苏打盐碱水灌溉的土壤添加石膏肥和有机肥后水溶性碳和微生物碳研究

Microbial biomass carbon (MBC), a small fraction of soil organic matter, has a rapid turnover rate and is a reservoir of labile nutrients. The water-extractable carbon pools provide a fairly good estimate of labile C present in soil and can be easily quantified. Changes in soil MBC and water-extractable organic carbon pools were studied in a 14-year long-term experiment in plots of rice-wheat rotation irrigated with canal water (CW), sodic water (SW, 10-12.5 mmol c L-1 residual sodium carbonate), and SW amended with gypsum with or without application of organic amendments including farmyard manure (FYM), green manure (GM), and wheat straw (WS). Irrigation with SW increased soil exchangeable sodium percentage by more than 13 times compared to irrigation with CW. Sodic water irrigation significantly decreased hot water-extractable organic carbon (HWOC) from 330 to 286 mg kg-1 soil and cold water-extractable organic carbon (CWOC) from 53 to 22 mg kg-1 soil in the top 0-7.5 cm soil layer. In the lower soil layer (7.5-15 cm), reduction in HWOC was not significant. Application of gypsum alone resulted in a decrease in HWOC in the SW plots, whereas an increase was recorded in the SW plots with application of both gypsum and organic amendments in both the soil layers. Nevertheless, application of gypsum and organic amendments increased the mean CWOC as compared with application of gypsum alone. CWOC was significantly correlated with MBC but did not truly reflect the changes in MBC in the treatments with gypsum and organic amendments applied. For the treatments without organic amendments, HWOC was negatively correlated with MBC (r = 0.57*) in the 0-7.5 cm soil layer, whereas for the treatments with organic amendments, both were positively correlated. Irrigation with SW significantly reduced the rice yield by 3 t ha-1 and the yield of rice and wheat by 5 t ha-1 as compared to irrigation with canal water. Application of amendments significantly increased rice and wheat yields. Both the rice yield and the yield of rice and wheat were significantly correlated with MBC (r = 0.49**-0.56**, n = 60). HWOC did not exhibit any relation with the crop yields under the treatments without organic amendments; however, CWOC showed a positive but weak correlation with the crop yields. Therefore, we found that under sodic water irrigation, HWOC or CWOC in the soils was not related to MBC.     

Responses of soil phosphorus pools accompanied with carbon composition and microorganism changes to phosphorus-input reduction in paddy soils

In rice-wheat rotation systems, changes in soil phosphorus(P) pools and microorganisms in rice-growing seasons have been studied;however, further investigations are required to test whether these indexes exhibit different responses in wheat-growing seasons. Additionally, such studies need to include potential variations in soil carbon(C) structure and microbial community composition. In this study, a long-term rice-wheat rotation P-input reduction experiment was conducted to observe the variations in soil P pools and C composition in the 7th wheat season and to investigate the responses of soil enzyme activity and microbial communities. Four P fertilization treatments were included in the experiment, i.e., P application for rice season only(PR), for wheat season only(PW), and for both rice and wheat seasons(PR+W) and no P application in either season(Pzero). Compared with PR+W treatment, Pzero treatment significantly decreased(P < 0.05) labile and stable P pools. Different P fertilization regimes altered soil microbial community composition and enzyme activity, whereas C composition did not vary. However, PW treatment resulted in relatively more O-alkyl-C than PR treatment and the highest number of microorganisms. Besides, the higher ratios of fungi/bacteria and Gram-positive bactetia/Gram-negative bactetia were related to labile C pools, particularly O-alkyl-C, as opposed to recalcitrant C. Our results clarified the status of soil P pools, C chemistry, and the response of microorganisms under dry-farming conditions in the P input-reduced rice-wheat rotation system.     

长期施用化肥和有机肥对太湖地区水稻土有机碳特征的影响

A long-term experiment set up in 1980 compared the effects of applying manures and chemical fertilizers on a paddy soil in the Taihu Lake region,China.Of the fourteen randomly distributed treatments consisting of different combinations of organic manure,inorganic nitrogen (N),phosphorus (P),and potassium (K),and rice straw,eight were selected for the present study in 2007.Application of organic manure plus straw significantly increased soil organic carbon (SOC) content of the topsoil (0-10 cm) compared to that of chemical fertilizers alone.The content of SOC was relatively stable in the 10-30 cm layer in the chemical fertilizer treatments and in the 20-40 cm layer in the manure treatments.The stable carbon isotope ratio (δ 13 C) ranged from 24‰ to 28‰ and increased gradually with depth.The content of SOC was significantly (P < 0.05) negatively correlated with δ 13 C.In the 0-20 cm layer,the δ 13 C value significantly decreased in the treatments of manure alone (M),manure and chemical N and P fertilizers (MNP),manure and chemical N,P,and K fertilizers (MNPK),manure,rice straw,and chemical N fertilizer (MRN),and chemical N fertilizer and rice straw (CNR),as compared with the no-fertilizer control.In the 30-50 cm layer,however,the ratio significantly increased in all the treatments except Treatment CNR.Mineralization of organic C peaked in the first 2-4 d of incubation and gradually leveled off thereafter over the first 3 weeks,being faster in the manure treatments than the chemical fertilizer treatments.The average rate of mineralization varied from 55.36 to 75.46 mL CO 2 kg-1 d-1 and that of stable mineralization from 10 to 20 mL CO 2 kg-1 d-1.In eight weeks of incubation,cumulative mineralization was always higher in the manure treatments than the chemical fertilizer treatments,being the highest in Treatment MRN.Combined humus in the soil was mainly (over 50%) composed of tightly combined fraction.The loosely combined humus and its ratio of humic acid (HA) to fulvic acid (FA) significantly increased with long-term application of organic manure and chemical fertilizers.It could be concluded that the cycle of organic C in the paddy soil ecosystem studied was stable over the long-term application of fertilizers and continued cultivation.     

采用土壤质量指数评估施肥对集约型稻麦轮作系统中土壤物理性质的影响

Soil quality assessment has been suggested as an effective tool for evaluating sustainability of soil and crop management practices.The objective of this study was to develop a sensitive soil quality index(SQI) based on bulk density(BD),water-holding capacity(WHC),water-stable aggregates(WSA),aggregate mean weight diameter(AMWD),total organic C(TOC) and C input to evaluate the important rice-wheat cropping system on an Inceptisol in India.A long-term experiment has been conducted for 18 years at the Indian Council of Agricultural Research-Indian Institute of Farming Systems Research,Modipuram,India.The treatments selected for this study were comprised of a no-fertilizer control and N,P and K fertilizers(NPK) combined with Zn and S fertilizers(NPK+ Zn+S),farmyard manure(NPK+FYM),green gram residues(NPK+GR) and cereal residues(NPK+CR),laid out in a randomized complete block design with three replications.Soil samples were collected and analyzed for BD,WHC,WSA and TOC.Correlation analysis revealed that both rice and wheat yields signi?cantly increased with the increases in AMWD,TOC and C input,but decreased with the increase in BD.The SQI values were then generated based on regression analysis of BD,WSA,AMWD,TOC and C input with rice and wheat yields for the 0–15 and 15–30 cm soil layers,respectively.Regression analyses between crop yields and SQI values showed a quadratic type of relation with the coeffcient of determination(R~2) varying from 0.78 to 0.89.With regard to soil sustainability,applying crop residues to both rice and wheat could maintain soil quality for a longer period,whereas the highest yields of both the crops were recorded in the NPK+Zn+S treatment.The regression equations developed in this study could be used to monitor soil quality in a subhumid tropical rice-wheat cropping system.     

在含盐新成土上施加有机肥和化学改良剂对土壤性质和作物产量的影响

A field experiment was conducted for two consecutive years in a farmer‘s field at Haji Mora Village, Dera Ismail Khan (D.I. Khan) in the Northwest Frontier Province (NWFP) of Pakistan to compare various management practices, such as the effect of various organic manures and gypsum in a rice-wheat cropping system on a saline-sodic Entisol (Zindani soil series). The treatments consisted of 1) a control (rice-wheat), 2) gypsum, 3) farmyard manure (FYM), 4) berseem (Trifolium alexandrinum L.) as green manure (GM), and 5) dhancha (Sesbania sp.) as GM. All treatments increased yields of both rice and wheat significantly (P (0.01) over the control, with the green manure treatments proving more economical than the others; while they decreased pH, electrical conductivity (EC), and sodium adsorption ratio (SAR) of the soil. Saturation percentage and available water of the soil were raised for all treatments due to an increase in organic matter content of the soil.     

有机物质对土壤溶液中铜形态的影响

Incubation of two soils,a red soil derived from granodiorte and a fluvo-aquic soil from alluvial deposit,with rice straw,Chinese milk vetch and pig manure under submerged condition were conducted to study the species of Cu in soil solutions as affected by the organic materials.The organic materials increased total soluble Cu by raising dissolved organic carbon(DOC) in soil solution when the solution pH values were below the range in which Cu deposited quickly.When the solution pH rose to this rage,the increase of DOC did not raise total soluble Cu.Total soluble Cu in all the treatments dropped with incubation time.After adding organic materials labile Cu dropped with incubation time and decreased sharply in the pH range of Cu precipitation.Addition of organic materials enhanced slowly labile Cu but depressed the ratio of labile Cu to total soluble Cu.Slowly labile Cu decreased with incubation time.Sepwise multiple linear regression analysis showed that total soluble Cu was positively correlated with Eh and DOC(P=0.0025),labile Cu was negatively correlated with pH(P=0.0118),and slowly labile Cu was positively correlated with Eh and DOC(P=0.0022).Both the labile and slowly labile Cu were correlated with total soluble Cu at extremely significant levels.     

Effect of Organic Manure Application on Physical Properties andHumus Characteristics of Paddy Soil

Long-term field experiment was established in 1978 on a coastal paddy soil to determine the effect of application of pig manure, rice straw and chemical N fertilizer on the physical property and humus characteristics of soil. Results showed that the porosity, the microstructural coefficient, the reactivities of organic C and N, the OlogK value, the degree of oxidation stability, the contents of o-alkyl C and alkyl C, and the ratio of aliphatic C to aromatic C of humic acid from soils received organic manure increased; whereas, the ratio of<10μm to >10μm of microaggregates, the humification degree of humus, the degree of organo-mineral complexation, the number-average molecular weight, the C/H ratio, the contents of carboxyl and aromatic C of HAs in them decreased. These results indicated that the application of organic manure not only improved the physical property of the paddy soil but also made the HA more aliphatic in structure and younger in origin.     

Soil phosphorus availability and rice phosphorus uptake in paddy fields under various agronomic practices

Agronomic practices affect soil phosphorus(P) availability, P uptake by plants, and subsequently the efficiency of P use. A field experiment was carried out to investigate the effects of various agronomic practices(straw incorporation, paddy water management, nitrogen(N) fertilizer dose, manure application,and biochar addition) on soil P availability(e.g., soil total P(STP), soil available P(SAP), soil microbial biomass P(SMBP), and rice P uptake as well as P use efficiency(PUE)) over four cropping seasons in a rice-rice cropping system, in subtropical central China. Compared to the non-straw treatment(control,using full dose of chemical N fertilizer), straw incorporation increased SAP and SMBP by 9.3%–18.5% and 15.5%–35.4%, respectively;substituting half the chemical N fertilizer dose with pig manure and the biochar application increased STP, SAP, and SMBP by 10.5%–48.3%, 30.2%–236.0%, and 19.8%–72.4%,respectively, mainly owing to increased soil P and organic carbon inputs;adding a half dose of N and no N input(reduced N treatments) increased STP and SAP by 2.6%–7.5% and 19.8%–33.7%, respectively, due to decreased soil P outputs. Thus, soil P availability was greatly affected by soil P input and use. The continuous flooding water regime without straw addition significantly decreased SMBP by 11.4% compared to corresponding treatments under a mid-season drainage water regime. Total P uptake by rice grains and straws at the harvest stage increased under straw incorporation and under pig manure application, but decreased under the reduced N treatments and under biochar application at a rate of 48 t ha-1, compared to the control. Rice P uptake was significantly positively correlated with rice biomass, and both were positively correlated with N fertilizer application rates, SAP, SMBP, and STP. Phosphorus use efficiency generally increased under straw incorporation but decreased under the reduced N treatments and under the manure application(with excessive P input), compared to the control. These results showed that straw incorporation can be used to increase soil P availability and PUE while decreasing the use of chemical P fertilizers. When substituting chemical fertilizers with pig manure, excess P inputs should be avoided in order to reduce P accumulation in the soil as well as the environmental risks from non-point source pollution.     

Air-drying changes the distribution of Hedley phosphorus pools in forest soils

Hedley labile phosphorus(P)pools in soil tend to be several times larger than annual forest requirements,even in highly weathered soils characterized by P limitation.The discrepancy between plant and soil P status could be partly attributable to the frequently adopted air-drying pretreatment that tends to increase soil P solubility.In this study,the effects of air-drying on the distribution of Hedley P fractions were examined using soils collected under 4 forest types at Gongga Mountain,southwestern China.The results showed that the microbial biomass P(Pmic)in the organic horizon decreased markedly after air-drying.The concentrations of Hedley labile P in the air-dried samples were 31%–73%more than those in the field-moist samples.Consequently,the air-drying-induced increments of Hedley labile P pools in the surface soil horizons were 0.8–3.8 times the annual plant P requirements.The organic horizon was more susceptible to the air-drying-induced increases in Hedley labile P than the mineral horizon,probably because of the stronger release of Pmicand disruption of soil organic matter.The quality of P,indexed by the ratio of Hedley labile P to slowly cycling P,shifted in favor of the Hedley labile fractions after air-drying,further revealing that air-drying changed the distribution of Hedley P pools in forest soils.These indicated that the effects of air-drying could not be ignored when interpreting the discrepancy between the P status of plants and the Hedley labile P pools in forest soils.To more efficiently evaluate the P status in forest soils via the Hedley fractionation procedure,the use of field-moist soils is recommended.     

有机物料对淹水土壤中施入的镉形态的影响

The effect of three organic materials(rice straw,Chinese milk vetch and pig manure)on the fractionation of cadmium added into two soils(a red soil and a fluvo-aquic soil) was studied using submerged incubation experiment.The organic materials increased soil soild organic carbon(SOC),pH value,the concentration of active Si in all the treatments and active Fe and Mn in some treatments.Accumulated SOC caused directly the increase of Cd bound to solid organic matter and consequently the decrease of exchangeable Cd.Higher active Si and pH,as well as lower Eh,were also responsible for the reduction of exchangeable Cd.Cd bound to mn oxide was positively correlated with pH values and rose significantly after one-month incubation,but decreased after three-month incubation.Cd bound to amporphous Fe oxide increased with the incubation time,but was not affected significantly by adding organic materials.     

不同森林植被下土壤活性有机碳的含量及动态变化

Soil organic matter （SOM） in forest ecosystems is not only important to global carbon （C） storage but also to sustainable management of forestland with vegetation types, being a critical factor in controlling the quantity and dynamics of SOM. In this field experiment soil plots with three replicates were selected from three forest vegetation types： broadleaf, Masson pine （Pinus massoniana Lamb.）, and Chinese fir （Cunninghamia lanceolata Hook.）. Soil total organic C （TOC）, two easily oxidizable C levels （EOC1 and EOC2, which were oxidized by 66.7 mmol L^-1 K2Cr2O7 at 130-140℃ and 333 mmol L^-1 KMnO4 at 25 ℃, respectively）, microbial biomass C （MBC）, and water-soluble organic C （WSOC） were analyzed for soil samples. Soil under the broadleaf forest stored significantly higher TOC （P ≤ 0.05）. Because of its significantly larger total soil C storage, the soil under the broadleaf forest usually had significantly higher levels （P ≤ 0.05） of the different labile organic carbons, EOC1, EOC2, MBC, and WSOC; but when calculated as a percentage of TOC each labile C fraction of the broadleaf forest was significantly lower （P ≤ 0.05） than one of the other two forests. Under all the three vegetation types temperature as well as quality and season of litter input generally affected the dynamics of different organic C fractions in soils, with EOC1, EOC2, and MBC increasing closely following increase in temperature, whereas WSOC showed an opposite trend.     

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.     

Soil aggregation and aggregate-associated organic carbon under typical natural halophyte communities in arid saline areas of Northwest China

Information on the effects of halophyte communities on soil organic carbon(SOC)is useful for sequestrating C in arid regions.In this study,we identified four typical natural halophyte communities in the Manasi River Basin in Xinjiang Province,Northeast China,namely,Karelinia caspia(Pall.)Less.,Bassia dasyphylla(Fisch.et C.A.Mey.)Kuntze,Haloxylon ammodendron(C.A.Mey.)Bunge,and Tamarix ramosissima Lour.We compared soil aggregation and aggregated-associated SOC under these communities.The aggregate fraction of 0.053–0.25 mm accounted for 47%–75%of the total soil mass,significantly more than the>0.25 and<0.053 mm fractions,under all the halophyte communities.Significant differences in soil aggregate size distribution were observed among the plant communities,with the H.ammodendron and B.dasyphylla communities showing the highest proportions of>0.25 mm aggregates(13.3%–43.8%)and T.ramosissima community having more<0.053 mm aggregates(14.1%–27.2%).Aggregate-associated SOC concentrations were generally the highest in the>0.25 mm fraction,followed by the<0.053 mm fraction,and were the lowest in the 0.053–0.25 mm fraction;however,because of their large mass,0.25–0.053 mm aggregates contributed significantly more to the total SOC.Total SOC concentrations(0–60 cm depth)decreased in the order of H.ammodendron(5.7 g kg^-1)>T.ramosissima(4.9 g kg^-1)>K.caspia(4.2 g kg^-1)>B.dasyphylla(3.4 g kg^-1).The H.ammodendron community had the highest total SOC and aggregate-associated SOC,which was primarily because aggregate-associated SOC content at the 0–10 and 10–20 cm depths under this community were higher than those under other plant communities.The H.ammodendron community could be beneficial for increasing SOC in saline soils in the arid region.     

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.     

长期不同施肥对潮土芽胞杆菌数量的影响及其优势度的季节变化

以河南封丘潮土养分平衡长期定位试验地为研究对象,于各季节分别采集耕作层土壤样品,比较不同施肥处理潮土芽胞杆菌数量及其占细菌总数的比例,并解析其与土壤养分之间的关系.结果发现,与不施肥对照相比,长期施肥尤其是施用有机肥和磷肥的处理土壤有机碳与速效氮、有效磷、速效钾等的含量趋于升高,除不施磷肥处理(NK)外其他施肥处理土壤有机碳含量在四季的增幅范围为0.91 ～7.00 g kg-1.长期不同施肥后土壤细菌与芽胞杆菌在数量上也发生了明显分异,且在各季均呈现稳定的梯度规律,即施肥处理(除NK外)显著高于不施肥处理、施有机肥处理显著高于施化肥处理、平衡施化肥处理高于缺素施肥处理,除NK外其他施肥处理与不施肥对照相比在四季的增幅范围力0.02～0.54 lg(CFU g-1).长期施化肥的处理芽胞杆菌占细菌数量的比例(即优势度)在冬、夏季高于春、秋季,而施有机肥的处理在不同季节保持相对恒定.相关性分析显示,芽胞杆菌数量与土壤有机碳和有效磷含量均呈极显著相关(p＜0.01).长期施用有机肥更有利于提高土壤肥力、促进土壤微生物生长繁育,且芽胞杆菌的数量可敏感地反映土壤肥力.     

Variations of SOC and MBC observed in an incubated brown loam soil managed under different tillage systems for 12 years

To assess changes in organic carbon pools, an incubation experiment was conducted under different temperatures and field moisture capacity (FMC) on a brown loam soil from three tillage practices used for 12 years: no‐till (NT), subsoiling (ST) and conventional tillage (CT). Total microbial respiration was measured for incubated soil with and without the input of straw. Results indicated that soil organic carbon (SOC) and microbial biomass carbon (MBC) under ST, NT and CT was higher in soil with straw input than that without, while the microbial quotient (MQ or MBC: SOC) and metabolic quotient (qCO₂) content under CT followed the opposite trend. Lower temperature, lower moisture and with straw input contributed to the increases in SOC concentration, especially under NT and ST systems. The SOC concentrations under ST, with temperatures of 30 and 35°C after incubation at 55% FMC, were greater than those under CT by 28.4% and 30.6%, respectively. The increase in MBC was highest at 35°C for 55%, 65% and 75% FMC; in soil under ST, MBC was greater than that under CT by 199.3%, 50.7% and 23.8%, respectively. At 30°C, the lower qCO₂ was obtained in soil incubated under NT and ST. The highest MQ among three tillage practices was measured under ST at 55% FMC, NT at 65% FMC and CT at 75% FMC with straw input. These data indicate the benefits of enhancing the MQ; the low FMC was beneficial to ST treatment. Under higher temperature and drought stress conditions, the adaptive capacity of ST and NT is better than that of CT.     

The Origin of Soil Organic C,Dissolved Organic C and Respiration in a Long‐Term Maize Experiment in Halle,Germany, Determined by 13C Natural Abundance

For a quantitative analysis of SOC dynamics it is necessary to trace the origins of the soil organic compounds and the pathways of their transformations. We used the ¹³C isotope to determine the incorporation of maize residues into the soil organic carbon (SOC), to trace the origin of the dissolved organic carbon (DOC), and to quantify the fraction of the maize C in the soil respiration. The maize‐derived SOC was quantified in soil samples collected to a depth of 65 cm from two plots, one ’︁continuous maize’ and the other ’︁continuous rye’ (reference site) from the long‐term field experiment ’︁Ewiger Roggen’ in Halle. This field trial was established in 1878 and was partly changed to a continuous maize cropping system in 1961. Production rates and δ¹³C of DOC and CO₂ were determined for the Ap horizon in incubation experiments with undisturbed soil columns. After 37 years of continuous maize cropping, 15% of the total SOC in the topsoil originated from maize C. The fraction of the maize‐derived C below the ploughed horizon was only 5 to 3%. The total amount of maize C stored in the profile was 9080 kg ha⁻¹ which was equal to about 31% of the estimated total C input via maize residues (roots and stubble). Total leaching of DOC during the incubation period of 16 weeks was 1.1 g m⁻² and one third of the DOC derived from maize C. The specific DOC production rate from the maize‐derived SOC was 2.5 times higher than that from the older humus formed by C₃ plants. The total CO₂‐C emission for 16 weeks was 18 g m⁻². Fifty‐eight percent of the soil respiration originated from maize C. The specific CO₂ formation from maize‐derived SOC was 8 times higher than that from the older SOC formed by C₃ plants. The ratio of DOC production to CO₂‐C production was three times smaller for the young, maize‐derived SOC than for the older humus formed by C₃ plants.     

不同植被恢复对侵蚀型红壤活性碳库的影响

为了解侵蚀型红壤不同植被恢复后,土壤有机碳的演变状况,采集了持续时间为17年和9年的2个定位试验点土壤样品,分析了土壤总有机碳、微生物量碳、水溶性碳和矿化态碳含量.结果表明侵蚀型红壤植被恢复后,土壤总有机碳和各类活性碳含量均明显增加,并随着恢复时间的延长,土壤各类碳含量显著上升.同样是杉木林,恢复17年的土壤(0～20 cm)总有机碳、微生物量碳、水溶性碳和矿化态碳的含量分别是恢复9年土壤的2.18倍、2.95倍、2.25倍和2.01倍.不同处理比较来看,木荷林土壤各类碳含量明显高于杉木林土壤,黑麦草处理矿化态碳含量明显高于恢复时间相同的杉木和胡柚处理.分析了各处理活性碳占总有机碳的比例发现,植被恢复17年的2个处理,土壤微生物量占总有机碳比例明显高于恢复9年的3个处理;恢复时间分别为17年和9年的2个杉木处理,土壤水溶性碳占总有机碳比例明显较高,而矿化态碳占总有机碳比例明显偏低;黑麦草处理矿化态碳占总有机碳比例明显高于恢复时间相同的杉木和胡柚处理.从相关分析来看,土壤总有机碳、微生物量碳、水溶性碳及矿化态碳两两之间相关性均达极显著水平(P＜0.01);土壤各类碳与土壤全氮、水解氮、有效磷含量之间也具有极显著相关性.