The Study On The Changes Of Soil Fertility In Coniferous Forest With Age And Silvicultural Measures Of Shanxi Taiyue Mountain

In this study,6 forest types(40-year,60-year and 80-years of Pinus tabulaeformis plantation,40-year of selective cutting Pinus tabulaeformis plantation,40-years of Larix plantation,40-year Pinus tabulaeformis and Larch mixed forest)were regarded as the research objects,through the stratification of the 6 forest types of soil sampling and analysis,the physicochemical and biological properties of soil of different forest types,including soil moisture content,soil bulk density,organic matter,total nitrogen,ammonium nitrogen,nitrate nitrogen,available potassium,available phosphorus,microbial biomass carbon and nitrogen of 10 kinds of index,and relying on the different types of on the evaluation of soil quality.The aim is to provide an important scientific basis for the management and development of forest and the sustainable utilization of forest soil resources.The results are as follows:Selective cutting measures reduce soil moisture content in the surface layer of Pinus tabulaeformis and increase the soil bulk density.After selective cutting,the soil nutrients(total nitrogen,nitrate nitrogen,ammonium nitrogen,organic matter,available potassium content)showed an overall upward trend,only to reduce the total phosphorus content,original Pinus tabulaeformis plantation soil microbial biomass carbon and nitrogen were higher than those of the non-selective cutting,comprehensive index of selective cutting soil was 0.533,selective cutting was 0.467.Thus,soil quality is better in selective forest.The order of soil bulk density of different forest age of Pinus tabulaeformis plantation is:40 years>60 years>80 years.The order of soil moisture content is:60 years>80 years>40 years.The content of total nitrogen,ammonium nitrogen,nitrate nitrogen,available potassium and available phosphorus increased with the increase of forest age,and there was a significant difference between some data.The content of MBC and MBN of Pinus tabulaeformis Plantation in 80 years was higher than that of 40 and 60 years,among which the content of MBN was significantly different.The comprehensive index of soil quality of the three plantations were 0.363,0.500 and 0.568.Therefore,with the increase of stand age,the soil quality evaluation index increased gradually.The soil moisture content of different forest types is:Larix pure forest>mixed forest>Pinus tabulaeformis pure forest.Soil bulk density is:Larch pure forest>Pinus tabulaeformis pure forest>mixed forest.The content of total nitrogen,organic matter,ammonium nitrogen and available phosphorus content in the soil of the mixed forest of Pinus tabulaeformis was the highest,and the content was the lowest in the pure forest of Pinus tabulaeformis.The trend of nitrate nitrogen content in general is Pinus tabulaeformis pure forest>Larix pure forest>mixed forest.The content of available potassium in the soil of the two species of mixed forest was significantly greater than that of the pure Larix Larix forest.The order of MBC content is:Larix pure forest>Pinus tabulaeformis pure forest>mixed forest.In 0-20cm soil layer,MBN content of three forest types is:Larix pure forest>Pinus tabulaeformis pure forest>mixed forest.The soil quality index as follows:mixed forest(SQI=0.53),Larix(SQI=0.48),Pinus(SQI=0.40),thus the optimal soil synthetic quality of mixed forest,followed by pure larch,Pinus tabulaeformis pure forest is the lowest.