤有机碳组分(活性有机碳和黑碳)也具有不同程度的影响。随着全球变化研究的深入,火烧作为森林主要管理措施对大气CO2浓度影响亦愈来愈受重视,今后应着重开展以下几方面研究:(1)扩大气候和经营管理的变化对森林土壤有机碳贮量时空动态影响研究;(2)深入探讨火烧影响土壤CO2释放的过程及机理;(3)加强火烧历史和频率对黑碳影响的研究;(4)从广度和深度上加强火烧等经营措施对亚热带森林土壤碳动态影响的研究。     

Changes in soil carbon sequestration and soil respiration following afforestation on paddy fields in north subtropical China

Aims Although many studies have reported net gains of soil organic carbon (SOC) after afforestation on croplands, this is uncertain for Chinese paddy rice croplands. Here, we aimed to evaluate the effects of afforestation of paddy rice croplands on SOC sequestration and soil respiration (R s). Such knowledge would improve our understanding of the effectiveness of various land use options on greenhouse gas mitigation in China.Methods The investigation was conducted on the Chongming Island, north subtropical China. Field sites were reclaimed from coastal salt marshes in the 1960s, and soils were homogeneous with simple land use histories. SOC stocks and R s levels were monitored over one year in a paddy rice cropland, an evergreen and a deciduous broad-leaved plantation established on previous paddy fields and a reference fallow land site never cultivated. Laboratory incubation of soil under fast-changing temperatures was used to compare the temperature sensitivity (Q 10) of SOC decomposition across land uses.Important findings After 15–20 years of afforestation on paddy fields, SOC concentration only slightly increased at the depth of 0–5cm but decreased in deeper layers, which resulted in a net loss of SOC stock in the top 40cm. Seasonal increase of SOC was observed during the rice-growing period in croplands but not in afforested soils, suggesting a stronger SOC sequestration by paddy rice cropping. However, SOC sequestered under cropping was more labile, as indicated by its higher contents of dissolved organic carbon and microbial biomass. Also, paddy soils had higher annual R s than afforested soils; R s abruptly increased after paddy fields were drained and plowed and remained distinctively high throughout the dry farming period. Laboratory incubation revealed that paddy soils had a much higher Q 10 of SOC decomposition than afforested soils. Given that temperature was the primary controller of R s in this region, it was concluded that despite the stronger SOC sequestration by paddy rice cropping, its SOC was less stable than in afforested systems and might be more easily released into the atmosphere under global warming.