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1.
A regression model of wet deposition on rainfall amount for non-seasalt sulfate (nss-SO4 2?) and nitrate (NO3 ?) was applied to a data set obtained through a nationwide survey from April 1989 to March 1993. Wet-only samples on a biweekly basis were collected at 29 sites over Japan. Reparameterized bivariate lognormal distribution was employed to describe the joint distribution of concentration (C) and rainfall amount (R) for each site. Ranges of geometric mean (μD) of biweekly deposition (D = C. R) for each site were 0.54–2.90 meq m?2 for nss-SU4 2?, and 0.21–1.36 meq m?22 for NO3 ?; that of biweekly rainfall amount (μR) was 24.1–78.0 mm. Urban or industrialized areas had high values of μD for these ions. Ranges of estimates of the slope of the regression equation of log(D/μD) on log(R/μR), were 0.45–0.99 for nss-SO4 2?, and 0.35–0.86 for NO3 ?; thus estimates of the slope for nss-SO4 2? tend to be larger than those for NO3 ?. The present analysis, consequently, statistically clarified some differences between the two ions in deposition processes which is understood in the light of current knowledge of atmospheric chemistry.  相似文献   

2.
Abstract

Denitrification products nitrous oxide ((N2O) and nitrogen (N2)) were measured in three flooded soils (paddy soil from Vietnam, PV; mangrove soil from Vietnam, MV; paddy soil from Japan, PJ) with different nitrate (NO3–) concentrations. Closed incubation experiments were conducted in 100-mL bottles for 7 d at 25°C. Each bottle contained 2 g of air-dried soil and 25 mL solution with NO3– (concentration 0, 5 or 10 mg N L?1) with or without acetylene (C2H2). The N2O + N2 emissions were estimated by the C2H2 inhibition method. Results showed that N2O + N2 emissions for 7 d were positively correlated with those of NO3– removal from solution with C2H2 (R2 = 0.9872), indicating that most removed NO3– was transformed to N2O and N2 by denitrification. In PJ soil, N2O and N2 emissions were increased significantly (P < 0.05) by the addition of greater NO3– concentrations. However, N2O and N2 emissions from PV and MV soils were increased by the addition of 0 to 5 mg N L?1, but not by 5 to 10 mg N L?1. At 10 mg N L?1, N2 emissions for 7 d were greater in PJ soil (pH 7.0) than in PV (pH 5.8) or MV (pH 4.3) soils, while N2O emissions were higher in PV and MV soils than in PJ soil. In MV soil, N2O was the main product throughout the experiment. In conclusion, NO3– concentration and soil pH affected N2O and N2 emissions from three flooded soils.  相似文献   

3.
Nitrate (NO-3) and nitrite (NO2-) leaching threatens groundwater quality.Soil C:N ratio,i.e.,the ratio of soil organic carbon to total nitrogen,affects mineralization,nitrification,and denitrification;however,its mechanism for driving soil NO-3 and NO-2 accumulation and leaching remains unclear.Here,a field investigation in a fluvo-aquic soil and a soil column experiment were performed to explore the relation...  相似文献   

4.
Abstract

A chelating resin procedure was developed to predict the plant uptake of Cd by municipal sewage sludges applied to land. Seventeen anaerobically digested sludges were sampled to give a range of total Cd content of 0.07 to 2.02 mmol/kg. Sludge suspensions [20 g in 100 mL 0.05 M Ca(NO3)2] were equilibrated with 1 g Chelex 100 resin placed in dialysis tubing and shaken at 200 rpm for 16 h. Resin‐extractable Cd was compared with sludge solution Cd (CdT and Cd2+) in equilibrium with 0.05 M Ca(NO3)2, and 0.05 M Ca(NO3)2 containing 50 (μM Na‐EDTA (ethylenediaminetetraacetate). Resin extractable Cd was correlated with Cd uptake by sudax, a sorghum/sudangrass hybrid (Sorghum bicolar), grown in Spinks loamy sand (Typic Udipsamment) amended with each of the sludges to give a constant Cd concentration of 22 μmol/kg soil.

Resin extractable Cd ranged from < 0.1 to 48 μmol/kg. Resin extracted between zero and 5.3% of total sludge Cd. Resin extractable Cd was highly correlated with CdT and Cd2+ in 0.05 M Ca(NO3)2 (R2 = 0.97 and 0.98, respectively), and with 0.05 M Ca(NO3)2 containing 50 μM NaEDTA (R2 = 0.97 and 0.98, respectively). There was a lower correlation with total sludge Cd and soil solution Cd (R2 = 0.53 and 0.63, respectively). Cadmium concentration in sudax was highly correlated with resin extractable sludge Cd (R2 = 0.92). When the two sludges with highest total sludge Cd were dropped, the correlation dropped (R2 = 0.57), but resin extractable Cd predicted Cd uptake as effectively as CdT and Cd2+ in Ca(NO3)2 or Ca(NO3)2/EDTA. Resin extraction appears to be a promising method of assessing the potential bioavailability of sludge Cd.  相似文献   

5.
Improving manure management to benefit both agricultural production and the environment requires a thorough understanding of the long‐term effects of applied manure on soil properties. This paper examines the effect of 25 annual solid cattle manure applications on soil organic carbon (OC), total N (TN), and KCl‐extractable NO3‐N and NH4‐N under both non‐irrigated and irrigated conditions. After 25 annual manure applications, OC and TN contents increased significantly with the rate of manure application at the top two sampling depths (0–15 cm and 15–30 cm), and the increases were not affected by the irrigation treatment. The NO3 content increased at all sampling depths with greater increases observed under non‐irrigated conditions, while NH4 content was not affected by manure application rates or the irrigation treatment. The changes in OC and TN at the surface (0–15 cm) and 15–30 cm depth were dependent on the cumulative weight of manure added over the years. The relationships between cumulative manure OC added and soil OC content and between cumulative manure TN added and soil TN content were linear and not affected by the irrigation treatment. For every ton of manure OC added, soil OC increased by 0.181 g kg–1 in the topsoil (0–15 cm). Similarly, for every ton of manure TN added, surface soil TN increased by 0.192 g kg–1. The linear relationship between manure C added and soil C content suggests that the soil had a high capacity for short‐term C sequestration. However, the total amount of NO3‐N in the soil profile (0–150 cm) was affected by both the manure application rates and the irrigation treatment. A large amount of NO3 accumulated in the soil, especially under non‐irrigated conditions. The extremely high level of NO3 in the soil increases the potential risk of surface and groundwater pollution and losses to atmosphere as N2O.  相似文献   

6.
Liming or vermicomposting eliminates pathogens from wastewater sludge, but might affect CO2 and N2O emissions when added to soil. Soil incubated at 40%, 60%, 80% and 100% of its water holding capacity (WHC) was amended with limed or unlimed wastewater sludge, vermicompost or inorganic fertilizer, while emissions of N2O and CO2 and mineral N concentrations were monitored in aerobic incubation experiment for 7 days. Application of unlimed wastewater sludge significantly increased the emission of CO2 compared to the unamended soil, but not the other treatments except when unlimed wastewater sludge was added to soil incubated at 60% WHC. The emission of CO2, was generally largest in soil incubated at 60% WHC and lowest in soil incubated at 100% WHC. The emission of N2O after 1 day was significantly larger in soil amended with unlimed wastewater sludge compared to the other treatments, but not when soil was incubated at 100% WHC. The emission of N2O increased with increased soil water content. The concentration of NH4+ was largest in soil amended with limed or unlimed wastewater sludge and lowest in the unamended soil and soil water content had no clear effect on it. In soil incubated at 40%, 60% and 80% WHC, the largest amount of NO3− was found in soil amended with inorganic fertilizer and vermicompost and the lowest in the soil amended with unlimed wastewater sludge. The concentration of NO3− in soil decreased when the soil water content increased in all treatments, except in the soil amended with unlimed wastewater sludge. It was found that water content affected the emission of CO2 of N2O and the concentration of NO3−, but not the amount of NH4+ and NO2− in soil. Application of unlimed wastewater sludge increased the emissions of CO2 and N2O and the concentrations of NH4+, but decreased the amount of NO3− in soil.  相似文献   

7.
The mineralization of nitrogen from soil organic matter is important when one tries to optimize nitrogen fertilization and assess risks of N losses to the environment, but its measurement is laborious and expensive. We have explored the possibilities for monitoring N mineralization directly using time domain reflectometry (TDR). Net N and S mineralization were monitored over a 101‐day period in two layers (0–30 and 30–60 cm) of a loamy sand soil during aerobic incubation in a laboratory experiment. At the same time electrical conductivity of the bulk soil, σa, was measured by TDR. A series of calibration measurements with different amounts of KNO3 at different soil moisture contents was made with the topsoil to calculate the electrical conductivity, σw, of the soil solution from σa and θ. The actual σw was determined from the conductivity of 1:2 soil:water extracts (σ1:2) with a mass balance approach using measured NO3– concentrations, after correction for ions present prior to the addition of KNO3. The average N mineralization rate in the topsoil was small (0.12 mg N kg?1 day?1), and, as expected, very small in the subsoil (0.023 mg N kg?1 day?1). In the top layer NO3– concentrations calculated from σa determined by TDR slightly underestimated measured concentrations in the first 4 weeks, and in the second half of the incubation there was a significant overestimation of measured NO3–. Using the sum of both measured NO3– and SO42– reduced the overestimation. In the subsoil calculated NO3– concentrations strongly and consistently overestimated measured concentrations, although both followed the same trend. As S mineralization in the subsoil was very small, and initial SO42– concentrations were largely taken into account in the calibration relations, SO42– concentrations could not explain the overestimation. The very small NO3– and SO42– concentrations in the B layer, at the lower limit of the concentrations used in the calibrations, are a possible explanation for the discrepancies. A separate calibration for the subsoil could also be required to improve estimates of NO3– concentrations.  相似文献   

8.
The production of nitrous oxide (N2O) is a widespread trait in fungi and is of interest because denitrifying fungi lack the N2O reductase gene (nosZ) that regulates N2O reduction to nitrogen gas (N2). The adaptive ability of soil fungi is better than that of bacteria in acidic soils. We investigated the N2O reduction potential, described by the N2O product ratio (RN2O), N2O/(N2O+N2), in soils of different types of fields under crop cultivation with different fertilizer inputs and a bare fallow field with no fertilization as a control. The fungi-to-bacteria abundance ratio (RF/B) was negatively correlated (P < 0.01) with the natural pH of the soil; however, the high value of RF/B measured in vineyards was due to the large inputs of manure. When the denitrification potential was measured at natural pH values of soils, RN2O was negatively correlated (P < 0.01) with soil pH. When the denitrification potential was measured after short-term modifications of soil pH, however, no significant correlation was found between RN2O and the modified pH. Based on stepwise multiple regression analysis, soil pH and residual nitrate (NO3-) were the key factors regulating N2O reduction in soils at natural pH values (R2=0.88, P < 0.001), whereas the key factor was the soil residual NO3- alone (R2=0.83, P < 0.001) when the soil pH was modified. When the effect of the soil chemical properties was weakened, a high RF/B value had the potential (P < 0.01) to affect N2O reduction; however, the role of fungi was offset by the presence of denitrifying bacteria. These results provide evidence that compared to the indirect effects of RF/B, the direct effects of the soil chemical properties have a greater effect on N2O reduction in fertilized soils.  相似文献   

9.
Agrichemicals usually contaminate groundwater via preferential flow, therefore determination of the preferential flow characteristics of soil is needed. One model that predicts solute transport due to preferential flow is the mobile–immobile (MIM) solute-transport model, which partitions total water content (θ; m3 m?3) into mobile (θm) and immobile fractions (θim). In undisturbed soils, a method is proposed for determining the MIM model parameters, i.e. immobile water fraction (θim), mass transfer coefficient (α) and hydrodynamic dispersion coefficient (D h). Breakthrough curves were obtained for five different soil textures in three replicates, by miscible displacement of Cl? in undisturbed soil columns. Cl? breakthrough curves were evaluated in terms of the MIM model. Analysis suggests that the values of D h and α increased with lighter soil textures and θim increased with heavier soil textures. The values of θim ranged from 5.31 to 14.28% in different soil textures. Furthermore, values of θim were found to be related to soil clay content. Values of α ranged from 0.0257 to 0.32 h?1 and values of D h ranged from 0.36 to 11.2 cm2 h?1 in different soil textures. A significant linear correlation was obtained between α, θim, D h and soil saturated hydraulic conductivity (K s) and pore water velocity (v). A multivariate pedotransfer function was developed to estimate α, θim and D h based on the geometric mean (d g) and the standard deviation (σg) of the diameter of soil particles and soil organic matter content. The pedotransfer functions for D h, θim and α were validated by independent data sets from other investigators.  相似文献   

10.
【目的】探究库布齐沙地人工林滴灌下土壤水分运移规律以及其与土壤分形特征的关系,以期为人工林滴灌策略制定提供参考。【方法】以典型人工林为研究对象,基于激光粒度衍射法测得土壤粒径分布并计算单重及多重分形维数,通过大田试验明确灌水及水分再分布过程湿润锋动态变化规律,并采用通径和冗余分析等手段探究湿润锋运移与分形特征的联系。【结果】1)库布齐沙地滴灌人工林湿润锋水平及垂向运移可分别用对数函数(R2=0.941~0.990)和幂函数(R2=0.958~0.996)描述；2)砂粒含量高于70%、黏粒低于2.5%土壤条件下,利用粉粒、黏粒含量构建的多元回归模型能较好地计算停灌后二维水分运移距离(R2=0.839~1.0),但对停灌前适用性较差(R2=0.243~0.403)；3)单重分形维数D和信息维数D1、信息维数/容量维数D1/D0、关联维数D2均与砂粉比呈负相关,而滴灌形成的湿润体体积与砂粉比正相关,且D较D0、D1、D1/D0、D2更能解释土壤砂粉比差异对湿润锋运移的影响。【结论】滴灌下人工林水分运移满足函数定量关系,砂粒占比高于70%且黏粒低于2.5%时,土壤质地越粗则湿润体体积越大,可在灌溉策略制定时进行土壤粒径分析,节约决策成本。与库布齐沙地相似环境条件下,滴灌时长6h流量3.0L.h-1时,速生杨和榆树林在停灌后48h需启动下次灌溉,沙柳和旱柳林则不需要。  相似文献   

11.
Reactions of elements with the water mineral interface are important and affect their bioavailability and transportation within soil. Effects of metal sorption on X-ray-diffraction (XRD-photographs) of clay minerals have been not studied. Therefore, sorption experiments were done on clay fractions of two calcareous soils using 12 concentrations of 0–2000 mg L?1 Zn(NO3)2 and Cu(NO3)2. Langmuir and Freundlich isotherms’ coefficients were determined. After sorption, XRD-diffraction were prepared and compared with those of initial samples. Langmuir (R2 = 0.996–0.999 and SE = 0.001–0.002) and Freundlich equation were the best-model for Zn and Cu-sorption, respectively. Sorption energy was higher for Zn than Cu, whereas the maximum concentration of sorbed-Cu was higher than that of Zn. Distribution coefficient (Kd) of Cu were more (threefold) than that of Zn. The Kd values representing the slope of Freundlich isotherms decreased according to linear regression equations (R2 = 0.72–0.91) as the equilibrium concentrations of metals increased. No significant differences were observed among XRD-photographs of applied concentrations (some negligible differences were found in position/sharpness of peaks). Dry-XRD-method resulted in omission of intensity peaks at 2θ which may interfere in recognition of clays that show a maximum intensity >1.4 nm in the mentioned 2θ. Zinc can become more leachable especially in Shekarbani-soil-series, whereas, Cu highly adsorb on clay minerals and can show less tendency to transportation.  相似文献   

12.
This paper questions whether the presence of biosolids amendment in metal‐spiked soils alters the outcome of soil‐based assays of metal bioavailability. The effects of biosolids amendment on the efficacies of six soil metal bioavailability assays (total recoverable, EDTA, Ca(NO3)2, soil solution, diffusive gradient in thin films and free ion activity) were assessed against metal concentrations in wheat shoots (Triticum aestivum) germinated in three contrasting soils, each previously incubated for either 2 weeks or 6 months following treatment with Cd, Cu, Ni and Zn +/? biosolids amendment. Overall, Ca(NO3)2 was the most accurate method to predict Cd (r2 = 0.62), Ni (r2 = 0.73) and Zn (r2 = 0.55) bioavailability in soils and therefore was used to compare variations in responses between biosolids and nonbiosolids‐amended soils. Comparisons between these two groups revealed no significant differences in linear relationships for all four metals and soil types assessed. These findings not only support Ca(NO3)2 as a robust and valid method for determining soil metal bioavailability across metal matrices and soil types, but also that the presence of biosolids does not compromise the predictive power of this assay or any of the others examined.  相似文献   

13.
Diffusion coefficients (D) of CO2 at 0–10 cm layers in undisturbed and tilled soil conditions were estimated using the Penman (Penman HL. 1940. Gas and vapor movement in soil, 1. The diffusion of vapours through porous solids. J Agric Sci. 30:437–463), Millington–Quirk (Millington RJ, Quirk JP. 1960. Transport in porous media. In: Van Baren FA, editor. Transactions of the 7th International Congress of Soil Science. Vol. 1. Amsterdam: Elsevier. p. 97–106), Ridgwell et al. (Ridgwell AJ, Marshall SJ, Gregson K. 1999. Consumption of atmospheric methane by soils: A process-based model. Global Biogeochem Cy. 13:59–70), Troeh et al. (Troeh FR, Jabro JD, Kirkham D. 1982. Gaseous diffusion equations for porous materials. Geoderma. 27:239–258) and Moldrup et al. (Moldrup P, Kruse CW, Rolston DE, Yamaguchi T. 1996. Modeling diffusion and reaction in soils: III. Predicting gas diffusivity from the Campbell soil–water retention model. Soil Sci. 161:366–375) models. Soil bulk density and volumetric soil water content (θv) at 0–10 cm were measured on 14 April, 2 June and 12 July 2005 at 0–10 cm depth in no-till (NT) and conventional till (CT) malt barley and undisturbed soil grass–alfalfa (UGA) systems. Air-filled porosity (ε) was calculated from total soil porosity and θv measurements. Both soil air porosity and estimated CO2 diffusivity at the 0–10 cm depth were significantly affected by tillage. Results of CO2 diffusion coefficients in the soil followed trends similar to those for soil ε data. The CT tended to have significantly greater estimated soil CO2 diffusion coefficients than the NT and UGA treatments. The relationship between D/D 0, and air-filled porosity was well described by a power (R 2 = 0.985) function. The model is useful for predicting CO2 gas-diffusion coefficients in undisturbed and tilled soils at various ranges of ε where actual gas D measurements are time-consuming, costly and infeasible.  相似文献   

14.
Abstract

A better understanding of nitrogen (N) availability to crops remains an essential key for a productive and safe production system. The main objective of this study was to evaluate the potential of anionic exchange membranes (AEMs) as part of a soil‐testing procedure to predict in situ soil NO3‐N availability for forage and corn produced in eastern Canada. The AEMs were buried in the surface horizon (0–15 cm) at four experimental sites for forage and at one site for corn. Treatments consisted of five NH4NO3 rates (0, 60, 120, 180, and 240 kg N ha?1) in forage and of six anhydrous ammonia (0, 50, 100, 150, 200, and 250 kg N ha?1) in corn production. In all sites, NO3 ? adsorbed on AEMs (NO3AEMs) increased significantly with N fertilizer rates, indicating the ability of the AEMs to detect differences between N fertilizer treatments and to predict the soil N availability to crops. The NO3AEMs fluxes were significantly related to soil NO3‐N concentration as extracted by water or KCl (0.66≤R2≤0.95). Significant relationships between crop N uptake and NO3AEMs were obtained (0.52≤R2≤0.94), suggesting that AEMs can be used as an index of soil N availability. Results indicated that AEMs provide a reasonably accurate evaluation of N availability to forage and corn. Because of their low cost, simplicity, and consistency over years, soils, and crops, AEMs could be efficiently used in soil N availability analysis.  相似文献   

15.
The aim was to describe Cd sorption in spatially variable sandy soils of the ‘Fuhrberger Feld’ catchment area as a prerequisite for prognosis of Cd transport in soil and of the threat of groundwater pollution. Thus, the possibility is evaluated to derive a generalized Freundlich equation based on multiple regressions relating the retention parameters k and M (from isotherm data of part 1 of this study) to basic soil properties (pedotransfer functions). For the parameter M (exponent), the correlation ‘measured vs estimated’ was weak (r2 < 0.5) whereas k was well predictable by pedotransfer functions. The best regression was obtained if organic carbon (OC). clay content and H+ activity were combined as independent variables (r2 up to 0.96). The obtained k values were much higher than those from comparable literature models, probably due to lower ionic strength and different composition of our background solutions used for the isotherms. As a critical evaluation, the estimates for k were used to derive solute Cd concentrations (Cest) which then were compared to measured data (range 0.1–3 μg L?1). The best but still unsatisfactory r2 was 0.77, obtained if Gest was compared to Cd in 0.01 Mc Ca(NO3)2 equilibria (Cd0). Cd in fresh soil solution (Cdz) showed no significant correlation with Cest, except for one relationship where OC had been excluded from the preceding multiple regression of k. Generally, the role of the variable OC remained unclear. Direct multiple regressions of measured solute Cd vs soil properties (bypassing k, no sorbed fraction) yielded much closer correlations, with r2 = 0.9 for Cd0 vs OC, H+ activity, clay (log data, OC decreases C) and r2 = 0.7 for Cd2 vs OC, H+ activity, clay (log data, OC enhances C).  相似文献   

16.
Pedo-transfer functions (PTFs) have been widely used to estimate soil hydraulic properties in the simulation of catchment eco-hydrological processes. However, the accuracy of existing PTFs is usually inadequate for use. To develop PTFs for local use, soil columns were collected from a double rice-cropped agricultural catchment in subtropical central China. The PTFs for saturated soil hydraulic conductivity (Ks) and parameters (θs, α, and n) of the van Genuchten model for the soil water retention curve (SWRC) were obtained based on soil’s basic properties, and compared with models developed by Li et al. in 2007 and Wösten et al. in 1999, respectively. Our results indicated that Ks in the range of 0.04–1087 cm d?1 and θs in the range of 0.34–0.51 cm3 cm?3 were both well estimated with the R2adj of 0.72 and 0.87, respectively, but α (0.04–0.65 cm?1) and n (1.05–1.21) were relatively poorly predicted with the respective R2adj of 0.38 and 0.55, despite the use of more input parameters. Our local derived PTFs outperformed the other two existing models. However, if the local PTFs for paddy soils are not available, the Wösten et al. 1999 model can be proposed as a useful alternative. Therefore, this study can improve our understanding of the development and application of PTFs for predicting paddy soil hydraulic properties in China.  相似文献   

17.
Abstract

Simple microdiffusion methods are described for determination of NH4 +, NO3 ‐, and NO2 ‐ in soil extracts. These methods involve diffusion of NH3 in a 473‐mL (1‐pint) wide‐mouth Mason jar, the diffused NH3‐N being collected in 3 mL of boric acid‐indicator solution in a 60 mm (dia.) Petri dish suspended from the Mason jar lid, for quantitative determination by titrimetry (0.0025 M H2SO4). Magnesium oxide is used to liberate NH4 +; Devarda's alloy is used to reduce NO3‐ and NO2 ‐ to NH4 +; and sulfamic acid is used to eliminate NO2 ‐. Depending upon the volume of soil extract (10–50 mL), diffusion at room temperature (a20°C) was complete in 18–72 h with orbital shaking, and in 24–86 h without shaking. The methods gave quantitative recovery of NH4 +, NO3 ‐, and NO2 ‐added to soil extracts. A potential source of interference in the methods involving use of Devarda's alloy is the liberation of NH4 +‐N from alkali‐labile organic‐N compounds.  相似文献   

18.
青海云杉造林密度与水源涵养功能的响应关系   总被引：1，自引：1，他引：0  
以青海省大通县安门滩小流域7种造林密度的青海云杉人工林为研究对象,利用浸水法、环刀法测定林下枯落物、草本层及0—60cm土壤层的持水量,定量评价不同密度的青海云杉人工林水源涵养功能。结果表明:(1)不同造林密度下的林分枯落物最大持水量变化范围为1.97～7.60m3/hm2,枯落物持水量最大的造林密度为1 725株/hm2,造林密度为2 300株/hm2的枯落物持水量最小;不同造林密度的林下草本层持水量变化范围为1.97～7.17m3/hm2,林下草本层持水量最大的造林密度为1 575株/hm2。(2)0—60cm土层的水源涵养功能与土壤物理性质、土壤渗透性及贮水性密切相关,土壤容重的变化范围为1.20～1.43g/cm~3,土壤总孔隙度变化范围为46.53%～53.30%,土壤容重与土壤总孔隙度随造林密度变化趋势呈负相关,密度1 575株/hm~2的林地具有最小的土壤容重和最大的土壤总孔隙度;土壤渗透性能主要取决于土壤的非毛管孔隙度,二者呈显著性相关,密度为1 575株/hm~2的土壤渗透性能最强,密度为2 300株/hm2的林分土壤渗透性最差;0—60cm土层的饱和蓄水量变化范围为2 792.50～3 197.90m3/hm2,造林密度为1 575株/hm2的土壤饱和蓄水量最大。(3)利用林地总贮水量评价水源涵养功能,林地总贮水量大小依次为D1575(3 207.37m3/hm2)D2300(3 164.67m3/hm2)D1900(3 157.17m3/hm~2)D1650(3 141.12m3/hm2)D1475(3 105.91m3/hm2)D1725(2 998.32m3/hm2)D1350(2 803.68m3/hm2)。研究结果说明造林密度为1 575株/hm2的青海云杉林水源涵养能力较好,这与当地2m×3m的造林规格相匹配,为青海黄土高原高寒区的青海云杉人工林可持续经营提供理论依据。  相似文献   

19.
In this study, the effect of land-use treatments and the feasibility of fractal dimension to quantify soil aggregate stability were investigated in the central Zagrous, Iran. For this purpose, the non-linear fractal dimension (Dnl), linear fractal dimension (Dl) and the mean weight diameter (MWD) of aggregates were compared. Soil samples from three sites with four adjacent land-use types, namely: forest area (F), cultivated lands adjacent to forest (CAF), pasture (P) and cultivated lands adjacent to pasture (CAP) were collected. Results showed that soils under cultivated lands had higher bulk density (BD) (1.30–1.38 Mg m?3) compared to the adjacent soils under forest (1.19 Mg m?3) and pasture (1.21 Mg m?3). In the 0–15 cm layer, soil organic matter (SOM) content in the cultivated plots were respectively 30% and 31% lower compared to the forest and pasture soils. The lowest CVs belonged to Dnl (5–8%) demonstrating that Dnl was more accurate than Dl (8–14%) and MWD (30–53%) methods. CAP had the largest value of Dnl, while P had the smallest value of Dnl. Difference of Dnl between forest and pasture was not significant, whereas both of them significantly differed from CAF and CAP. Dl did not differ significantly between forest and CAF. There were significant differences between forest and pasture for the measured MWD. Both fractal dimensions had negative correlation with MWD, SOM, hydraulic conductivity (HC) and macroaggregates (>0.25 mm) and positive correlation with BD and total porosity (TP).  相似文献   

20.
Laboratory incubations were conducted to study the effect of sodium chloride (NaCl) on denitrification and respiratory gases (CO2, O2) from soil treated with ammonium or nitrate and incubated at 20 % moisture. The same samples were assayed for denitrifying enzyme activity (DEA) after incubation at 40 % moisture with glucose and NO3–. Under aerobic conditions (20 % water content), a flush of activity was observed at 6 hours after start of incubation and subsided to negligible levels at 12 hours. Sodium chloride significantly depressed N2O and CO2 emissions and O2 consumption. Significantly more loss of N2O occurred from NH4+‐ than NO3–‐treated soil at all NaCl levels and was attributed to higher microbial activity. A highly significant positive correlation was obtained between N2O emission and respiratory gases. The respiratory quotient (CO2 evolved/O2) was higher for NH4+‐treated soil and decreased with the amount of NaCl. At 40 % moisture, N2O emissions were higher than at 20 % and peaked at 37 hours followed by a sharp decrease. Short‐term incubations of soil with NH4+ or NO3– did not have an effect on denitrifying enzyme activity (DEA) while NaCl had a positive effect, particularly in previously NO3–‐treated soil.  相似文献   

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