施用秸秆及接种蚯蚓对土壤颗粒有机碳及矿物结合有机碳的影响

在连续四年稻麦轮作的小区试验中,通过测定作物收获后表层土壤(0～5cm、5～10cm、10～20cm)中有机碳(SOC)、颗粒有机碳(POC)和矿物结合有机碳(MOC)含量的变化,研究施用秸秆(表施或混施)和接种蚯蚓(Metaphireguillelmi)对SOC、POC及MOC的影响。结果表明:无论是否接种蚯蚓,经连续四年施用秸秆后,土壤0～5cm、5～10cm、10～20cm及0～20cm各土层的SOC和POC含量、0～5cm土层中MOC含量、10～20cm土层w(POC)/w(MOC)值均显著增加;混施秸秆相比表施秸秆更有利于各土层SOC与5～10cm土层POC含量提高。在施用秸秆条件下,接种蚯蚓使0～20cm耕作层土壤中POC和MOC含量有增加趋势;在秸秆施用且接种蚯蚓时,0～20cm耕作层的w(POC)/w(MOC)值均显著升高(与对照相比),表明秸秆施用且接种蚯蚓有助于土壤有机碳活性的提高。田间施用秸秆及接种蚯蚓对于促进农田土壤有机碳库增加及加快土壤有机碳循环与转化均有重要的意义。     

Particulate organic carbon and nitrogen in the eastern pacific ocean

Particulate organic carbon and nitrogen in sea water were measured in samples collected along a line 155°W; 50° N-15°S, during the cruise of R.V. “Hakuho-Maru” (KH-69-4). High concentrations of particulate matter were generally found at or near the sea surface; the concentrations decreased rapidly with depth. A consistent minimum was located in the depth range 150 to 250 m through the entire section sampled. The subsurface maximum layers roughly coincided with the chlorophyll maximum, but several irrregularities were noted. One of the most remarkable features of the vast stratum below 200 m depth was the presence of distinctively regional variation in concentration of particulate material through the entire section. In the section, we could define at least 6 large water parcels, vertically oriented, all with significantly different concentrations of both carbon and nitrogen. Variation in the deep water ranged from less than 5 μgC/l to more than 50 μgC/l. Correlation analysis between carbon concentration and apparent oxygen utilization (AOU) of ambient water for all samples showed that the carbon from particle-poor water parcels consistently decreased with increasing AOU, levelling to a practically constant low of around 5 to 10 μgC/l, whereas the carbon from particle-rich parcels was anomalously high (10 to 50 μgC/l) in the range of high AOU, and showed no consistent trend of convergence. The intergrated amount of particulate carbon in the total water column at each station was in the range 20 to 150 gC/m². More than 90% of this total amount was in the water column below 200 m depth, and the correlation of total amount of particulate material between the surface layer (0 to 200 m) and the water column below 200 m depth was highly significant. These observations are considered to indicate that the downward transport of these materials may be much quicker than so far estimated, at least in some localized areas.     

Particulate organic carbon and nitrogen in the adjacent seas of the Pacific Ocean

Particulate organic carbon (POC) and nitrogen in sea water were measured in samples collected in the adjacent seas of the Pacific Ocean during the cruises of T. S. Oshoro-Maru (1969, 1970) and the R. V. Hakuho-Maru (KH-70-4, KH-72-1). High values were obtained in the northern North Pacific and the Bering Sea, the concentration of particulate carbon in the upper 50-m layer ranged from 35 to 550 g Cl^-1. In the deep waters of these area, values above 50 g Cl^-1 were frequently observed. The lowest values in the surface layer and deeper layers were obtained in the Japan Sea (23 gCl^-1) and in the South China Sea (7 g Cl^-1) respectively. A consistent minimum was located in the intermediate waters (100–400 m) throughout the entire region studied. Variation with depth was generally irregular with marked peak values in different layers. The POC distribution consited of these peak values and a relatively uniform background concentration. These background values slightly decreased with increasing depth and were different locally. Correlation analysis between carbon concentration and apparent oxygen utilization (AOU) of ambient water for the samples in the Japan Sea and the Sulu Sea showed that there was no systematic decrease of particulate carbon with increasing AOU. In these areas, the carbon concentration scattered in the higher AOU domain ranged from 10–100 g Cl^-1. These observations support the conception that downward transport of particulate matter from the overlying surface layer in the adjacent seas of the Pacific Ocean may be fairly rapid.     

Examining the coupling of carbon and nitrogen cycles in Appalachian streams: the role of dissolved organic nitrogen

Although regional and global models of nitrogen (N) cycling typically focus on nitrate, dissolved organic nitrogen (DON) is the dominant form of nitrogen export from many watersheds and thus the dominant form of dissolved N in many streams. Our understanding of the processes controlling DON export from temperate forests is poor. In pristine systems, where biological N limitation is common, N contained in recalcitrant organic matter (OM) can dominate watershed N losses. This recalcitrant OM often has moderately constrained carbon:nitrogen (C:N) molar ratios (approximately 25-55) and therefore, greater DON losses should be observed in sites where there is greater total dissolved organic carbon (DOC) loss. In regions where anthropogenic N pollution is high, it has been suggested that increased inorganic N availability can reduce biological demand for organic N and therefore increase watershed DON losses. This would result in a positive correlation between inorganic and organic N concentrations across sites with varying N availability. In four repeated synoptic surveys of stream water chemistry from forested watersheds along an N loading gradient in the southern Appalachians, we found surprisingly little correlation between DON and DOC concentrations. Further, we found that DON concentrations were always significantly correlated with watershed N loading and stream water [NO3-] but that the direction of this relationship was negative in three of the four surveys. The C:N molar ratio of dissolved organic matter (DOM) in streams draining watersheds with high N deposition was very high relative to other freshwaters. This finding, together with results from bioavailability assays in which we directly manipulated C and N availabilities, suggests that heterotrophic demand for labile C can increase as a result of dissolved inorganic N (DIN) loading, and that heterotrophs can preferentially remove N-rich molecules from DOM. These results are inconsistent with the two prevailing hypotheses that dominate interpretations of watershed DON loss. Therefore, we propose a new hypothesis, the indirect carbon control hypothesis, which recognizes that heterotrophic demand for N-rich DOM can keep stream water DON concentrations low when N is not limiting and heterotrophic demand for labile C is high.     

Dynamics of nitrogen and dissolved organic carbon at the Hubbard brook experimental forest

The factors controlling spatial and temporal patterns in soil solution and streamwater chemistry are highly uncertain in northern hardwood forest ecosystems in the northeastern United States, where concentrations of reactive nitrogen (Nr) in streams have surprisingly declined over recent decades in the face of persistent high rates of atmospheric Nr deposition and aging forests. Reactive nitrogen includes inorganic species (e.g., ammonium [NH4+], nitrate [NO3-]) and some organic forms (e.g., amino acids) available to support the growth of plants and microbes. The objective of this study was to examine controls on the spatial and temporal patterns in the concentrations and fluxes of nitrogen (N) species and dissolved organic carbon (DOC) in a 12-year record of soil solutions and streamwater along an elevational gradient (540-800 m) of a forested watershed at the Hubbard Brook Experimental Forest (HBEF) in the White Mountains of New Hampshire, USA. Dissolved organic N and DOC concentrations were elevated in the high-elevation spruce-fir-white birch (SFB) zone of the watershed, while NO3- was the dominant N species in the lower elevation hardwood portion of the watershed. Within the soil profile, N retention was centered in the mineral horizon, and significant amounts of N were retained between the lower mineral soil and the stream, supporting the idea that near- and in-stream processes are significant sinks for N at the HBEF. Temporal analysis suggested that hydrologic flow paths can override both abiotic and biotic retention mechanisms (i.e., during the non-growing season when most hydrologic export occurs, or during years with high rainfall), there appears to be direct flushing of N from the organic horizons into the stream via horizontal flow. Significant correlations between soil NO3- concentrations, nitrification rates and streamwater NO3- exports show the importance of biological production as a regulator of inorganic N export. The lack of internal production response (e.g., mineralization, nitrification) to a severe ice storm in 1998 reinforces the idea that plant uptake is the dominant regulator of export response to disturbance.     

Using a CHN analyzer to reduce carbonate interference in particulate organic carbon analyses

Using a CHN analyzer at a reduced temperature (720°C), the organic carbon of particulates taken from water is oxidized while little, if any, dissociation of carbonate occurs. When necessary for increased precision or for samples with a high CaCO₃ content, the small interference of carbonate with organic C determinations can be quantified by running representative samples at different oxidation time intervals and interpolating to time zero. By running replicates, one at 720°C and one at 1100°C, data on organic and inorganic carbon and on nitrogen are obtained with the analyzer.     

祁连山中部土壤颗粒组分有机质碳含量及其与海拔和植被的关系

调查分析了祁连山中段不同海拔土壤颗粒有机碳及其与植被的关系.结果显示,土壤颗粒组分比例在0～15 cm和15～35cm土层随海拔升高而呈现下降趋势(P>0.2);土壤颗粒有机碳比例在0～15 cm土层随海拔升高也呈现下降趋势(P≤0.001).土壤颗粒组分比例0～15 cm土层在阴坡3 000 m～3 500 m、15～35 cm土层在阴坡3 200 m和3 500 m及半阴坡2 200和2 800 m处较高;土壤颗粒有机碳比例0～15 cm土层在阴坡3 000 m和3 200 m、半阴坡2 200 m和2 800 m,以及15～35 cm土层在阴坡3 200 m和3 500 m、阳坡3 300 m和3 500 m处较高(P<0.05).土壤颗粒有机碳和颗粒组分碳含量随海拔升高变化不显著(P<0.9).土壤颗粒有机碳含量0～15cm土层在阴坡3 000 m～3 500 m、15～35 cm土层在阴坡3 000 m～3 500 m及阳坡3 300m处较高;土壤颗粒组分碳含量0～15 cm土层在阴坡3 000 m～3 400 m和阳坡3 300 m,以及15～35 cm土层在阴坡3 200 m和3 400 m及阳坡3 300 m处较高.土壤颗粒组分比例0～15 cm土层在森林和灌丛草甸中较高;15～35 cm土层在森林、灌丛草甸和干旱草原中较高(P<0.05).土壤颗粒有机碳比例0～15 cm土层在荒漠草原和干旱草原,以及15～30 cm土层在森林和灌丛草甸中较高(P<0.05).土壤颗粒组分碳含量0～15 cm和15～35 cm土层在森林和灌丛草甸中较高(P<0.05).土壤颗粒有机碳含量0～15cm和15～35cm土层在森林中最高(P<0.05).土壤颗粒组分碳含量和颗粒有机碳含量与土壤有机碳含量有显著的正相关性(P<0.001),土壤颗粒有机碳含量与颗粒组分碳含量也有显著的正相关性(P<0.001),土壤颗粒组分比例与有机碳含量相关性不显著(P=0.15),土壤颗粒有机碳含量与颗粒组分比例有显著正相关性(P<0.005).结果说明祁连山中部北坡土壤有机碳稳定性受植被和海拔共同影响,荒漠草原和干旱草原表层土壤有机碳稳定性较低,森林和灌丛草甸土壤中非保护性碳含量较高.     

Heating induced changes in mineral nitrogen and organic carbon in relation with temperature and time

Heating effects on carbon and mineral nitrogen contents of soils within different land use types were investigated in this study. With this intention we collected soil samples from 3 different land use types which are abandoned agricultural lands (AAL), shrub land (SL) and Oak forest land (OFL) and are in neighborhood with each other. The sampling was made at mid-summer to provide a better correspondence between factual buming conditions as well. Soils are slightly acidic (pH between 4.60-5.72) and sandy, sandy loamy textured. At the study site the vegetation type is pasture at AAL, Cystus and Rubus sp. dominated shrubs at SL and mixture of Oak species such as Quercus petrea, Q. robur Q. cerris and Q. frainetto at OFL. The results we found revealed that heating temperature has more remarkable effect on C losses and soil NH4+-N re-mineralization and losses of NH4+-N. Besides we could not detect remarkable differences between total N and NO3- amounts. Heating time created significant differences between NH4+-N amounts for different land use types where SL soils showed significant difference for all temperature levels. Heating soils at 100 degreesC created only slight differences at C and NH4+-N budgets but heating at 200 degreesC caused to striking results at NH4+-N budgets and heating at 350 degreesC led to only slight increase at NH4+-N budget. As the temperature increased the C loss also increased linearly.     

芦芽山土壤有机碳和全氮沿海拔梯度变化规律

研究不同海拔梯度和坡向的土壤碳氮分布,能在较小的空间尺度上反映不同气候状况下土壤碳氮分布规律,揭示多个互相关联的环境因子对土壤碳氮分布规律的综合影响。对山西省北部芦芽山芦芽山沿海拔梯度土壤有机碳和全氮含量的变化规律进行了分析。自海拔1703.1 m至2756.3 m每上升约50 m设置一个样带（共计21块）,每样带内布设30 m＆#215;30 m样地3个,每个样地内“S”形布点,分3层（0~10、10~25、25~40 cm）钻取土样。结果表明,在研究海拔范围内土壤垂直剖面自表层向下有机碳质量分数分别为（35.71±13.32）、（29.18±12.85）和（26.39±12.74） g＆#183; kg-1,全氮质量分数分别为（2.83±0.93）、（2.38±0.84）和（2.12±0.80） g＆#183; kg-1。土壤有机碳和全氮含量的分布特征均表现为随海拔升高而增加的趋势,与海拔呈极显著的线性正相关。土壤有机碳含量与海拔线性模型的回归系数在10~25 cm土层最大,而全氮与海拔线性模型的回归系数随土层深度增加而递减。土壤有机碳含量最高值出现在较高海拔处寒温性针叶林下,而土壤全氮含量最高值出现在最高海拔的亚高山草甸。碳氮含量的剖面分布呈现为表层（0~10 cm）最高,随深度下降而递减。研究区土壤C/N值介于5~19,最小值为海拔最高（2756.3 m）的亚高山草甸,而最大值为较高海拔分布的寒温性针叶林（2332.6 m）,沿海拔梯度表现呈“Λ”型的变化趋势。     

利用方式对紫色水稻土有机碳与颗粒态有机碳的影响

土壤是陆地生态系统中重要的动态碳库,其微小的变化可能带来对全球大气CO2浓度的较大变化。颗粒态有机碳在土壤中周转速度较快,比土壤总有机碳更易受土地利用方式的影响,对于评价土地利用变化对土壤碳固定过程影响具有重要意义。采集不同的耕作、轮作和施肥处理的14年28茬的紫色土长期试验土壤,分析有机碳与颗粒态有机碳含量在土壤及不同深度分布特点,结果表明:长期垄作免耕并实行水稻(Oryza sativa)油菜(Brassica)轮作的利用方式下,0～10cm土层土壤有机碳与颗粒态有机碳含量明显高于其他利用方式下,而稻油水旱轮作平作利用方式下最低。整个耕层0～30cm深度的土壤有机碳含量介于8.92～29.98g·kg-1之间,颗粒态有机碳含量变幅为0.54～3.43g·kg-1之间,且存在随深度递增而降低的趋势。土壤有机碳与颗粒态有机碳都可用作评价利用方式影响紫色水稻土土壤质量变化与固碳能力的有效指标,但颗粒有机碳对于管理措施的响应更为敏感。从总有机碳与颗粒有机碳的关系来看,不同管理下有机碳的增加与土壤物理保护能力的提高有关。垄作免耕(稻油)的利用方式最有利于有机碳的保护和稳定。     

溶解性有机质在红壤水稻土碳氮转化中的作用

溶解性有机质(DOM)是土壤中活跃的C、N库,在土壤有机质分解转化等过程中有着重要的作用。但其在水田土壤C、N转化过程中究竟起多大作用仍不明确。本研究采用室内恒温培养法观测了DOM和红壤水稻土C、N矿化的关系。结果表明,去除DOM显著降低了培养期间土壤有机质的累计矿化量。其中土壤有机碳的累计矿化量下降了11.4%～20.8%(平均15.4%),且其影响主要体现在培养前期;土壤有机氮的累计矿化量下降了16.4～22.9%(平均19.2%)。研究结果初步表明,虽然DOM只占土壤有机质的很少一部分,但在红壤水稻土C、N矿化中起重要作用。     

The role of fungi in processing marine organic matter in the upwelling ecosystem off Chile

In a study that spanned from March 2007 through November 2009, we report high fungal biomass and over 90% of extracellular enzymatic activity occurring in the size classes dominated by fungi during periods of high autotrophic biomass in surface waters of the upwelling ecosystem off central-southern Chile (36°30.80′S–73°07.70′W). Fungal biomass in the water column was determined by the abundance of hyphae and was positively correlated with the concentration of the fungal biomarker 18:2ω6. High fungal biomass during active upwelling periods was comparable to that of prokaryotes (bacteria plus archaea) and was associated with an increase in phytoplankton biomass and in extracellular enzymatic hydrolysis in waters from the depth of maximum fluorescence. We show fungi as a new microbial component in the coastal upwelling ecosystem of the Humboldt Current System off central Chile. Our results suggest that the temporal pattern in fungal biomass in the water column during a year cycle is a reflection of their capacity to hydrolyze organic polymers and, in consequence, fungal biomass and activity respond to a seasonal cycle of upwelling in this ecosystem.     

Vertical and horizontal structure in the picoplankton communities of a coastal upwelling system

The distribution of prokaryotic and eukaryotic picoplankton in the west coast upwelling-region off the South Island of New Zealand was investigated during midwinter (1988) the time of year when several commercially important fish species migrate into the region to breed. Picoplanktonic cells were major contributors to the autotrophic biomass, with > 80% of the particulate nitrogen and 39 to 55% of the total chlorophylla contained in the <2µm size-fraction. The prokaryotic picoplankton concentrations ranged from 6.3 × 10⁵ to 2.1 × 10⁷ cell l^–1, and the eukaryotic picoplankton between 3.9 × 10⁵ to 1.2 × 10⁷ cells l^–1. Picoplankton numbers increased with distance offshore to a maximum of ~ 3.0 × 10⁷ cells l^–1 at ~ 35 km from the coast, and then diminished towards the outer shelf and open ocean. The ratio of prokaryotic to eukaryotic cells varied between 1.01 and 4.71 in the mixed layer. Both groups declined substantially beneath the pycnocline, with no evidence of deep maxima. Prokaryotic cells dominated the planktonic cell concentrations at all but two stations, but eukaryotic cells dominated picoplankton biovolume as a result of their larger average cell size. The prokaryotic to eukaryotic picoplankton cell-number ratios in this system were considerably lower than often recorded elsewhere, and were inversely correlated with nitrate concentration. These observations show that a eukaryoticdominated picoplankton community makes a substantial contribution to autotrophic biomass in this nutrient-rich upwelling system, and may thereby play a major role in the food-web dynamics of this coastal fishery.     

Fuzzy modelling of chlorophyll production in a Brazilian upwelling system

In the context of coastal management the aim of this paper is to present the development of a fuzzy model through the application of a Genetic algorithm in order to select the most appropriate set of variables and improve our understanding with a set of rules. The case studied is the chlorophyll response as bioindicator of ecological status in the Northeast coastal upwelling system of Rio de Janeiro state, Southeastern of Brazil. The prediction of the fuzzy model has shown an improved performance when compared to the traditional approaches as Multiple Regression modelling. The results show that the set of inferred rules can assess three different water masses. Despite the increased occurrence of upwelling is observed in spring–summer period and some instability of the model, it is able to forecast some chlorophyll peaks. We conclude that the sampling frequency is crucial to reach a better performance.     

冻融作用下盐碱水田土壤含水率和氮素对有机碳影响研究

选择吉林西部前郭县盐碱水田土壤,进行实验室模拟冻融实验：以-5℃冻结1 d、5℃消融1 d作为1次冻融循环,揭示不同含水率和含氮量处理条件下土壤有机碳（SOC）的变化规律。结果表明,土壤含水率和含氮量是影响SOC含量的2个重要因素,冻融次数、土壤含水率、土壤含氮量以及冻融次数和土壤含水率、冻融次数和土壤含氮量的交互作用对盐碱水田SOC含量的影响显著（P〈0.05）。在1~3次冻融循环过程中,SOC含量明显降低,随着循环次数的增加,SOC含量降低速度减缓;适量的氮素和较低的含水率有利于SOC的稳定,初始含水率为50%的SOC含量明显低于含水率30%和40%的土壤,加入20%硝酸铵的SOC含量明显低于对照组和加入10%硝酸铵的土壤。研究结果对深入研究季节冻土区冻融期盐碱水田SOC变化规律,评估全年候SOC储量有重要意义。     

Suspended particulate organic matter in a Mediterranean submarine cave

Submarine caves display a paucity of benthic density and biomass that may be related to low trophic resources. Analysis of organic carbon, organic nitrogen, carbohydrate, protein and lipid content of suspended particulate matter was made during the period July 1985–July 1987 in a Mediterranean cave (Marseille, France) in order to determine any differences in the particulate organic matter composition along an horizontal transect. Particulate organic matter content clearly declined from the entrance of the cave to the dark inner area. This impoverishment could not be explained by a simple decrease in a few organic compounds, but appeared to be related to the combination of a decrease in both the amount and the composition of the suspended particles. Three progressive levels of impoverishment were identified towards the dark inner area of the cave: (i) decreasing amounts of seston; (ii) decreasing organic content of particles; (iii) increasing proportions of the geopolymeric (i.e., humic) components in the remaining organic matter, indicating increased degradation. The cave appeared to be sharply divided into two distinct sections — a twilight outer section whose waters contained slightly lower amounts of particulate organic matter than the open sea, and a dark inner section, 8 to 10 m higher, separated from the outer section by a steep rise and with waters of low organic matter content. The water in the twilight section appeared to be in thermal equilibrium with the open sea, and that in the dark inner section displayed thermal stratification. These differences indicated the presence of two distinct water bodies with contrasting average residence times, estimated as 1 d in the outer twilight section and 8 d in the dark inner section. The joint action of sedimentation and degradation resulted in an abrupt depletion of particulate organic matter in the dark inner section accompanied by a decrease in the benthic fauna. The decline in benthic heterotroph populations is probably related to the abrupt transition to oligotrophic conditions.     

丘陵区坡面土壤有机碳及颗粒有机碳分布特征

测定了紫色丘陵区疏林地、荒草地和坡耕地三种土地利用方式下土壤有机碳和颗粒有机碳含量,探讨不同利用方式与坡位下土壤有机碳和土壤颗粒有机碳的分布特征.结果表明:不同土地利用方式下上坡位和中坡位土壤有机碳和颗粒有机碳含量均为疏林地＞坡耕地＞荒草地,而在下坡位两者含量变化差异较大;不同土地利用方式下各坡位土壤剖面有机碳含量均是在0～5 cm层富集,颗粒有机碳的含量也表现出一定在剖面分异性;不同土地利用方式土壤颗粒有机碳分配比例为(0.74±0.01)～(0.34±0.02),不同土地利用方式之间土壤颗粒有机碳分配比例差异较小.相关分析表明,不同利用方式下土壤有机碳、全氮和颗粒有机碳含量之间均呈显著的相关性.     

典型草原不同围封年限植被-土壤系统碳氮贮量的变化

以内蒙古太仆寺旗典型草原为研究对象,研究不同围封年限下的天然草地植物和土壤有机碳、全氮贮量的变化。结果表明：与自由放牧草地相比,重度退化草地采取生长季围封恢复措施后,群落植物和土壤环境在围封8、11、14、21、25年后均得到了明显的改善,地上植物和地下根系生物量及其碳氮贮量、土壤碳氮贮量明显增加,土壤容重降低。自由放牧地和围封8、11、14、21年植物-土壤系统碳贮量分别为7 357.93、7 988.27、8 413.18、12 878.82、8 934.66 g.m-2,氮贮量分别为427.78、494.28、575.49、707.35、615.09 g.m-2。草地围封至14年植物和土壤各项理化性质达到最大值,使得植物-土壤系统的碳氮贮量分别是自由放牧地的1.75和1.65倍,说明植被与土壤间达到了良性循环的状态,退化草地正向演替。随着围封年限的继续增加,其各项指标出现下降趋势。由此可知,季节性围封措施在一定时间内可使退化草地的土壤-植物系统的碳氮贮量增加,草地在一定程度上得到恢复,但适宜的恢复时间和合理利用问题有待进一步讨论。     

A technique for collection of particulate organic matter in situ

A technique is described for concentrating and collecting particulate organic matter from water with minimal disturbance. This involves exposing in situ the surface of a Millipore^® filter monitor mounted on a simple vacuum flask assembly.     

土地利用方式对紫色土丘陵区土壤剖面碳、氮影响

采取野外调查与室内分析相结合的方法研究了紫色土丘陵区林地、撂荒地、水田、旱地土壤剖面(0～40 cm)有机碳、全氮变化特征.结果表明.有机碳、全氮均随土层深度增加而逐渐减小,且林地、撂荒地有机碳递减幅度高于水田、旱地.相对于撂荒地和旱地,水田、林地更利于有机碳、全氮的积累.林地有机碳和全氮在0～5 cm土层表现出绝对优势;随土层递增,与水田、撂荒地和旱地的差异逐渐减小.水田有机碳和全氮在大于10 cm土层显示最大值.而撂荒地有机碳和全氮仅在土壤表层高于旱地.有机碳与全氮存在显著正相关关系;w(C)/w(N)随土层深度增加而降低,且林地、撂荒地降低幅度较大.因此相对于水田、旱地,林地和撂荒地w(C)/w(N)仅在0～10 cm显示较大值.可见,土地利用方式对陆地生态系统碳、氮蓄积有明显影响,通过旱地还林或撂荒可以增加土壤特别是表层土壤对碳、氮的积累.