Title Measuring mortality of different species stump with DBH in anaturally regenerated clearcut subtropical forest

Within the framework of a series of forest recovery researches of a subtropical evergreen broadleaved forest, this study was carried out to measure mortality rates of tree stumps changed by species diameter at breast height (DBH) based on the surveys of 62 woody species and 1,893 tree stems taller than 1.2 m in four 20 m X 10 m plots were recorded in 1993. At an August 1998 tree census five years after clearcut, all sprouting stems higher than 1.0 m were identified, and the statuses of all the residual stumps were checked. The investigation showed that 382 stumps were dead without any living sprouts whereas 1,511 stumps were survived with living sprouts. The further studies showed that the mortality rates of stumps did not vary with DBH of the stand, but vary with the species DBH remarkably. The mortality rates by stump DBH within species for these whose total stump numbers ^10 stems in the study plots were divided into four patterns: (a)With the increasing DBH, the mortality rates increased, (b) Inversely, with the increasing DBH in a certain extent, the mortality rates decreased, (c) With an increasing DBH, the mortality rates decreased at first and then increased to some extent, (d) The mortality rates were independent of DBH. The above results suggested that different species might have different mortality patterns, and that different tree species might have different rational DBH ranges for sprout natural regeneration. This knowledge could be much useful for forest recovery forecasting when the severe forest disturbances occurred in subtropical regions.