Influencing Factors And Spatial Patterns Of Soil Nutrients In Hickory Forest

In terrestrial ecosystems,soil nutrients play a main control function in tree growth and nutrient cycling,and the detailed information of the spatial distribution of their contents is crucial for soil nutrient maintenance.In this study,the effects of climate,topography,parent material,stand structure and management measures factors on the contents of soil macronutrients(soil organic carbon(SOC),hydrolyzed nitrogen(HN),available phosphorus(AP)and available potassium(AK))and micronutrients(manganese(Mn),zinc(Zn),copper(Cu)and calcium(Ca))in 382 plots(312 Tianmu Mountain plots and 70 Dabie Mountain plots)at a depth of 0-30 cm were analyzed,taking the Carya cathayensis forest and the Carya dabieshanensis forest as the research objects.The key factors controlling the change of soil nutrient contents were revealed and the spatial patterns of soil nutrients were explored.The major results are as follows.(1)Effects of climate,topography,parent material,stand structure and management measures on soil nutrient contents.The contents of soil organic carbon,hydrolyzed nitrogen,available phosphorus,available potassium and zinc decreased with the augment of mean annual temperature and increased with the augment of mean annual precipitation.Soil manganese,copper and calcium were significantly positively associated with mean annual temperature and negatively associated with mean annual precipitation.The change order of soil macronutrients and micronutrients contents on different slopes was as follows:flat slope>gentle slope>slope.There were different variations in soil nutrient contents in diverse aspect.There were obvious differences in the contents of soil macronutrients and micronutrients in the soils developed from seven parent materials.Stand age,stand density,fertilization times and weeding times also had certain effects on soil nutrients.(2)Random forest was used to analyze the importance of variables in Tianmu Mountain plots,Dabie Mountain plots and their total plots data,respectively.The results showed that mean annual temperature and mean annual precipitation were the key factors driving the contents of soil macronutrients and micronutrients of hickory forest.Mean annual temperature was the primary factor affecting soil organic carbon,hydrolyzed nitrogen,available potassium,manganese and calcium contents.Mean annual precipitation was the primary factor affecting soil zinc content.Parent material was another important factor affecting soil nutrient content,especially soil available phosphorus and micronutrients.Parent material was the primary factor affecting soil available phosphorus and copper contents,and was the second important factor affecting soil manganese,zinc and calcium.(3)Based on Determination coefficient(R~2),Root mean square error(RMSE),Meanabsolute error(MAE)of random forest,it was found that the model using total plots data had the best prediction effect.On this basis,the spatial distribution of soil nutrients of hickory forest in Tianmu Mountain and Dabie Mountains was plotted respectively.It was found that the soil nutrient contents of hickory forest in Dabie Mountain were generally higher than those of hickory forest in Tianmu Mountain,especially soil organic carbon,available phosphorus and copper.The contents of soil organic carbon,available phosphorus and copper in hickory forest of Dabie Mountain ranged from 20.17-43.94g/kg,9.12-34.00mg/kg and 1.89-5.63mg/kg,respectively.The soil organic carbon,available phosphorus and copper of Tianmu Mountain hickory forest were only 17.72-25.93g/kg,5.57-15.72mg/kg and 0.60-1.35mg/kg.