Analysis And Evaluation Of The Coupling Relationship Between Vegetation Restoration Model And Soil Quality At Baihetan Hydropower Station

The construction activities of water conservancy and hydropower projects have brought huge econoric benefits,but also produced a large number of geotechnical slag dump,which affects the ecological environment and social healthy development of the project construction site.Therefore,according to the specific conditions of the durp site of hydropower station,it is of great significance to carry out the study of vegetation restoration optimization to promote the restoration and reconstruction of the ecological environment of hydropower station.In this paper,the slag dump of Baihetan Hydrop ower Station is selected as the experimental area to carry out the coupling test of vegetation restoration and soil quality.Based on plant investigation,dominant plants were selected and 24 different vegetation restoration modes were set up to analyze and study the interaction effects of plant growth characteristics and soil chemical and biological properties.Finally,based on comprehensive evaluation and analysis,vegetation types and allocation modes suitable for vegetation restoration in the study area were optimized.The main research results are as follows:(1)Through vegetation survey,there were 41 species of shrub seed plants,belonging to 24 families and 39 genera.Four kinds of shrub and herb were selected,and 24 restoration modes were set.The vegetation coverage and plant height of shrub-grass combinatton were better than that of single vegetation restoration model;the herbaceous vegetation restoration pattern had the highest growth rate of 1.599%/d for Cynodon dactylon(L.)Pers.and the highest root length and total biomass of 26.9cm and 6.21g·plant-1 for Medicago sativa L.,respectively;the shrub vegetation restoration pattern had the highest growth rate(0.419cm/d),root length(44.9cm)and total biomass(195.49g·plant-1.)were the highest.(2)In herbaceous vegetation restoration mode,the water content of Cynodon dactylon(L.)Pers.was the highest in all soil layers,which was 4.068 times and 4.017 times of that in the control group.Soil pH showed a decreasing trend,and the whole soil in the study area was alkaline or neutral;the contents of soil nutrients such as alkali-hydrolyzed nitrogen,available phosphorus,available potassium and organic matter were increased compared with those in the bare soil,and the content differences were significant,among them,the content of alkalihydrolyzed nitrogen(75.315mg/kg)and organic matter(22.57g/kg)was the highest in Crotalaria pallida Ait.+Paspalum notatum Flugge,the highest available phosphorus content was found in Crotalaria pallida Ait.+Trifolium repens L.(22.986mg/kg),and the highest available potassium content was found in Dodonaea viscosa(L.)Jacq.+Cynodon dactylon(L.)Pers.(67.02mg/kg).(3)Soil enzyme activity in different vegetation restoration modes was higher than that in bare land,and the improvement effect was different.The soil urease,phosphatase,sucrase and catalase activities were the highest in all soil layers of the shrub and grass combination vegetation restoration model of Crotalaria pallida Ait.+Cynodon dactylon(L.)Pers.,and the soil bacterial diversity and evenness index of Crotalaria pallida Ait.+Cynodon dactylon(L.)Pers.were the highest;Proteobacteria was the most abundant phylum,accounting for 23.64%～41.02%,followed by Acidobacteria,accounting for 5.31%～18.58%;The dominant soil bacteria was Sphingomonas.In addition,microbial diversity was affected by organic matter and soil enzyme activity.(4)According to the comprehensive score of soil quality by principal component analysis,among the different vegetation restoration modes,the combination mode of Crotalaria pallida Ait.+Paspalum notatum Flugge has the best effect on soil quality improvement,followed by Crotalaria pallida Ait.+Cynodon dactylon(L.)Pers.,and then Dodonaea viscosa(L.)Jacq.+Cynodon dactylon(L.)Pers.and Crotalaria pallida Ait.+Trifolium repens L.(5)The results of sub-systems S(x)and P(y),S(x)/P(y)、CSP and DC were the highest among different vegetation restoration models in the combined shrub and grass vegetation restoration model of Crotalaria pallida Ait.+Cynodon dactylon(L.)Pers.and Crotalaria pallida Ait.+Paspalum notatum Flugge.Both of them were highly coordinated soil vegetation synchronization model.Based on the comprehensive evaluation of grey relational degree theory,the optimal vegetation allocation scheme of the study area was determined to be Crotalaria pallida Ait.+Cynodon dactylon(L.)Pers.and Crotalaria pallida Ait.+Paspalum notatum Flugge.