Analysis on classified stem transformation characteristic of Larix gmelinii natural forest at Daxingan Mountains
大兴安岭兴安落叶松(Larix gmelinii)天然林分级木转换特征

On the basis of setting sample plots and making trunk analysis, this study analyzed the transformation characteristics in different classified stems structures (dominant stem, average stem and overtopped stem) of Larix gmelinii natural forest. The results show : (1) each different structure of L.gmelinii classified stems has different transformation age, direction and transformation rate. The transformation rate of L.gmelinii classified stems is 29.4%, where dominant stem, average stem and overtopped stem are 35.3%, 41.2% and 11.8%. In the transformation rates of classified stems, the interconversion proportion between dominant stem and average stem is high, from dominant stem to average stem is 83.3% and from average stem to dominant stem is 85.7%; from dominant stem to overtopped stem is only 16.7%, the transformation from overtopped stem to dominant stem is not observed, while the transformation from overtopped stem to average stem is observed, 88.2% of overtopped stem has no transformation to other classified stems, considering management and tending of forests those overtopped trees should be removed. (2) The stand age is within 36-65a, the transformation rate tends to increase, as the stand gets old. When the ages are within 30-39a, 50-59a and 60-69a, the transformation rates are 0, 33.3% and 46.7%. (3) The transformation rate of classified stems tends to increase with the stand density increment. When the stand density is up to 2,500 trees·hm-2, the main transformation appears between dominant stems and average stems. When the stand density is over 2,500 trees·hm-2, transformed phenomenon between overtopped stem and other classified stems appears. (4) According to forest types, the transformation rate and direction are different. The transformation rates of Herbage-Larix gmelinii and Ledum-Larix gmelinii are 50% and 9.5%. (5)The horizontal stands patterns show that the transformation rate of classified stems is different. The transformation rates of clustered distribution and random distribution are 61.1% and 13.3%.