草原及开垦后土壤有机质性质研究

从土壤有机无机复合状况、腐殖质结合形态和腐殖质组成等方面,研究了供试土壤(草原淡黑钙土、草原风沙土和已开垦的风沙土)有机质的性质．结果表明,不同土壤类型及利用方式对土壤有机质性质的影响有很大的差异．与风沙土相比,淡黑钙土的全土碳、生物量碳、重组碳、可提取腐殖物质(HE)、松结态腐殖质的含量和全土腐殖化度较高．风沙土种向日葵后其全土碳、生物量碳、重组碳和HE含量及各种结合形态腐殖质含量均下降,但腐殖化程度相差不大．     

内蒙古锡林河流域主要类型草原土壤中CH_4和CO_2浓度的变化

于 1999年生长季对内蒙古锡林河流域主要类型草原土壤中 CH4和 CO2 浓度进行测定 ,结果表明 :CH4浓度沿土壤剖面逐渐降低 ,而且不同土壤深度之间差异显著 ,而 CO2 浓度呈现出沿土壤剖面增加的趋势。草甸草原、羊草 (L eymus chinesis)草原和大针茅 (Stipa grandis)草原土壤中 CH4的浓度差异显著 ,季节变化明显 ,但是三类草原土壤中 CO2 浓度变化不大。测定结果还表明 :一定时间尺度上 ,放牧对草原土壤中 CH4和 CO2 的浓度没有显著影响。     

Influence of soil depth on the decomposition of Bouteloua gracilis roots in the shortgrass steppe

The distribution and turnover of plant litter contribute to soil structure, the availability of plant nutrients, and regional budgets of greenhouse gasses. Traditionally, studies of decomposition have focused on the upper soil profile. Other work has shown that temperature, precipitation, and soil texture are important determinates of patterns of decomposition. Since these factors all vary through a soil profile, it has been suggested that decomposition rates may vary with depth in a soil profile. In this work, we examine patterns of root decomposition through a shortgrass steppe soil profile. We buried fresh root litter from Bouteloua gracilis plants in litterbags at 10, 40, 70, and 100 cm. Litterbags were retrieved six times between July 1996 and May 1999. We found that the decomposition rate for fresh root litter was approximately 50% slower at 1 m than it was at 10 cm. After 33 months, 55% of the root mass buried at 10 cm remained, while 72% of the root mass buried at 1 m was still present. This corresponds to a 19-year residence time for roots at 10 cm and a 36-year residence time for roots at 1 m. Mass loss rates decreased linearly from 10 cm to 1 m. Patterns of total carbon and cellulose loss rates followed those of mass loss rates. Roots at 1 m tended to accumulate lignin-like compounds over the course of the experiment. Differences in the stabilization of lignin may be a consequence of differences in microbial community through a shortgrass steppe soil profile.     

西藏高原退化土壤的生物学肥力及其变化特征

通过3年田间定位试验,对施肥条件下退化山地灌丛草原土生物学肥力的变化进行了研究.结果表明,不施肥状态下的耕层土壤有机质含量较试前呈微弱下降,施肥条件下土壤生物学肥力呈现出相对一致的特征,表现在耕层土壤有机质相对较高的积累速率、腐殖质结构明显改善以及土壤细菌的显著增殖等方面,但土壤微生物区系仍处于极不协调状态;随着有机肥或化肥的递增,0～30和30～60 cm土层有机质含量均有显著提高的趋势,其年均累积量分别达1.35和0.67 g·kg^-1;0～30和30～60 cm土层腐殖质碳占有机碳比重、胡敏酸碳占腐殖质碳比重亦均随有机肥或化肥递增而趋于提高;不同培肥方式对土壤细菌的繁殖与活动均具有极为显著的促进作用,2～30和30～60 cm土层细菌数量与有机质含量分别呈极显著和显著正相关（r＝0.7194、0.6042）,对土壤真菌、放线菌的影响则不甚明显;多数施肥处理下,不同土层固氮菌、纤维素分解菌数量低于不施肥处理,耕层土壤固氮菌与纤维素分解菌数量呈负相关（r=-0.4799）     

Temporal and vertical changes in the humus form profile during a primary succession of Pinus sylvestris

The development of the humus form profile during a primary succession of Pinus sylvestris has been studied along chronosequences on dunes and in blow-outs. Attention was given to vertical variation within the humus form and how this changes during profile development. The mor-type ectorganic profile features marked vertical gradients of several soil attributes, while its constituting horizons show no or only small changes of chemical properties during succession. These changes in particular involve increasing calcium and nitrogen concentrations in the organic matter. After an initial high rate of organic matter accumulation in the successive organic horizons, these rates are strongly reduced, suggesting the attainment of a dynamic equilibrium within the time span of the chronosequences on dunes and blow-outs. Blow-outs differ from dunes in the sense that they have a lower amount of organic matter and a higher F/H ratio. This different ratio likely relates to microclimatic conditions less conducive to decomposition.An attempt is made to explain the vertical trends in terms of processes affecting the characteristics of the organic horizons. Main conclusions are that the development of the ectorganic profile results from a combined effect of decay dynamics, rhizosphere processes and atmospheric deposition, which cannot be unentangled quantitatively with the data available. Furthermore, the distinction between F and H horizons has morphological rather than chemical or ecological relevance, as major vertical changes occur within the F horizon.     

Carbon stock evaluation from topsoil of forest stands in NE Italy

Gas emissions from anthropic activities, particularly CO2, are responsible for global warming. Soil is a major carbon sink on a planetary level, thereby contributing to mitigate greenhouse effect. In the present work, the objectives were: 1) to evaluate the topsoil carbon stock of different forest stands in NE Italy, and 2) to outline the relationships among humus forms, soil organic matter dynamics, and actual carbon stock under different vegetation coverage, with reference to climate change. Five forest stands and the related topsoils, were selected in the Dolomites area. The humus forms were examined in the field and samples were carried to the lab for further physical-chemical analyses. The carbon stock for each soil was calculated by means of pedotransfer functions. The less developed humus forms, as the Dysmull and the Hemimoder, presented the highest carbon storage capacity (168 t/y and 129 t/y), followed by Lithoamphimus (123 t/y) and Eu-amphimus (96 t/y), and by Oligomull (86 t/y). Organic horizons proved to recover 36% of the total carbon stocked along the soil profile, and this points to humus layers as a fundamental tool in carbon stock evaluation. Positive correlations between elevation, humus forms and soil carbon pools were found.     

稻田免耕和稻草还田对土壤腐殖质和微生物活性的影响

为了阐明免耕和稻草还田土壤固碳机制,研究了无稻草还田免耕（NT）、无稻草还田常耕（CT）、稻草还田免耕（NTS）和稻草还田常耕（CTS）对水稻不同生育期不同土层（0—5,5—12,12—20cm）土壤腐殖质形态、含量及微生物活性的影响。结果表明,免耕（NT和NTS）处理显著增加0—5 cm土层土壤游离松结态、联结态和稳紧结态腐殖质含量和游离松结态腐殖质占总腐殖质的比例,且免耕对土壤各结合态腐殖质含量的影响程度有随生育期的推后而增加的趋势;5—12cm和12—20cm土层土壤各结合态腐殖质含量和0—20cm各土层微生物活性有减少趋势;在水稻分蘖期免耕对微生物活性影响很弱,在水稻拔节—灌浆期免耕处理显著降低5—12 cm土层土壤微生物活性,相反,免耕却增加水稻成熟期0—5 cm土层的微生物活性;另一方面,稻草还田（CTS和NTS）显著提高土壤各结合态腐殖质含量,尤其是0—5 cm土层、游离松结态腐殖质及水稻生育后期;CTS处理显著增加分蘖期—孕穗期0—20 cm土层的呼吸强度,而稻草还田显著增加孕穗期—成熟期0—5cm土层的纤维素分解强度。可见,通过增加土壤腐殖质含量和各结合态腐殖质含量并改变微生物活性免耕有利于表土层碳的固定作用,而免耕与稻草还田相结合更有利于土壤碳的积累。     

内蒙古锡林河流域主要类型草原土壤中CH4和CO2浓度的变化

 于1999年生长季对内蒙古锡林河流域主要类型草原土壤中CH4和CO2浓度进行测定,结果表明：CH4浓度沿土壤剖面逐渐降低,而且不同土壤深度之间差异显著,而CO2浓度呈现出沿土壤剖面增加的趋势。草甸草原、羊草(Leymus chinesis )草原和大针茅(Stipa grandis)草原土壤中CH4的浓度差异显著,季节变化明显,但是三类草原土壤中CO2浓度变化不大。测定结果还表明：一定时间尺度上,放牧对草原土壤中CH4和CO2的浓度没有显著影响。     

Humus profiles of Siberian soils under different forming conditions

Humus profiles of Siberia soils under different conditions and models of soil formation are considered in the paper. It is shown that the humus profiles of soils formed in the regions of displacement of landscape and soil borders and developed according to the polygenetic model as well as the soils of synlithogenous type of pedogenesis have a complicated structure. Simple structure of the humus profile characterizes soils developing within the framework of a simple (ideal, normal) model of soil formation.     

长白山森林土壤真菌区系研究

本研究对长白山自然保护区不同海拔、林型、土壤剖面的森林土壤真菌进行分离鉴定,从而为建立森林真菌资源库提供种质资源,并为森林生物资源管理提供科学依据。在该地区6个不同林型中,采用“之”形路线及土壤剖面取样法多点采集土壤样品,按照标准方法初步分离鉴定出真菌28个属,其中包括1个中国新纪录属,即球壳属(Sphaerodes)。研究结果表明,土壤真菌区系与森林(植被)类型、土壤剖面层次密切相关:美人松落叶松林、红松阔叶林和红松云冷杉林土壤真菌的种类明显多于鱼鳞云冷杉林、岳桦林和高山苔原带;土壤不同剖面层次上的真菌种群数量高低依次为落叶层>腐殖质层>土壤层;同一林型下不同土壤层面上优势菌属的组成也具有一定的差异,且不同层面上也存在着其特有的优势菌属。     

Relationship Between Root Biomass and Soil Organic Matter Pools in the Shortgrass Steppe of Eastern Colorado

We examined the distribution of soil organic carbon (SOC) fractions and roots with depth to improve our understanding of belowground carbon dynamics in the shortgrass steppe of northern Colorado. Weaver and others (1935) found that the surface 15 cm of soil contained over 70% of the total roots found in a tallgrass prairie soil profile, while only accounting for 40% of the profile soil organic matter. We asked whether the relationship between roots and SOC that Weaver and others (1935) found in the tallgrass prairie was also found in the shortgrass steppe. Weaver and others (1935) suggested that the dissimilarity between belowground biomass and SOC with depth is the result of variability in decomposition rates. In an effort to determine whether patterns of SOC are the result of short-term plant input patterns or decomposition, we measured the ¹⁴C content of potentially mineralizable C and particulate organic matter (POM) C ten years after pulse labeling shortgrass steppe vegetation. We also estimated the mass specific decomposition rate constant (kPOM) for POM C through a shortgrass steppe soil profile. We found that the distribution of roots and SOM in the shortgrass steppe were similar to those observed in tallgrass prairie (Weaver and others 1935), with a higher proportion of total root biomass in the surface soils than total soil organic matter. Fifty-seven percent of root biomass was found in the surface 15-cm, while this same soil layer contained 23 percent of profile soil organic C. We measured the highest accumulation of ¹⁴C at the soil surface (12.0 ng ¹⁴C·m^-2·cm^-1 depth), with the least accumulation from 75-100 cm (0.724 ng ¹⁴C·m^-2·cm^-1 depth). The highest values of potentially mineralizable C were at the soil surface, with no significant differences in total mineralizable C among the 10-100 cm soil depths. The contribution of POM C to total C reached a profile minimum at the 15-20 cm depth increment, with profile maxima in the surface 5 cm and from 75-100 cm. We estimated that the proportion of particulate organic matter lost annually (kPOM) reached a profile maximum of 0.097 yr^-1 within the 10-15 cm depth increment. The 75-100 cm depth increment had the lowest kPOM value at 0.058 yr^-1. Thus, within the same physical fraction of SOC, decomposition rates vary with depth by nearly twofold. This pattern of high decomposition rates from 10-15 cm with lower decomposition rates at the soil surface and deeper in the soil profile may be the result of higher water availability in sub-surface soils in the shortgrass steppe.     

黄土高原典型区域土壤腐殖酸组分剖面分布特征

黄土高原作为典型的气候敏感带和生态环境脆弱区,诸多因素影响着这个区域的土壤有机碳及其组分的分布特征。本文以黄土高原典型区域土壤剖面 0—200 cm土样为对象,分析了土壤腐殖酸、胡敏酸（HA）和富里酸（FA）含量随地理位置及土层深度的分布特征,并进一步探讨了土壤腐殖酸、HA和FA与全氮含量及土壤颗粒组成的关系。结果表明,黄土高原主要类型土壤腐殖酸、HA和FA含量均较低,且存在明显地理位置和土层分异性：从南到北同层次土壤腐殖酸、HA和FA含量均显著降低,同一区域随土层深度增加各组分含量均表现为在 0—40 cm土层明显下降, 40—120 cm土层稍有下降,120 cm土层以下基本稳定;土壤腐殖酸占有机碳比例变化范围为26.6%—54.7%,相对较小,且在整个剖面变化幅度不大,从南向北土壤腐殖酸占有机碳比例有增加趋势;土垫旱耕人为土在 0—40 cm、 40—120 cm和 120—200 cm土层中HA占腐殖酸比例分别为39.8%、49.0%和53.5%,HA/FA分别为0.66、0.96和1.15,黄土正常新成土在以上土层中HA占腐殖酸比例分别为26.3%、33.9%和42.3%,HA/FA分别为0.36、0.51和0.73,干润砂质新成土在以上土层中HA占腐殖酸比例分别为13.4%、37.1%和45.2%,HA/FA分别为0.16、0.59和0.82,说明黄土高原南北主要类型土壤腐殖酸品质总体较差,均属富里酸型土壤,且从南到北腐殖酸品质逐渐下降;土壤腐殖酸、HA和FA均与全氮含量呈极显著线性相关（P<0.01）,土壤有机碳、腐殖酸及HA含量与粘粒及砂粒百分含量亦呈高度线性相关（P<0.01）。     

高寒草原土壤有机碳及土壤碳库管理指数的变化

高寒草原对高寒生态系统的稳定具有重大意义。为探明高寒草原土壤有机碳（SOC）、土壤活性有机碳（ASOC）变化,以及草地退化对土壤碳库稳定性的影响,对藏北高原正常、轻度和严重退化高寒草原表层（0-10 cm）、亚表层（10-20 cm）土壤进行了初步研究。结果表明：（1）轻度、严重退化草地各土层SOC、ASOC均呈不同程度的下降。其中,退化草地SOC的降幅均以表层最大,且各土层降幅均随草地退化加剧而下降;退化草地ASOC的降幅则均以亚表层最大,但各土层ASOC的降幅随草地退化加剧而提高。（2）正常草地、轻度和严重退化草地表层ASOC比率分别为16.8%、21.3%、16.6%,亚表层分别为21.8%、18.1%和16.0%;土壤碳库活度与ASOC比率的变化趋势完全一致。因此,轻度退化草地SOC的不稳定性主要体现在表层土壤。（3）退化草地表层、亚表层碳库管理指数（CMI）均呈显著下降,但表层降幅相对较低;与严重退化草地比,轻度退化草地不同土层CMI明显提高。（4）高寒草原环境中,正常草地、轻度和严重退化草地各土层SOC、ASOC间则均呈一定程度的负相关,表明土壤微生物对SOC、ASOC的影响和作用可能不同。     

长期施肥条件下水稻土腐殖质组成及稳定性碳同位素特性

利用太湖地区26年水稻土长期定位施肥试验,分析了长期不同施肥处理对土壤剖面有机碳分布和稳定性碳同位素自然丰度(δ¹³C)的影响,以及土壤中不同结合态腐殖质组成的变化.结果表明：长期施肥使水稻土表层土壤有机碳含量显著升高,不同处理土壤剖面有机碳含量与土层深度呈极显著指数负相关(P<0.01);施化肥处理10～30 cm土层和施有机肥处理20～40 cm土层有机碳含量变化相对稳定;随土层深度增加,土壤δ¹³C值逐渐升高,其变化范围在-24‰～-28‰,不同处理土壤剖面有机碳含量与δ¹³C值呈显著线性负相关(P<0.05);0～20 cm土层,仅施有机肥处理(M0)、有机肥+氮+磷处理(MNP)、有机肥+氮+磷+钾处理(MNPK)、有机肥+秸秆+氮处理(MRN)以及秸秆+氮处理(CRN)的δ¹³C值明显降低;30～50 cm土层,除CRN外,有机肥和化肥处理土壤的δ¹³C值均明显升高;不同处理土壤中结合态腐殖质均以紧结合态腐殖质(胡敏素)为主,其含量在50%以上,其余部分为松结合态和稳结合态腐殖质;长期施肥使土壤松结合态腐殖质含量及富啡酸(FA)与胡敏酸(HA)比值(HA/FA)升高.     

Root system responses of Japanese red cedar saplings to acidic conditions

Stemflow from Japanese red cedar (Cryptomeria japonica) enters forest soil at a low pH. We evaluated the responses of the root system of Japanese red cedar saplings to acidic conditions, used to simulate this situation, in two different growth media, a brown forest soil (BS) and a Yahagi sand (YS). Soils were acidified by the addition of solutions at pH 2.0, 3.0 and 5.5 (control). Root morphology, root surface area index, root respiration activity and root biomass were measured. In the pH 3.0 treatment, no significant effects were found on the root systems compared with the controls in either soil, except for a slight difference in root-tip diameter in the Yahagi sand. In the pH 2.0 treatment, the surface area index and dry weight ratios of the whole root in the Yahagi sand were significantly lower than those in the other treatments. No significant effects on the whole root were observed in the brown forest soil. These results suggest that detrimental effects of acidic solutions on the root systems would be less significant in brown forest soil, which contains humus, than in the Yahagi sand, which lacks humus. They also suggest that the threshold pH value causing visible morphological changes on the roots of Japanese red cedar saplings falls in the pH range between 2 and 3. White roots in the pH 2.0 treatment had low respiration activity and showed visible morphological changes in both soils. These responses were presumably related to the effects of excess Al in the soil solution. White roots in the pH 2.0 treatment typically produced exodermis. The results suggest that stemflow with a pH of 3.0 has no effects on the root systems of Japanese red cedar, and that the morphology of white roots was adversely affected not by treatment at pH 2.0 but by excess water-soluble Al in the soil.     

人类活动对锡林郭勒地区主要草原土壤有机碳分布的影响

 内蒙古锡林郭勒地区3类主要草原土壤有机碳含量呈现规律性变化,其顺序为：黑钙土>栗钙土>棕钙土。同时,有机碳沿土壤剖面自上而下逐渐降低,且主要分布在0～15cm处。草甸草原植被下的黑钙土不同层次有机碳含量因农垦分别损失34％～38％,损失主要发生在0～35cm处。分析结果表明,放牧强度在短时期内对典型草原植被下的栗钙土有机碳含量没有显著影响。     

Humus Form Development during Forest Restoration in Exclosures of the Tigray Highlands, Northern Ethiopia

Forest restoration in protected exclosures has become a common practice to fight land degradation in the highlands of northern Ethiopia. Insights into ecosystem processes governing restoration in these formerly degraded areas are gained through the study of humus forms and factors influencing humus formation during vegetation recovery. Humus forms of 135 sample plots located in different land use types were morphologically described. The subsequent classification into six humus form types was based on principal component analysis and cluster analysis. Where areas are closed for a longer time, humus profiles are commonly more developed and higher organic matter accumulation is noticed as well as increased nutrient stocks. The combined effects of seasonal drought conditions and low fresh litter quality account for an overall slow decomposition, which explains the high importance of litter input for organic matter accumulation. Based on a correlation analysis, vegetation cover, litter production, litter quality, soil nutrient content, soil moisture, and topography were identified as important factors influencing humus formation. It is inferred that humus formation leads to improvements in soil fertility and structure, microclimate development, and soil protection and therefore forms part of the restoration processes taking place in exclosures.     

Allocation of mass and stability of soil aggregate in different types of Nei Mongol grasslands北大核心CSCD

Aims: Soil aggregate is an important component of soil structure, playing an important role in the physical and biological protection mechanism of soil organic carbon (SOC) through isolating SOC from microorganisms. As far as we know, there are few studies, however, on exploring the spatial distribution of soil aggregate at the regional scale. Our objective was to investigate the mass allocation and stability of soil aggregate in different types of Nei Mongol grasslands. Methods: We have established 78 sites with a size of 10 m × 10 m across the transect of Nei Mongol grasslands and collected soil samples from different soil depth up to 1 m. We used wet sieving method to separate different sizes of aggregate partition and used mean mass diameter (MMD) and geometric mean diameter (GMD) in order to evaluate the stability of soil aggregate. The two-way ANOVA was used to test the difference of mass percentage and stability of soil aggregate in different grassland types and soil depths. In addition, a linear regression analysis was used to analyze the correlations of mass percentage and stability of soil aggregate with both mean annual precipitation (MAP) and mean annual temperature (MAT). Important findings: The results showed that the mass percentages of soil aggregate were highest in meadow steppe, while almost equal in typical steppe and desert steppe. However, no significant patterns were found along the soil depth. The mass percentage of soil aggregate fractions were positively correlated with MAP in all soil layers, but negatively correlated with MAT except the layer of 70-100 cm. For the stability of soil aggregate, at 0-10 and 10-20 cm, MMD and GMD of meadow steppe were significantly greater than those of typical and desert steppes, whereas no significant differences among three grassland types were found for other soil layers. Besides, MMD and GMD in meadow steppe and typical steppe gradually decreased along the soil depth.     

荒漠草原区柠条固沙人工林地表草本植被季节变化特征

研究荒漠草原人工林固沙区地表草本植被季节变化特征及其和柠条林龄的关系,对于分析柠条人工林地表草本植物的季节适应性和制订合理的人工林管理措施均具有重要的科学意义。选择6、15、24年生和36年生柠条人工林为研究对象,通过调查每个样地5月、8月和10月地表草本植物密度、物种数、盖度和高度,分析了荒漠草原区柠条人工固沙林生长过程中地表草本植被季节变化特征及其影响因素。结果表明,地表草本植物物种数在柠条林龄6和15a时受季节改变的影响较小,在24a之后受到季节变化的显著影响(P0.05)。地表草本植物密度在柠条林龄6a时受季节改变的影响较小,但在15a之后季节变化显著影响地表草本植物个体数分布(P0.05),而且在10月具有最多的地表草本植物个体数。地表草本植被盖度和高度均受到季节变化的显著影响(P0.05),而受林龄的影响较小;不同年龄林地地表草本植被盖度和高度均表现为10月和8月较高,5月较低。研究表明,荒漠草原柠条人工林固沙区,柠条林发育生长和灌木形态的改变不仅影响土壤营养条件,而且还可以调控由于季节改变而引起的土壤温湿度变化,柠条林龄和季节更替二者交互作用,共同影响地表草本植被的季节变化特征。