造林恢复植被后土壤的化学计量学特征对其碳组分的影响

Afforestation is recognized as an important driving force for soil organic C(SOC) dynamics and soil element cycling.To evaluate the relationships between soil C:N:P stoichiometry and SOC fractions,soil C:N:P stoichiometry distributions at 0–200 cm soil depths were analyzed and the contents of SOC fractions were evaluated in 9 typical land-use systems on the Loess Plateau of China.The contents of light fraction organic C,particulate organic C(53,53–2 000,and2 000 μm),labile organic C,microbial biomass C,and dissolved organic C decreased with increasing soil depth and were higher in afforested soil than in slope cropland soil.Compared with the slope cropland,different vegetation types influenced soil C:N,C:P,and N:P ratios,especially when C:P and N:P ratios were significantly higher(P0.05).Moreover,SOC fractions at the 0–10 and 10–40 cm depths were particularly affected by soil C:P ratio,whereas those at the 40–100 and 100–200 cm soil depths were significantly affected(P0.05) by soil N:P ratio.These results indicate that changes in SOC fractions are largely driven by soil C:P and N:P ratios at different soil depths after afforestation.     

施肥对土壤不同碳形态及碳库管理指数的影响

分析了施肥对土壤活性碳（ＣＡ）、微生物生物量碳（ＣＭＢ）、矿化碳（ＣＭ）及碳库管理指数（ＣＰＭＩ）的影响。结果表明,不同土壤ＣＡ、ＣＭＢ、ＣＭ及ＣＰＭＩ的大小为：水稻土〉黄棕壤〉红壤〉潮土。施肥对ＣＡ和ＣＰＭＩ,ＣＭＢ和ＣＭ的影响分别为：处理３〉处理〉处理１〉处理４〉ＣＫ,处理３〉处理５〉处理４〉处理１〉ＣＫ。在提高ＣＡ、ＣＭＢ、ＣＭ及ＣＰＭＩ方面,稻草肥、绿肥优于厩肥,厩肥高量施用优于常量施用。     

Is thermal oxidation at different temperatures suitable to isolate soil organic carbon fractions with different turnover?

Findings of previous studies suggest that there are relations between thermal stability of soil organic matter (SOM), organo‐mineral associations, and stability of SOM against microbial decay. We aimed to test whether thermal oxidation at various temperatures (200°C, 225°C, 275°C, 300°C, 400°C, or 500°C) is capable of isolating SOM fractions with increasing stability against microbial degradation. The investigation was carried out on soils (Phaeozem and Luvisol) under different land‐use regimes (field, grassland, forest). The stability of the obtained soil organic carbon (SOC) fractions was determined using the natural‐¹³C approach for continuously maize‐cropped soils and radiocarbon dating. In the Luvisol, thermal oxidation with increasing temperatures did not yield residual SOC fractions of increasing microbial stability. Even the SOC fraction resistant to thermal oxidation at 300°C contained considerable amounts of young, maize‐derived C. In the Phaeozem, the mean ¹⁴C age increased considerably (from 3473 y BP in the mineral‐associated SOC fraction to 9116 y BP in the residual SOC fraction after thermal oxidation at 300°C). An increasing proportion of fossil C (calculated based on ¹⁴C data) in residual SOC fractions after thermal oxidation with increasing temperatures indicated that this was mainly due to the relative accumulation of thermally stable fossil C. We conclude that thermal oxidation with increasing temperature was not generally suitable to isolate mineral‐associated SOC fractions of increasing microbial stability.     

Soil carbon pools and fluxes after land conversion in a semiarid shrub-steppe ecosystem

Worldwide soil carbon (C) losses associated with agricultural expansion and intensification have contributed significantly to increased atmospheric CO₂. Soil disturbances resulting from land use changes were shown to modify the turnover of C and the formation of soil organic matter. A native semiarid shrub-steppe ecosystem recently converted into an irrigated agricultural development in the Columbia Basin of Washington State was evaluated for several abiotic indicators that might signal changes in an ecosystem during the initial stages of conversion and disturbance. Soil samples were collected in March of 2003 and 2004 from nine sites that included native shrub-steppe and agricultural fields converted in 2001 and 2002. Disturbance from conversion to irrigated crop production influenced total organic C and nitrogen (N) storage, C and N mineralization, and C turnover. Cultivated fields had greater concentrations of total organic C and N and higher cumulative C and N mineralization than native sites after 3 years of cultivation. Soil organic C was divided into three pools: an active pool (C _a) consisting of labile C (simple sugars, organic acids, the microbial biomass, and metabolic compounds of incorporated plant residues) with a mean residence time of days, an intermediate or slow pool (C _s) consisting of structural plant residues and physically stabilized C, and a resistant fraction (C _r) consisting of lignin and chemically stabilized C. Extended laboratory incubations of soil with measurements of CO₂ were used to differentiate the size and turnover of the C _a and C _s functional C pools. The active pools were determined to be 4.5 and 6.5% and slow pools averaged 44 and 47% of the total C in native and cultivated fields, respectively. Cultivation, crop residue incorporation, and dairy manure compost amendments contributed to the increase in total soil C.     

用DEA法的两个模型测算农机化贡献率的算法研究

测算农机化贡献率的主要目的是从数量关系上认识农机化对农业增产增收带来的实际作用大小。在实践上有助于从总体上把握农业机械化的发展水平、发展潜力和发展趋势，在理论上研究产业系统单因素的贡献率具有学术意义。该文提出了综合运用DEA法的C²R和C²GS²两个模型，测算农机化贡献率的基本方法。该算法克服了现有DEA算法测算农机化贡献率时无法考虑技术进步所做的贡献而导致农机化贡献率偏大的问题，使测算结果更接近真实情况。     

泰国东部土地由森林转化为玉米地引起土壤有机碳流失及其储量的降低

Soil organic carbon(SOC) content and its stable carbon isotopic composition(within the upper 1 m) were measured to determine the e?ect of land-use changes from dry evergreen forest to maize fields in eastern Thailand.Digital land cover maps,derived from aerial photography and satellite images for years 1989,1996,and 2002 were used in association with field surveys and farmer interviews to derive land-use history and to assist in study site selection.Conversion from forest to maize cultivation for the duration of 12 years reduced SOC stocks at the rate of 6.97 Mg C ha-1 year-1.Reduction was most pronounced in the top 10 cm soil layer,which was 47% after 12 years of cultivation.Stable carbon isotope data revealed that the main fraction lost was forest-derived C.Generally low input rates of maize-derived C were not sufficient to maintain SOC at the level prior to forest conversion.After 12 years of continuous maize cultivation,the maize-derived C fraction made up about 20% of total SOC(5 Mg ha-1 of the total 25.31 Mg ha-1).     

The initial rate of C substrate utilization and longer-term soil C storage

The initial reaction of microbial transformation and turnover of soil carbon inputs may influence the magnitude of longer-term net soil C storage. The objective of this study was to test the merit of the hypothesis that the more rapid substrates are initially utilized, the longer the residual products remain in the soil. We used simple model C compounds to determine their decomposition rates and persistence over time. Pure ¹⁴C compounds of glucose, acetate, arginine, oxalate, phenylalanine, and urea were incubated in soil for 125 days at 24°C. Total respired CO₂ and ¹⁴CO₂ was quantitatively measured every day for 15 days and residual soil ¹⁴C after 125 days. The percent ¹⁴C remaining in the soil after 125 days of incubation was positively and significantly correlated with the percent substrate utilized in the first day of incubation. The ¹⁴C in the microbial biomass ranged from 4–15% after 15 days and declined through day 125, contributing significantly to the ¹⁴C that evolved over the longer time period. Priming of ¹²C soil organic matter (SOM) was negative at day 3 but became positive, reaching a maximum on day 12; the total increase in soil C from added substrates was greater than the primed C. The primed C came from ¹²C SOM rather than the microbial biomass. This data supports the concept that the more rapidly a substrate is initially mineralized, the more persistent it will be in the soil over time.     

改种玉米连续3年后稻田土壤有机碳分布和13C自然丰度变化

耕作制更替下土壤有机碳的变化是阐明土地利用变化下土壤碳循环改变及其全球变化效应的重要方面。本研究选择了太湖地区毗邻的一块长期稻油轮作的稻田和一块稻田改种玉米3年的旱田，采集其剖面不同深度的土壤样品，分别测定全土和分离的土壤团聚体颗粒组中总有机碳（TOC）、土壤溶解有机碳（DOC）和微生物生物量碳（sMBC），并对选择性样本测定了有机质的δ^13 C值，分析改种玉米后水稻土有机碳储量及其同位素组成的变化。结果表明，改种玉米3年后，耕层土壤TOC明显下降，而DOC和SMBC都有增加的趋势；改种玉米后2—0．2mm粗团聚体颗粒组的TOC含量降低，而其他团聚体颗粒组TOC无显著变化。玉米地表层土壤（0—15cm）原土及各粒级团聚体的δ^13 C值均明显高于原稻田。改种玉米后进入水稻土中的源于玉米的新碳绝大部分集中在0—20cm土层，且主要富集在粗团聚体颗粒组中。计算表明，粗团聚体颗粒组中有机碳更新周期明显较短。水田转变成旱地后，耕层土壤有机碳分解加速，碳储量快速减少。这说明水稻土中物理保护的有机碳可能因耕作改变下团聚体破坏而快速分解。     

基于C2C网站的农产品网络营销实现

本文首先介绍了网络营销的含义，并说明采用网络营销的方法推销农产品的意义，然后对当前重要的网络营销网站淘宝网、易趣网及拍拍网上农产品的销售情况进行说明，最后说明采用C2C网站进行网络营销时如何解决安全问题。     

Soil organic carbon accumulation and carbon costs related to tillage, cropping systems and nitrogen fertilization in a subtropical Acrisol

Conservation management systems can improve soil organic matter stocks and contribute to atmospheric C mitigation. This study was carried out in a 18-year long-term experiment conducted on a subtropical Acrisol in Southern Brazil to assess the potential of tillage systems [conventional tillage (CT) and no-till (NT)], cropping systems [oat/maize (O/M), vetch/maize (V/M) and oat + vetch/maize + cowpea (OV/MC)] and N fertilization [0 kg N ha⁻¹ year⁻¹ (0 N) and 180 kg N ha⁻¹ year⁻¹ (180 N)] for mitigating atmospheric C. For that, the soil organic carbon (SOC) accumulation and the C equivalent (CE) costs of the investigated management systems were taken into account in comparison to the CT O/M 0 N used as reference system. No-till is known to produce a less oxidative environment than CT and resulted in SOC accumulation, mainly in the 0–5 cm soil layer, at rates related to the addition of crop residues, which were increased by legume cover crops and N fertilization. Considering the reference treatment, the SOC accumulation rates in the 0–20 cm layer varied from 0.09 to 0.34 Mg ha⁻¹ year⁻¹ in CT and from 0.19 to 0.65 Mg ha⁻¹ year⁻¹ in NT. However, the SOC accumulation rates peaked during the first years (5th to 9th) after the adoption of the management practices and decreased exponentially over time, indicating that conservation soil management was a short-term strategy for atmospheric C mitigation. On the other hand, when the CE costs of tillage operations were taken into account, the benefits of NT to C mitigation compared to CT were enhanced. When CE costs related to N-based fertilizers were taken into account, the increases in SOC accumulation due to N did not necessarily improve atmospheric C mitigation, although this does not diminish the agricultural and economic importance of inorganic N fertilization.     

Effect of labile and recalcitrant carbon on heterotrophic nitrification in a subtropical forest soil

Carbon (C) is an important factor controlling heterotrophic nitrification in soil, but the effect of individual C components (e.g., labile and recalcitrant C) is largely unclear. We carried out a C amendment experiment in which either labile C (glucose) or a recalcitrant C (cellulose and biochar) was added to a subtropical forest soil. A ¹⁵N-, ¹³C-tracing and MiSeq sequencing study was performed to investigate soil gross heterotrophic nitrification rates, carbon utilization for soil respiration and microbial biomass production and microbial composition, respectively. After 2 days, results showed a significant increase of gross heterotrophic nitrification rate in glucose (GLU) (on average 3.34 mg N kg⁻¹ day⁻¹), cellulose (CEL) (on average 0.21 mg N kg⁻¹ day⁻¹) and biochar (BIO) (on average 0.13 mg N kg⁻¹ day⁻¹) amendment in comparison with the unamended soil (CK) (on average 0.01 mg N kg⁻¹ day⁻¹; p < 0.05). The contribution of heterotrophic nitrification to total soil nitrification was significantly larger in GLU (average 85.86%), CEL (average 98.52%) and BIO (average 81.25%) treatments compared with CK (average 33.33%; p < 0.01). After 2-month amendment, the gross rates remarkably decreased in GLU (average 0.02 mg N kg⁻¹ day⁻¹), and the contribution to total nitrification (average 8.73%) were significantly lower than that in CK (p < 0.05). A decrease in the proportion of heterotrophic nitrification to total nitrification in soil was also observed in CEL (average 38.40%) and BIO (6.74%) treatments. Nevertheless, BIO amendment (compared to CK, GLU and CEL) showed the highest gross heterotrophic nitrification rate, accompanied by a notably higher abundance of specific heterotrophic nitrifiers, i.e. Trichoderma, Aspergillus and Penicillium. These results point to a stimulatory effect of C addition on soil heterotrophic nitrification in the short term, while the stimulatory impact of C amendment diminishes with the decline in easily available C. In addition, a shift of the microbial composition in the long term can possibly be sustained for longer if additional recalcitrant C is available to heterotrophic nitrifiers. The dynamic response of heterotrophic nitrification to labile and recalcitrant C in this study offered an explanation for the positive effect of plantation and plant root exudation on the process.     

不同气候带水稻土有机碳δ13C及胡敏酸结构特征变化

选取位于吉林龙井、河南封丘、浙江慈溪和江西进贤的4种水稻土剖面,分析比较了不同气候带水稻土剖面和各粒级复合体的有机碳及其δ13C值的分布特征,探讨了不同水稻土胡敏酸结构和功能基团构成的差异,旨在为深入研究水稻土有机碳动态变化和运转机理提供参考依据。结果表明:不同气候带水稻土剖面中,有机碳δ13C值均随着土层深度的增加逐渐升高;样点位置愈往北,水稻土表层有机碳δ13C值愈高。各样点水稻土表层有机碳主要集中在<10μm复合体部分,其有机碳分配系数均大于50%。水稻土不同粒级复合体δ13C值随着粒级的减小不断升高,高δ13C的老碳在细粒中富集;水稻土表层<10μm复合体中有机碳的降解程度为:封丘>慈溪>进贤>龙井。各样点水稻土胡敏酸结构大致相似,封丘和龙井的水稻土胡敏酸含有较多CO基团,氧化程度较高,另外,其胡敏酸的芳化度和聚合程度也高于慈溪和进贤的水稻土。     

土壤中14C-甲磺隆存在形态的动态研究

利用同位素示踪技术 ,在实验室条件下研究了1 4 C -甲磺隆在 1 5种不同土壤中存在形态的动态变化。结果表明 ,土壤pH值与甲磺隆1 4 C残留物的降解半衰期、残留量及可提取态残留量呈显著的正相关 ,而与结合态残留量呈显著负相关 ;土壤微生物的活性越强 ,甲磺隆降解速率越快 ,但结合态残留量也越高 ;土壤中各腐殖质组分和粘粒的含量也影响甲磺隆在土壤中的降解速率和存在形态。土壤中甲磺隆的残留符合一级反应动力学指数方程C =C0 e-kt,拟合方程的复相关系数达到极显著水平。甲磺隆残留与土壤性质之间经逐步回归分析可得到拟合效果较好的方程 ,由各自变量的决定系数可知 ,土壤pH值、微生物生物量碳和有机碳中富啡酸碳所占的比例是影响甲磺隆在土壤中残留的主要因素     

Do cover crops impact labile C more than total C? Data synthesis

The potential of cover crops (CC) to increase total soil organic C (SOC) concentration can be inconsistent, but labile SOC is considered to be more sensitive to management than total SOC. This leads to two questions: Do CCs impact labile SOC more than total SOC? Do CCs increase labile SOC more rapidly than total SOC? This review compares CC impacts on labile and total SOC based on CC studies reporting both parameters up to 31 Dec 2022. Labile and total SOC concentrations were measured in 31 CC study locations. Cover crops increased labile SOC concentration in 58% (18 of 31) and had no effect in 42% (13 of 31) of locations, suggesting CCs do not increase labile SOC in all cases. Within the 18 locations, CCs increased labile SOC without increasing total SOC in only 19% (6 of 31 locations), while in the rest (12 of 31) of locations, CCs increased both labile and total SOC. Thus, CCs increased labile SOC more rapidly than total SOC in only one-fifth of cases. Also, the few studies that monitored changes in labile SOC with time found CCs do not always increase labile more rapidly than total SOC. In the 12 locations where CCs increased both labile and total SOC, CCs increased labile SOC by 54 ± 30% and total SOC by 23 ± 10%, indicating CCs can increase labile SOC by about two times compared with total SOC in some locations. Increased CC biomass production and reduced residue decomposition can increase labile SOC. Overall, CCs increase labile SOC in most cases but may not always increase labile SOC more rapidly than total SOC although more CC studies monitoring changes in SOC pools with time are needed to better understand CC impacts on SOC fractions under different CC management scenarios and climatic conditions.     

秸秆添加对石灰性土壤有机与无机碳释放的影响

在富含碳酸盐的石灰性土壤上,土壤本身CO2释放不仅来自土壤有机碳（SOC）的分解,也源于无机碳（SIC）的溶解。在秸秆还田下,石灰性土壤CO2释放来源达到三个（秸秆碳、SOC和SIC）,由于区分技术的限制,当前区分CO2释放三源的研究,尚少见报道。以华北石灰性农田土壤为研究对象,采用13C标记玉米秸秆添加土壤进行室内培养32周,设置4个处理,分别为无添加对照（CK）、低量秸秆添加（S1,相当于田间秸秆还田量9.6 t?hm-2）、中量秸秆添加（S2,秸秆还田量28.8 t?hm-2）和高量秸秆添加（S3,秸秆还田量48.0 t?hm-2）,利用秸秆碳、SOC与SIC之间的δ13C差异,借助稳定同位素溯源模型IsoSource,区分土壤CO2的释放来源,明确秸秆添加对石灰性土壤有机与无机碳释放的影响。结果表明,随着培养时间的进行,土壤释放CO2中源于秸秆的贡献呈下降趋势;秸秆分解对土壤CO2释放的贡献随着秸秆添加量增加而增加,对于S1、S2和S3处理,土壤释放CO2中源于秸秆、SOC和SIC的贡献比值约分别为3:3:4、5:2:3和6:2:2;与CK相比,S1处理降低SOC分解的激发效应（程度为9%）,S2和S3处理反而增加了SOC分解的激发效应（程度分别为22%和57%）;秸秆和SOC矿化增加SIC溶解的释放,随秸秆添加量增加而增加,S1、S2和S3处理提高SIC源CO2的释放程度分别为368%、561%和652%。因此,秸秆添加不仅影响SOC源CO2的释放,也增加了SIC源CO2的释放,若忽略SIC溶解对土壤CO2释放的贡献,可能导致SOC矿化量的高估,进而影响SOC激发效应评估的准确度。     

施肥对黑土活性有机碳和碳库管理指数的影响

运用更有效的量化指标来了解和表征土壤碳库的变化是研究土壤碳库动态平衡的基础,也是评价土壤肥力和生态系统的可持续性的必要手段。我们采用土壤碳库管理指数,讨论了国家黑土肥力监测区内的不同施肥情况下土壤碳库的变化。结果显示:施肥与否、施肥种类和数量均对土壤活性有机碳和土壤碳库管理指数有非常显著的影响,施肥尤其高量有机肥与化肥(NPK)配施。更有助于土壤活性有机碳的增加,相应地也就提高了土壤碳库管理指数(CMPI),M2+CK、M4+CK、MO+NPK、M1+NPK、1.5M1+NPK、M2+NPK、M4+NPK各施肥处理对土壤活性有机碳提高的贡献率分别高达15.6％、24.8％、63.6％、135.1％、144.2％、185.9％和256.5％,对土壤碳库管理指数的提高系数达0.48、0.72、1.17、3.21、4.70、7.86和10.44。农业生产中必须切实地重视高量有机肥与化肥(NPK)的配施,以求保持土壤肥力,提高土壤质量,使土壤碳库处于良性状态,最终达到维持土壤的可持续利用之目的。     

Modeling carbon dynamics in subsoils using simple models

Soil C dynamics below the plow layer have been little studied, despite a suspected large C‐stabilization potential of subsurface horizons. The objective of this study was to test two simple models (model A: single compartment for C₃‐ and for C₄‐derived C; model B: division of C₃‐ and C₄‐derived C into active and passive compartments) in their ability to simulate the C dynamics in subsoil horizons of a Haplic Phaeozem after conversion from C₃ (rye) to C₄ cropping (maize). The models were calibrated on an unfertilized maize soil and then validated on a maize soil with NPK fertilization. Both models simulated well C₃‐C and C₄‐C dynamics in the investigated soil depths (20–40 cm and 40–60 cm). In all cases, the model efficiency EF was > 0, which indicated that the simulated values described the trend in the measured data better than the mean of the observations. However, we observed some inconsistency in the obtained parameter set (e.g., a higher proportion of passive C for C₄‐derived than for C₃‐derived C or a very low decomposition rate constant for passive C₄‐C in 40–60 cm), which we assume to result from data restrictions on the investigated soils. More detailed data on SOC pools and turnover rates in subsoils which are generally not yet available for most experimental plots is vitally needed—especially for applying more sophisticated C‐dynamics models.     

Redistribution of crop residues during row cultivation creates a biologically enhanced environment for soil microorganisms

Formation of ridges during row cultivation creates microsites that could enhance spatial heterogeneity of soil properties, such as organic C, and thereby influence soil microbial communities. A study was conducted during 2003 near Shelton, NE, on a corn (Zea mays L.) field mapped using apparent electrical conductivity (ECa). New ridges were built each year with a row cultivator when corn reached the V3–V4 growth stage. Cultivation increased labile C fractions and soil microbial biomass in the row position for all ECa classes. Canonical discrimination analysis showed no clear differences in relative abundance of specific microbial groups among ECa classes or between row and furrow position, except for enhanced mycorrhizal biomass in the row. Microbial biomass responded strongly to changes in C redistribution, but was not accompanied by a significant change in the abundance of specific microbial groups. Labile C fractions (coarse and fine particulate organic matter) and crop residues in diverse stages of decomposition are associated with diverse microbial groups. Thus, row cultivation for weed control creates a biologically enhanced root zone that may improve early season performance of corn.     

Alterations of soil aggregates and intra-aggregate organic carbon fractions after soil conversion from paddy soils to upland soils: Distribution, mineralization and driving mechanism

Investigating the impacts of soil conversion on soil organic carbon(OC) content and its fractions within soil aggregates is essential for defining better strategies to improve soil structure and OC sequestration in terrestrial ecosystems. However, the consequences of soil conversion from paddy soil to upland soil for soil aggregates and intra-aggregate OC pools are poorly understood. Therefore, the objective of this study was to quantify the effects of soil conversion on soil aggregate and intra...     

相比其他传统作物作为生物能源作物柳枝稷种植土壤上的有机碳库研究

Switchgrass (Panicum virgatum L.) has been proposed as a sustainable bioenergy crop because of its high yield potential, adaptation to marginal sites, and tolerance to water and nutrient limitations. A better understanding of the potential effects of biomass energy crop production practices on soil biological properties and organic matter dynamics is critical to its production. Our objective was to evaluate changes in C pools under a warm-season perennial switchgrass in different soils compared to typically-grown crops collected at College Station, Dallas, and Stephenville, TX in February 2001. Sampling depths were 0-5, 5-15, and 15-30 cm. Switchgrass increased soil organic C (SOC), soil microbial biomass C (SMBC), mineralizable C, and particulate organic matter C (POM-C) compared to conventional cropping systems. Soil C concentrations were in the order: long-term coastal bermudagrass [Cynodon dactylon (L.) Pers.]> switchgrass or kleingrass (Panicum coloratum L.) planted in 1992> switchgrass 1997> conventional cropping systems. Soil C concentrations tended to increase with increasing clay content. Greater microbial biomass C followed the order of Dallas> College Station> Stephenville, and ranged from approximately 180 mg C kg-1 soil at Stephenville to 1 900 mg C kg-1 soil at Dallas. Particulate organic C was more sensitive than other fractions to management, increasing as much as 6-fold under long-term coastal bermudagrass compared to conventional cropping systems. Our study indicated that conversion of conventional cropping systems into switchgrass production can sequestrate more SOC and improve soil biological properties in the southern USA.