黄土丘陵区典型植被土壤物理性质差异及其对导水特性影响

选取黄土丘陵区12种典型植被样地,通过测定各样地不同土层植物残体生物量、土壤容重、毛管孔隙度、非毛管孔隙度及饱和导水率,研究各指标随土层深度和植被类型的变化规律及其对土壤饱和导水率的影响。结果表明:(1)除容重随土层深度增加外,植物残体、毛管孔隙度、非毛管孔隙度和饱和导水率均随土层深度减少,其中植物残体大多集中于表层土壤(0—10 cm),占总残体生物量的51.4%～85.7%。(2)不同植被类型其植物残体及土壤物理性质存在显著差异,乔木林地植物残体、农耕地土壤容重、灌木林地非毛管孔隙度及饱和导水率均最大,而毛管孔隙度与不同土地利用类型间无显著差异。(3)饱和导水率随植物残体生物量密度(0—10 cm)和土壤容重呈幂函数减小,随毛管孔隙度和非毛管孔隙度呈幂函数增大;土壤容重(BD)和非毛管孔隙度(NCP)是影响土壤饱和导水率(K_s)的主要因素,且土壤饱和导水率可表示为两者的综合非线性方程(K_s=0.6BD~(-4.717)NCP~(0.203),P0.01,R~2=0.63,NSE=0.50)。此外,沙棘灌木林地平均饱和导水率最大,有利于降雨过程中土壤水分入渗,具有较强的水土保持功能。本研究结果可为黄土高原植被恢复生态水文效益评价提供理论依据。     

Spatial heterogeneity of loess contour tilled microtopographic slope in rainfall erosion

Loess tilled surface is the geographical unit for the quantitative study of the soil erosion process. Contour tillage has been proved to be the most effictive measure for soil and water conservation in the Chinese Loess Plateau. Studies on the spatial heterogeneity of loess tilled surfaces will contribute to the understanding of the mechanism of erosion evolution. For this, a laboratory experiment was performed on contour tilled sloping surfaces where the hydrological-erosive processes were simulated. At different erosion stages, point cloud measurements were made using a terrestrial laser scanning system (TLS); then the heterogeneity depending on detrending and directionality were analysed by both the semivariogram method and the rescaled range analysis method. Results showed that: (1) the fractal dimensions D_S and D_R were equivalent when determined from either the semivariogram method or the rescaled range analysis method, although the semivariogram method appears to be more reliable in identifying the specific stage of the erosion evolution process; (2) the contour tilled microtopographies had an anisotropy behavior depending on direction; (3) the fractal dimension (either D_S or D_R) in different erosion stages was less than 1.5, which indicates that the microtopography of the sloping surface exhibits characteristics of persistent fractional Brownian motion and positive spatial autocorrelation. Irrespective of tillage measure and slope percentage, the sloping surface can be regarded as having random roughness. The results reveals a quantitative relationship between microtopography and sloping erosion. Also, it may provide guidance for further studies regarding the spatial variability and heterogeneity of various tilled slopes on the microtopographic scale.     

Spatial patterns of soil respiration in a spruce-fir valley forest,Northeast China

Purpose

The quantification of spatial patterns of soil respiration (R_S) is an important step in modelling soil carbon budgets. This study aims to characterise the spatial variability of R_S using traditional and geostatistical analyses in a mature temperate forest during the growing season, with emphases on temporal variation in the spatial patterns and soil properties and stand structural parameters driving the variability of R_S.

Materials and methods

R_S, soil temperature and soil water content were sampled at 780 positions in a 9.12-ha permanent plot in a spruce-fir valley forest in the spring, summer and autumn of 2015. Furthermore, edaphic properties were measured adjacent to each sampling point, and all trees with DBH (diameter at breast height of tree) greater than 1 cm were mapped in the plot.

Results and discussion

R_S showed strong spatial variation across the three measurement campaigns, with the autocorrelation length ranging from 10 to 17 m. The spatial variability of R_S in the spring period was relatively higher than that of summer and autumn. Soil water content was confirmed to be the primary factor driving spatial R_S, followed by soil temperature, soil organic carbon, total nitrogen, C:N, pH and the maximum DBH within radius of 4 m of sampling points. The multiple regression model fitted by soil properties and stand structural parameters could account for 11–32% of the spatial variation of R_S. However, the involved factors in the regression model varied with season, and soil temperature was more important in controlling the spatial variability of R_S in the spring period.

Conclusions

The study highlights that soil water content and soil temperature play the most important role in determining the spatial patterns of R_S across the growing season.

     

晋西北黄土丘陵区土壤饱和导水率的空间分布特征及影响因素

土壤饱和导水率（K_s）是反映土壤入渗性能与土壤持水能力的重要参数，为探究流域尺度下土壤K_s的空间分布特征及影响因素，更好地掌握土壤水文过程与调节机理，选取晋西北黄土丘陵区朱家川流域横向梯度（上游、中游、下游）不同土地利用方式下的土壤（70个样点）为研究对象，采用定水头法测定土壤K_s，并获取样点地形因子和其他土壤理化性质，通过建立土壤K_s偏最小二乘回归模型（PLSR），分析影响土壤K_s空间分布格局的主要因素。结果表明：（1）除土壤容重和砂粒含量为弱变异外，区域土壤理化性质其余因子均为中等变异；土壤K_s在横向梯度下表现为上游 > 中游 > 下游；（2）不同土地利用方式下土壤K_s差异显著（P<0.05），由高到低顺序为林地 > 农地 > 草地；（3）林地（VIP=1.997）与草地（VIP=1.710）利用方式、土壤容重（VIP=1.548）、土壤有机质（VIP=1.323）、大团聚体（VIP=1.266）、粉粒含量（VIP=1.062）和黏粒含量（VIP=1.049）是土壤K_s变化的主要因素，林地利用方式影响程度最大。土地利用、土壤性质、地形因子均是影响黄土丘陵区土壤K_s空间分布的主要因素，是用来模拟预测土壤K_s空间分布的重要因子。     

Prediction of Spatial Variability of Phosphorous Over the St-Esprit Watershed

Spatial data analysis tools for predicting the variability of non-point source pollutants minimize the time, effort and cost involved in extensive and exhaustive real field data measurements. In this study, exploratory data analysis, fitting of semivariogram models, and kriging techniques of geostatistics were used to develop the spatial variability map of soil phosphorous saturation (P _sat) percentage over the St-Espirit watershed (2610 ha), located in Quebec, Canada. The P _sat measured values for the 281 geo referenced land parcel units (LPU) within the watershed were interpreted and analyzed using the ArcGIS^® tool. The geostatistical extension module of ArcGIS^® was used for exploratory data analysis, semivariogram model fitting, and development of a P _sat prediction map using the ordinary kriging technique. Using these geostatistical procedures and adjustment of lag sizes and lag intervals representing the data sets, it was estimated that the spherical semivariogram model fitted well to represent the P _sat variability with residual sum square (RSS) of 0.0003 and coefficient of determination (R ²) of 0.98. Further, the developed model was used to predict the P _sat variability over the St. Esprit watershed using the 1605 geo-referenced LPU locations. The generated spatial variability map was geo-spatially processed with the natural drainage network and land use feature classes of the watershed to ascertain the phosphorous loading and locate vulnerable LPUs for phosphorous management. It was observed that the P _sat levels were higher at the up stream locations and near the drainage channels than the locations close to watershed outlet. Also, the land pockets with more than 60% agricultural land use resulted in supra-optimal P _sat values (10% > P _sat < 20%), out of which 8.5 to 16.3 ha agricultural land of the St. Esprit watershed exhibited critical agro-environmental threshold P _sat values (P _sat > 20%). It was also revealed that, around 23.5% of the watersheds cropped area has reached these threshold levels which necessitate judicious P input management.     

Spatial and temporal variability of some soil physical properties following tillage of a Nigerian Paleustult

The objective of this study was to evaluate quantitatively the magnitude of the spatial and temporal variation for 7 soil physical properties on a conventionally-tilled Nigerian Paleustult. A 0.4-ha plot was disc-ploughed, disc-harrowed twice, subjected to tractor-wheel traffic at regular space intervals and then seeded to maize (Zea mays, L.). There were significant differences in the physical properties owing to tillage position (spatial variability) and date of sampling (temporal variability), more so in the 0–10-cm layer than in the 10–20-cm layer. In the surface layer, bulk density (Db) and penetrometer resistance (PR) were significantly higher (P ⩽ 0.01) along the tyre marks (maximum Db = 1.76 Mg m⁻³) than in the uncompacted crop row (maximum Db = 1.35 Mg m⁻³) and interrow positions (maximum Db = 1.46 Mg m⁻³). Saturated hydraulic conductivity (K_sat), total porosity (TP) and macroporosity (M) were significantly lower along the tyre mark than in the crop row and interrow positions. K_sat ranged from 0.6 to 42.8 cm h⁻¹, TP, from 0.34 to 0.50 cm³ cm⁻³ and M from 0.06 to 0.25 cm³ cm⁻³ along the tyre mark and crop row positions, respectively. Significant temporal changes were noticed only in K_sat, soil moisture content (MC) and PR. K_sat increased steadily with time along the tyre mark, but showed an irregular trend in the other two positions. PR did not change with time along the tyre marks but it increased significantly with time along the other two positions. MC changed according to the periodicity of rainfall. Only TP varied, owing to tillage position × date interaction. The 10–20-cm layer was spatially less variable but temporally more viarable than the surface layer. Only K_sat and PR showed significant changes owing to the tillage positions, but Db, K_sat, PR and moisture retained at 10 kPa suction (τv10) showed significant temporal changes. Only τv110 varied owing to position × date interaction in this layer.     

Regional pattern of the mobile water fraction in soils as determined by disc infiltrometer experiments

In order to characterize the partitioning of solutes into the mobile and the immobile fraction of pore water at the soil surface, field measurements of infiltration in unsaturated loamy sands were carried out using a disc infiltrometer in a region of about 10 km² at the Lüneburger Heide, Germany. The aims of these measurements were to obtain the mobile water fraction and the hydraulic properties of the soil, to relate them to other measured soil properties like the soil texture, and to assess their spatial variability in the region. From the infiltration results we obtained the hydraulic conductivity K₀ and the sorptivity S₀ using a three-dimensional infiltration analysis and the two-term infiltration equation, respectively. The mobile water fraction θ_m/θ of the soil was estimated from the infiltration results of a second disc infiltrometer filled with bromide solution. The estimated values of K₀ and S₀ were in good agreement with those reported in the literature as typical for loamy sands. The average value of θ_m/θ was calculated to be 71 % under the experimental conditions. Neither the horizontal spatial distribution of water and bromide concentration beneath the disc infiltrometer nor the change of the infiltrometer during the experiment had a notable influence on the experimental results. The spatial variability of the data was analyzed by means of variograms. All variograms were spatially structured and indicated a high small scale variation of the variables. In conclusion, the technique applied is suitable for the estimation of the hydraulic and solute transport properties of soils, especially at larger scales.     

渝东北紫色土饱和导水率传递函数研究

为研究渝东北紫色土理化性质在垂直空间上的分布情况以及对饱和导水率的影响,进而建立饱和导水率与各理化性质间的关系函数,推求饱和导水率的传递函数,选择渝东北开州区、云阳县等7个区县内45个紫色土典型田块为研究区域,运用Excel 2013和Matlab 2015b软件统计分析后,利用多元非线性回归法推求并验证了渝东北紫色土饱和导水率传递函数模型和模型参数。研究表明:①研究区土壤饱和导水率变化范围在0.16～195.68 cm/d,变化范围广,空间变异系数大,变异性较强;同一采样点深度越大,饱和导水率越小;②土壤饱和导水率与有机质含量有显著的指数函数关系,与饱和含水量有较强的二次函数关系,与土壤容重和土壤颗粒的相关性不大;③本次试验建立的土壤饱和导水率传递函数模型及模型系数检验合格,预测值与实际测算值误差较小,精度良好,可用于渝东北紫色土饱和导水率的预测工作。     

Variability in Soil Hydraulic Conductivity and Soil Hydrological Response Under Different Land Covers in the Mountainous Area of the Heihe River Watershed,Northwest China

Understanding the variability in soil hydraulic conductivity in the mountainous headwaters is critical to the modeling of mountainous runoff and the water resources management of river basins, especially in the arid and semiarid areas. In this study, a total of 32 soil profiles with five layers within 0–70 cm were sampled under different land cover types: forest, meadow, high coverage grassland (HCG), medium coverage grassland (MCG), and barren land in the upper stream of the Heihe river watershed, Northwest China. Saturated hydraulic conductivity (K _S) was measured for each sample. The vertical variation of K _S and soil hydrological response under different land covers were analyzed. Results show that K _S value in layer 5 was significantly lower than the values of above four layers. K _S decreased in the order of forest, meadow, HCG, MCG, and barren land, corresponding to the degree of vegetation degradation. The K _S decreased with depth under forest, HCG, and barren land, but increased first and then decreased under meadow and MCG. The dominant stormflow paths for different land covers were different: forest was dominated by deep percolation, HCG was dominated by subsurface flow (SSF), meadow was prevailed by Hortonian overland flow and had no SSF, while MCG and barren land were also dominated by Hortonian overland flow, but still formed SSF. This result provides important information for improving the accuracy of mountainous hydrological modeling and, in turn, leading to sustainable management of water resources in the study watershed. Copyright © 2016 John Wiley & Sons, Ltd.     

Spatial variability of soil properties and wheat yields in an irrigated field

Abstract

An irrigated farmer's field at Hafizabad village in Dera Ismail Khan District of Northwest Frontier Province of Pakistan was sampled at a regular grid spacing of 50x15 m from surface (15 cm) to study the spatial variability of soil properties and wheat yield. The farm measured 250x75 m. Soil samples collected were analyzed for soil pH, lime content, organic matter, mineral nitrogen (N), ammonium bicarbonate (AB)‐DTPA‐extractable phosphorus (P) and potassium (K), and soil texture. A uniformly trial on wheat with a uniform rate of 120 kg N ha^‐1, 90 kg P₂O₅ ha^‐1, and 60 kg K₂O ha^‐1 was laid out. The results showed that the soil P had the highest coefficient of variation (CV 46%) followed by organic matter (36.20%) and clay content (33.81%). Grain yield had also a considerable variation in the field (CV=31.84%). Geostatistical technique of semivariogram analysis showed that mineral N, AB‐DTPA‐extractable K, sand, silt, and clay content had the strong spatial structure. Maps of soil fertility and crop productivity of the farm was prepared using modern geostatistical technique of kriging. The farm was divided into different management zones based on these maps for fertility management.     

Assessment of soil erosion at large watershed scale using RUSLE and GIS: a case study in the Loess Plateau of China

Soil erosion is a serious problem in the Loess Plateau of China, and assessment of soil erosion at large watershed scale is urgently need. This study used RUSLE and GIS to assess soil loss in the Yanhe watershed. All factors used in the RUSLE were calculated for the watershed using local data. RUSLE‐factor maps were made. The mean values of the R‐factor, K‐factor, LS‐factor, C‐factor and P‐factor were 970 209 MJ km⁻² h⁻¹ a⁻¹, 0·0195 Mg h MJ⁻¹ mm⁻¹, 10·27, 0·33359 and 0·2135 respectively. The mean value of the annual average soil loss was found to be 14 458 Mg km⁻² per year, and the soil loss rate in most areas was between 5000 and 20 000 Mg km⁻² per year. There is more erosion in the centre and southeast than in the northwest of Yanhe watershed. Because of the limitations of the RUSLE and spatial heterogeneity, more work should be done on the RUSLE‐factor accuracy, scale effects, etc. Furthermore, it is necessary to apply some physical models in the future, to identify the transport and deposition processes of sediment at a large scale. Copyright © 2005 John Wiley & Sons, Ltd.     

Soil and nutrient losses due to root crops harvesting: a case study from southwestern Iran

Although root crops are widely cultivated in Iran, little is known about soil loss due to crop harvesting (SLCH). We assessed the annual exported soil, soil organic matter (SOM) and nutrients from 47 farms under root crops in southwestern Iran. Soil losses for garlic, potato, sugar beet, radish and beetroot were estimated as 6.27, 2.52, 2.26, 4.10 and 6.95, Mg ha^?1, respectively, which on average was of the order of soil losses by water erosion in the watershed basins of Iran. Total N, P₂O₅ and K₂O losses were estimated as 36.61, 1.10 and 31.50 kg ha^?1 and their costs as 18.24, 0.74 and 19.93 USAlthough root crops are widely cultivated in Iran, little is known about soil loss due to crop harvesting (SLCH). We assessed the annual exported soil, soil organic matter (SOM) and nutrients from 47 farms under root crops in southwestern Iran. Soil losses for garlic, potato, sugar beet, radish and beetroot were estimated as 6.27, 2.52, 2.26, 4.10 and 6.95, Mg ha^?1, respectively, which on average was of the order of soil losses by water erosion in the watershed basins of Iran. Total N, P₂O₅ and K₂O losses were estimated as 36.61, 1.10 and 31.50 kg ha^?1 and their costs as 18.24, 0.74 and 19.93 US$ ha^?1, respectively. For the whole country, total soil, N, P₂O₅, K₂O and SOM losses for garlic, potato and sugar beet were estimated as 731.7 × 10³, 836, 27, 476 and 14.5 × 10³ Mg, respectively (radish and beetroot were excluded due to no reliable data on their planted areas). Correlation analysis showed no significant relationship between soil properties and SLCH (except soil moisture content for radish and clay content for beetroot). The findings indicated that the exported soil, SOM and nutrients were at such levels that SLCH should be considered in soil erosion studies.     

基于地形因子的土壤侵蚀评价指数修正 ——以陕北安塞集水区为例

地形是影响土壤流失的重要因素,小流域尺度上的土壤侵蚀评价指数(SL_(sw))对于地形的研究过于简单,因此本研究对SL_(sw)中的地形因子(G)进行修正,进而得出G因子修正后的土壤侵蚀评价指数(SL_(sw)_G)。以黄土丘陵沟壑区——安塞集水区为研究区,基于GIS技术,利用2006—2012年安塞集水区的数字高程模型(DEM)数据、水文观测站的日降雨量数据、土壤采样数据和土地利用数据,计算研究区2006—2012年逐年的SL_(sw),利用安塞集水区实测的输沙量,验证修正的SL_(sw)_G指数的有效性,并分析安塞集水区土壤侵蚀强度的时空变化特征。结果表明,修正前后土壤侵蚀情况分布基本相同,均呈现东南部地区SL_(sw)指数高,而西北部地区相对较低。在安塞集水区东南部,由于人为因素的影响,土壤保持措施相对较弱,同时土壤中黏粒和粉粒质量较轻,黏粒和粉粒湿时有明显的黏结性,降雨过程中容易被水冲刷;根据土壤采样点的采样数据表明,东南部地区土壤中黏粒和粉粒的含量较高,较容易造成土壤侵蚀。修正前后指数通过T检验得出,SL_(sw)和SL_(sw)_G具有方差齐次性,P=0.0370.05;通过与实测输沙量的比较,修正后SL_(sw)_G与实测输沙量的相关系数大于修正前SL_(sw)与实测输沙量的相关系数(0.390.36),修正后的相关性较修正前的相关性有所增加,说明修正是有效的,修正后的SL_(sw)指数能够更好地评价研究区域土壤侵蚀状况。     

Exploring the variation in soil saturated hydraulic conductivity under a tropical rainforest using the wavelet transform

Saturated hydraulic conductivity (K_s) of the soil is a key variable in the water cycle. For the humid tropics, information about spatial scales of K_s and their relation to soil types deduced from soil map units is of interest, as soil maps are often the only available data source for modelling. We examined the influence of soil map units on the mean and variation in K_s along a transect in a tropical rainforest using undisturbed soil cores at 0–6 and 6–12 cm depth. The K_s means were estimated with a linear mixed model fitted by residual maximum likelihood (REML), and the spatial variation in K_s was investigated with the maximum overlap discrete wavelet packet transform (MODWPT). The mean values of K_s did not differ between soil map units. The best wavelet packet basis for K_s at 0–6 cm showed stationarity at high frequencies, suggesting uniform small‐scale influences such as bioturbation. There were substantial contributions to wavelet packet variance over the range of spatial frequencies and a pronounced low frequency peak corresponding approximately to the scale of soil map units. However, in the relevant frequency intervals no significant changes in wavelet packet variance were detected. We conclude that near‐surface K_s is not dominated by static, soil‐inherent properties for the examined range of soils. Several indicators from the wavelet packet analysis hint at the more dominant dynamic influence of biotic processes, which should be kept in mind when modelling soil hydraulic properties on the basis of soil maps.     

Spatial variability of water retention parameters and saturated hydraulic conductivity in a calcareous Inceptisols (Khuzestan province of Iran) under sugarcane cropping

The objective of this study was to quantify inherent spatial variability and spatial cross-correlation of the van Genuchten retention parameters and saturated hydraulic conductivity (K_s) of surface and subsurface layers in a calcareous Inceptisols (Khuzestan province, Iran) under sugarcane cropping. Measurements were performed on 100-cm³ undisturbed soil cores collected at 94 locations along a 30-m-long transect with horizontal sampling distance intervals of 0.3 and 1 m at soil depths of 0–40 and 40–80 cm, respectively. Spatial variability was investigated using conventional statistics and geostatistical techniques. Coefficient of variation (CV) varied from 8.2% (for shape parameter, n at 40–80 cm depth) to 256.7% (for K_s at 0–40 cm depth). The n parameter and saturated water content, θ_s, showed a small-scale spatial heterogeneity with a maximum CV of 11.3% for the first depth and 9.2% for the second depth. Most of the hydraulic parameters at both depths showed a spatial structure and convex experimental semivariograms with dominant spherical models with the influence range of 3.2–41 m. In most cases, the extent of spatial correlation scales of cross-semivariograms for pairs of cross-correlated hydraulic variables was found to be different with reference to those relating to the direct semivariograms of correlated variables.     

青海省东部不同土地利用方式下土壤饱和导水率分布及其影响因素

研究高寒地区土壤饱和导水率分布特征及其影响因素可为评估脆弱生态系统水源涵养能力和构建区域水文模型提供参数.通过测定青海省东部南北样线24个样点(0—30 cm)土壤基本理化性质和饱和导水率(Ks),分析了不同土地利用方式下Ks分布特征及其影响因素.结果表明:Ks均值表现为林地(1.89 cm/h)>草地(1.62 cm...     

Spatial scaling of soil salinity indices along a temporal coastal reclamation area transect in China using wavelet analysis

High spatial variability of soil salinity in coastal reclamation regions makes it difficult to obtain accurate scale-dependent information. The objectives of this study were to describe the spatial patterns of saline-sodic soil properties (using soil pH, electrical conductivity (EC_1:5) and sodium ion content (SIC) as indicators) and to gain knowledge of the scaling relationships between those variables. The soil pH, EC_1:5 and SIC data were measured at intervals of 285 m along a 13,965-m temporal transect in a coastal region of China. The spatial variability of soil pH was weak but it was strong for soil EC_1:5 and SIC at the measurement scale. There was a significant positive correlation between soil EC_1:5 and SIC, while correlations between soil pH and either EC_1:5 or SIC were weak and negative. For each saline-sodic soil parameter, the variability changed with the decomposition scales. The high-variance area at the larger scales (≥570 m) occupied less than 10% of the total area in the local wavelet spectrum, which meant that the spatial variations of the salinity indicators were insignificant at these scales. For local wavelet coherency, at a scale of 1500–2800 m and a sampling distance of 0–4500 m, the covariance was statistically significant between any two of the saline-sodic soil parameters.     

Spatial Distribution of Surface Soil Acidity,Electrical Conductivity,Soil Organic Carbon Content and Exchangeable Potassium,Calcium and Magnesium in Some Cropped Acid Soils of India

Land degradation is a global problem. Best management of degraded land can be done by evaluating the spatial variability of soil properties including chemical properties of degraded land and mapping such variations. Since, a significant portion of arable land in India is chemically degraded due to soil acidity; the present study was conducted to study the spatial variability of soil acidity (pH), electrical conductivity (EC), soil organic carbon (OC) content, exchangeable potassium (K⁺), calcium (Ca²⁺) and magnesium (Mg²⁺) contents in some cropped acid soils of India. A total of four hundred (one hundred from each series) representative surface (0–0.15 m depth) soil samples were collected from arable soils representing four soil series namely Hariharapur, Debatoli, Rajpora and Neeleswaram situated in Orissa, Jharkhand, Himachal Pradesh and Kerala states of India, respectively, and were analyzed. Soil acidity (pH between 3.90 and 6.45) showed a low variability, in contrast to other soil properties, which showed moderate variability. The coefficients of variation varied from 32.4 to 74.3, 31.2 to 50.9, 45.6 to 100, 71.9 to 93.0 and 59.0 to 79.8% for EC (mean between 0.05 and 0.09 dS m⁻¹), OC (mean between 0.29 to 1.86%), exchangeable K⁺ (mean between 39.1 and 77.7 mg kg⁻¹), Ca²⁺ (mean between 148 and 293 mg kg⁻¹) and Mg²⁺ (mean between 111 and 191 mg kg⁻¹), respectively. Soil pH and OC content were positively and significantly correlated with exchangeable K⁺, Ca²⁺ and Mg²⁺ content. Geostatistical analysis revealed that the best fit models were gaussian, exponential and spherical for different soil properties with moderate to strong spatial dependency. Copyright © 2014 John Wiley & Sons, Ltd.     

石灰岩与白云岩坡地土壤饱和导水率对比研究

[目的]对比研究不同下垫面特征和土地利用方式对两类坡地表层土壤性质及其土壤饱和导水率(Ks)的影响。[方法]以喀斯特地区不同岩性下垫面的石灰岩和白云岩两类坡地表层土壤为研究对象,采用Guleph稳定入渗仪和土壤分析的方法。[结果](1)石灰岩和白云岩表层土壤在受到放牧作用影响后,土壤均呈现显著退化趋势,其容重、黏粒含量增大,孔隙度、有机质含量降低。(2)石灰岩和白云岩两类坡地表层土壤在未受到人为干扰的自然植被条件下,由于表层岩溶带的发育,Ks都很高,平均值分别为328.6和257.2mm/h。其中,石灰岩坡地相比白云岩坡地,Ks具有更高的空间变异性,二者Ks变异系数变化范围分别为90.71%~95.62%和59.60%~67.32%。(3)受到放牧作用影响后,石灰岩和白云岩坡地表层土壤Ks相比自然植被状态下呈显著降低趋势,Ks分别降低52.2%和86.7%,白云岩坡地Ks降低程度大,高于石灰岩坡地。