Spatial Variability Of Soil Clay Content And Cation Exchange Capacity In The South Slope Of Qinling Mountains In Shannxi Province

Qinling is an important ecological barrier in central China and has an important ecological role to China’s economic development.The growth of forests in the forests of the Qinling Mountains is related to the development of ecological functions.The effective functioning of ecological functions is closely related to the fertility of the soil in the forest.The soil fertility depends to a certain extent on the soil clay content and cation exchange capacity.In this study,soil clay content and cation substitutions in forest lands on the southern slope of the Qinling Mountains were studied in order to elucidate the soil fertility potential,the differences under different forest areas and site factors,and finally provide scientific basis for forest management and forest cultivation in the Qinling Mountains.Through the measurement and analysis,the following results are obtained:（1）The average soil clay content in the southern slope of Qinling,Shaanxi is 14.60%,the highest value is 32.80%,the lowest value is 5.60%;the average value of cation exchange capacity is 158.43 mmol·kg^-1,the highest value is 568.30 mmol·kg^-1,and the lowest value is16.80 mmol·kg^-1.It is showed that the soil fertility on the southern slope of the Qinling Mountains is at a relatively high level.（2）In the studied area,the clay content and soil cation exchange capacity in the forest area of Longcaoping reached the highest,which were 16.54%and 207.45 mmol·kg^-1,respectively.The Changqing Forest Region showed the minimum values of 11.16%and 98.82mmol·kg^-1,respectively.The order of the clay content in different forest areas is:Longcaoping Forest Region>NIngdong Forest Region>Taibai Forest Region>Ningxi Forest Region>Changqing Forest Region;The order of soil cation substitutions in different forest areas is:Longcaoping Forest Region>Ningxi Forest Region>Taibai Forest Region>NIngdong Forest Region>Changqing Forest Region.（3）With the increase of altitude,the clay content increased first and then decreased,and the cation exchange capacity showed an upward trend.There were significant or extremely significant differences among the elevation gradients.With the change of slope position,the clay content and the cation substitution value showed higher values in the middle and lower slopes,and they showed the lowest value in the upslope,and the difference was significant.The distribution of clay content and cation substitution on the aspect of slope shows:shady slope>sunny slope.With the increase of slope,the clay content first decreased and then increased,and the cation exchange capacity decreased continuously.There is no significant difference between slopes.Among them,elevation and slope position have a great influence on the distribution of soil clay content and cation exchange capacity,while other site factors have no effect on it.