| The spatial heterogeneity of soil water physical properties,pH and nutrients in Miyaluo subalpine dark coniferous forest of western Sichuan was studied,and it was of positive significance for understanding soil quality,sustainable utilization of soil resources and regional ecological restoration in the subalpine forest area of western Sichuan.The experimental site was a 9.6 hm2(400 m×240 m)subalpine dark coniferous dynamics forest plot in Bipenggou,Miyaluo,western Sichuan,China.By combining field sampling,laboratory measurement,geostatistical analysis and Pearson correlation analysis,we analyzed spatial distribution characteristics and correlations of 0-10 cm surface physical and chemical properties,including soil bulk density(SBD),soil water content(SWC),soil maximum moisture capacity(SMC),soil capillary moisture capacity(SCC),soil minimum moisture capacity(SNC),soil capillary porosity(SCP),soil non-capillary porosity(SNP),soil total porosity(STP),soil pH,soil organic carbon(SOC),total nitrogen(TN),total phosphorus(TP),total potassium(TK),ammonium nitrogen(AN),nitrate nitrogen(NN),available phosphorus(AP),iron(Fe),manganese(Mn),copper(Cu)and zinc(Zn)in the subalpine dark coniferous forest,so that provide scientific basis for sampling design,spatial interpolation and spatial distribution map making of soil physical and chemical properties and soil resource management in subalpine forest of western Sichuan Province.The main results were as follows:(1)There were differences in the mean content,degree of variation and statistical probability distribution types of soil water physical properties,pH and nutrients in 0-10 cm surface soil of Miyaluo alpine dark coniferous forest in western Sichuan.Firstly,the average value of SCP is greater than that of SNP,and the variation degree of SWC was the most intense,but the variation degree of STP was the weakest.SBD,SCP,SNP,STP belong to normal distribution,while SWC,SMC,SCC,SNC belonged to lognormal distribution.Secondly,the mean value of soil carbon,nitrogen,phosphorus potassium nutrients was in the order of SOC>TK>TN>TP,and the mean value of available nutrients was in the order of AN>AP>NN.The variation degree of NN and AP was the strongest,and the variation degree of pH was the weakest.Soil pH,SOC,TN,TP,TK,AN,NN,AP all belonged to lognormal distribution.Thirdly,the order of the mean value of soil trace elements was Fe>Mn>Zn>Cu,The variation degree of soil Mn was the most intense,and the variation degree of Zn and Fe was the weakest.The distribution of soil Cu,Zn,Mn belong to logarithmic normal,and that of soil Fe belong to normal distribution.The variation degree of soil physical properties,soil major element properties and trace element properties all belonged to the medium degree of variation.(2)The spatial heterogeneity characteristics of soil water physical properties,pH and nutrients were different,and the optimal fitting model types and fitting parameters of semivariance models were also different.Firstly,The semi-variance functions of soil physical and chemical properties had good fitting results.When the spherical model was used to describe the SMC,the fitting degree of the model was the highest,and the fitting effect of the exponential model was the best for other soil water physical properties.SMC and SNP showed strong spatial autocorrelation,while SBD,SMC,SCC,SNC,SCP,STP showed moderate spatial autocorrelation.The order of the range size of the semivariance models of the water physical properties of soil was SCP>STP>SCC>SWC>SNC>SBD>SMC>SNP.Secondly,when the spherical model,spherical model and Gaussian model were used to describe the SOC,TP,and TN,respectively,the fitting degree of the model was the highest.The fitting effect of the exponential model was the best for pH,TP,AN,NN and AP.There was a strong spatial autocorrelation between NN and AP.Soil pH,SOC,TN,TP,TK and AN had moderate spatial autocorrelation.The order of the range size of the semivariance function of soil pH、C、N、P、K nutrients was TP>TK>SOC>TN>AN>pH>AP>NN.Thirdly,the fitting degree of the model was the highest when the exponential model was used to describe the soil trace elements Fe,Mn,Cu,Zn.The spatial autocorrelation of Cu and Mn in soil was strong,and the spatial autocorrelation of Zn and Fe in soil was moderate.The order of the range of the semi-variance function of soil trace element properties was the soil Zn>Fe>Mn>Cu.(3)Soil water physical properties,pH and nutrients showed different spatial heterogeneity.The enrichment area,patch shape,size and spatial distribution continuity of soil properties were different.Firstly,the spatial distribution patterns of SWC,SMC,SCC,SNC,SCP,STP were similar,and the low values of them were all distributed in the west of the plot,while the high values were mainly distributed in the middle of the plot in large patches,with obvious transition phenomenon between patches.Secondly,the spatial distribution patterns of SOC,TN,TP and NN were similar,the low values of them were distributed in the west of the plot in a north-south direction,while the high values were mainly distributed in patches of different areas in the middle and east of the plot.The high values of TK were mainly distributed in a north-south stripe,while the low values were distributed in a large area patchy in the west,middle and east of the dynamic plot.The low value of soil pH was mainly distributed on the west side of the dynamic sample plot,while the high value was mainly distributed on the northeast side of the dynamic sample plot,and there was also a small banded distribution on the west side.The distribution pattern of NN and AP was weak and showed patchy distribution in small area.Thirdly,the low values of soil trace elements Cu,Zn,Fe and Mn were mostly distributed in the west side of the dynamic sample plot,while the high values of soil Cu and Mn were mainly distributed in the east side of the sample plot in irregular patches.The high value of soil Fe was mainly distributed in the middle and east of the plot in a large area,the low value of soil Zn was distributed in the west side of the dynamic plot,and the high value of it was distributed in the east side of the plot,and its spatial distribution was relatively simple.(4)There was a universal and significant correlation between soil water physical properties,pH and nutrients,and the positive and negative correlations were different.Firstly,SWC,SMC,SCC,SNC,SCP,STP had extremely significant positive correlation(P<0.01).SBD was significantly negatively correlated with all other soil water physical properties(P<0.01).This indicated that there was a close relationship between soil water holding capacity and soil capillary properties.Secondly,There were significant correlations(P<0.05)or extremely significant correlations(P<0.01)between SOC and all the other major elements.SOC may be an important source of other soil nutrients.There was no significant correlation between pH and AP,but there was significant correlation(P<0.05)or extremely significant correlation(P<0.01)between pH and other soil C,N,P,K nutrients.These results indicate that the change of pH has an effect on many ecological processes,such as decomposition and transformation of different nutrients.There were significant correlations(P<0.05)or extremely significant correlations(P<0.01)between TN and other soil nutrients,and there were significant correlations(P<0.05)or extremely significant correlations(P<0.01)between TP and other soil nutrients.AN and NN were significantly positively correlated with TN(P<0.01),indicating that TN was an important source of soil inorganic nitrogen.Thirdly,soil pH and SOC both were significantly positively correlated with Cu,Zn,Fe,Mn.There was a significant negative correlation between SBD and soil C,N,P,K nutrients(P<0.01).SWC,SMC,SCC,SNC,SCP,STP were significantly positively correlated with SOC,TN,TP,AN(P<0.01).What’s more,the significant correlation between soil trace elements and C,N,P,K nutrients indirectly leaded to the general and extremely significant correlation between soil trace elements and soil water physical properties. |
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