典型喀斯特林地土壤养分空间变异的影响因素

为了探明喀斯特森林生态系统土壤养分空间异质性的成因及其对养分生物地球化学过程的指示意义,该研究以广西木论国家级自然保护区典型喀斯特峰丛洼地为研究对象,利用地统计学和经典统计方法分析了土壤养分的空间变异特征,并探讨了其主要影响因子。结果表明,研究区土壤有机碳(SOC)和全氮(TN)的块金值/基台值较大,分别为49.9%和28.6%,表现为中等程度的空间自相关,全磷(TP)和全钾(TK)的块金值/基台值较小,分别为10.4%和2.9%,表现为强烈的空间自相关,说明随机因素对TP和TK的影响相对较小;逐步回归分析表明,各环境因子对TK的方差解释最大,对SOC的方差解释最小。其中,土壤交换性Ca2+离子和凋落物中N含量是SOC和TN的主要控制因素,随着交换性Ca2+和凋落物中N含量升高,土壤SOC和TN积累增加;TP的控制因素比较单一,仅受凋落物中P含量影响。TK的影响因素比较复杂,除主要受交换性Ca2+控制外,凋落物N:P比、海拔高度和黏粒含量也有显著影响。     

氮肥施用对砖红壤硝态氮和盐基离子淋失特征的影响

氮肥品种的合理选用对作物增产增收、 土壤酸化改良有重要的影响。本文以海南省海口市观澜湖采集的砖红壤为研究对象,采用室内土柱模拟试验,对尿素、 硝酸铵和硫酸铵3种氮肥处理下砖红壤硝态氮及盐基离子（Ca2+、 Mg2+、 K+、 Na+）淋失特征进行了研究。结果表明, 1）硝态氮累积淋溶量表现为硫酸铵硝酸铵尿素N0,且硝态氮的淋溶量与施肥量呈正相关关系,整个淋溶过程中硝态氮累积淋溶量（y kg/hm2）与施肥量（x kg/hm2）之间满足线性方程 y=3.3064x+315.74（R2=0.8848）; 2）尿素、 硝酸铵、 硫酸铵处理整个淋溶过程的盐基离子淋溶量均表现为 Ca2+Mg2+K+Na+,且盐基离子淋溶总量（kg/hm2）表现为硫酸铵（1821.12）硝酸铵（1080.27）尿素（872.24）N0（417.23）; 3）砖红壤盐基离子迁移速率表现为硫酸铵（26.28%）硝酸铵（13.37%）尿素（11.78%）,尿素、 硝酸铵和硫酸铵处理分别以线性方程 y=0.1178x+123.18（R2=0.9121）、 乘幂方程 y=15.634x0.4423（R2=0.9259）和对数方程 y=128.38e0.0007x（R2= 0.9244）的拟合度最高。     

碱金属离子在汞金属界面吸附作用的量子化学研究

应用量子化学方法对碱金属离子在汞金属界面的吸附作用进行了研究.选取汞金属界面的3个典型的位置（空穴、桥位和顶点）,采用MP2方法计算得到Li＋、Na＋、K＋3种离子在汞表面不同位置的吸附能.结果表明：3种金属离子都是在空穴位置有较大的吸附能,然后是桥位和顶点位置;对于平衡结构,从Li＋到Na＋和K＋,随着离子半径的增大,离子与汞金属界面的平衡距离在逐渐增大,吸附作用逐渐减弱,而且离子与汞之间的电荷转移在逐渐减小.     

酸性土壤交换性钙、镁测定方法的探讨

通过对酸性土壤交换性钙、镁、钾、钠、速效钾和阳离子交换量不同提取方法和不同振荡时间的测定结果的比较分析,得出同一处理液（即2g土样加50ml1N乙酸铵振荡10min）可同时测定交换性钙、镁、钾、钠、速效钾和阳离子交换量,此方法与GB7865—87、GB7866—87、GB7856—87、GB7863—87测定结果无显著差异,且方法更加简单、快速,分析成本大大降低,极大地提高了工作效率,是在批量测试时值得推广的方法。     

Evaluation of multi-nutrient extractants for determination of available P,K, and micronutrient cations in soil

Sixty soil samples (0–0.15 m depth) collected randomly from different districts of Himachal Pradesh were used to evaluate ammonium bicarbonate-diethylenetriaminepenta acetic acid (AB-DTPA) and acid ammonium acetate-ethylene diamine tetra acetic acid (AAAc-EDTA) over standard methods for P, K, and micronutrient cations. Among Olsen P, Bray P1, AB-DTPA P, and AAAc-EDTA P, available P (kg ha^?1) varied from 7.8 to 44.3, 9.5 to 61.1, 6.5 to 38.8, 10.5 to 52.1; available K (kg ha^?1) among NH4OAc, AB-DTPA, and AAAc-EDTA ranged from 103.6 to 372.3, 86.6 to 364.9, and 74.6 to 362.5. In case of micronutrients cations, AB-DTPA in general, extracted more amounts as compared to DTPA alone. AAAc-EDTA correlated highly with the Olsen P. AB-DTPA-K and AAAc-EDTA-K correlated well with standard method (NH4OAc) however; AAAc-EDTA had higher correlation with AB-DTPA for K extractability. Among methods for micronutrients highest significant correlations were observed between AB-DTPA and DTPA for Cu, Fe, and Zn.     

Spatial prediction of saline and sodic soils in rice‒shrimp farming land by using integrated artificial neural network/regression model and kriging

In the context of widespread saline and sodic soil, mapping and monitoring spatial distribution of soil salinity and sodicity are important for utilization and management in agriculture lands. In this study, two-stage assessment was proposed to predict spatial distribution of saline and sodic soils. First, artificial neural network (ANN) and multiple linear regressions (MLR) model were used to predict sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP) based on soil electrical conductivity (EC) and pH. Then, the Kriging interpolation method combined with overlay mapping technique was used to perform saline spatial predictions in the study area. The model accuracy level is evaluated based on coefficient of determination (R²) and root mean square error (RMSE). In the first stage, the values of R² and RMSE of SAR and ESP were 0.94, 0.17 and 0.94, 0.24 for ANN, and 0.35, 0.52 and 0.34, 0.76 for MLR, respectively. Similarly, in the second stage, the RMSE of ANN-Kriging were much closer to 0 and relatively lower than MLR-Kriging and Kriging. The results show that ANN-Kriging can be used to improve the accuracy of mapping and monitoring spatial distribution of saline and sodic soil in areas that develop the rice-shrimp cultivation model.     

Comparative study of three methods of determining cation exchange capacity of three major soils in the rainforest region of Southwestern Nigeria

The cation exchange capacity (CEC) of three benchmark soils in the rain forest region of Southwestern Nigeria, were measured by three standard CEC methods. Results obtained were compared with a view to selecting the best suited CEC method for the soils. The study sites were the Teaching and Research Farm of Obafemi Awolowo University, Ile-Ife, and Itagunmodi settlement. Two representative soil profile pits each were established in soils developed in coarse-grained granite and gneiss, fine-grained biotite gneiss and schist, and the amphibolite. The three methods gave different CEC values in the order of CEC-pH 8.2 > CEC-pH 7 > ECEC. There was a significant correlation between soil organic matter (SOM) and the CEC obtained by each of the three methods (P ≤ 0.05), meanwhile, total clay showed no significant correlation. ECEC provided the best estimate of the CEC for the soils and adequate SOM management is crucial to enhance sustainable productivity of the soils.     

不同植被覆盖对养分在土壤水稳性团聚体中分布特征的影响

研究了重庆缙云山不同植被覆盖下土壤结构的稳定性,以及土壤有机碳和养分在水稳性团聚体中的分布特征.结果表明:不同植被覆盖对土壤水稳性团聚体的分布和土壤结构稳定性有显著影响.竹林土壤>0.25 mm水稳性团聚体含量以及土壤结构的稳定性显著低于马尾松林和草地土壤.植被覆盖对养分在土壤水稳性团聚体中的分布模式没有显著影响,在>2mm水稳性团聚体和<0.053 mm粒级的粉砂与粘粒组分中,有机碳、全氮、全磷以及交换性K~+、Na~+、Ca~(2+)、Mg~(2+)的浓度最高;地表植被覆盖的变化对有机碳、全氮、全磷和交换性盐基离子在各粒级水稳性团聚体中的含量产生显著影响,草地和竹林土壤有机碳和全氮显著高于马尾松林土壤,主要表现在0.25-0.053 mm粒级水稳性团聚体中有机碳和全氮含量,草地和竹林土壤显著高于马尾松林土壤;而草地土壤>2 mm水稳性团聚体和<0.053 mm粒级的粉砂与粘粒组分中的磷显著高于马尾松林和草地土壤.不同植被覆盖下土壤水稳性团聚体中交换性盐基离子均以Ca~(2+)、Mg~(2+)为主,占交换性盐基总量(Total exchangeable bases TEB)的91.8%～92.9%.草地土壤各个粒级的TEB都要大于其他两种植被覆盖下的土壤.     

Consistent patterns of N distribution through soil profiles in diverse alpine and tundra ecosystems

We studied the vertical patterns of δ¹⁵nitrogen in total N and exchangeable NH₄⁺-N through soil profiles in diverse alpine and tundra ecosystems. Soil samples were analyzed from 11 sites located in three mountain areas: NW Caucasus (Russia), the Khibiny Mountains (NW Russia) and Abisko region (N Sweden). Despite differences in the profile patterns of organic matter, nitrogen accumulation and nitrogen availability, we found consistent patterns of ¹⁵N distribution through all studied soil profiles. The δ¹⁵N values of total N were in general about zero or positive in the surface horizon and increased with soil depth. In contrast with total N, the δ¹⁵N values of exchangeable NH₄⁺-N were in general about zero or negative in the surface horizons and decreased with soil depth. NH₄⁺-N was significantly ¹⁵N-depleted compared with total N in all mineral horizons, while in the surface organic horizons differences between isotopic composition of total N and NH₄⁺-N were mostly not significant. We do not know the exact mechanism responsible for ¹⁵N depletion of NH₄⁺-N with soil depth and further research needs to evaluate the contributions of natural processes (higher nitrification activity and biological immobilization of “lighter” NH₄⁺-N near the soil surface) or artifacts of methodological procedure (contribution of the ¹⁵N-enriched microbial N and dissolved organic N near the soil surface). Nevertheless, our finding gives a new possibility to interpret variability in foliar δ¹⁵N values of plant species with different rooting depth in alpine and tundra ecosystems, because plants with deeper root systems can probably consume “lighter” rather than “heavier” NH₄⁺-N.     

云南曲靖植烟土壤交换性钙、镁与关联土壤属性的特征研究

利用GPS定位采集云南曲靖核心烟田耕层土壤样品651个,测定土样交换性钙、镁及pH、有机质、全氮、全磷、全钾含量,研究交换性钙、镁分布特征及其与土壤其他属性的关系。结果表明:①交换性钙、镁含量均值分别为3 054.3、258.12 mg/kg,变异幅度较大,且两者含量属适宜的占比较低,仅为6.3%和29.8%,总体含量丰富。不同烟区间交换性钙、镁含量差异较大;②交换性钙、镁含量与pH及有机质、全氮、全磷含量呈极显著正相关,交换性钙含量与全钾含量相关性不显著,交换性镁含量与全钾含量呈极显著正相关。采用曲线估计分析每两个属性之间的回归关系,共建立9个拟合曲线函数方程,决定系数为0.118～0.285,拟合误差均在3%以内,拟合优度较好,调节土壤pH、有机质、全氮、全磷和全钾含量对钙镁养分的平衡有重要影响。