植物性系统在群落更新、适应性和未来发展中起着重要作用。为了明确喀斯特森林性系统数量特征及其与环境因子的关系, 本研究采用相邻格子法从茂兰白鹇山山脚到山顶连续设置11个垂直样地, 同时采用该方法从山体中部沿同一等高线连续设置21个水平样地, 分析了研究区样地内胸径大于1 cm的木本植物性系统数量特征, 采用独立样本t检验分析了垂直样地与水平样地植物数量与性系统的差异, 采用冗余分析(RDA)探究了性系统数量特征与环境因子的相关性。结果表明: (1)样地内共有木本植物286种14,622株, 其中两性花植物156种(54.5%) 8,235株; 雌雄同株异花植物57种(20.0%) 3,838株; 雌雄异株植物73种(25.5%) 2,549株。垂直方向上, 随着海拔升高雌雄同株异花植物的植株数量显著增加, 两性花植物的物种比例显著下降; 坡位上表现为中坡位植物性系统多样性较低; 水平方向上, 两性花、雌雄同株异花与雌雄异株植物的植株数量、物种比例、性系统多样性指数都无明显规律。(2)雌雄同株异花植物的植株数量和物种比例在垂直样地与水平样地间有显著差异(P < 0.05); 雌雄异株与两性花植物的植株数量与物种比例无显著差异。(3)环境因子对木本植物的性系统数量特征有一定影响, 其中海拔的影响达到极显著水平(P < 0.01), 坡位的影响达到显著水平(P < 0.05)。总体上, 茂兰喀斯特森林木本植物性系统表现出与其他地区不同的丰富性、多样性和复杂性, 但大部分物种种群较小, 其数量分布特征可能是对喀斯特生境异质性适应的结果。

Aims: Plant sexual systems play an important role in community regeneration, adaptability and future development. The purpose of this study is to clarify the quantitative characteristics of karst forest sexual systems and its relationship with environmental factors.

Methods: In this study, the adjacent grid method was used to establish 11 vertical plots from the foot to the top of Baixian Mountain in Maolan and 21 horizontal plots from the middle of the mountain, along the same contour line. The quantitative characteristics of woody plant sexual systems with DBH greater than 1 cm in the sample plots were characterized and analyzed. An independent sample t test was used to analyze in the number and sexual system of plants in the sample plots. Redundancy analysis (RDA) was conducted to explore the correlation between quantitative characteristics of sexual systems and environmental factors.

Results: In the sample plots, there were 14,622 woody plants of 286 species. These species are composed of 156 hermaphroditic (54.5%), 57 monoecious (20.0%) and 73 dioecious (25.5%) species. Vertical sample plots located at higher altitude had a significantly greater number of monoecious species and significantly lower proportion of bisexual species. While sample plots located on the mountain slope had a lower diversity of plant sexual systems. In the horizontal sample plots, there were no obvious patterns observed among the number of individual of plants, species proportion and sexual system diversity index of hermaphrodite plants, monoecious plants and dioecious plants. Independent sample t test showed that there were significant differences in the number of plants and the species proportion between the vertical sample plot and the horizontal sample plots (P < 0.05), but no significant differences were observed in the number of plants nor the proportion between dioecious and hermaphrodite species. RDA showed that environmental factors influence the quantitative characteristics of different sexual systems. Altitude had an extremely significant (P < 0.01) effect and slope position was significant as well (P < 0.05).

Conclusion: The woody plant sexual systems in Maolan karst forest are different from other areas in aspects of richness, diversity, and complexity. Most species populations of woody plant are small and their quantitative distribution characteristics may be the result of adaptation to the heterogeneity of karst habitats.