19a生半天然杉阔混交林乔木层层次结构分化明显,应用最大受光面法可将乔木层明显划分为2个亚层,第Ⅰ亚层树高≥13.0 m。林分平均胸径13.7 cm,平均树高14.6 m,株数密度2 867株/hm²,单位面积蓄积量309.7 m³/hm²。第Ⅰ亚层和第Ⅱ亚层的平均胸径分别为17.1 cm和10.3 cm,平均树高分别为16.4 m和10.6 m;第Ⅰ亚层和第Ⅱ亚层的株数分别占全林的43.60%和56.40%,单位面积蓄积量分别占全林的74.98%和25.02%。乔木层共有17种树种,杉木占绝对优势,重要值为61.88%;第Ⅰ亚层有8种树种,第Ⅱ亚层有17种树种,杉木在第Ⅰ亚层和第Ⅱ亚层均占绝对优势,重要值分别为76.20%和58.31%。乔木层物种丰富度S、多样性指数SW、均匀度E和生态优势度ED分别为17,1.46,0.36和0.62,其中第Ⅰ亚层分别为8,0.83,0.28和0.78;第Ⅱ亚层分别为17,1.80,0.44和0.51。

The tree stratum of 19 year-old semi-natural forest of Cunninghamia lanceolata and broad-leaved trees was stratified obviously to 2 sub-strata (sub-stratum I and sub-stratum II) by MLRP (Maximum Light Receiving Plane) method.The tree height in sub-stratum I was higher than or equal to 13.0 m.Its average stand DBH,height,density and growing stock in tree stratum were 13.7 cm,14.6 m,2 867 N/hm² and 309.7 m³/hm² respectively.Its average stand DBH in sub-stratum I and sub-stratum II were 17.1cm and 10.3 cm respectively.Its average stand height in sub-stratum I and sub-stratum II were 16.4 m and 10.6 m respectively.Its percentage of stand density in sub-stratum I and sub-stratum II were 43.60% and 56.40% respectively.Its percentage of growing stock in sub-stratum I and sub-stratum II were 74.98% and 25.02% respectively.There were 17 tree species in tree stratum and C.lanceolata was the absolutely dominant tree species,with the important value of 61.88%.There were 8 and 17 tree species in sub-stratum I and sub-stratum II respectively.The important value of C.lanceolata (the absolutely dominant tree species) in sub-stratum I and sub-stratum II was 76.20% and 58.31% respectively.Its species richness (R),Shannon-Wiener index (SW),evenness (E) and ecological dominance (ED) in tree stratum were 17,1.46,0.36 and 0.62 respectively,which in sub-stratum I was 8,0.83,0.28 and 0.78 respectively.And the value in sub-stratum II were 17,1.80,0.44 and 0.51 respectively.