| The forest soil ecosystem contains rich biological resources,which interact with each other and have multiple functions such as promoting nutrient cycling,regulating climate,and maintaining ecological stability.However,in recent years,it has suffered from various pollutants such as organic pesticides,heavy metals,and microplastics.Soil quality continues to deteriorate and ecological function levels continue to decline.In order to curb the further spread of pollutants,China has carried out long-term soil monitoring work.Currently,heavy metal elements,organic pesticides and polycyclic aromatic hydrocarbons are mainly measured by setting risk screening values and control values.However,the problem of soil pollution prevention and control is not limited to this.We need to explore potential issues from the perspective of ecological function and incorporate biotechnology into the environmental monitoring system.This is the development trend of future soil environmental quality monitoring.Soil biology is an important component of soil that flows energy and exchanges materials with the environment;it is a potential evaluation indicator for assessing ecological status.This study selected Chongqing as a research area;screened out a set of biological indicators suitable for forest soils based on their characteristics through literature review and field investigation;established a biological evaluation method through experimental analysis;evaluated the ecological functional status of forest soils in Chongqing.This study conducted investigations on 68 soil sites in 25 districts(counties)of Chongqing.Based on the environmental conditions and relevant literature of the research area,soil enzyme activity,nematode and bacterial biomass,and bacterial diversity were selected as primary indexes representing three functional categories:biological activity,ecological carrying capacity,community structure and function.The final set of forest soil biological indicators was chosen through experimental methods.Coupled with enzyme-linked technology,PCR absolute fluorescence quantification and high-throughput sequencing technology were used to determine whether the experimental data met the requirements of the evaluation method.Spatial interpolation was used to analyze the spatial distribution differences of enzyme activity and biomass in different districts(counties).Bioinformatics analysis was carried out for bacterial diversity including OTU analysis,alpha diversity analysis,inter-group difference analysis,environmental factor correlation analysis and functional prediction model etc.,to investigate the bacterial community structure and function at each of these 68 soil sites.After processing the experimental data of various indicators using mathematical models,11 secondary indexes were finally determined and the correlation analysis was conducted among them.The results showed that there were mutual relationships between the biological indicators and each indicator met the requirements of the biological evaluation method.Finally,a forest soil biological indicator system was proposed,and AHP hierarchical analysis method,principal component analysis method and entropy value method were used to optimize primary and secondary indicators by assigning different weight values to obtain an optimized forest soil biological evaluation method.After further normalizing the data of 11 biological indicators,comprehensive evaluation index was used to calculate the comprehensive evaluation index for 68 sampling points.According to their scores on comprehensive evaluation index,ecological functional status was classified as follows: two sampling points had excellent ecological function status;six had good ecological function status;thirty-two had moderate ecological function status;twenty-four had poor ecological function status;four had very poor ecological function status.Finally,based on the comprehensive evaluation index score,spatial interpolation analysis was conducted to visualize the ecological function status of 25 districts(counties)in Chongqing.The areas with good and poor ecological function status were identified.It can be concluded that biological assessment methods can scientifically analyze the soil environment of forest land,where different biological indicators play different roles in ecological functions.This method can be an important technology for future soil environmental monitoring.Meanwhile,correlation analysis was established between environmental factors collected on-site and experimentally determined biological indicators.The study found that altitude,cation exchange capacity,p H value and different biological indicators have certain correlations.However,forest soil is a complex ecosystem affected by various environmental factors and human interference which provides feasible ideas for future large-scale spatial comprehensive research.This study has significant implications for addressing forest soil pollution problems and extreme climate change. |
