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Liu Y.-B.,Beijing Normal University | Liu Y.-B.,Institute of Forestry Science | Wang Q.-C.,Northeast Forestry University | Wang C.-Y.,Institute of Forestry Science | And 2 more authors.
Chinese Journal of Ecology | Year: 2012

The decline of the productivity and soil fertility of larch (Larix gmelinii) plantation is an urgently addressed issue in forestry production. Especially for the second generation larch plantation, whether its close-to-nature transformation can improve the soil fertility, soil microbial diversity, and soil nutrient contents is lacked of in-depth study. In this paper, an investigation was made on the effects of close-to-nature transformation of the second generation larch plantation on the soil microbial diversity and structure as well as the soil nutrient contents within two years of the transformation. The results showed that there was a close correlation between gap size and soil microbial diversity. After the first year of transformation, the soil microbial diversity in small gaps (25 m) had a significant increase, with the Shannon index, richness index, and evenness index being higher than those in large gaps (100 m) and the control (no-thinning). In the second year of transformation, less difference was observed in the three indices among the three treatments. The Shannon index and richness index were higher in the first year than in the second year, while the evenness index was in adverse, suggesting that in the first year of transformation, soil microbial diversity was higher but in uneven distribution. The soil microbial genetic similarity in small gaps was similar to that in the control; while in large gaps, this similarity was significantly different from the other two treatments, because of the greater changes of microclimate conditions in large gaps resulting in an intense change in soil microbial diversity. In the first year of transformation, soil nutrient contents had a significant increase. The soil available P content in large gaps was increased by 80%, and that in small gaps was increased by 52%: soil available N content was also increased; while soil available K content had less increase. In the second year, soil nutrient contents were decreased, but the decrements differed between large gaps and small gaps. The soil available P content had a significant decrease in large gaps, but the soil nutrient contents had less decrease in small gaps. This study provided evidences for the feasibility and scientific implementation of close-to-nature forest management.

Xu J.-L.,Zhejiang University of Science and Technology | Xu J.-L.,Institute of Forestry Science | Mao Y.-M.,Zhejiang University of Science and Technology | Zheng C.-Z.,Zhejiang University of Science and Technology | And 5 more authors.
Forest Research | Year: 2014

Effect of thinning intensity (heavy thinning, moderate thinning and unthinning) and times of thinning (thinning once or twice a rotation) on stand growth and timber outturn of Chinese fir (Cunninghamia lanceolata) were studied in Kaihua, Zhejiang Province. The first experiment was to cultivate big-diameter timber stand and thinned in the seventh year and fourteenth year, respectively, while the second experiment was to cultivate middle-diameter timber stand and thinned in the twelfth year. The results showed that there were no significant difference in tree height and total basal area among three thinning treatments in 22-year-old big-diameter timber stand and 19-year-old middle-diameter timber stand. The diameter at breast height (DBH) increased with the increase of thinning intensity. The average DBH value of big-diameter timber stand with heavy thinning and moderate thinning treatments increased by 13.78% and 9.69%, respectively, compared with the unthinned stand, while the DBH of middle-diameter timber stand with heavy thinning and moderate thinning treatments increased by 12.28 % and 7.02%. Thinning significantly increased the stem volume per tree, the living tree volume (LTV) of stand decreased with the increasing thinning intensity in the two experiments. In the first experiment, there was no significant differences in the LTV of 22-year-old stand among three thinning treatments (P≤0.05). In the second experiment, the LTV of 19-year-old stand in the heavy thinning treatment was significantly lower than that in unthinned stand, there was no significant difference in LTV between the moderate thinning treatment and heavy thinning or unthinned treatments (P≤0.05). The total stand volume (TSV) and total wood outturn (TWO) reduced with the increasing thinning intensity in the two experiments, there were no significant differences in TSV and TWO among the three thinning treatments (P≤0.05). It is concluded that thinning intensity can not effectively increase the live tree volume and timber outturn, and the times of thinning has an important effect on timber outturn and timber size. For big-diameter timber cultivation of Chinese fir, twice thinning with 50% thinning intensity is appropriate in a rotation. It is suitable for middle-diameter timber cultivation with once moderate thinning (approximate 25%).

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