陆地生态系统可溶性有机氮研究进展

可溶性有机氮(dissolved organic nitrogen DON)的流动是陆地生态系统氮循环的重要组成部分。本文就陆地生态系统DON的来源、组成、性质;森林生态系统DON的流动、季节动态以及DON在氮循环中的地位等方面作了概括和探讨。今后的陆地生态系统DON的研究应该集中在以下几个方面：确定陆地生态系统中DON的各分室DON的浓度、流量;DON的源与汇问题;量化不同生态系统中DON库的大小和组成;研究DON在氮的矿化、微生物的固持、以及植物吸收等氮循环过程中的地位;对比研究DON与DOC(dissolved organic carbon)的动态差别;探讨DON与植物营养和碳积累的关系等。     

Dissolved organic matter quantity and quality from freshwater and saltwater lakes in east-central Alberta

Concentrations of dissolved organic matter (DOM) in surface waters of sub-humid to semi-arid lakes in east-central Alberta increase with increasing salinity and water residence time from about 20 to 330 mg L^–1 as dissolved organic carbon (DOC). This pattern is opposite to that observed among freshwater lakes spanning a gradient in water residence times, and is probably caused by evaporative concentration of refractory DOM. The proportion of total DOC, operationally defined as humic substances using XAD-8 resin, was high, though similar to surface waters typically referred to as "humic", and independent of salinity. Very long water residence times (hundreds of years) in saline lakes favors evapoconcentration of low-color, low molecular weight DOM, with N-content characteristic of allochthonous DOM.     

森林生态系统可溶性碳和颗粒碳通量

可溶性碳(Dissolved carbon,DC)和颗粒碳(particulate carbon,PC)通量作为森林生态系统碳收支的重要组分,在森林固碳功能的评价和模型预测中具有重要意义,但常因认识不足、测定困难等而在森林碳汇研究中被忽略。综述了森林生态系统DC和PC的组成、作用、相关生态过程及其影响因子,并展望了该领域应该优先考虑的研究问题。森林生态系统DC和PC主要包括可溶性有机碳、可溶性无机碳和颗粒有机碳,主要来源于生态系统的净初级生产量。DC和PC是森林土壤的活性碳库,主要以大气沉降、穿透雨和凋落物的形式输入森林土壤系统,并通过土壤呼吸、侧向运输及渗透流失的方式输出生态系统。从局域尺度看,DC和PC通量受根系分泌、细根分解、微生物周转等生物过程的影响较大;从区域尺度看,它们受土壤和植被特性、生态过程耦联关系、气候因子以及全球变化的综合影响。该领域应该优先考虑:(1)探索不同时空尺度下森林生态系统DC和PC通量的控制因子及其耦联关系,揭示其中的驱动机理;(2)探索DC和PC与其它森林生态系统碳组分的相互关系及转化,阐明DC和PC通量与其它养分之间潜在的生态化学计量关系;(3)探索全球变化,特别是人类活动(如森林经营)和极端干扰事件(如林火、旱涝、冰冻、冻融交替等)对森林生态系统DC和PC通量的影响。     

Nitrogen solutes in an Adirondack forested watershed: Importance of dissolved organic nitrogen

Nitrogen (N) dynamics were evaluated from 1 June 1995 through 31 May 1996 within the Arbutus Lake watershed in the Adirondack Mountains of New York State, USA. At the Arbutus Lake outlet dissolved organic nitrogen (DON), NO₃ ^- and NH₄ ⁺ contributed 61%, 33%, and 6% respectively, to the total dissolved nitrogen (TDN) flux (259 mol ha^-1 yr^-1). At the lake inlet DON, NO₃ ^-, and NH₄ ^- constituted 36%, 61%, and 3% respectively, of TDN flux (349 mol ha^-1 yr^-1). Differences between the factors that control DON, NO₃ ⁺, and NH₄ ⁺ stream water concentrations were evaluated using two methods for estimating annual N flux at the lake inlet. Using biweekly sampling NO₃ ^- and NH₄ ⁺ flux was 10 and 4 mol ha^-1 yr^-1 respectively, less than flux estimates using biweekly plus storm and snowmelt sampling. DON flux was 18 mol ha^-1 yr^-1 greater using only biweekly sampling. These differences are probably not of ecological significance relative to the total flux of N from the watershed (349 mol ha^-1 yr^-1). Dissolved organic N concentrations were positively related to discharge during both the dormant (R² = 0.31; P < 0.01) and growing season (R² = 0.09; P < 0.01). There was no significant relationship between NO₃ ^- concentration and discharge during the dormant season, but a significant negative relationship was found during the growing season (R² = 0.29; P < 0.01). Biotic controls in the growing season appeared to have had a larger impact on stream water NO₃ ^- concentrations than on DON concentrations. Arbutus Lake had a major impact on stream water N concentrations of the four landscape positions sampled, suggesting the need to quantify within lake processes to interpret N solute losses and patterns in watershed-lake systems.     

森林生态系统DOM的来源、特性及流动

可溶性有机物质（Dissolved Organic Matter)是森林生态系统主要的可移动碳库及重要的养分库。系统综述了森林生态系统DOM的来源,组成,性质,季节动态;DOM释放与存留机制及影响因素,森林生态系统DOM的流动及干扰对DOM动态影响等,已有研究表明DOM的森林生态系统C、N、P循环,成土作用,污染物迁移等方面起着重要作用。今后森林生态系统DOM的研究应集中于以几方面：（1）确定森林生态系统中DOM源和汇;（2）评价森林水文条件对DOM释放与存留的调节作用;（3）探讨全球气候变化对森林生态系统DOM的影响;（4）可溶性有机氮（Dissolved Organic Nitrogen),可溶性有机磷（Dissolved Organic Phosphorus)动态与可溶性有碳（Dissolved Organic Carbon）动态的差别。     

Nitrogen mineralization in upland Precambrian Shield catchments: Contrasting the role of lichen-covered bedrock and forested areas

The upland boreal forest at the Experimental Lakes Area (northwestern Ontario, Canada) is characterized by treed soil islands interspersed within lichen and moss-covered bedrock outcrops. N mineralization was 2.5-fold and net nitrification was 13-fold higher on an areal basis over bedrock surfaces because of high mineralization rates under lichen and moss patches. The higher average soil temperature in lichen and moss patches could not account for the difference in mineralization rates. Lichens did not provide a significant additional source of N because they did not fix atmospheric N. A refractory conifer litter with a high C:N probably favours the immobilization of N in forest islands. Buried bag and in situ core incubations yielded similar net N mineralization rates but core incubations underestimated net nitrification rates. Both methods did not adequately measure dissolved organic N (DON) production rates because soil disturbance caused high initial DON concentrations. The higher export of mineral N from bedrock surfaces is probably a combination of the lower retention of N in precipitation and leaching of mineralized N from lichen and moss patches.     

Shifting stoichiometry: Long-term trends in stream-dissolved organic matter reveal altered C:N ratios due to history of atmospheric acid deposition

Dissolved organic carbon (DOC) and nitrogen (DON) are important energy and nutrient sources for aquatic ecosystems. In many northern temperate, freshwater systems DOC has increased in the past 50 years. Less is known about how changes in DOC may vary across latitudes, and whether changes in DON track those of DOC. Here, we present long-term DOC and DON data from 74 streams distributed across seven sites in biomes ranging from the tropics to northern boreal forests with varying histories of atmospheric acid deposition. For each stream, we examined the temporal trends of DOC and DON concentrations and DOC:DON molar ratios. While some sites displayed consistent positive or negative trends in stream DOC and DON concentrations, changes in direction or magnitude were inconsistent at regional or local scales. DON trends did not always track those of DOC, though DOC:DON ratios increased over time for ~30% of streams. Our results indicate that the dissolved organic matter (DOM) pool is experiencing fundamental changes due to the recovery from atmospheric acid deposition. Changes in DOC:DON stoichiometry point to a shifting energy-nutrient balance in many aquatic ecosystems. Sustained changes in the character of DOM can have major implications for stream metabolism, biogeochemical processes, food webs, and drinking water quality (including disinfection by-products). Understanding regional and global variation in DOC and DON concentrations is important for developing realistic models and watershed management protocols to effectively target mitigation efforts aimed at bringing DOM flux and nutrient enrichment under control.     

The effect of land use on dissolved organic carbon and nitrogen uptake in streams

1. Agricultural and urban land use may increase dissolved inorganic nitrogen (DIN) concentrations in streams and saturate biotic nutrient demand, but less is known about their impacts on the cycling of organic nutrients. To assess these impacts we compared the uptake of DIN (as ammonium, NH₄⁺), dissolved organic carbon (DOC, as acetate), and dissolved organic nitrogen (DON, as glycine) in 18 low‐gradient headwater streams in southwest Michigan draining forested, agricultural, or urban land‐use types. Over 3 years, we quantified uptake in two streams in each of the three land‐use types during three seasons (spring, summer and autumn). 2. We found significantly higher NH₄⁺ demand (expressed as uptake velocity, V_f) in urban compared to forested streams and NH₄⁺V_f was greater in spring compared to summer and autumn. Acetate V_f was significantly higher than NH₄⁺ and glycine V_f, but neither acetate nor glycine V_f were influenced by land‐use type or season. 3. We examined the interaction between NH₄⁺ and acetate demand by comparing simultaneous short‐term releases of both solutes to releases of each solute individually. Acetate V_f did not change during the simultaneous release with NH₄⁺, but NH₄⁺V_f was significantly higher with increased acetate. Thus, labile DOC V_f was not limited by the availability of NH₄⁺, but NH₄⁺V_f was limited by the availability of labile DOC. In contrast, neither glycine nor NH₄⁺V_f changed when released simultaneously indicating either that overall N‐uptake was saturated or that glycine and NH₄⁺ uptake were controlled by different factors. 4. Our results suggest that labile DOC and DON uptake can be equivalent to, or even higher than NH₄⁺ uptake, a solute known to be highly bioreactive, but unlike NH₄⁺ uptake, may not differ among land‐use types and seasons. Moreover, downstream export of nitrogen may be exacerbated by limitation of NH₄⁺ uptake by the availability of labile DOC in headwater streams from the agricultural Midwestern United States. Further research is needed to identify the factors that influence cycling of DOC and DON in streams.     

城市土壤活性碳、氮分布特征及影响因素

为揭示城市绿地土壤活性碳氮分布特征及影响因素,选取合肥市不同类型绿地(蜀山森林公园、公园绿地、道路绿地、学校绿地、居住区绿地、工厂绿地)土壤为研究对象,对其0 ～ 30 cm土壤微生物量碳(MBC)、微生物量氮(MBN)、溶解性有机碳(DOC)、溶解性有机氮(DON)等活性组分进行研究.结果表明,绿地类型对土壤活性碳氮含量影响显著(P＜0.05),各活性碳氮含量随土层深度的增加而降低.城区内各人工绿地土壤活性碳氮含量均低于郊区蜀山森林公园绿地:MBC下降了46.81％ ～ 64.39％,MBN下降了49.90％ ～80.13％,DOC下降了28.95％ ～45.52％,DON下降了5.67％ ～48.90％,表明土地利用变化是导致绿地土壤活性碳氮变化的主要因素.相关分析表明,研究区域内MBC与MBN、DON正相关(P＜0.01),MBN与DOC正相关(P＜0.01),DOC与DON正相关(P＜0.01).研究还发现,土壤pH与活性碳、氮间均呈负相关关系(P＜0.01),表明适当降低城市土壤碱性污染物的侵入有利于土壤活性碳氮的积累.     

氮素添加和CO2浓度升高对白羊草根际和非根际土壤水溶性有机碳、氮的影响

采用盆栽控制试验对黄土丘陵区白羊草在不同CO₂浓度(400和800 μmol·mol^-1)和施氮水平(0、2.5、5.0 g N·m^-2·a^-1)条件下根际和非根际土壤水溶性有机碳(DOC)和水溶性有机氮(DON)的变化特征进行研究.结果表明: CO₂浓度升高对白羊草根际和非根际土壤DOC、水溶性总氮(DTN)、DON、水溶性铵态氮(NH₄⁺-N)、水溶性硝态氮(NO₃^--N)含量均无显著影响.施氮显著提高了根际和非根际土壤DTN、NO₃^--N含量和根际土壤DON含量,显著降低了根际土壤DOC/DON.在各处理条件下,根际土壤DTN、NO₃^--N和DON含量均显著低于非根际土壤,根际土壤DOC/DON显著高于非根际土壤.短期CO₂浓度升高对黄土丘陵区土壤水溶性有机碳、氮含量无显著影响,而氮沉降的增加在一定程度上改善了土壤中水溶性氮素缺乏的状况,但并不足以满足植被对水溶性氮素的需求.     

The Role of Dissolved Organic Carbon, Dissolved Organic Nitrogen, and Dissolved Inorganic Nitrogen in a Tropical Wet Forest Ecosystem

Although tropical wet forests play an important role in the global carbon (C) and nitrogen (N) cycles, little is known about the origin, composition, and fate of dissolved organic C (DOC) and N (DON) in these ecosystems. We quantified and characterized fluxes of DOC, DON, and dissolved inorganic N (DIN) in throughfall, litter leachate, and soil solution of an old-growth tropical wet forest to assess their contribution to C stabilization (DOC) and to N export (DON and DIN) from this ecosystem. We found that the forest canopy was a major source of DOC (232 kg C ha^–1 y^–1). Dissolved organic C fluxes decreased with soil depth from 277 kg C ha^–1 y^–1 below the litter layer to around 50 kg C kg C ha^–1 y^–1 between 0.75 and 3.5m depth. Laboratory experiments to quantify biodegradable DOC and DON and to estimate the DOC sorption capacity of the soil, combined with chemical analyses of DOC, revealed that sorption was the dominant process controlling the observed DOC profiles in the soil. This sorption of DOC by the soil matrix has probably led to large soil organic C stores, especially below the rooting zone. Dissolved N fluxes in all strata were dominated by mineral N (mainly NO₃⁻). The dominance of NO₃^– relative to the total amount nitrate of N leaching from the soil shows that NO₃^– is dominant not only in forest ecosystems receiving large anthropogenic nitrogen inputs but also in this old-growth forest ecosystem, which is not N-limited.     

茯苓碳氮磷化学计量学特征

为探明茯苓的碳、氮、磷生态化学计量学特征,采集了云南省11个州、市42个居群的茯苓样本,分析了其菌核与表皮中碳(C)、氮(N)、磷(P)的化学计量特征.结果 表明:茯苓菌核中C、N、P的含量分别为40.24％-43.58％、0.176％-0.532％和0.020％-0.077％;C∶N、C∶P和N∶P的范围分别为93....     

Dynamics of dissolved organic nitrogen in subalpine Castle Lake,California

Dissolved organic nitrogen (DON) concentrations were measured in meso-oligotrophic Castle Lake, California during the ice-free season in 1982, 1983 and 1984. No consistent relationships were found between DON and particulate-N, primary productivity rates or chlorophyll concentrations. However, increases in DON concentrations were observed in the early growing season of 1982 and 1984 when water temperature was rising and a diatom bloom was senescing. DON increased at a high rate (0.31 mg atom N m^–3 day^–1), and then rapidly disappeared. Sediment released appared to be the most important source of DON. Dissolved free amino acids were always less than 7.5% of the DON pool, and did not vary in the composition of specific amino acids during the growing season.     

土壤溶解性有机物对CO_2和N_2O排放的影响

农田土壤是温室气体的重要排放源,溶解性有机物作为土壤微生物容易利用的基质,其含量变化与温室气体的产生和排放密切相关。基于室内培养试验,对溶解性有机物影响土壤CO2、N2O的排放过程进行了分析。设置空白(CK)、单施秸秆(S)、单施氮肥(N)、秸秆和氮肥(S+N)4个不同的处理,对添加不同物质条件下土壤溶解性有机碳(DOC)、溶解性有机氮(DON)和CO2、N2O的排放动态进行了研究,对DOC和DON影响CO2、N2O的排放过程进行了探讨。结果表明:不同处理的温室气体排放通量和土壤DOC、DON含量差异显著;各处理的CO2排放通量和DOC动态随培养时间的延长呈现逐渐减小的趋势,S和S+N处理的N2O排放和DON动态呈现先增大后减小的趋势;S+N处理的CO2排放量最高,DON含量也显著高于其他处理,单施秸秆(S)处理的N2O排放量和DOC含量显著高于其它处理,单施氮肥(N)对土壤CO2的排放量和DOC含量的影响较小;土壤CO2和N2O的排放通量与土壤DOC和DON含量呈显著的相关性,相关系数(R2)达0.6以上,说明溶解性有机物的含量和动态对CO2、N2O的排放过程产生显著影响。     

菌渣化肥配施对稻田土壤微生物量碳氮和可溶性碳氮的影响

菌渣作为一种养分丰富的有机物料还田,可减少化肥施用,同时保持土壤肥力;而土壤微生物量碳、氮和可溶性碳、氮是土壤活性碳氮库的重要组成部分,其含量和比例变化对土壤肥力均具有重要作用。因此,探讨不同比例菌渣化肥配施对土壤微生物量碳、氮及可溶性碳、氮的影响,评价菌渣在优化土壤肥力方面的生态作用具有重要意义。本研究在水稻田间定位试验条件下,设置3个化肥水平(C) 0%、50%、100%,菌渣相对用量(F) 0%、50%、100%,共9个处理,分析了各处理土壤微生物量碳(MBC)、氮(MBN)和可溶性碳(DOC)、氮(DON)的变化特征,及其占土壤有机碳(SOC)和全氮(TN)的比例与相关关系。结果表明:菌渣化肥配施后,微生物量碳和可溶性碳、氮均在C100F50最高,微生物量氮在C50F100最高,与不施肥处理相比,分别显著增加了49.40%、43.65%、83.52%、207.19%;MBC/SOC和DOC/SOC均随着菌渣化肥配施量的增加而减少,MBN/TN和DON/TN均在C100F50最高。相关分析表明,MBC、DOC与SOC,MBN与TN均呈极显著正相关,DON和TN呈显著正相关。总体来讲,菌渣化肥配施能够显著提高土壤微生物量碳、氮和可溶性碳、氮含量,但不是随着用量的增加一直呈增加趋势,高量菌渣或者化肥下会有降低趋势;菌渣化肥配施降低了土壤微生物量和可溶性碳氮比,因此适宜的菌渣化肥配施是提高土壤有机碳周转速度、微生物活性及其氮素供应能力和有效性的最佳选择。     

Dissolved organic matter in small streams along a gradient from discontinuous to continuous permafrost

The Yenisei river passes every type of permafrost regime, from south to north, being characterized by increasing continuity of the permafrost and by decreasing thickness of the active layer. We used that situation to test the hypothesis that amounts and properties of dissolved organic matter (DOM) in small streams draining forested catchments respond to different permafrost regimes. Water samples were taken from eight tributaries along the Yenisei between 67°30′N and 65°49′N latitude. The samples were analysed for dissolved organic carbon (DOC) and nitrogen (DON) and DOM was characterized by its chemical composition (XAD‐8 fractionation, sugars, lignin phenols, amino acids, protein, UV and fluorescence spectroscopy), and its biodegradability. Most properties of the tributary waters varied depending on latitude. The higher the latitude, the higher were DOC, DON and the proportion of the hydrophobic fraction of DOC. The contribution of hexoses and pentoses to DOC were higher in southern tributaries; on the other hand, phenolic compounds were more abundant in northern tributaries. Mineralizable DOC ranged between 4% and 28% of total DOC. DOM in northern tributaries was significantly (P<0.05) less biodegradable than that in southern tributaries reflecting the differences in the chemical properties of DOM. Our results suggest that the differences in DOM properties are mainly attributed to differences of permafrost regime, affecting depth of active layer, soil organic matter accumulation and vegetation. Soil organic matter and vegetation determine the amount and composition of DOM produced in the catchments while the depth of the active layer likely controls the quantity and quality of DOM exported to streams. Sorptive interactions of DOM with the soil mineral phase typically increase with depth. The results imply that a northern shift of discontinuous permafrost likely will change in the long term the input of DOM into the Yenisei and thus probably into the Kara Sea.     

Soil organic matter and litter chemistry response to experimental N deposition in northern temperate deciduous forest ecosystems

The effects of atmospheric nitrogen (N) deposition on organic matter decomposition vary with the biochemical characteristics of plant litter. At the ecosystem‐scale, net effects are difficult to predict because various soil organic matter (SOM) fractions may respond differentially. We investigated the relationship between SOM chemistry and microbial activity in three northern deciduous forest ecosystems that have been subjected to experimental N addition for 2 years. Extractable dissolved organic carbon (DOC), DOC aromaticity, C : N ratio, and functional group distribution, measured by Fourier transform infrared spectra (FTIR), were analyzed for litter and SOM. The largest biochemical changes were found in the sugar maple–basswood (SMBW) and black oak–white oak (BOWO) ecosystems. SMBW litter from the N addition treatment had less aromaticity, higher C : N ratios, and lower saturated carbon, lower carbonyl carbon, and higher carboxylates than controls; BOWO litter showed opposite trends, except for carbonyl and carboxylate contents. Litter from the sugar maple–red oak (SMRO) ecosystem had a lower C : N ratio, but no change in DOC aromaticity. For SOM, the C : N ratio increased with N addition in SMBW and SMRO ecosystems, but decreased in BOWO; N addition did not affect the aromaticity of DOC extracted from mineral soil. All ecosystems showed increases in extractable DOC from both litter and soil in response to N treatment. The biochemical changes are consistent with the divergent microbial responses observed in these systems. Extracellular oxidative enzyme activity has declined in the BOWO and SMRO ecosystems while activity in the SMBW ecosystem, particularly in the litter horizon, has increased. In all systems, enzyme activities associated with the hydrolysis and oxidation of polysaccharides have increased. At the ecosystem scale, the biochemical characteristics of the dominant litter appear to modulate the effects of N deposition on organic matter dynamics.     

短轮伐期毛白杨不同密度林分土壤有机碳和全氮动态

采用裂区试验设计,于2005—2008年连续4年测定了不同造林密度(2 m×2 m、2 m×3 m、2 m×3.5 m、2 m×4 m、2 m×5 m、3 m×3 m、3 m×4 m)下2年生三倍体毛白杨(B304)和对照二倍体(1319)人工林土壤有机碳和全氮含量,以明确不同密度林分土壤有机碳和全氮动态变化规律及其相关性。结果表明:(1)受造林密度、生长时间及其交互作用的显著影响,4年生长期内林地土壤有机碳含量呈先降后升的变化特点。其中,2008年B304在2 m×3 m造林密度下土壤有机碳含量显著高于其它年份,说明此造林密度有利于发挥三倍体毛白杨林土壤固碳的生态功能。(2)4年生长期内,土壤全N含量受生长时间及其与造林密度的交互作用的显著影响。在3 m×3 m造林密度下,二倍体毛白杨林地土壤全N含量逐年降低,而三倍体毛白杨2007年的土壤全N含量显著增加,该造林密度利于三倍体毛白杨林地土壤N的积累。(3)土壤有机碳/全氮比值变化与有机碳含量变化规律一致,且均在2006年达到最低值。(4)在2008年,三倍体毛白杨在2 m×3 m和2 m×3.5 m造林密度下土壤有机碳与全N含量呈现显著正相关关系,而2 m×5 m造林密度下的二倍体毛白杨林地呈显著性负相关关系,体现了毛白杨林地土壤有机碳与全N含量复杂的相关性。     

松嫩平原玉米带土壤碳氮储量的空间特征

利用第二次全国和县级土壤普查的382个典型土壤剖面资料和1∶50万数字化土壤图建立土壤剖面空间数据库,利用土壤类型法估算松嫩平原玉米带土壤碳、氮储量,分析土壤有机碳、氮密度的空间分布特征,探讨土壤有机碳、氮密度与土壤类型和土地利用类型之间的关系.结果表明:松嫩平原玉米带土壤有机碳、氮储量分别为(163.12±26.48)Tg和(9.53±1.75)Tg,土壤碳、氮储量主要集中在草甸土、黑钙土和黑土等土类中.土壤有机碳、氮密度分别为5.51～25.25和0.37～0.80kg·m-2,土壤C/N值大致在7.90～12.67.土壤有机碳、氮密度的空间分布均表现为东部和北部高、西部低.在不同土地利用类型中,旱田土壤的有机碳密度最高,为(19.07±2.44)kg·m-2;林地土壤的氮密度最高,为(0.82±0.25)kg·m-2;水田土壤的碳、氮密度均较低.     

内蒙古自治区土壤有机碳、氮蓄积量的空间特征

采用全国策二次土壤普查中内蒙古自治区的典型土种剖面资料,在剖面深度的基础上,用地统计学和地理信息系统(GIS)方法,分别按土壤类型和土地覆被类型计算了土壤有机碳、氮密度,分析了内蒙古自治区土壤有机碳、氮蓄积量的空间分布特征,探讨了土壤有机碳、氮蓄积量与主要气候要素的关系．结果表明,内蒙古自治区土壤有机碳密度处于3．24-43．24kg·m^-3之间,土壤有机氮密度处于269．56-3085．60g·m^-3之间,土壤碳、氮比(C／N)大致在4．46-17．13之间．土壤有机碳、氮密度与温度呈负相关,相关系数分别为0．557和0．460(n＝245);与年均降水量呈正相关,但相关性不是很强,相关系数分别为0．285和0．203．从内蒙古自治区东北地区到西南地区,土壤有机碳、氮蓄积量随着温度递升和降水量递减呈现降低的趋势。