关键词: 崇州林场, 柳杉, 近自然改造, 林分空间结构, 混交度, 大小比数, 角尺度

Abstract:

Pure plantation improvement is an emphasis-field in close-to-nature forest management. This article reports a case of close-to-nature forest improvement in an artificial woods of Cryptomeria fortunei at Chongzhou Forest Farm, Southwestern China. In this investigation, the authors selected some C. fortunei which could be cultivated well as “target trees", and the companion species Cunninghamia lanceolata reserved as “ecological target trees", others surrounding trees were selected-cut as “disturbing trees", due to heterogeneity could be rather improving stand mingling, thereby the stand spatial structure of C. fortunei plantation could be modified optimizingly. It is expected that the paces of turning pure plantation into fixed forest were anticipated to be accelerated. Alteration of the spatial structure of C. fortunei plantation after close-to-nature forest improvement was analyzed in advance by employing four structure parameters: mingling, neighborhood comparison, neighborhood pattern and opening degree. The results showed, the mingling of C. fortunei was improved relatively after thinning, whereas that C. lanceolata was decreased. On the contrary, the neighborhood comparison of C. fortunei and C. lanceolata were both increased. The latter, however, had a more significant increase than the former. As to the distribution of neighborhood pattern, it kept the uniform pattern along before and after the treatment. Opening degree of the two investigated trees were both improved obviously, caused by the distance between each individual being increased after thinning. We access the conclusion that the individual dominant status, the degree of spatial separation, as well as the space sizes occupied by each stem, were ameliorated well after the treatment. The modification was beneficial to both native species invasion and the target stem diameter. Nevertheless, distribution pattern reconstruction was lagged evidently, owing to neighborhood pattern remained uniform pattern after manual thinning. Our study could be instructive to close-to-nature plantation management in terms of the theory and practice aspects.

Key words: Chongzhou forest farm, Cryptomeria fortunei, close-to-nature forest modification, stand spatial structure, mingling, neighborhood comparison, neighborhood pattern