广东南岭20 hm2样地华南五针松空间分布与生境特征研究

Spatial distribution and habitat characteristic of Pinus kwangtungensis in the Guangdong Nanling 20 hm2 forest dynamics plot

关键词:  华南五针松, 径级分布, 空间分布, 生境偏好, 环境因子

Key words:  Pinus kwangtungensis, size-class distribution, spatial distribution, habitat preference, environmental factors

摘要:

华南五针松(Pinus kwangtungensis)是中国特有种和二级保护植物,因环境变化和人为干扰而导致其生境受损、种群逐渐衰退。为了解华南五针松的种群现状、空间分布格局和生境特征,该研究在广东南岭国家级自然保护区建立了20 hm²的永久监测样地,对样地内胸径≥1 cm的木本植物进行监测,测量土壤、地形等多种环境因子,并采用径级分析预测种群的发展趋势和空间点格局(L function)方法分析个体的空间分布及建立零膨胀泊松(Zero-inflated Poisson,ZIP)回归模型,探讨影响个体分布的重要环境因子。结果表明:(1)华南五针松径级分布近似“钟型”(“bell-shaped”),小径级的个体数量较少,种群更新受限制; 华南五针松偏好海拔较高且地形陡峭的山坡和山脊,呈现较强的生境特异性。(2)空间点格局分析结果显示,个体为显著的聚集分布,其分布格局主要由扩散限制和生境异质性导致。(3)ZIP的结果显示,华南五针松分布的区域(0到1),土壤铵态氮和速效钾含量较高,有机质含量低; 多种环境因子对其多度产生影响(1到N),多度与海拔、物种多样性和平均胸径虽为正相关关系,但与树高、铵态氮、总磷和总钾含量为负相关关系。综上认为,不稳定的径级结构及聚集分布导致的种内竞争将加速其种群的衰退,应重点保护高海拔及土壤养分较低的生境,并减少人为干扰维持其原生生境,该研究结果可用于指导华南五针松的保护和恢复。

Abstract:

Understanding the ecological processes that affect species distribution patterns is fundamental to the conservation and restoration of rare and endangered species. Pinus kwangtungensis is an endemic and Class-II protected plant in China. However, environmental change and human disturbance result in habitat damage and population decline. In order to understand current situation of its population, spatial distribution pattern and habitat characteristics, and to guide the conservation and restoration of this species, we established a 20 hm² forest dynamics plot in the Nanling National Nature Reserve, Guangdong Province. All woody plants with diameter at breast height ≥1 cm were monitored, and multiple environmental factors, including soil and topography, were measured. We used a size-class analysis to predict population trends, the spatial point pattern analysis(L function)to reveal spatial distribution of individuals, and established a Zero-Inflated Poisson(ZIP)regression model to explore the important environmental factors that affect individual distribution. The results were as follows:(1)size-class distribution was “bell-shaped”, the number of small size-class individuals was low, indicating that population regeneration was limited. P. kwangtungensis preferred the slopes and ridges with high altitude and steep terrain, showing a strong habitat specialization.(2)Spatial point pattern analysis(L function)presented that spatial distribution was significantly aggregated compared with null models, which might cause by dispersal limitation and habitat heterogeneity.(3)The ZIP regression model showed that high soil ammonium nitrogen, available potassium and low organic matter content associated with the occurrence of P. kwangtungensis (from 0 to 1), and the abundance(from 1 to N)was positively correlated with altitude, species diversity, and mean DBH, but negatively correlated with tree height, ammonium nitrogen, total phosphorus, and total potassium. The results indicate that the unstable size-class structure and intraspecific competition caused by spatial aggregation will accelerate the decline of the population, we suggest that the habitats with low soil nutrients at high elevations should be conserved preferentially, and reduce anthropogenic disturbance to maintain the original habitats.