Soil Quality Changes In The First Rotation Of Cunninghamia Lanceolata Rotating Liquidambar Formosana And Sassafras Tzumu

Chinese fir（Cunninghamia lanceolata）is a unique fast-growing and coniferous timber species in China,and is the highest proportion of plantation trees in southern China.Chinese fir has a pivotal role in China’s plantation forests,and has provided a large amount of timber and other resources for China’s economic development.In order to prevent the decline of soil quality due to continuous planting of Chinese fir and to promote the sustainable development of Chinese fir plantation forests,in this study,the stand growth,soil physicochemical properties,and soil quality of the three stands were analyzed and compared between the rotated plantations of Liquidambar formosana and Sassafras tzumu and C.lanceolata second-generation stands.The main results obtained are as follows.1.The average tree height of the C.lanceolata second-generation forest was lower than those of the plantations of L.formosana and S.tzumu.Similarly,the mean DBH of C.lanceolata second-generation stands was lower than those of the L.formosana and S.tzumu stands.2.Different stands type had significant effects on soil nutrient indicators,in terms of soil physical properties,the rotated plantations of L.formosana and S.tzumu increased soil water content and improved soil physical properties.In addition,the different stands had significant effects on soil chemical properties,such as soil p H,SOC,TP,Mg,NH₄⁺-N,NO₃^--N,DOC,MBC,and MBN（P<0.05）.Among the three soil layers,the soil p H in C.lanceolata second-generation stand was the lowest,indicating that continuous planting of C.lanceolata may accelerate the soil acidification process.Soil SOC,TP,NH₄⁺-N,DOC,MBC,and MBN contents were also the lowest in C.lanceolata second-generation stand,suggesting that rotated L.formosana and S.tzumu plantations could improve some nutrient indicators in the soil.3.The content of soil TP in C.lanceolata second-generation forests was only 0.22-0.23g.kg^-1,which is a low level,indicating that soil TP may be a limiting element in the growth and development of C.lanceolata second-generation forests.By rotation of L.formosana and S.tzumu trees,the content of soil TP was increased to some extent,but the soil TPs in L.formosana and S.tzumu forests were still low,which was probably related to the low level of soil phosphorus in the our study site.4.SQI was averaged over the three soil layers,ranked as:L.formosana stand>S.tzumu stand>C.lanceolata second-generation stand.Continuous planting of C.lanceolata can decline soil quality.In summary,there were differences in stand growth,soil physicochemical properties and soil quality among different stand types.Our results indicate that rotation of broadleaved species plantations such as L.formosana and S.tzumu can promote stand growth,improve soil physicochemical properties and enhance soil quality.