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Scientia Silvae Sinicae ›› 2015, Vol. 51 ›› Issue (4): 8-15.doi: 10.11707/j.1001-7488.20150402

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Impacts of Different Thinning Intensities on Growth of Cupressus funebris Plantation and Understory Plants

Gong Gutang1, Niu Mu2, Mu Changlong1, Chen Junhua1, Li Yanqiong1, Zhu Zhifang1, Zheng Shaowei1   

  1. 1. Sichuan Academy of Forestry Chengdu 610081;
    2. College of Forestry, Beijing Forestry University Beijing 100083
  • Received:2014-05-19 Revised:2014-11-30 Online:2015-04-25 Published:2015-05-20

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Abstract:

【Objective】 Aimed at the problems of high stand density, poor timber productivity, low coverage of understory vegetation and poor natural regeneration of Cupressus funebris plantation in hilly areas in central Sichuan, a thinning experiment was carried out to analyze the impacts of different thinning intensities on the stand growth and the understory plants and to provide guidance for managing eco-economic protection forests in the region. 【Method】 A 25 years old cypress plantation was used for the experiment, four thinning intensities (20%-25%, 15%-20%, 10%-15%, and control) were used with a randomized block experimental design. DBH, height, volume, biodiversity, and number of naturally regenerated seedlings were measured to determine their responses to different thinning intensities.【Result】The results indicated that the mean stand DBH and current annual increment (CAI) of DBH were significantly different among various thinning intensities, and a higher thinning intensity led to a higher DHB increment. The maximum mean height (10.7 m) occurred in stands with 20%-25% thinning intensities, but not significantly different from those of thinning intensity of 15%-20% and 10%-15%.However, significant differences were found in the height CAI among the four thinning intensities. Standing volume was 97.35, 93.43, and 93.19 m3 ·hm-2 respectively in stand with thinning intensity of 20%-25%, 15%-20%, and 10%-15%, and were lower than that of the control. But the volume CAI was 6.11, 4.58, and 3.66 m3 ·hm-2a-1 respectively and higher than that of the control. The Simpson index of shrubs and herbs for stand thinned at 20% -25% was 0.769 5 and 0.444 6, Shannon-Wiener index was 1.702 5 and 0.769 0 respectively, and the values of both indices were higher than that of the other thinning intensities. The number of naturally-regenerated seedlings was significantly different among different thinning intensities only for seedlings of 5-30 cm in height, but no significant differences for seedlings of 30-50 and 50-150 cm height classes. A comprehensive evaluation showed that the highest score was found for the thinning intensity of 20%-25%, and the total score decreased with the lowering of thinning intensity. 【Conclusion】The growing space and nutritional condition were effectively improved for the retained trees after thinning, stand DBH and height were increased with the increase of thinning intensity. However, the stand volume was not significantly different among the four thinning intensities. Besides, thinning at appropriate intensities can increase the biodiversity indices of shrubs and herbs, the quantity of naturally regenerated seedlings also increased with the increase of thinning intensity. 20%-25% was the better one among the 4 thinning intensities for silvicultural interventions for the middle aged cypress plantation in the region.

Key words: thinning intensity, Cupressus funebris plantation, stand growth, biodiversity, natural regeneration

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