研究植物种内、种间竞争关系是探究植物濒危原因的重要方式之一, 根据竞争来源和竞争预测模型可以制定具有针对性的保护策略。本文以雅安周公山峨眉含笑(Michelia wilsonii)野生种群为研究对象, 使用逐步扩大范围法确定峨眉含笑的竞争范围半径, 运用Hegyi单木竞争模型计算竞争指数(competition index, CI), 分析其种内、种间竞争关系。结果表明: 峨眉含笑的最适竞争范围半径是10 m, 能较好地反映其种内竞争强度; 峨眉含笑的竞争压力主要来自种内, 种内竞争指数(348.72, 62.52%)远大于种间竞争指数(209.03, 37.48%); 小树、中树阶段个体的竞争强度较大, 平均竞争指数(3.97、3.14)远高于总体平均竞争指数(2.68); 内有21种竞争木, 其中杉木(Cunninghamia lanceolata)、华中樱桃(Prunus conradinae)、细刺枸骨(Ilex hylonoma)是峨眉含笑的主要竞争树种; 胸径与竞争指数间服从指数函数关系(CI = 3.8907e^-0.048x, R² = 0.1087, P < 0.01), 随着对象木胸径的增大, 竞争指数不断降低, 当胸径达到30 cm后, 竞争强度基本稳定。综上, 小树、中树阶段的峨眉含笑个体受到极强的种内竞争, 初入老树阶段的个体受到较强的种间竞争。为更好地保护峨眉含笑的天然种群, 降低竞争对种群更替的影响, 在林分管理中需要促进小树、中树的个体更新, 减轻植株间的竞争消耗, 加速峨眉含笑的生长和维持种群稳定。

Aims: Competition can affect the growth of individual trees and is a key factor that shapes the structure and drive the dynamic change of forest communities. It plays an important role in population spatial distribution patterns, population dynamics and succession process. For endangered plants, intraspecific and interspecific competition can be driving factors that cause plant mortality. Forestry management departments can formulate targeted conservation strategies based on the predicted competition sources. In order to explore endangered reasons and provide protection measures, the intraspecific and interspecific competition of a wild Michelia wilsonii (yellow lily-tree) population at Zhougong Mountain in Ya’an was studied.

Methods: The intraspecific and interspecific competitive relationship was analyzed, competition radius was determined by gradually extending range method, and competition index (CI) was calculated by using the Hegyi competition model.

Results: A radius of 10 m was the most reasonable competition range of the M. wilsoniipopulation in this study, which best reflects the intensity of intraspecific competition. The mean competition index of individuals in the small and medium diameter class (3.97 and 3.14, respectively) was greater than the total mean competition index (2.68). The competitive pressure of M. wilsonii primarily came from the intraspecies, and the intraspecific competition (348.72, 62.52%) was stronger than that of interspecific competition (209.03, 37.48%). In addition, as the diameter class increased, the intraspecific, interspecific, and total competition indices decreased. This indicated that as M. wilsonii individuals became larger, they were released from competition, and they became a dominant species of the population. The intraspecific and total competition also peaked at 7.5-12.5 cm and 32.5-37.5 cm, respectively, while interspecific competition peaked only at 32.5-37.5 cm. Of the 21 competitive trees in this population Cunninghamia lanceolata, Prunus conradinae, and Ilex hylonoma were the most important. The relationship between diameter at breast height (DBH) and competition index of M. wilsonii was approximately an exponential function (CI = 3.8907e^-0.048x, R² = 0.1087, P < 0.01), with the competition index decreasing continuously with the increase of the objective trees’ DBH. When the DBH reached 30 cm, the competitive intensity plateaus.

Conclusion: Individual M. wilsonii in the small and medium tree stages were clustered and influenced by strong intraspecific competition. Individuals entering the old tree stage, were subjected to strong interspecific competition, and sporadic individuals grew vigorously. To better protect M. wilsoniipopulation, the relationship among forest competition, spatial patterns, and population renewal should be fully considered in stand protection and management. Appropriate human intervention measurements for the small and medium diameter class should be carried out to promote the regeneration of small and medium trees, to reduce the competitive exclusion among plants, and accelerate plant growth and conservation of population.