Abstract:

The distribution of Cephalotaxus hainanensis in the wild is infrequent, and it possesses a limited ability to regenerate naturally. This species is under serious threat due to deforestation by humans, resulting in a significant decline in its population size. To explore the composition of species and the interspecific relationships within the Cephalotaxus hainanensis community, understand the mechanisms contributing to its endangerment, establish appropriate habitats for population restoration, and develop targeted protection measures, this study conducts an analysis on species diversity and the flora composition of associated tree species within Cephalotaxus hainanensis community plots in Hainan Tropical Rainforest National Park through field surveys. This study employed statistical methods such as the variance ratio (R_v), χ²-test, association coefficient (A_C), percentage co-occurrence (P_C), Pearson correlation coefficient (r_p), and Spearman rank correlation coefficient (r_s), to comprehensively explore overall correlations, the significance of interspecific associations, and the strength of associations among 16 common tree species within the Cephalotaxus hainanensis community. The results indicate that within 8 sample plots measuring 20 m in length and width, a total of 105 species belonging to 78 genera and 44 families of woody tree species were identified. The plant flora was predominantly tropical, accounting for 65.9% of the total number of families. The overall correlation of 16 common tree species showed no significant negative correlation (R_v=0.534, statistics W=4.27); χ²-test results indicate that the number of negatively correlated species pairs exceeded the number of positively correlated species pairs, and there were no significant correlations among species pairs in the community. There were nine species pairs with an A_C>0.67 and seven species pairs with a P_C>0.75, and the correlation between most species was weak. Cephalotaxus hainanensis had significant positive correlation only with Syzygium globiflorum (P = 0.018). The correlation tests of r_p and r_s indicate that there were more significantly negative associations among species pairs than significantly positive associations. Cephalotaxus hainanensis was significantly negatively correlated with Tabernaemontana bovin (P=0.027), and the vast majority of species pairs were not significantly correlated. In summary, the overall structure of the Cephalotaxus hainanensis community is relatively loose, and species may be subject to frequent changes. The community is still in an unstable stage, and the Cephalotaxus hainanensis tend to survive independently. To address the risk of population decline in Cephalotaxus hainanensis, individual protection should be strengthened, and the habitat of the community should be properly transformed to increase the population size.

Key words: Cephalotaxus hainanensis, interspecific association, national park, associated tree species, flora

摘要：

海南粗榧（Cephalotaxus hainanensis）野外分布稀少，自然更新能力弱，加之受到人类砍伐的严重威胁，种群数量急剧减少。为探明海南粗榧所在群落树种组成与种间关系，分析其种群濒危机制，创造海南粗榧种群恢复的适宜生境，制定针对性保护措施，通过在野外实地调查海南热带雨林国家公园海南粗榧群落样地的基础上，对群落伴生树种的物种多样性、区系组成进行分析，并采用方差比率法（R_v）、χ²检验、联结系数（A_C）、共同出现百分率（P_C）、Pearson相关系数（r_p）和Spearman秩相关系数（r_s）对海南粗榧群落16种常见树种的总体关联性、种间联结显著性及关联强度进行探讨分析。结果表明，在8个20 m×20 m样地中，共发现乔木树种44科78属105种；植物区系以热带性质为主，占总科数的65.9%；16种常见树种总体关联性表现为不显著的负关联（R_v =0.534，统计量W=4.27），物种的独立性较强；χ²检验结果表明负关联种对数（41对）多于正关联种对（33对），群落中无显著关联种对；A_C>0.67的种对9对，P_C>0.75的种对7对，大多数树种间联结性较弱，海南粗榧仅与短药蒲桃存在显著正关联（P=0.018）；相关性检验r_p与r_s显示显著负关联种对多于显著正关联种对，海南粗榧与药用狗牙花呈显著负相关（P=0.027），绝大多数种对不显著相关。综上所述，海南粗榧群落整体结构较为松散，物种可能存在较为频繁更迭，群落尚处不稳定阶段，海南粗榧趋于独立存活。为缓解海南粗榧种群存在的衰退现象，应对其个体采取就地保护措施，适当改造群落生境，进行人工补植，扩大其种群数量。

关键词: 海南粗榧, 种间联结, 国家公园, 伴生树种, 植物区系