Evaluation Of Forest Soil Properties And Its Spatial Distribution In Luoding,Guangdong Province

Forest soil is an important part of the forest ecosystem.The quality of forest soil had an important influence on forest growth,forest quality,and forest ecological environment.Analyzing the fertility and the heavy metal pollution level of forest soil is of great significance for improving forest quality,promoting forest regeneration,and achieving sustainable development of forest ecology.In this paper,Luoding City,Guangdong Province was taken as the research area.Eight kinds of forest stands,including mixed broadleaf-conifer forest,coniferous forest,broad-leaved forest,Cunninghamia lanceolata plantation,Acacia plantation,Eucalyptus urophylla plantation,Pinus massoniana plantation and economic forest were chosen,and their bulk density,porosity,water content,nutrient elements,and heavy metal elements content and their correlations in 0¹0cm depth of soil were analyzed.And the soil fertility quality and heavy metal pollution levels were comprehensively accessed.Finally,the ArcGIS technology was used to explore the spatial distribution characteristics of forest soil properties.The main results were as follows:?1?The soil texture of the eight forest stands were loam soils.These soils had good soil water permeability and aeration.There were not significantly different in,the bulk density and the total porosity among these soils.The largest porosity,non-capillary porosity,aeration porosity,and capillary water capacity was found in the soil of Cunninghamia lanceolata plantation?46.26%?,economic forest?11.24%?,Eucalyptus urophylla plantation?24.40%?,and Cunninghamia lanceolata plantation(378.3 g·kg^-1),respectively.?2?The pH values of soils in all stands were lower than 4.5,showing strong acidity.In these soils,the content of soil organic matter was 25.2³2.48 g·kg^-1,the content of alkaline hydrolysis nitrogen was 106.31¹40.20 mg·kg^-1,the range of available phosphorus was1.33².35 mg·kg^-1,and the range of available potassium was 56.61⁹1.27 mg·kg^-1.In particular,the organic matter content and available nutrients in the coniferous mixed forest were lower than those of other forest stands.The contents of organic matter,available potassium,and alkali-hydrolyzable nitrogen of the economic forest were significantly higher than those of other forest stands.?3?Correlation analysis showed that the bulk density was significantly negatively correlated with natural water content,capillary water holding capacity,total porosity,capillary porosity,non-capillary porosity,soil porosity,organic matter,available potassium,and available nitrogen.There was a significant positive correlation between pH?H₂O?and organic matter.There was a significant positive correlation between organic matter and available phosphorus,available potassium and aavailable nitrogen.The soil was highly significantly positively correlated with soil pH?KCl?,and it was extremely polar with available potassium.?4?Through the comprehensive evaluation of the soil fertility quality of eight forest stands,it was found that the forest soil fertility in Luoding County was moderate.The order of soil fertility quality among the forest stands was:Cunninghamia lanceolate plantation?0.544?>economic forest?0.500?>mixed broadleaf-conifer forest?0.493?>Acacia plantation?0.474?>broad-leaved forest?0.473?>Pinusmassoniana plantation?0.467?>Eucalyptus urophylla plantation?0.463?>coniferous forest?0.430?.In the pure forest,the best soil fertility was found in the Cunninghamia lanceolate plantation,and the lowest was in Eucalyptus urophylla plantation.In the mixed forests,the soil fertility in the economic forest was the best,and the coniferous forest had the lowest score.?5?The results of soil heavy metal analysis in eight stands showed that the contents of Pb,Zn,Ni,Cr,and Cu in the study area did not exceed the soil background values of Guangdong province,and the overall level was at a clean level.Taking the soil environmental background value of Guangdong Province as the reference value,Cu was the early warning level,and the single pollution index of Zn,Pb,Cd,Ni was the clean level;the order of Nemero integrated pollution levels among the eight kinds of forests was:Broad-leaved forest>coniferous forest>Pinus massonianaplantation>Cunninghamia lanceolate plantation=economic forest>Eucalyptus urophylla plantation=broad-leaved forest>Acacia plantation.And eight species of forest stand all belonged to the degree of minor ecological hazards,sorts from the largest to the lowest:coniferous and broad-leaved forest>economic forest>Cunninghamia lanceolata plantation>broad-leaved forest>Pinus massoniana plantation>Eucalyptus urophylla plantation>coniferous forest>Acacia plantation.?6?Based on ArcGIS,inverse distance weight interpolation for soil fertility status and heavy metal pollution level in Luoding County.Results showed that the spatial distribution of forest soil fertility quality in Luoding County was generally higher in the west,lower in the east,and gradually decreases from west to east.The soil fertility quality scores in the northern part of the attached town,Linbin Town,Silun Town,Demarcation Town,South of Luojing Town,and South Jinji Town were higher than 0.5;soil fertility in Pingtang Town and Langtang Town were relatively poor.The spatial distribution of heavy metal pollution in forest soils in Luoding County were generally as follows:slight pollution in the southwest and northeast,and cleanliness in the south and north.Minor pollution was mainly concentrated at the junction of Longwan Town,Pingtang Town and Jinji Town,and south of Fenjie Town.