桂西南喀斯特季节性雨林东京桐群落物种多样性的时序动态

Temporal dynamics of species diversity of Deutzianthus tonkinensis community in karst seasonal rainforest of Southwest Guangxi

关键词:  东京桐, β多样性, 时序动态, B-C图, 弄岗国家级自然保护区

Key words:  Deutzianthus tonkinensis, β-diversity, temporal dynamics, B-C plot, Nonggang National Nature Reserve

摘要:

东京桐(Deutzianthus tonkinensis)是国家二级重点保护野生植物,以其为建群种的群落是北热带喀斯特季节性雨林主要珍稀植被类型之一,蕴含丰富的生物多样性和特有种类,具有重要的生态价值和经济价值。然而,其群落物种多样性的动态特征及驱动机制目前仍不清楚。为探明东京桐群落时序动态及其驱动因素,该文基于广西弄岗1个1 hm²东京桐群落长期固定监测样地3次周期性的复查数据,分析其群落物种多样性在2012—2022年间的时序动态变化,探讨地形因子对群落物种多样性动态的影响。结果表明:(1)优势种重要值保持稳定,胸高断面积增加,物种多度下降。(2)共有18个稀有种与偶见种退出群落; 物种丰富度减少了14%,Shannon-Wiener指数显著下降(P<0.05)。(3)对β多样性具有显著贡献的样方数减少了2%,80%的样方时间β多样性指数下降,样地的物种减少明显超过了物种增加。(4)海拔对样地内物种减少具有显著影响(P<0.05)。综上表明,虽然东京桐群落结构在10年间总体保持稳定,但α多样性与β多样性均变化明显,稀有种与偶见种丧失驱动了多样性变化,地形因子中的海拔对物种多样性的变化具有显著影响。该研究结果对深入认识喀斯特季节性雨林生物多样性动态及其驱动机制具有重要意义。

Abstract:

Deutzianthus tonkinensis, classified as a national secondary key protected wild plant in China, serves as the foundational species in communities that constitute one of the primary rare vegetation types within the northern tropical karst seasonal rainforests. These communities harbor rich biodiversity and numerous endemic species, possessing significant ecological and economic values. However, the temporal dynamics of species diversity within these communities and their underlying driving factors remain poorly understood. To investigate the temporal dynamics and identify the driving factors of species diversity in D. tonkinensis communities, this study conducted three cycles of periodic re-surveys within a 1 hm² long-term monitoring plot in Nonggang, Guangxi Zhuang Autonomous Region. The objective was to analyze the changes in species diversity from 2012 to 2022 and to explore the impacts of topographic factors on these dynamics. The results were as follows:(1)The importance values of dominant species remained stable. Concurrently, there was an increase in the basal area at breast height, indicating the growth of these species. However, species abundance declined, suggesting a shift in the population structure within the community.(2)A total of 18 rare and occasional species withdrew from the community, resulting in a 14% reduction in species richness. Additionally, the Shannon-Wiener index, a measure of species diversity, declined significantly(P<0.05), indicating a loss of biodiversity within the community.(3)The number of quadrats that significantly contributed to β-diversity, which reflects the variation in species composition among different locations within the community, decreased by 2%. Furthermore, the temporal β-diversity index declined in 80% of the quadrats, indicating that species loss significantly exceeded species gains within the plot. This suggests a trend of homogenization in species composition over time.(4)Elevation had a significant impact on species loss within the plot(P<0.05). This finding highlights the importance of topographic factors, particularly elevation, in shaping the species diversity dynamics within the community. In conclusion, while the overall community structure of Deutzianthus tonkinensis remained stable over the past ten years, significant changes were observed in both α-diversity and β-diversity. The loss of rare and occasional species drove these diversity changes, indicating a potential threat to the biodiversity of the community. Among the topographic factors, elevation emerged as a significant influence on species diversity changes. These research findings are crucial for enhancing our understanding of biodiversity dynamics and their driving mechanisms in karst seasonal rainforests, which are essential for conservation efforts and sustainable management strategies.