典型黑土区坡面侵蚀-沉积对土壤微生物养分限制的影响

在典型黑土区黑龙江省克山县选取开垦百年坡耕地,采用^(210)Pb_(ex)示踪技术估算坡面侵蚀-沉积速率,并划分土壤侵蚀强度等级[包括沉积(DS)、轻度侵蚀(LE)、中度侵蚀(ME)、强烈侵蚀(IE)和极强烈侵蚀(SE)],对比不同土壤侵蚀强度等级下土壤碳氮磷含量、微生物生物量和酶活性的差异,通过酶计量矢量模型量化土壤微生物养分限制对土壤侵蚀-沉积的响应.结果表明:坡耕地土壤侵蚀-沉积速率变化于-782.7~10914.5t/(km^(2)·a)之间,其平均侵蚀速率为3507.6t/(km^(2)·a);土壤LE和ME主要发生在坡上部和沉积部位周围,IE和SE主要发生在坡中部,而DS主要位于坡脚.土壤碳氮磷含量和微生物生物量总体随土壤侵蚀强度等级增加而降低.土壤碳获取酶活性(BG+CBH)和氮获取酶活性(NAG+LAP)在坡面DS部位最高;而土壤磷获取酶活性(ACP)在坡面SE部位最高.酶计量矢量模型表明土壤微生物受到相对碳和磷限制;土壤微生物相对碳限制随土壤侵蚀速率的增加和沉积速率的降低呈线性下降趋势,而土壤微生物相对磷限制则随土壤侵蚀速率的增加和沉积速率的降低呈线性增加趋势,表明土壤微生物受到土壤磷素的限制作用相对突出.土壤养分含量和微生物生物量解释了坡面不同土壤侵蚀强度等级下土壤酶活性和微生物养分限制变化的60.1%,其中土壤有机碳(SOC)含量在条件效应下的解释度最高,其解释度为17.4%.总之,土壤侵蚀-沉积对土壤质量的影响是土壤性质和微生物养分限制共同作用的结果.

海底峡谷侵蚀-沉积作用与天然气水合物成藏

近年来海底峡谷和海域天然气水合物的调查和研究表明,二者在空间分布上具有一定的相似性,同时海底峡谷强烈的侵蚀作用和良好的内部建造,与海域天然气水合物的聚集、分布和成藏具有直接或间接的关联。通过对目前海底峡谷和海域天然气水合物的资料调研和系统分析,指出海底峡谷和海域天然气水合物的相关性主要表现在3个方面:侵蚀-沉积作用与有利沉积体的分布、侵蚀-沉积作用与含烃流体渗漏的相互作用、侵蚀-沉积作用与海域天然气水合物的动态成藏。将海底峡谷和水合物的关联性应用到珠江口盆地海底峡谷群,初步分析了二者的关联。研究认为该区域的海底峡谷将会对有利沉积体进行破坏和改造,使其表现为"斑状/补丁状"的平面分布特征,影响了水合物的分布和实际产出;此外,峡谷侵蚀-沉积作用导致了先前形成的水合物的分解,一部分的甲烷等气体将会进入到海水之中,而受有利沉积体上部细粒均质层的遮挡,大部分的含气流体将被"继续"限制在有利沉积体之中而形成新的水合物,这可能是该区域内细粒沉积物中水合物饱和度较高的原因。

河流碳输移与陆地侵蚀-沉积过程关系的研究进展

河流碳输移与陆地侵蚀-沉积过程紧密相关。首先就机械和化学风化两种不同的陆地侵蚀机制在提供河流碳源方面所发挥的不同作用作了详细论述,并比较了季风流域和非季风流域间河流碳输移在通量及性质上的差异。之后对陆地碳沉积机制进行了归纳,指出了包括大坝截留,河漫滩、河口-近岸带沉积及陆地碳沉降等几种可能的陆源碳踪迹。陆地环境的截留效应相对于侵蚀尚不太清楚,今后应加强对陆地碳沉积的研究,进一步明确各种碳沉积的作用机制及其对全球陆地碳汇的贡献量。此外,人类活动对陆地侵蚀-沉积过程及河流碳循环所产生的直接或间接的影响也有待于今后继续深入探索。

典型黑土区侵蚀-沉积对土壤微生物数量空间分布的影响

研究土壤微生物群落对土壤侵蚀-沉积的响应可为农业生态系统功能提升提供重要指导。选择黑龙江省典型薄层黑土区宾县宾州河流域为研究区,分析土壤微生物数量的空间分布特征,并结合;Cs示踪方法估算土壤侵蚀模数,进一步分析坡面和流域尺度土壤侵蚀-沉积对土壤微生物数量的影响。结果表明:季节变化对土壤微生物数量的影响非常明显,夏季土壤微生物数量显著高于秋季;其中,土壤细菌数量对季节变化反应最敏感,其在夏季坡面不同部位和流域不同位置较秋季分别增加1.4~2.6倍和1.4~2.2倍。土壤侵蚀强度的空间分布对土壤微生物群落空间分布有重要影响。土壤细菌数量在坡下部沉积区和流域下游轻度侵蚀区所占比例最高,分别为84.4%和85.4%。除土壤真菌数量外,土壤微生物数量、细菌和放线菌数量均与土壤侵蚀模数有显著负向线性关系,相关系数分别为-0.595、-0.554和-0.291。坡面和流域尺度土壤侵蚀-沉积使土壤理化性质产生空间差异,进而对土壤微生物群落数量的空间分布产生影响。

中国东北雅鲁河流域侵蚀-沉积数据集

利用30 m分辨率ASTER GDEM数据,将中国东北雅鲁河流域划分为2,850个坡面,计算各单一坡面的平均坡度和平均坡长;并与扎兰屯气象数据和全球土地覆盖数据Glob Cover2009和土壤数据经过处理后,输入WEPP模型(水蚀预报模型),得到雅鲁河流域的侵蚀-沉积数据,确定了14个侵蚀-沉积平衡点。由这些平衡点形成的界限,与传统的根据高程和坡度来定性划分该区域的界限基本吻合,为定量区划提供了一种新方法。

中国东北甘河流域侵蚀-沉积基础数据集

大兴安岭是中国地势第二、三级阶梯东北部分界线,长期以来这只是个定性的界定,没有精确的界线,研究其过度地带的甘河流域侵蚀-沉积过程对定量提取第二、三级阶梯分界线具有重要意义。本数据集的研发需要经过以下步骤:(1)利用日降雨量、日最高温度、日最低温度等气象数据建立气候数据库;(2)基于ASTERGDEM数据利用水文分析方法建立坡面数据库;(3)利用土地利用与分类数据建立作物管理数据库;(4)利用土壤类型和土壤理化性质资料建立土壤数据库;(5)将建立的甘河流域气候数据库、土壤数据库、坡面数据库和作物管理数据库输入水蚀预报模型(Water Erosion Prediction Project,WEPP),并进行运算,最终获得中国东北甘河流域侵蚀-沉积基础数据集。本文以此数据集为基础,利用侵蚀量-沉积量与地形因素(坡度和坡长)的关系获取甘河流域的侵蚀-沉积平衡点,定量提取第二、三阶梯分界线,并与定性提取的大兴安岭东坡和东北平原的界线进行对比分析,结果显示,侵蚀-沉积平衡点处于大兴安岭与东北平原的过渡地带,且与定性提取界线基本吻合,并具有更准确的地理定位,这充分体现了中国东北甘河流域侵蚀-沉积基础数据集的重要学术价值。

中国东北洮儿河流域侵蚀-沉积基础数据集

利用30m分辨率ASTERGDEM数据,将东北洮儿河流域划分为5243个单一坡面,计算各单一坡面的平均坡度和平均坡长;并与乌兰浩特气象数据、全球土地覆盖数据GlobCover2009和土壤数据经过处理后,输入水蚀预报模型WEPP,得到洮儿河流域的侵蚀-沉积数据,确定了13个侵蚀-沉积平衡点(坡面)。由这些平衡点形成的界限,与传统的根据高程和坡度来定性划分该区域的界限基本吻合,为定量区划提供了一种新方法,为该区域研究提供了新数据。

侵蚀—沉积连续地形中土壤碳库的空间分异

侵蚀和再沉积过程可导致土壤碳库在空间上重新分布,但至今对这一过程中不同碳库的迁移和再分布特点还了解不多。在浙江省亚热带地区选择了由严重侵蚀区—轻微侵蚀区—坡脚堆积区—坡底堆积区组成的侵蚀—沉积系列连续地形,分别采集了4个代表性土壤剖面,研究了不同地形部位土壤碳库的分异特征,探讨了侵蚀—再沉积过程中各种碳库的转归。结果表明,土壤有机总碳及各组分碳均是:严重侵蚀区<轻微侵蚀区<坡脚堆积区<坡底堆积区。侵蚀区土壤总有机碳自上而下明显下降,而堆积区土壤有机碳库分布较深,垂直变化相对平缓。黑碳极易随地表径流发生迁移,呈由高处逐渐向低处明显富集的趋势。堆积区为连续地形中的碳汇。

Characteristics of Wind Erosion and Deposition in Oasis-desert Ecotone in Southern Margin of Tarim Basin,China

The oasis-desert ecotone is a fragile ecological zone that is affected both by oasis and desert conditions. To understand the impact of the differences in wind power, and the influence of wind erosion and deposition on the ecotone, meteorological data and con- temporaneous wind erosion and deposition data were collected on the southern margin of Tarim Basin with serious sand-blown hazards. The wind velocity, average wind velocity, sand drift potential （DP）, resultant sand drift potential （RDP）, and sand transportation rate decrease significantly and successively across four landscape types with increasing vegetation coverage （VC）. Flat surfaces and areas of shifting sandy ground experience intense wind erosion with fast movement of mobile sand dunes; semi-fixed sand areas experience ex- tensive wind deposition but only slight wind erosion; and fixed sand areas experience only slight wind erosion and deposition. Volume of wind erosion on bare newly reclaimed farmland is up to 6.96 times that of bare shifting sandy ground. Wind erosion volume per unit area and VC follow an exponential function relationship in natural conditions, while wind deposition volume per unit area does not conform to any functions which has close relationship with vary topography and arrangement patterns of vegetation besides for VC. The results indicate that the volume of wind erosion has a close correlation with VC, and different types and distribution patterns of topog- raphy and vegetation also profoundly influence the wind deposition volume in the field, and underground water tables in different land- scape types control the plant community distribution. Keywords： wind erosion; wind deposition; oasis-desert ecotone; vegetation coverage （VC）; topography; Cele County

Interpreting sedimentation dynamics at Longxi catchment in the Three Gorges Area,China,using Cs-137 activity,particle size and rainfall erosivity

Reservoir sedimentation dynamics were interpreted using Cs-137 activity, particle size and rainfall erosivity analysis in conjunetion with sediment profile coring. Two sediment cores were retrieved from the Changshou reservoir of Chongqing, which was dammed in 1956 at the outlet of Longxi catchment in the Three Gorges Area using a gravity corer equipped with an aerylie tube with an inner diameter of 6 em. The extracted cores were sectioned at 2 cm intervals. All sediment core samples were dried, sieved （〈2 mm） and weighed. 137Cs activity was measured by y-ray spectrometry. The particle size of the core samples was measured using laser particle size granulometry. Rainfall erosivity was calculated using daily rainfall data from meteorological records and information on soil conservation history was collated to help interpret temporal sedimentation trends. The peak fallout of 137Cs in 1963 appeared at a depth of 84 cm in core A and 56 cm in core B. The peaks of sand contents were related to the peaks of rainfall erosivity which were recorded in 1982, 1989, 1998 and 2005, respectively. Sedimentation rates were calculated according to the sediment profile chronological controls of 1956, 1963, 1982, 1989, 1998 and 2oo5. The highest sedimentation rate was around 2.0 cm·a^-1 between 1982 and 1988 when the Chinese national reform and the Household Responsibility System were implemented, leading to accelerated soil erosion in the Longxi catchment. Since 1990s, and particularly since 2005, sedimentation rates clearly decreased, since a number of soil conservation programs have been carried out in the catchment. The combined use of ^137Cs chronology, particle size and rainfall erosivity provided a simple basis for reconstructing reservoir sedimentation dynamics in the context of both physical processes and soil restoration. Its advantages include avoiding the need for full blown sediment yield reconstruction and the concomitant consideration of core correlation and corrections for autochthonous inputs and reservoir trap efficiency.

Two-dimensional Numerical Model for Debris Flows in the Jiangjia Gully,Yunnan Province

Debris flows are recurrent natural hazards in many mountainous regions.This paper presents a numerical study on the propagation of debris flows in natural erodible open channels,in which the bed erosion and sedimentation processes are important.Based on the Bingham fluid theory,a mathematical model of the two-dimensional non-constant debris flow is developed.The governing equations include the continuity and momentum conservation equations of debris flow,the sediment convection-diffusion equation,the bed erosion-deposition equation and the bed-sediment size gradation adjustment equation.The yield stress and shear stress components are included to describe the dynamic rheological properties.The upwind control-volume Finite Volume Method (FVM) is applied to discretize the convection terms.The improved SIMPLE algorithm with velocity-free-surface coupled correction is developed to solve the equations on non-orthogonal,quadrilateral grids.The model is applied to simulate a debris flow event in Jiangjia Gully,Yunnan Province and to predict the flow pattern and bed erosion-deposition processes.The results show the effectiveness of the proposed numercial model in debris flow simulation and potential hazard analysis.

Historical Sediment Record of ^(137)Cs, δ-HCH, and δ^(13)C Reflects the Impact of Land Use on Soil Erosion

This paper reports the concentrations of 137Cs, hexaehlorocyclohexane （HCH）, dichlorodiphenyltrichloroethanes （DDT） and its main degradation products, δ3C, and organic carbon in pond sediments （O-210 cm, sectioned by 2-20 cm interval） and surface soils （the 0-3 cm horizon） collected in 2OlO from Chenjia catchment, which is located in Yanting county in the hilly central Sichuan of China. α-, β-, and γ-HCH, DDT, and DDD were not detected throughout the sediment profile. Trace concentrations of δ-HCH （0.89-29.31 ng g^-1） and p,p＇- DDE （1.85-6.02 ng g^-1） were detected only in top 40 cm sediment. The 137Cs fallout peak in 1963 （corresponding to the 55-60 cm depth）, the sedimentary signature left by the last year of HCH use in 1989 （an additional indicator at 20-25 cm）, and the obvious original channel bed prior to the construction of the pond in 1956 were used as temporal markers to estimate changes in average sedimentation rate between different periods due to changes in land use. Continuous, marked decrease in average sedimentation rate （i.e., 3.79, 1.35 and 1.07 cm year-1 in 1956-1963, 1963-1989, and 1989-2010, respectively） over time was observed, probably due to the reforestation, abandoning of steep sloping farmland for afforestation and natural re-vegetation （implementation of the Grain for Green Program）, and the conversion of part of gently sloping farmlandterraces to orchard land since the 1980s, especially since the 1990s. This was corroborated by the observed decrease （more negative） in δ3C of sediment towards the surface, which indicates increased relative contribution of eroded soil particles coming from slopes with increased tree cover in sediment source area. Combined use of 137Cs, δ-HCH, and δ3C record in sediments has been demonstrated to be a powerful approach to reconstruction of response in sedimentation rate to historical land use changes.

Assessment of Seasonal Sedimentation in Rain-fed Irrigation Reservoirs by a Hillslope Erosion Modeling Approach

A distributed hillslope model is presented for the computation of seasonal sediment loads flowing into the rain-fed irrigation reservoirs (tanks) from the mountainous catchments in Sri Lanka. The model is based on the subdivision of the catchment into hillslopes and application of a sediment transport capacity equation at hillslope scale and computation of sediment loads transported to the tanks. Coarse and fine sediment loads due to hourly excess rainfall during a season are separately estimated. The model depends on fewer parameters and can be easily calibrated for a tank. The model calibration only requires measurements of coarse and fine sediment loads transported into the tank due to several rainfalls of different intensities from a representative subcatchment of the tank. Coarse sediment loads are measured by using a sediment trap installed across an ephemeral stream draining the subcatchment. Fine sediment loads are obtained by measuring the discharge and accompanied sediment concentrations over the sediment trap. The model is calibrated, verified and applied for an irrigation tank in Sri Lanka to estimate the seasonal sedimentation loads.

Degradation of Soils in the Lowland of Kur-Araz

The research works were carried out for determination of the washout, types, sorts and level of the development reasons of degradation with the purpose of preparation of the measures of fight against degradation in the soils in 2005-2009 in the lowland of Kur-Araz. The investigations were fulfilled by using of geographical and stasionar methods. It is revealed that 333.6 thous, ha of the soils of the lowland of Kur-Araz have been exposed to erosion. 97.4 thousand ha of them have been exposed to rainstorm erosion, 127.1 thous, have been exposed to irrigative and 122.1 thous, ha to wind erosion. The most dangerous of them are considered irrigative erosion. Under the influence of erosion process in deposited over the length of furrow, deposits the changes happened in maintenance of humus and nutritions elements. In dependence on slope and water expenditure on 1 ha 2.23-14.86 t of soil are leached. As a result of out wash from 1 ha of soil 55.88-304.59 kg of humus, 4.06-20.80 kg of nitrogen, 4.57-26.55 of phosphorus and 57.40-372.99 of potassium are lost. The soil is exposed to degradation and as a result a process of desertification begins. On the basis of the quantitative an intensity of soil outwash the possible losses of dry matter including humus and main elements of nutrition of plants as a result of erosion, their deposit with the water way, are calculated, too.

Large-area Analysis of Soil Erosion and Landslides Induced by Rainfall: A Case of Unsaturated Shallow Deposits

Unsaturated shallow soil deposits may be affected by either superficial soil erosion or shallow landslides in adjacent or overlapping source areas and in different seasons when a different soil suction exists.The triggering analysis of both these processes is a relevant issue for the hazard analysis while the literature mostly provides specific approaches for erosion or for landslides.The paper proposes a largearea analysis for a case study of Southern Italy,consisting of unsaturated shallow deposits of loose pyroclastic(air-fall) volcanic soils that have been repeatedly affected by erosion and landslides in special seasons.For a past catastrophic event, the simulated source areas of shallow landslides are smaller than those observed in the field while the simulated eroded areas with thickness greater than 5cm are comparable with the in-situ evidences, if the analysis takes into account high rainfall intensity and a spatially variable soil cover use.More in general, the results of the paper are consistent with the previous literature and also provide a methodological contribution about the application of distinct tools over large area.The added value is that the paper shows how the combination of distinct large-area analyses may help with understanding the dominant slope instability mechanisms.Only once this goal is fully achieved, can specific physically-based analyses be confidently performed at detailed scales and for smaller specific areas.

Transport simulation of sorptive contaminants considering sediment-associated processes

Sediment-associated processes, such as sediment erosion, deposition, and pore water diffusion/advection affect sorptive contaminant transport. By considering these processes, we developed an equation to simulate contaminant transport. Erosion and deposition processes are considered as erosion and deposition fluxes of sediment, and adsorption-desorption processes of contaminants by sediment are simulated using the Langmuir Equation. Pore water diffusion is calculated based on the contaminant concentration gradient across the sediment-water interface. Pore water advection is estimated using pore water contained in the sediments of erosion flux. The equation is validated to simulate total phosphorus concentrations in Guanhe estuary in the northern Jiangsu, China. The simulated total phosphorus concentrations show better agreement with field observations compared to estimations that do consider sediment-associated processes.

Effects of Protective Structures in Morpho-Sedimentological Changes： A Case Study of Rufisque＇s Coast, Petite C6te, Senegal

Protective structures, built in the 1980＇s in order to reduce or stop coastal erosion in Rufisque, involved a modification of the coastal morpho-sedimentary landscape and have intensified the coastal dynamics. The diachronic study of beach profiles, before and after the seawalls construction showed that these protective structures accentuated the coastal erosion, with more important sedimentary deficits at the ends of the structures. Today, the Rufisque coast is characterized by a set of sedimentary cells whose morphological evolution and annual sedimentary dynamics are controlled by seasonal forcing： sedimentary deposits in dry season and erosion in wet season. However, this alternation of deposits and erosion phase shows spatiotemporal disparities. These disparities are very marked between a northwestern area characterized by concave profiles and a southeastern area （the bay of Rufisque） characterized by convex profiles and a much more important sedimentary deficit. The results also showed that these methods of shoreline protection are not durable measurements （degradation of the structures） and have exacerbated the vulnerability to coastal erosion as well as those of the coastal populations.

黑土坡耕地有机碳变化及固碳潜力分析

东北黑土区自开垦以来有机质含量逐渐降低,有机碳库长期处于亏缺状态,理论上也具有较大的固碳潜力。以典型黑土区长期传统作业的坡耕地(30—60 a)为研究对象,通过测定不同坡位(坡上侵蚀区和坡下沉积区)、不同土层(表土和底土)有机碳分布特征,估算不同开垦年限黑土固碳潜力及其恢复至固碳潜力所需的时间。结果表明:(1)总有机碳、有机碳密度以及碳饱和水平均表现为沉积区显著大于侵蚀区,表土显著大于底土,且均在开垦30a坡耕地达到最大值;(2)固碳潜力表现为侵蚀区(1.24—2.89 kg/m^2)显著大于沉积区(0.79—1.04 kg/m^2),底土(0.83—3.59 kg/m^2)显著大于表土(0.6—2.53 kg/m^2),随着开垦年限的增加表现为开垦30 a显著小于开垦40 a、60 a;(3)黑土坡耕地(30—60 a)侵蚀区和沉积区土壤(0—50 cm)达到固碳潜力分别需要20—181 a和13—66 a。黑土坡耕地固碳潜力的时空变异性在农业经营以及修复管理过程中需引起重视,以实现黑土资源的可持续利用。