长期施肥条件下土壤碳氮循环过程研究进展

土壤是主要的陆地生态系统碳库,碳、氮通过大气-作物-土壤界面进行周转和协同转化。长期施肥通过改变土壤物理、化学和生物学性质,进而影响土壤有机碳、氮储量的稳定性。土壤有机质是评价土壤质量的重要指标,具有农艺和环境双重功能。有机-无机肥配施不仅可显著提高土壤肥力,并且可减少农田土壤温室气体排放,保持农田土地的可持续利用。本文就土壤碳、氮消长动态研究以及有机质周转的同位素示踪测试技术等作一简要综述。     

FACE 条件下休闲和秸秆还田对稻麦轮作农田麦季土壤酶活性的影响

利用中国唯一的江都FACE(Free-airCO2 enrichment,开放式空气CO2浓度升高)平台,研究了大气CO2浓度升高下休闲(fallow,不种作物,但翻耕和施肥与其他处理相同)和秸秆还田对土壤脱氢酶、β-葡萄糖苷酶、转化酶、芳基硫酸酯酶和荧光素二乙酸酯水解(FDA)的影响。研究结果表明:大气CO2浓度升高对于休闲土壤酶活性没有影响。在没有秸秆还田的情况下,大气CO2浓度升高刺激了土壤中脱氢酶、β-葡萄糖苷酶、转化酶、芳基硫酸酯酶的活性和FDA水解,增加幅度分别达到了14.88%、19.41%、11.69%、17.12%和4.47%。除转化酶外,秸秆还田使土壤酶活性增加。随着秸秆还田量的增加,FACE效应先增加后消失。     

关于土壤-作物生态系统中镉的研究

系统地介绍了国际上有关土壤-作物生态系统中镉的含量、形态、分布及其对生物危害等方面的研究成果。     

蚯蚓对土壤碳氮循环关键过程的影响及其机制研究进展

蚯蚓作为典型的大型土壤动物,对土壤结构和功能的形成具有重要的影响,被称作土壤生态系统工程师.国内外关于蚯蚓对土壤理化性质、土壤微生物群落组成、有机质分解和土壤矿化等方面的研究较多,但其对土壤碳、氮循环关键过程的系统总结较少.本文总结了蚯蚓通过摄食、挖洞、产生蚓粪及促进团聚体形成等活动对土壤碳氮循环产生的直接影响,及对微...     

利用作物模型研究气候变化对农业影响的发展过程

模型模拟是研究气候变化对农业生产影响的有效途径,得到了广泛关注和应用。本文着重介绍了利用作物模型研究气候变化对农业生产影响的发展过程,即从最初通过人为改变气候参数模拟气候变化对农业的可能影响,到与气候情景结合模拟未来气候变化对农业的可能影响及近年来与其它模型结合综合模拟未来气候变化对农业的影响,并通过对气候变化农业影响模型模拟研究中经验模型与机理模型、站点尺度与区域尺度、确定性气候情景与概率气候情景几个关键问题的评述,指出了存在的问题及未来发展趋势。     

草原生态系统土壤-植被组分中氮、磷、钾、钙和镁的循环

本文研究了内蒙古锡林河流域两种典型草原的生产力、营养元素在生态系统中的分配及其循环.研究表明,除C和N在植物组分中贮量稍高以外,P、K、Ca和Mg的99%以上存于土壤分室中.而植物组分中的营养元素则主要贮存于根系之中.1985年至1986年,羊草草原地上凋落物的形成量为234克·米^-2,大针茅草原为88.4克·米^-2;同期凋落物的消失量分别为219.6和91.1克·米^-2;从活根向死根生物量的年转移量分别为1712和920克·米^-2;根系的降解速率分别为0.00355和0.00365克·克^-1·天^-1.文中给出了诸元素在生态系统中的循环图,讨论了两类草原生态系统中元素循环的特点.     

小麦-玉米-大豆轮作下黑土农田土壤呼吸与碳平衡

农田生态系统是陆地生态系统的重要组成部分,探讨农田生态系统的土壤呼吸与碳平衡对于科学评价陆地生态系统在全球变化下的源汇效应具有重要意义。基于中国科学院海伦农业生态实验站的长期定位试验,对不同施肥处理下黑土小麦-玉米-大豆轮作体系2005—2007年的作物固碳量与土壤CO2排放通量进行了观测,并对该轮作体系下黑土农田生态系统的碳平衡状况进行了估算。结果表明:在小麦-玉米-大豆轮作体系中,作物固碳量的高低表现为:玉米>大豆>小麦,平均值分别为6 513 kg(C).hm-2、4 025 kg(C).hm-2和3 655kg(C).hm-2。从作物生长季土壤CO2排放总量来看,3种作物以大豆农田生态系统的土壤CO2排放总量最高,平均值达4 062 kg(C).hm-2;其次为玉米,为3 813 kg(C).hm-2;而小麦最低,为2 326 kg(C).hm-2。3种作物轮作下NEP(净生态系统生产力)均为正值,表明黑土农田土壤-作物系统为大气CO2的"汇",不同作物系统的碳汇强度表现为玉米>小麦>大豆,三者的平均值分别为3 215 kg(C).hm-2、1 643 kg(C).hm-2和512 kg(C).hm-2。长期均衡施用氮、磷、钾化肥或氮、磷、钾化肥配施有机肥后,小麦、玉米和大豆农田生态系统的固碳量和土壤CO2排放总量均明显增加,并在氮、磷、钾配施有机肥处理下达到最高。不同的施肥管理措施将改变土壤-植物系统作为大气CO2"汇"的程度,总体表现为化肥均衡施用下NEP值较高,而化肥与有机肥配施下农田生态系统的NEP值较低。     

岳桦和暗针叶林两种植被类型下土壤碳氮元素的转化过程

Soil samples were taken from an Ermans birch (Betula ermanii)-dark coniferous forest (Picea jezoensis and Abies nephrolepis) ecotone growing on volcanic ejecta in the northern slope of Changbai Mountains of Northeast China, to compare soil carbon (C) and nitrogen (N) transformations in the two forests. The soil type is Umbri-Gelic Cambosols in Chinese Soil Taxonomy. Soil samples were incubated aerobically at 20℃ and field capacity of 700 g kg^-1 over a period of 27 weeks. The amount of soil microbial biomass and net N mineralization were higher in the Ermans birch than the dark coniferous forest (P < 0.05), whereas the cumulative C mineralization (as CO₂ emission)in the dark coniferous forest exceeded that in the Ermans birch (P < 0.05). Release of the cumulative dissolved organic C and dissolved organic N were greater in the Ermans birch than the dark coniferous forest (P < 0.05). The results suggested that differences of forest types could result in considerable change in soil C and N transformations.     

金沙江干热峡谷中退化的土壤生态系统生物学特征初探

Distribution characteristics of soil animals,microorganisms and enzymatic activity were studied in the dry red soil and Vertisol ecosystems with different degradation degrees in the Yuanmou dry hot valley of the Jinsha River,China.Results showed that Hymenoptera,Araneae and Collembola were the dominant groups of soil animals in the polts studied.The numbers of groups and individuals and density of soil animals in the dry red soil series were higher than those in the Vertisol series,and the numbers of individuals and density of soil animals decreased with the degree of soil degradation.Bacteria dominated microbiococnosis not only in the dry red soils but also in the Vertisols.Microbial numbers of the dry red soil series were higher than those of Vertisol series,and decreased with the degree of soil degradation.The activities of catalase,invertase,urease and alkaline phosphatase declined with the degradation degree and showed a significant decline with depth in the profiles of both the dry red soils and the Vertisols,but activities of polyphenol oxidase and acid and neutral phosphatase showed the same tendencies only in the Vertisols.It was concluded that the characteristics of soil animals,microorganisms and enzymatic activity could be used as the bio-indicators to show the degradation degree of the dry red soils and Vertisols.Correlation among these soil bio-indicators was highly significant.     

Repeated CO2 pulse-labelling reveals an additional net gain of soil carbon during growth of spring wheat under free air carbon dioxide enrichment (FACE)

Rising levels of atmospheric CO₂ have often been found to increase above and belowground biomass production of C3 plants. The additional translocation of organic matter into soils by increased root mass and exudates are supposed to possibly increase C pools in terrestrial ecosystems. Corresponding investigations were mostly conducted under more or less artificial indoor conditions with disturbed soils. To overcome these limitations, we conducted a ¹⁴CO₂ pulse-labelling experiment within the German FACE project to elucidate the role of an arable crop system in carbon sequestration under elevated CO₂. We cultivated spring wheat cv. “Minaret” with usual fertilisation and ample water supply in stainless steel cylinders forced into the soil of a control and a FACE plot. Between stem elongation and beginning of ripening the plants were repeatedly pulse-labelled with ¹⁴CO₂ in the field. Soil born total CO₂ and ¹⁴CO₂ was monitored daily till harvest. Thereafter, the distribution of ¹⁴C was analysed in all plant parts, soil, soil mineral fractions and soil microbial biomass. Due to the small number of grown wheat plants (40) in each ring and the inherent low statistical power, no significant above and belowground growth effect of elevated CO₂ was detected at harvest. But in comparison to ambient conditions, 28% more ¹⁴CO₂ and 12% more total CO₂ was evolved from soil under elevated CO₂ (550 μmol CO₂ mol⁻¹). In the root-free soil 27% more residual ¹⁴C was found in the FACE soil than in the soil from the ambient ring. In soil samples from both treatments about 80% of residual ¹⁴C was found in the clay fraction and 7% in the silt fraction. Very low ¹⁴C contents in the CFE extracts of microbial biomass in the soil from both CO₂ treatments did not allow assessing their influence on this parameter. Since the calculated specific radioactivity of soil born ¹⁴CO₂ gave no indication of an accelerated priming effect in the FACE soil, we conclude that wheat plants grown under elevated CO₂ can contribute to an additional net carbon gain in soils.     

Promise and pitfalls of modeling grassland soil moisture in a free-air CO2 enrichment experiment (BioCON) using the SHAW model

Free-air carbon dioxide (CO₂) enrichment (FACE) experiments provide an opportunity to test models of heat and water flow under novel, controlled situations and eventually allow use of these models for hypothesis evaluation. This study assesses whether the United States Department of Agriculture SHAW (Simultaneous Heat and Water) numerical model of vertical one-dimensional soil water flow across the soil-plant-atmosphere continuum is able to adequately represent and explain the effects of increasing atmospheric CO₂ on soil moisture dynamics in temperate grasslands. Observations in a FACE experiment, the BioCON (Biodiversity, CO₂, and Nitrogen) experiment, in Minnesota, USA, were compared with results of vertical soil moisture distribution. Three scenarios represented by different plots were assessed: bare, vegetated with ambient CO₂, and similarly vegetated with high CO₂. From the simulations, the bare plot soil was generally the wettest, followed by a drier high-CO₂ vegetated plot, and the ambient CO₂ plot was the driest. The SHAW simulations adequately reproduced the expected behavior and showed that vegetation and atmospheric CO₂ concentration significantly affected soil moisture dynamics. The differences in modeled soil moisture amongst the plots were largely due to transpiration, which was low with high CO₂. However, the modeled soil moisture only modestly reproduced the observations. Thus, while SHAW is able to replicate and help broadly explain soil moisture dynamics in a FACE experiment, its application for point- and time-specific simulations of soil moisture needs further scrutiny. The typical design of a FACE experiment makes the experimental observations challenging to model with a one-dimensional distributed model. In addition, FACE instrumentation and monitoring will need improvement in order to be a useful platform for robust model testing. Only after this can we recommend that models such as SHAW are adequate for process interpretation of datasets from FACE experiments or for hypothesis testing.     

Carbon dynamics in a temperate grassland soil after 9 years exposure to elevated CO2 (Swiss FACE)

Elevated pCO₂ increases the net primary production, C/N ratio, and C input to the soil and hence provides opportunities to sequester CO₂-C in soils to mitigate anthropogenic CO₂. The Swiss 9 y grassland FACE (free air carbon-dioxide enrichment) experiment enabled us to explore the potential of elevated pCO₂ (60 Pa), plant species (Lolium perenne L. and Trifolium repens L.) and nitrogen fertilization (140 and 540 kg ha⁻¹ y⁻¹) on carbon sequestration and mineralization by a temperate grassland soil. Use of ¹³C in combination with respired CO₂ enabled the identification of the origins of active fractions of soil organic carbon. Elevated pCO₂ had no significant effect on total soil carbon, and total soil carbon was also independent of plant species and nitrogen fertilization. However, new (FACE-derived depleted ¹³C) input of carbon into the soil in the elevated pCO₂ treatments was dependent on nitrogen fertilization and plant species. New carbon input into the top 15 cm of soil from L. perennne high nitrogen (LPH), L. perenne low nitrogen (LPL) and T. repens low nitrogen (TRL) treatments during the 9 y elevated pCO₂ experiment was 9.3±2.0, 12.1±1.8 and 6.8±2.7 Mg C ha⁻¹, respectively. Fractions of FACE-derived carbon in less protected soil particles >53 μm in size were higher than in <53 μm particles. In addition, elevated pCO₂ increased CO₂ emission over the 118 d incubation by 55, 61 and 13% from undisturbed soil from LPH, LPL and TRL treatments, respectively; but only by 13, 36, and 18%, respectively, from disturbed soil (without roots). Higher input of new carbon led to increased decomposition of older soil organic matter (priming effect), which was driven by the quantity (mainly roots) of newly input carbon (L. perenne) as well as the quality of old soil carbon (e.g. higher recalcitrance in T. repens). Based on these results, the potential of well managed and established temperate grassland soils to sequester carbon under continued increasing concentrations of atmospheric CO₂ appears to be rather limited.     

FACE条件下小麦冠层能量平衡和水分利用率的变化

本文利用中国开放式CO2浓度增高(Free-air CO2 Enrichment,简称FACE)系统平台,于2007年3月19日至5月24日小麦拔节至成熟期进行小麦冠层微气候及相关项目的连续观测,并结合能量平衡分析,研究中国FACE系统对小麦冠层能量平衡各分量的变化特征及水分利用率的影响.能量平衡分析结果表明,小麦冠层白天总显热通量FACE均高于对照,而总潜热通量FACE均低于对照,潜热通量FACE与对照的差异日最大值变化在-12～-63 W˙m-2之间,显热通量FACE与对照的差异最大值变化在12～78 W-m-2之间.能量平衡是小气候变化的根本,利用p-M方程反演出的冠层群体气孔导度与实测的气孔导度相关关系较好,证明能量平衡的计算结果及小气候观测数据基本正确.观测期间内模拟计算结果表明,CO2浓度升高使小麦的水分利用减小约25.5 mm,结合生物量的增加,FACE条件下小麦水分利用率增加约19%.     

Dynamics of labile and recalcitrant soil carbon pools in a sorghum free-air CO2 enrichment (FACE) agroecosystem

Experimentation with dynamics of soil carbon pools as affected by elevated CO₂ can better define the ability of terrestrial ecosystems to sequester global carbon. In the present study, 6 N HCl hydrolysis and stable-carbon isotopic analysis (δ¹³C) were used to investigate labile and recalcitrant soil carbon pools and the translocation among these pools of sorghum residues isotopically labeled in the 1998-1999 Arizona Maricopa free air CO₂ enrichment (FACE) experiment, in which elevated CO₂ (FACE: 560 μmol mol⁻¹) and ambient CO₂ (Control: 360 μmol mol⁻¹) interact with water-adequate (wet) and water-deficient (dry) treatments. We found that on average 53% of the final soil organic carbon (SOC) in the FACE plot was in the recalcitrant carbon pool and 47% in the labile pool, whereas in the Control plot 46% and 54% of carbon were in recalcitrant and labile pools, respectively, indicating that elevated CO₂ transferred more SOC into the slow-decay carbon pool. Also, isotopic mixing models revealed that increased new sorghum residue input to the recalcitrant pool mainly accounts for this change, especially for the upper soil horizon (0-30 cm) where new carbon in recalcitrant soil pools of FACE wet and dry treatments was 1.7 and 2.8 times as large as that in respective Control recalcitrant pools. Similarly, old C in the recalcitrant pool under elevated CO₂ was higher than that under ambient CO₂, indicating that elevated CO₂ reduces the decay of the old C in recalcitrant pool. Mean residence time (MRT) of bulk soil carbon at the depth of 0-30 cm was significantly longer in FACE plot than Control plot by the averages of 12 and 13 yr under the dry and wet conditions, respectively. The MRT was positively correlated to the ratio of carbon content in the recalcitrant pool to total SOC and negatively correlated to the ratio of carbon content in the labile pool to total SOC. Influence of water alone on the bulk SOC or the labile and recalcitrant pools was not significant. However, water stress interacting with CO₂ enhanced the shift of the carbon from labile pool to recalcitrant pool. Our results imply that terrestrial agroecosystems may play a critical role in sequestrating atmospheric CO₂ and mitigating harmful CO₂ under future atmospheric conditions.     

Seasonality of soil biological properties in a poplar plantation growing under elevated atmospheric CO2

Microorganisms are the regulators of decomposition processes occurring in soil, they also constitute a labile fraction of potentially available N. Microbial mineralization and nutrient cycling could be affected through altered plant inputs at elevated CO_2. An understanding of microbial biomass and microbial activity in response to belowground processes induced by elevated CO₂ is thus crucial in order to predict the long-term response of ecosystems to climatic changes. Microbial biomass, microbial respiration, inorganic N, extractable P and six enzymatic activities related to C, N, P and S cycling (β-glucosidase, cellulase, chitinase, protease, acid phosphatase and arylsulphatase) were investigated in soils of a poplar plantation exposed to elevated CO_2. Clones of Populus alba, Populus nigra and Populus x euramericana were grown in six 314 m² plots treated either with atmospheric (control) or enriched (550 μmol mol⁻¹ CO₂) CO₂ concentration with FACE technology (free-air CO₂ enrichment). Chemical and biochemical parameters were monitored throughout a year in soil samples collected at five sampling dates starting from Autumn 2000 to Autumn 2001.

The aim of the present work was: (1) to determine if CO₂ enrichment induces modifications to soil microbial pool size and metabolism, (2) to test how the seasonal fluctuations of soil biochemical properties and CO₂ level interact, (3) to evaluate if microbial nutrient acquisition activity is changed under elevated CO₂.

CO₂ enrichment significantly affected soil nutrient content and three enzyme activities: acid phosphatase, chitinase and arylsulphatase, indicators of nutrient acquisition activity. Microbial biomass increased by a 16% under elevated CO₂. All soil biochemical properties were significantly affected by the temporal variability and the interaction between time and CO₂ level significantly influenced β-glucosidase activity and microbial respiration. Data on arylsulphatase and chitinase activity suggest a possible shift of microbial population in favour of fungi induced by the FACE treatment.     

开放式空气CO2浓度升高对水稻/小麦轮作土壤速效钾的影响

采用FACE（Free air carbon dioxide enrichment）技术,研究了不同施N水平下,大气CO2浓度升高对水稻/小麦轮作土壤速效钾的影响。结果表明,相对于对照处理,在不同氮水平下CO2浓度升高使作物生物量增加,导致作物生长季对土壤钾的吸收增加,但并没有降低作物主要生长期土壤（0―5、5―15 cm土层）速效钾的含量;CO2浓度升高使土壤速效钾增加的幅度在作物根际达6.3%~22.3%,在行间达3.7%~11.2%,且土壤速效钾增加的幅度在小麦季大于水稻季。表明根系对土壤速效钾的影响很大,因此,短期内土壤钾含量不会成为限制因素而影响作物对高CO2浓度的响应,反而会增加土壤钾的有效性。但在土壤肥力较低的土壤上可能会产生消极影响。     

高浓度CO2下长白松幼苗土壤和根系呼吸

The objectives of this study were to investigate the effect of higher CO2 concentrations （500 and 700 μmol mol^-1） in atmosphere on total soil respiration and the contribution of root respiration to total soil respiration during seedling growth of Pinus sylvestris vat. sylvestriformis. During the four growing seasons （May-October） from 1999 to 2003, the seedlings were exposed to elevated concentrations of CO2 in open-top chambers. The total soil respiration and contribution of root respiration were measured using an LI-6400-09 soil CO2 flux chamber on June 15 and October 8, 2003. To separate root respiration from total soil respiration, three PVC cylinders were inserted approximately 30 cm deep into the soil in each chamber. There were marked diurnal changes in air and soil temperatures on June 15. Both the total soil respiration and the soil respiration without roots showed a strong diurnal pattern, increasing from before sunrise to about 14：00 in the afternoon and then decreasing before the next sunrise. No increase in the mean total soil respiration and mean soil respiration with roots severed was observed under the elevated CO2 treatments on June 15, 2003, as compared to the open field and control chamber with ambient CO2. However, on October 8, 2003, the total soil respiration and soil respiration with roots severed in the open field were lower than those in the control and elevated CO2 chambers. The mean contribution of root respiration measured on June 15, 2003, ranged from 8.3% to 30.5% and on October 8, 2003, from 20.6% to 48.6%.     

大气CO2浓度升高对温带森林土壤微生物活性的影响

Microorganisms play a key role in the response of soil ecosystems to the rising atmospheric carbon dioxide (CO2) as they mineralize organic matter and drive nutrient cycling. To assess the effects of elevated CO2 on soil microbial C and N immobilization and on soil enzyme activities, in years 8 (2006) and 9 (2007) of an open-top chamber experiment that begun in spring of 1999, soil was sampled in summer, and microbial biomass and enzyme activity related to the carbon (C), nitrogen (N) and phosphorus (P) cycling were measured. Although no effects on microbial biomass C were detected, changes in microbial biomass N and metabolic activity involving C, N and P were observed under elevated CO2. Invertase and dehydrogenase activities were significantly enhanced by different degrees of elevated CO2. Nitrifying enzyme activity was significantly (P < 0.01) increased in the August 2006 samples that received the elevated CO2 treatment, as compared to the samples that received the ambient treatment. Denitrifying enzyme activity was significantly (P < 0.04) decreased by elevated CO2 treatments in the August 2006 and June 2007 (P < 0.09) samples. β-N-acetylglucosaminidase activity was increased under elevated CO2 by 7% and 25% in June and August 2006, respectively, compared to those under ambient CO2. The results of June 2006 samples showed that acid phosphatase activity was significantly enhanced under elevated CO2. Overall, these results suggested that elevated CO2 might cause changes in the belowground C, N and P cycling in temperate forest soils.