Spatial Distribution Characteristics Of Soil Nutrients And The Influencing Factors In Huoditang Of Qinling Mountains

Qinling is an important ecological function region in China that has many animal and plant species.It is a crucial region for studying material accumulation and nutrient circulation in forest ecosystems.forest soil is essential to all forest resources.Huoditang is located on the southern slope of Qinling Mountains.It is representative and it is an ideal region to study various types of ecosystems in a small research area.Analyzing spatial distribution characteristics of soil nutrients and the influencing factors is beneficial to not only properly assess the service functions of regional ecosystems,but also promote biodiversity conservation and high-quality development.Geostatistics combined with GIS and classical statistics were used to discuss the spatial pattern of soil total carbon(TC),total nitrogen(TN),total hydrogen(TH),total sulfur(TS),available potassium(AK),available phosphorus(AP)and their influencing factors.This research also discussed the optimal interpolation method and optimal sampling number in Huoditang forest region of Qinling Mountains so that to further clarify the Qinling Mountains landscape pattern and forest ecosystem and to provide relevant theoretical support.The main results are as follows:(1)The soil nutrients in Huoditang forest region of Qinling Mountains all showed moderate variation,it indicated that the spatial distribution of each element was uneven and all had strong spatial heterogeneity.The order of variation degree of soil nutrients in the study area was AK>TC>AP>TS>TN>TH.(2)The semivariance function analysis showed that the nugget ratio of all soil nutrient elements in the study area was less than 0.25 and all showed a strong spatial correlation.The best semi-variance function fitting models for TC,TN,and AK in the forest area were all Gaussian model,TH and TS were spherical model,and AP was exponential model.(3)After used five spatial interpolation methods to predict the spatial distribution of soil nutrients in the study area and verified the accuracy,it was found that the optimal interpolation method for soil TC,TN,TH,TS and AP were ordinary kriging,and the optimal interpolation method for AK was radius basis function.The distribution patterns of TC and TN in Huoditang region were similar,with high distribution content in northwest and northeast,and low in the east and west.Approximately 90 percent of TN in the study area reached the level of primary nutrients,indicated that the content of TN was rich in the study area.The content of TH was low in the east and west,and high in the northwest,followed by the northeast,central and south.TS was generally low in the east and west and high in the south,with large patches in the low content areas.AK showed a pattern of relatively high content levels in the central,eastern,and northeastern regions,and low in the northern and southeastern regions.AP had an area with a high content in the center of region.It is surrounded by an area where the content gradually increased from the center to the boundary,which could be approximated as a ring,and the AP content was lower between the ring and the center.(4)As the quantity of samples in the study area decreased,the range of soil nutrients content was reduce and the spatial autocorrelation gradually weakened.The correlation coefficient of the semivariogram model was reduced and the model fitting effect became worse.All in all,the number of soil samples for TC,TN,TH,TS and AK in the study area should be no less than 116,and AP should be no less than 143.Generally,the optimal sampling number of soil nutrient elements in the Huoditang forest area should be no less than143.(5)There was a general correlation among soil nutrients in the study area.There was no significant correlation between soil nutrients and mean annual precipitation or mean annual temperature.Soil nutrients and topographical factors such as altitude,slope and aspect had a significant correlation.It showed that as the altitude increased,the content of soil nutrients increased.And the content in the northern slope was higher than that in the southern slope.As the slope increased,the content of each soil nutrient showed a decreasing trend,and the difference was significant among different slopes.The performance of soil nutrients was also different under different forest types.TC,TN,TS,AK and AP differed significantly among different forest types,while TH was not significant among different forest types.On the whole,the content of soil nutrients of Quercus aliena var.acuteserrata forest was the least,and Pinus armandii and Pinus tabulaeformis forests were higher.