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In order to explore the characteristics of soil enzymes and their relationship with physicochemical properties in forest soils of Beijing mountainous area and further evaluate their fertility levels,the activity and kinetic characteristics of enzymes（urease,polyphenol oxidase,peroxidase,catalase） were studied in different soil layers under four kinds of.broad-leaved forests（Robinia pseudoacacia, Castanea mollissima,Quercus dentata,mixed Betula platyphylla-Populus davidiana） and four kinds of coniferous forests（Larix principis-rupprechtiii,Platycladu sorientalis,Pinus bungeana,Pinus tabulaeformis） and Vitex negundo forest.The study area is located in Beijing Wulin Mountain, Shisanling Region and Miyun Reservoir.Correlation analysis and principal component analysis（PCA） were used to reveal the relationship between soil enzymes and soil physicochemical properties.The results showed that the activity,Vo,Vmax and Vmax/Km of urease and catalase decreased with the increase of soil depth,but Km varied irregularly with soil depth.The reactive initial velocity（Vo） increased with the increase of substrate concentration,the parabola of enzyme（urease,polyphenol oxidase,peroxidase） substrate concentration-reactive initial velocity function was smooth,but which of catalase looked like "M".The parameters of soil enzymes varied in different forest types,indicating different characteristics of soil enzyme reaction.For broad-leaved forests,soil enzymatic reactions of urease and catalase under mixed B.platyphylla-P.davidiana plantation were characteristic,polyphenol oxidase and peroxidase were opposite;urease and polyphenol oxidase of R.pseudoacacia were better than peroxidase and catalase;except urease,the three other enzymes of Q.dentate plantation performed better.Indicators of catalase under C.mollissima plantation at the highest level.For coniferous forests, the performance of soil urease and catalase under L.principis-rupprechtiii were better than polyphenol oxidase and peroxidase;the activities of soil urease,catalase and polyphenol oxidase under p.orientalis were higher than other plantations,while the kinetic characteristics not;the performance of peroxidase under P.tabulaeformis plantation was best.The soil physicochemical properties varied in different forest types,the whole conditions of mixed B.platyphylla-P.davidiana and L.principis-rupprechtiii were best.The activity,Vmax and Vmax/Km of urease and catalase had significant correlations with soil organic matter content,total nitrogen content and other physicochemical properties,thus the activity, Vmax and Vmax/Km of urease and catalase can be used to indicate soil fertility levels,while those of polypenol oxidase and peroxidase can not.The integrated scores from PCA suggested that the soil fertility levels of different forests:mixed B.platyphylla-P.davidiana,R.pseudoacacia and L.principis-rupprechtiii at the highest level,followed by V.negundo,C.mollissima,P.orientalis and P. bungeana at the middle level,Q.dentate and P.tabulaeformis were lowest.
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