滇西北金沙江流域云南红豆杉群落种内与种间竞争

Intra-and interspecific competitions of Taxus yunnanensis population in Jinsha River Basin of northwest Yunnan Province,Southwest China

通过对滇西北金沙江流域云南红豆杉群落45株对象木及205株竞争木的调查,运用Hegyi的单木竞争指数计算了濒危保护植物云南红豆杉的种内和种间竞争强度。结果表明:云南红豆杉的种内竞争强度随径级的分布呈偏峰曲线,径级在5～10cm时最大,然后随径级的增加竞争强度呈减少的趋势;云南红豆杉的种间竞争强度(133.61)显著高于其种内竞争强度(76.88),其竞争压力主要来自于种间竞争;云南红豆杉的物种种内种间竞争强度大于丽江铁杉、亮叶杜鹃、红桦、川杨、川滇高山栲、少毛云南楤木等当地常见乔木物种,它们的竞争强度都在5以上;云南红豆杉与整个林分及伴生树种的竞争指数与对象木的胸径之间呈显著负相关,且均服从幂函数关系(CI=aDb),对象木胸径越大,其竞争压力越小。

Based on the investigations of 45 objective trees and 205 competitive trees of Taxus yunnanensis population in the Jinsha River Basin of northwest Yunnan Province and by using He gyi＇ s singletree competition index model, this paper analyzed the intra and interspecific compe tition intensities of endangered plant T. yunnanensis. The intraspecific competition intensity of T. yunnanensis decreased with its increasing diameter at breast height （DBH） , presenting a par tial peak curve, whereas the intraspecific competition intensity of T. yunnanensis was the highest at its DBH 510 cm, and then showed a decreasing trend with the increase of the DBH. The in terspecific competition intensity （ 133.61 ） of T. yunnanensis was significantly higher than the in traspecific competition intensity （76.88）, indicating that the competitive stress of the T. yun nanensis population was mainly come from interspecific competition. The intra and interspecific competition intensities of T. yunnanensis were larger than those of the local common tree species Tsuga forrestii, Betula albosinensis, Populus szechuanica, Quercus aquifolioides, and Aralia thomsonii var. glabrescens, with the competition indices being 〉5. The competition index of T. yunnanensis with the objective trees in the whole forest stand was significantly negatively correla ted with the DBH of the objective trees, and nearly conformed to power function （CI=aDb）. The larger the DBH of the objective trees, the smaller the competitive stress of the T. yunnanensis population.