水杉人工林抚育间伐效果比较及其经济效益分析

在水杉人工林内设立标准地，定量机械间伐，定期测定生长量，对其抚育间伐效果及经济效益进行分析，结果表明：（１）不同初植密度的林分采用较小的强度Ｐｎ＝２５％、３３％进行间伐，与对照林分相比，平均每公顷生长量分别提高５．９７ｍ３、９．２７ｍ３，增加９．５７％、１４．８７％；采用较大强度Ｐｎ＝５０％进行间伐，与对照林分相比，平均每公顷生长量下降９．７ｍ３，减少１５．５７％。（２）抚育间伐过的林分（间伐强度Ｐｎ＝２５％、３３％、５０％）与对照林分相比，单位面积保留木平均生长率分别提高１．３４％、２．００％、１．９７％。（３）抚育间伐的林分与对照林分相比，平均每公顷总产值和利润分别增加６２７８元、５７８４元，增长７．７％、９．５％。

IMPACTS OF THINNING ON THE VOLUME INCREMENT AND REVENUES REVENUES OF METASEQUOIA GLYPTOSTROBOIDES PLANTATIONS

In this Paper, authors have established experimental plots of quantitative mechanical thinning and also measured periodically the volume increment of thinned stands in order to investigate impacts of thinning on the growth and revenues of Metasequoia glyptostroboides plantations. The main results could be briefly described as follows: (1)The average volume increment of stands with low thinning intensities of 25% and 33% increased by 5.97 m 3 and 9.27 m 3 per hactare (or accounted for 9.57% and 14.87% of the total volume) respectively compared with control stand. However, that with a heavy thinning intensity of 50% decreased by 9.7 m 3 per hactare (or accounted for 15.57% of the total volume). (2)The mean growth rates of maintained trees with three thinning intensities described above increased by 1.34%, 2.00% and 1.97% respectively in comparison with non thinning control stand. (3)The total production value and net revenue of the thinned stands increased by 6 278 yuan and 5 784 yuan per hactare (or accounted for 7.7% and 9.5% of the total revenue ) respectively.