Stand Increment and Diversity of Understory Species in Cunninghamia lanceolataPlantation Mixed with Different Rare Tree Species

In March 2016, several rare tree species were replanted in 21-23-year Cunninghamia lanceolata plantation, in Jiande Forest Farm ofZhejiang province. In October 2021, permanent sample plots of plantation with 5 different distribution patterns were established for determination ofstand increment. The result showed that DBH, tree height and crown width growth of C. lanceolata in the sample plots were higher than that in the control (pure C. lanceolata plantation). There were obvious differences in the growth of rare tree species among different distribution patterns. MeanDBH, mean height and crown diameter growth in sample plots of C. lanceolata-Taxus wllichiana var. mairei-Phoebe chekiangensis-C. japonicum, C.lanceolata-Phoebe zhennan had the largest value, 4.57 cm, 3.79 cm, 5.69 m, 3.82 m, 2.14 m and 2.08 m. T. wllichiana var. mairei and Cinnamomumjaponicum had the best stem form, with the rate of 90%-100%. Understory species diversity was ordered by stand of C. lanceolata-T. wallichiana var.mairei-Ph. chekiangensis-C. japonicum > stand of C. lanceolata-C. camphora-Ph. chekiangensis-Ph. sheareri > stand of C. lanceolata-Ormosiahosiei ? C. lanceolata-Ph. chekiangensis ? C. lanceolata-Ph. zhennan ? the control.