Small-Scale Spatial Variability of Soil Nutrients and Vegetation Properties in Semi-Arid Northern China

A field experiment was conducted at Kezuohouqi County, Inner Mongolia Autonomous Region of China, which was located on the southeastern edge of the Horqin Sandy Land, to study the spatial variability of soil nutrients for a smallscale, nutrient-poor, sandy site in a semi-arid region of northern China; to investigate whether or not there were 'islands of fertility' at the experimental site; and to determine the key nutrient elements that sustained ecosystem stability. Results obtained from geostatistical analysis indicated that the spatial distribution pattern of soil total nitrogen (STN) was far different from those of soil organic matter (SOM), total phosphorus (STP), and total potassium (STK). Compared to SOM, STP, and STK, STN had a lower structural heterogeneity ratio and a longer range, while other elements were all similar. In addition, STN had an isotropic spatial structure, whereas the others had an anisotropic spatial structure. The spatial structure patterns of herbage species, cover,and height also differed, indicating that spatial variability was subjected to different ecological factors. Differences in the spatial variability patterns among soil nutrients and vegetation properties showed that soil nutrients for a small-scale were not the primary limiting factors that influenced herbage spatial distribution patterns. Incorporating spatial distribution patterns of tree species, namely, Pinus sylvestris var. mongolica Litv. and shrub Lespedeza bicolor Turcz. in a research plot and using fractal dimension,SOM, STP, and STK were shown to contribute to the 'islands of fertility' phenomenon, however STN was not, possibly meaning that nitrogen was a key limiting element. Therefore, during restoration of similar ecosystems more attention should be given to soil nitrogen.

Multifractal characteristics and spatial variability of soil particle-size distribution in different land use patterns in a small catchment of the Three Gorges Reservoir Region,China

Characterizing soil particle-size distribution is a key measure towards soil property.The purpose of this study was to evaluate the multifractal characteristics of soil particle-size distribution among different land-use from a purple soil catchment and to generalize the spatial variation trend of multifractal parameters across the catchment.A total of 84 soil samples were collected from four kinds of land use patterns(dry land,orchard,paddy,and forest)in an agricultural catchment in the Three Gorges Reservoir Region,China.The multifractal analysis method was applied to quantitatively characterize the soil particle size distribution.Six soil particle size distribution(PSD)multifractal parameters(D(0),D(1),D(2),(35)a(q),(35)f[a(q)],α(0))were computed.Additionally,a geostatistical analysis was employed to reveal the spatial differentiation and map the spatial distribution of these parameters.Evident multifractal characteristics were found.The trend of generalized dimension spectrum of four land use patterns was basically consistent with the range of 0.8 to 2.0.However,orchard showed the largest monotonic decline,while the forest demonstrated the smallest decrease.D(0)of the four land use patterns were ranked as:dry land<orchard<forest<paddy,the order of D(1)was:dry land<paddy<orchard<forest,D(2)presented a rand-size relationship as dry land<forest<paddy<orchard.Furthermore,all land-use patterns presented asΔf[α(q)]<0.The rand-size relationship ofα(0)was same as D(0).The best-fitting model for D(0),D(1),D(2)andΔf[α(q)]was spherical model,forΔα(q)was gaussian model,and forα(0)was exponential model with structure variance ratio was 1.03%,49.83%,0.84%,1.48%,22.20%and 10.60%,respectively.The results showed that soil particles of each land use pattern were distributed unevenly.The multifractal parameters under different land use have significant differences,except forΔα(q).Differences in the composition of soil particles lead to differences in the multifractal properties even though they belong to the same soil texture.Farming behavior may refine particles and enhance the heterogeneity of soil particle distribution.Our results provide an effective reference for quantifying the impact of human activities on soil system in the Three Gorges Reservoir region.

On Spatial Variability and Distribution of Soil Nutrients in Different Nitraria tangutorum Bobr.Populations in Tsaidam Basin

In this paper,six important distribution areas of Nitraria tangutorum Bobr.in Tsaidam Basin were selected as research objects,to study spatial variability and distribution of soil nutrients in different N.tangutorum populations and analyze the relationship between soil nutrient contents and geographical location,by measuring soil pH and the contents of organic matter（OM）,total nitrogen（N）,total phosphorus（P）,total potassium（K）,hydrolysis N,available P and available K in soils.Results showed that：（1） soil nutrient contents among different populations showed significant spatial variability,and soil depth had a significant effect on soil nutrients contents,but the variation rules were not obvious.（2）Average pH and average contents of OM,total N,total P,total K,hydrolysis N,available P and available K in soils with different depths（0-15,15-30,30-45 cm） varied in the range of 8.37-9.21,3.34-20.68,0.18-1.21,0.35-0.75,16.12-22.04,5.13-553.28,1.10-52.54 and 103.83-562.28 mg/kg,respectively.（3） The analysis results of correlation between average values of pH and contents of nutrient indexes in soils with different depths（0-15,15-30,30-45 cm） showed that the correlation of these indexes were different.（4）OM and total N contents in soils with different depths（0-15,15-30,30-45 cm） all had a significant positive correlation with latitude and negative correlation with longitude and altitude,and the correlation of available P and available K contents in surface soils（0-15 cm） with latitude,longitude and altitude were significant positive,significant negative and significant negative,respectively;moreover,longitude and latitude also showed a significant impact on soil available K contents with the depth of 30-45 cm.In addition,comprehensive analysis result of nutrient contents showed that N.tangutorum populations in Huaitou Tala Town had the highest fertility,and the fertility levels of N.tangutorum populations in Chaka Town and Wulan Keke Town were relatively lower.

Spatial variability of soil total nitrogen,phosphorus and potassium in Renshou County of Sichuan Basin,China

Understanding soil nutrient distributions and the factors affecting them are crucial for fertilizer management and environmental protection in vulnerable ecological regions.Based on 555 soil samples collected in 2012 in Renshou County,located in the purple soil hilly area of Sichuan Basin,China,the spatial variability of soil total nitrogen(TN),total phosphorus(TP)and total potassium(TK)was studied with geostatistical analysis and the relative roles of the affecting factors were quantified using regression analysis.The means of TN,TP and TK contents were 1.12,0.82 and 9.64 g kg^(–1),respectively.The coefficients of variation ranged from 30.56 to 38.75%and the nugget/sill ratios ranged from 0.45 to 0.61,indicating that the three soil nutrients had moderate variability and spatial dependence.Two distribution patterns were observed.TP and TK were associated with patterns of obvious spatial distribution trends while the spatial distribution of TN was characterized by higher variability.Soil group,land use type and topographic factors explained 26.5,35.6 and 8.4%of TN variability,respectively,with land use being the dominant factor.Parent material,soil group,land use type and topographic factors explained 17.5,10.7,12.0 and 5.0%of TP variability,respectively,and both parent material and land use type played important roles.Only parent material and soil type contributed to TK variability and could explain 25.1 and 13.7%of TK variability,respectively.More attention should focus on adopting reasonable land use types for the purposes of fertilizer management and consider the different roles of the affecting factors at the landscape scale in this purple soil hilly area.

云南元谋冬早蔬菜主产地土壤肥力的空间变异特征与评价

【目的】明确云南元谋露天冬早蔬菜主产地的土壤肥力空间变异特征,为该区域的土壤培肥管理提供科学依据。【方法】在元谋县蔬菜主产区的露天菜地区域选择28个样点,采集土壤样品,测定其pH、电导率、含水率、容重以及有机质、全盐、有效磷、速效钾、硝态氮、交换态钙和交换态镁的含量共11项土壤肥力指标,并采用ArcGIS分析其空间变异特征。选择隶属度函数曲线并确定隶属度函数,根据各项土壤肥力指标的权重值和隶属度值计算土壤肥力指标的综合得分;再采用主成分分析和聚类分析分别对菜地土壤肥力进行综合评价。【结果】元谋县典型露天菜地土壤的平均pH值为7.54,属于弱碱性土壤,有机质和速效钾含量较高,有效磷含量处于中等偏上水平。土壤有机质与交换态镁含量的空间分布特征非常相似,土壤电导率、全盐量和有效磷含量的空间分布较为一致。土壤肥力单项指标分析显示:元谋老城乡和黄瓜园镇的隶属度值雷达图面积较大,4个乡镇的pH值、速效钾、电导率、全盐量等指标变异较小,而有机质、交换态镁、有效磷等指标变异较大。主成分分析显示:前3个主成分贡献了原始数据信息总量的70.670%,其中有机质的权重系数最大(0.1128),其次为交换态镁(0.1125)和有效磷(0.1123)。元谋菜地土壤肥力的综合得分为0.247~0.903,其中60.7%的样点低于平均值,主要集中在物茂乡和元马镇。聚类分析显示:全县菜地样点可划分为肥力良好型(39.29%)和肥力中等型(60.71%)。【结论】元谋县大部分区域的露天菜地土壤肥力水平良好,其中,有机质、交换态镁和有效磷对土壤肥力的贡献率较大,在该县菜地土壤肥力中起重要作用,但局部区域的土壤肥力亟待改良。

Sampling Size Requirements to Delineate Spatial Variability of Soil Properties for Site-Specific Nutrient Management in Rubber Tree Plantations

Site-specific nutrient management is an important strategy to promote sustainable production of rubber trees in order to obtain high yields of natural rubber. Making effective nutrient management decisions for rubber trees depend on knowing the spatial variations of soil fertility properties in advance. In this study the Kriging geostatistical method was used to examine the spatial variability of soil total nitrogen(TN), organic matter(OM), available phosphorus(AP) and available potassium(AK) in a typical hilly rubber tree plantation in Hainan, China. The spatial variability of the soils was small for the TN and OM and had medium variability for the AP and AK variables. Anisotropic semivariograms of all soil properties revealed that elevation and building contour ledge can profoundly affect the spatial variability of soil properties in the plantation, except for the AK variable. Soil samples had to be collected in alignment with the direction of elevation and perpendicular to the direction of building contour ledges, which was needed to obtain more reliable information within the study area in the rubber tree plantation. In formulating a sample scheme for AK, the distribution features of the soil’s parent material should be considered as the influence factor in the study field. The Kriging method used to guide the soil sampling for spatial variability dertermination of soil properties was about 2-5 times more efficient than the classic statistical method.

基于模糊c-均值聚类的亚热带丘陵区土壤肥力空间分异与管理分区

[目的]亚热带丘陵区地形复杂,土壤肥力空间变异大,科学地将土壤按照相似地力进行分区,是实现丘陵区土壤精确管理,优化土壤培肥技术的理论基础。[方法]研究对象位于亚热带丘陵区的典型小流域-湖南省长沙县金井镇,2009年在全镇范围内(112 km~2)密集布置946个样点采集土壤样品,以测定的土壤肥力指标为数据源,包括土壤有机碳(SOC)、全氮(TN)、全磷(TP)、速效氮(AN)、有效磷(AP)和pH,采用地统计学和模糊c-均值聚类算法,分析流域土壤肥力的空间异质性;采用主成分分析法进行土壤肥力分区,并根据数据的差异显著性和变异系数对分区结果进行验证。[结果]除pH外,流域内土壤有机碳、全氮、全磷、速效氮和有效磷均存在中等至强的空间变异,变异系数(CV)介于36%~125%。基于主成分分析和模糊c-均值聚类可将研究区划分为3个肥力管理分区:MZ1、MZ2和MZ3,分区后各土壤肥力指标的变异系数(CV)不同程度地降低,以pH变异系数降幅最小(6%),AP变异系数降幅最大(96%)。同一分区内主要土壤肥力指标趋于同质化,分区间则异质化显著(P<0.01)。分区间水稻产量差异明显,MZ1区晚稻产量和早晚稻总产量显著高于MZ2和MZ3 (P<0.01)。MZ1、MZ2和MZ3区土壤pH值分别为4.12、4.04和4.00,均属于极酸水平;SOC分别为15.15、14.38和12.24 g/kg,均处于高水平;TN也为高水平(1.56、1.48和1.34 g/kg);TP为高至很高水平(0.86、0.69和0.60 g/kg);AN则处于很低至低水平(41.08、35.33和26.16 mg/kg);AP为中低水平(8.63、4.46和3.39 mg/kg)。[结论]亚热带丘陵区地形地貌复杂,是土壤肥力空间变异较大的主要影响因素。通过土壤肥力管理分区,可有效降低区域内肥力指标的变异程度,优化复杂丘陵区耕地管理措施。本研究区域中MZ1、MZ2和MZ3区均应着重改良土壤酸化现象,提高肥料氮素利用率,避免过量施用化学氮肥;MZ1区可适当减施磷肥,避免关键生育期过量施用磷肥;MZ2和MZ3区可以考虑适量施用生物酶活化磷肥或增施有机肥,以提高作物对磷素的利用效率。

基于环境变量筛选与机器学习的土壤养分含量空间插值研究

为了提高农田土壤养分含量空间插值精度,准确掌握土壤养分的空间分布特征,以新疆玛纳斯河流域绿洲为研究区域,测定土壤有机质含量、全氮含量、有效磷含量、速效钾含量、pH值和盐分含量,协同经度、纬度、地形、气象和植被指数因子作为环境变量,经过皮尔逊相关系数(Person correlation coefficient,PCC)、方差膨胀系数(Variance inflation factor,VIF)和极端梯度提升(Extreme gradient boosting,XGBoost)算法进行变量筛选,采用决策树(Decision tree,DT)、随机森林(Random forest,RF)、径向基函数神经网络(Radial basis function,RBF)和长短期记忆网络(Long short-term memory,LSTM)4种机器学习模型与普通克里格(Ordinary Kriging,OK)方法,对研究区农田土壤有机质、全氮、有效磷和速效钾含量进行空间插值。结果表明:研究区土壤有机质、全氮、有效磷、速效钾含量分别为0.226~32.275 g/kg、0.117~1.272 g/kg、3.159~53.884 mg/kg和81.510~488.422 mg/kg,变异系数为30.636%~43.648%,均属于中等程度变异。PCC、VIF和XGBoost变量筛选均表明,土壤有机质、全氮、有效磷和速效钾间具有一定的关联性,可用于目标属性空间插值的环境变量,但不同变量筛选方法对经度、纬度、地形、气象和植被指数因子筛选结果具有一定的差异性。XGBoost方法可以更有效地筛选出对空间插值结果重要的环境变量,且基于此方法筛选变量后建立的模型精度明显优于PCC和VIF筛选变量后建立的模型精度,而且协同环境变量的机器学习模型精度普遍优于未加入环境变量的OK模型精度,同一土壤养分含量空间插值模型精度从大到小依次为RF、LSTM、RBF、DT、OK,其中基于XGBoost筛选出的变量对土壤有机质、全氮、有效磷和速效钾含量构建的RF空间插值模型精度相较于未加入环境变量的OK模型有显著提高,决定系数分别提高43.02%、101.00%、86.04%和137.89%,均方根误差分别降低27.39%、42.78%、13.12%和28.39%,平均绝对误差分别降低29.01%、43.84%、11.20%和29.62%。利用RF模型对研究区农田土壤养分进行反演得到土壤有机质和全氮含量具有较强的空间分布一致性,含量较高的主要集中在研究区南部和东部区域,有效磷和速效钾含量具有一定的空间相似性,东南部、中北部区域含量较低。综上,XGBoost变量筛选方法结合RF模型可以更好地实现土壤养分空间插值,可作为土壤养分空间插值的有效方法。

基于地统计分析的核桃园土壤养分空间特征研究

【目的】探究核桃园土壤养分的空间特征,了解土壤肥力状况,为核桃园管理单位划分提供依据,从而实现精准施肥。【方法】以湖北保康核桃园为研究对象,采用地统计学和内梅罗法相结合的方法,分析了110块样地的土壤pH值、养分空间特征及肥力水平。【结果】(1)保康县核桃园土壤pH均值为6.68,以中性和微酸性土壤为主,具有弱变异性;有机质、水解性氮、有效钾、有效磷含量(w,后同)均值分别为27.63 g·kg^(-1)、109.41 mg·kg^(-1)、125.43 mg·kg^(-1)和23.74 mg·kg^(-1),具中等变异。(2)中等肥力核桃园占78.3%,肥沃核桃园占20.7%,水解性氮是土壤肥力的主要限制因子;土壤肥力指数与核桃干果每666.7 m2产量呈显著正相关。(3)水解性氮、有效钾含量主要受自然结构的影响,呈现显著空间正向聚集性;有机质、有效磷含量受自然结构和人为因素的双重影响,具有空间正相关性,但空间聚集效应不显著。(4)海拔与水解性氮含量、有效磷含量、土壤肥力指数呈极显著正相关,与有机质含量呈显著正相关,而与有效钾含量无显著相关性。【结论】该地区土壤pH值适宜核桃生长,现存核桃园整体肥力中等偏上,提高土壤肥力能够增加核桃干果产量。土壤空间变异主要受自然结构的影响,其中海拔是影响土壤肥力的关键因素,可以作为核桃园管理单元划分的重要依据。在土壤管理中,需要增施氮肥以提高林地土壤综合肥力。

高寒山区生长季土壤水分时空变异特征及其影响因素

土壤水分是高寒山区生态环境稳定与否的重要反馈。了解高寒山区土壤水分的时空变异特征有利于优化对水资源的管理,对进一步保护当地脆弱的生态环境具有重要意义。在2023年的5—10月对典型高寒山区(沙柳河流域)进行了土壤水分的连续定点观测,共设置8个不同样地,基于各样地间的主要差异,选择植被类型、坡向和海拔做为主要控制对象,探究不同植被类型、坡向和海拔高度对高寒山区土壤水分的时空变异特征的影响。研究发现:不同植被类型下的土壤水分差异较小,植被类型对土壤水分的时空变化特征影响较弱;坡向对土壤水分的影响明显,阴坡比阳坡土壤水分条件更优,波动变化更小;3500—3600 m海拔区间内,阴坡在生长季中期的土壤水分低于阳坡,不同坡向的土壤水分在表层0—20 cm具有明显的差异;3600—3700 m海拔区间内,阴坡在生长季后期的土壤水分低于阳坡,不同坡向的土壤水分在深度0—40 cm土层具有明显的差异;生长季内各海拔区间的土壤含水量从大到小依次为:3900—4000 m>3700—3800 m>3300—3400 m>3500—3600 m;生长季内各海拔区间土壤水分的变异系数从大到小依次为3900—4000 m>3300—3400 m>3700—3800 m>3500—3600 m;海拔对0—40 cm土层土壤水分的影响程度较高,从大到小依次为:30—40 cm土层>0—10 cm土层>10—20 cm土层>20—30 cm土层,但40—60 cm土层的土壤水分对海拔的响应程度较弱。

陆良植烟土壤养分丰缺状况与时空变异特征分析

为探明陆良烟区植烟土壤养分演变规律和分布状况,以烟区450份土壤样品为研究对象,运用经典统计方法、地统计学和地理信息技术分析该区域的土壤养分丰缺情况及其时空变异特征。结果表明:2008-2021年陆良县植烟土壤pH、有机质、碱解氮、有效磷磷和速效钾含量均值分别为6.01、2.64%、108.47 mg/kg、41.69 mg/kg和200.93 mg/kg,除pH中等变异外均属于强变异;且pH、有机质和碱解氮含量适宜,但需提高土壤pH、改善土壤有机质和氮肥的占比分别为37.42%、27.62%和37.64%;同时有效磷和速效钾含量丰富,且丰富和适宜范围内占比分别达到89.09%和83.07%。陆良县植烟土壤时间上整体表现为pH和有机质年份间无显著差异,但呈现降低趋势;碱解氮年份间差异显著且呈现先增加后降低趋势;有效磷和速效钾年份间差异显著且呈现先降低后增加趋势。空间上pH呈现西部低到东部适宜过渡,而北部和南部稍偏高趋势;有机质由西部向中部再向东部逐渐增加趋势;碱解氮处于90~120 mg/kg范围面积最多,有效磷位于高和很高范围内面积最大,速效钾从西部到东部逐渐升高;且pH、速效磷和速效钾的空间变异主要由人为因素等作用结果。

张家川县耕地土壤肥力评价及空间分布特征

本研究通过对张家川县闫家乡、张家川镇、恭门镇3个乡镇的耕地土壤肥力指标进行测定,采用主成分分析法评价了土壤肥力质量,并结合GIS分析了各肥力指标及土壤综合肥力的空间变异性。结果表明:研究区耕地土壤呈碱性,其中恭门镇南部地区耕地土壤碱性较强;有机质含量中等,闫家乡有机质含量最丰富,达到16.75 mg/kg;全氮含量较丰富而速效氮缺乏,空间分布均呈现从西到东逐渐升高的特征;速效钾、有效磷的含量丰富,分别呈现东高西低、南低北高的分布趋势。主成分分析结果表明,张家川镇、恭门镇土壤速效养分供应能力强,但保肥能力较差;闫家乡土壤养分蓄积能力强。土壤综合肥力质量从高到低依次为闫家乡、张家川镇、恭门镇,呈现出东高西低的空间分布趋势。综上,研究区内土壤养分及综合肥力分布不均,需协调氮、磷、钾肥施用比例,做到“因地、因苗、因水、因时”分期精准施肥。

Spatial interpolation of soil nutrients using algebra hyper-curve neural network

Spatial distribution of and interpolation methods for soil nutrients are the basis of soil nutrient management in precision agriculture.For study of application potential and characteristics of algebra hyper-curve neural network(AHCNN)in delineating spatial variability and interpolation of soil properties,956 soil samples were taken from a 50 hectare field with 20 m interval for alkaline hydrolytic nitrogen measurement.The test data set consisted of 100 random samples extracted from the 956 samples,and the training data set extracted from the remaining samples using 20,40,60,80,100 and 120 m grid intervals.Using the AHCNN model,three training plans were designed,including plan AHC1,using spatial coordinates as the only network input,plan AHC2,adding information of four neighboring points as network input,and plan AHC3,adding information of six neighboring points as network input.The interpolation precision of AHCNN method was compared with that of Kriging method.When the number of training samples was big,interpolation precisions of Kriging and AHCNN were similar.When the number of training samples was small,the precisions of both methods deteriorated.Since AHCNN method has no request on data distribution and it is non-linearization of neutron input variables,it is suitable for delineation of spatial distribution of nonlinear soil properties.In addition,AHCNN has an advantage of adaptive self-adjustment of model parameters,which makes it proper for soil nutrient spatial interpolation.After comparison of mean absolute error d,root mean squared error RMSE,and mean relative error%d,and the spatial distribution maps generated from different methods,it can be concluded that using spatial coordinates as the only network input cannot simulate the characteristics of soil nutrient spatial variability well,and the simulation results can be improved greatly after adding neighboring sample points’information and the distance effect as network input.When the number of samples was small,interpolation precision can be improved after properly increasing the number of neighboring sample points.It was also showed that evaluation of interpolation precision using conventional error statistic indexes was defective,and the spatial distribution map should be used as an important evaluation factor.

豫西南丘陵区植烟土壤养分时空变异特征及肥力评价

为明确豫西南丘陵区植烟土壤养分时空变化特征,选取内乡县2002、2020年植烟土壤数据,运用地统计学和地理信息系统(GIS)技术,分析土壤养分时空变异特征及空间分布格局,并采用模糊数学模型对土壤肥力进行综合评价。结果表明,18 a来,内乡县植烟土壤pH值平均值由7.74降至6.59,下降了1.15,速效钾和水溶性氯平均含量分别降低了7.31%、34.29%,有机质、碱解氮和有效磷平均含量分别增加了21.00%、109.77%、20.77%;土壤肥力指数由0.54提升至0.61,土壤肥力以Ⅲ级为主提升至以Ⅱ级为主;土壤pH值、碱解氮和水溶性氯含量空间变异较大,其中土壤pH值和水溶性氯含量偏高的植烟面积占比分别下降了79.14、16.84个百分点,碱解氮含量中等及以上植烟面积占比增加了97.46个百分点。2020年全县土壤肥力等级以良好为主,且相同等级区域呈集中分布,65.51%植烟区域碱解氮含量偏高,83.16%的植烟区域水溶性氯含量偏高,表明该研究区长期科学管理有效提高了植烟土壤肥力,但仍需因地制宜采取控氮、降氯措施,进一步提升植烟土壤肥力。

基于GIS的环巢湖地区土壤养分空间变异特征研究

为探究环巢湖地区土壤养分的空间自相关性及其变异规律,在研究区域共采集8073个土壤样品,基于GIS技术并使用地统计方法和Moran′s I指数法对土壤pH、有机质、全氮、碱解氮、有效磷、速效钾和缓效钾进行了系统分析。结果表明:土壤pH、有机质、全氮、碱解氮、有效磷、速效钾和缓效钾的均值分别为6.07、19.97 g·kg^(-1)、1.16 g·kg^(-1)、112.95 mg·kg^(-1)、18.21 mg·kg^(-1)、130.88 mg·kg^(-1)和378.58 mg·kg^(-1),除有效磷为强变异外,其他养分均为中等程度变异;pH、全氮、有效磷、速效钾和缓效钾半变异函数最佳拟合模型为指数模型,有机质和碱解氮为高斯模型;pH和速效钾为中等空间自相关性,其他养分空间自相关性均较弱,表明养分空间变异主要受人为活动等随机性因素影响;各养分均为极显著空间正相关,其空间相关性大小依次为有效磷>速效钾>pH>缓效钾>全氮>有机质>碱解氮,且有效磷的空间自相关性显著大于其他养分。总体上看,环巢湖地区养分分布较为分散,南北方向有逐渐上升或下降的趋势,且养分高低值聚集区域也有明显的南北分布。

大理典型植烟县烟田土壤速效养分时空变异特征

探明烟田土壤速效养分时空变异特征,为烤烟高产优质的施肥管理提供科学依据。应用地统计学等方法,分析了大理州祥云和弥渡两个典型植烟县1982、2012和2022年烟田土壤碱解氮、有效磷和速效钾的时空演变特征。1982-2022年祥云土壤碱解氮含量呈先增后降趋势,弥渡土壤碱解氮含量3个年度间无显著差异且以Ⅲ级为主(100~150 mg/kg),空间分布均匀。烟区土壤有效磷和速效钾含量均呈不同程度上升趋势,弥渡北部和祥云中西部高,其他区域低。近40年土壤速效养分块金效应由<25%上升至50%,表明养分空间变异的影响因素中地形等自然因素影响减弱,施肥等人为因素影响增强。土壤碱解氮含量一直处于中等水平(100~150mg/kg),磷钾肥施用导致有效磷和速效钾含量持续升高。根据土壤速效养分丰缺状况,祥云中北部、西部及弥渡北部区域烟田应“稳氮减磷钾”,其余区域需注意“稳氮控磷钾”。

渭-库绿洲土壤养分变异特征及空间分布

为探究渭干河-库车河三角洲绿洲(简称渭-库绿洲)土壤养分水平及空间分布规律,根据2020年土地利用数据,利用ArcGIS渔网工具生成覆盖耕地的1 km网格,基于1 km网格单元进行空间聚类为布设样点的数据参考,以农用地(包括耕地、园地)为主,兼顾样点空间分布均匀性,采用3S技术在耕地、园地和荒地3类土地利用类型上布设344个土壤表层样点,平均间距为1 km,其中耕地194个、园地64个、荒地86个,采用经典统计学、克里金插值法从耕地与荒地(荒地开垦为耕地前后)和不同土地利用类型两个视角,对比分析碱解氮、有效磷、速效钾变异特征。结果表明,渭-库绿洲表层土壤碱解氮含量由北端向周边呈放射状递减分布,有效磷含量由中心向东西两侧呈放射状递减分布,速效钾含量由西北端向周边呈放射状递增分布。园地的碱解氮最高,荒地的速效钾最高、有效磷最低。荒地开垦为耕地后,土壤碱解氮含量轻微增加,有效磷含量显著增加,速效钾含量显著降低。

大兴安岭南麓农田土壤速效养分空间异质性分析

以大兴安岭南麓阿荣旗全境农田土壤为研究对象,采用经典统计学对其土壤养分进行系统分析,探索大兴安岭南麓农田耕层土壤速效养分空间异质性。结果表明,土壤pH均值为6.02,总体呈弱酸性,适宜作物生长,变异度为2.06%~6.27%,为弱变异度;土壤速效钾均值为267.86 mg/kg,总体含量很丰富;土壤速效磷、碱解氮的含量均值为4.83、24.13 mg/kg,总体含量均很缺乏。速效钾、速效磷、碱解氮变异度均在10%~100%,为中等变异程度。在一定程度上,阿荣旗农田土壤各样点均存在显著的空间异质性。速效磷、碱解氮含量很缺。该研究为合理优化施肥方案、改善耕作方式、提高速效磷和碱解氮的积累、实现阿荣旗农田土壤养分平衡、提升地力提供科学依据,为构建大兴安岭南麓耕地地力评价体系提供技术支撑。

大兴安岭南麓农田土壤养分空间异质性分析

以大兴安岭南麓阿荣旗农田土壤为研究对象,探索阿荣旗农田土壤养分空间异质性。结果表明,阿荣旗农田土壤有机质、全钾、全磷、全氮含量分别为47.48、29.31、1.57、2.27 g/kg,土壤养分总体含量丰富,适宜作物生长,土壤各养分变异度均在10%~100%,为中等变异程度且各样点单因素显著,各样点存在显著的空间异质性。为合理优化施肥方案,改善耕作方式,实现阿荣旗农田各样点土壤养分平衡、地力提升提供科学依据,为构建大兴安岭南麓耕地地力评价体系提供理论支撑。

宁夏河东沙地生物土壤结皮及其下伏土壤养分的空间分布特征

为了揭示沙地生物土壤结皮的生长发育情况及其下伏土壤养分的空间分布特征,选择宁夏河东沙地为研究区,通过野外采样和室内实验,应用经典统计学、地学统计学和地理系统预测,分析了藻类和藓类结皮及其下伏0-5、5-10 cm土层土壤有机碳(SOC)、全氮(TN)、全磷(TP)含量以及结皮层厚度的空间分布特征。结果表明:(1)SOC、TN、TP质量分数的变异系数(CV)呈中等变异,CV_(TN )(57.1%)>CV_(SOC )(48.7%)>CV_(TP )(30.5%),生物土壤结皮对下伏土壤养分影响显著,其中藓类结皮对SOC和TN的影响更显著,藻类结皮则对TP的影响更显著;(2)藻类结皮下5-10 cm土层TN质量分数呈现强烈空间自相关性,块金系数(N/S)为20.3%,其余土层的SOC、TN、TP质量分数空间自相关性中等,TP质量分数空间变异由随机因素主导,SOC和TN则由结构因素主导;(3)在区域尺度和剖面尺度上,生物土壤结皮及下伏土壤的养分空间分布特征差异显著,结皮层土壤SOC质量分数中部和北部高、南部低,TN质量分数中南部高、西北部低,TP质量分数中东部高、西北部低,均呈条带状分布,0-5、5-10 cm土层SOC和TP质量分数呈中部高四周低的分布特征,TN质量分数呈南部和东部高、西部和中部低的分布特征,SOC与TP形成了典型的“肥岛”,而TN则形成了典型的“水岛”;研究区内TN的空间分布与SOC和TP的空间分布特征不一致,但是与藻类结皮层厚度的空间分布有较高的相似性。这表明,生物土壤结皮能够影响其下伏土壤的养分空间分布。此结果可以为研究旱区荒漠生态系统中生物土壤结皮的生态功能提供数据参考。