木莲(Manglietia fordiana)的适生分布、影响因子与保护空缺研究

生境保护是维持生物多样性的基本途径,南方山地阔叶林维系着当地的生物多样性热点,而由于保护覆盖不足,保护效果亟待提高。以典型山地阔叶林树种木莲（Manglietia fordiana）为例,通过大尺度采集发生点,预测适生分布,获知影响其适生分布的关键因子。同时,以九连山种群进行案例研究,调查地方尺度下木莲植株的发生,了解其在山地地形、植被类型的选择特征。用MaxEnt构建最佳模型预测适生区,结果显示木莲适生区主体位于中国南部、西南部山地（如戴云山、南岭、罗霄山、武夷山等）,向北延至大别山南坡,向西达横断山脉。木莲适生分布主要受最干月降水量（bio14,贡献率34.6%）、海拔高度（19.2%）、温度季节性变化标准差（bio4,15.6%）、最暖季降水量（bio18,12.0%）、最冷月最低温度（bio6,7.0%）影响,其60%适生概率范围或生态位bio14为30-55mm、海拔为400-1500m、bio18为500-800mm等。在适生区基础上,叠加考虑阔叶林分布,并选择其偏好海拔高度（>700m）提取获得木莲优先保护区,经与现有自然保护区叠加分析后,进行空缺识别,结果显示优先区保护覆盖为4.1%-6.0%,而高适生区保护覆盖也<10%（占比8.03%）,覆盖比重较低。而沿<400m、400-700m、>700m海拔梯度显示>700m区域保护比重（8.7%）明显高于400-700m （4.4%）与<400（2.3%）组,说明前期保护区设计基本遵从优先区保护原则,能有效保护木莲高适生区。同样的,九连山保护区案例显示,当地木莲51.4%高适宜生境受到核心区的严格保护。研究结果表明,仍需在黄山-天目山区、苗岭东段、高黎贡山北段与南段、中越边界山区与广东西南山区6个空缺提高保护覆盖,通过建立新的自然保护区,优化当前保护网络,提高山地阔叶林的整体保护水平。

Distribution, influencing factors and gaps analysis of Manglietia fordiana: implications of conservation to mountain broad-leaved forests

Habitat protection is a basic way to maintain biodiversity. The mountain broad-leaved forest in southern China is the hotspot of biodiversity. However, due to the lack of protection coverage, the conservation level needs to be improved. In this study, Manglietia fordiana, a typical mountain broad-leaved forest species, was taken as an example. Through large-scale collection of occurrence, the suitable distribution was predicted, and the key factors with high contribution to the distribution were discovered. At the same time, a case study of Jiulian Mountain was carried out to investigate the occurrence of M. fordiana at local scale, aiming to understand the preference characteristics among elevation gradients and vegetation types. MaxEnt was used to establish the best model to predict the suitable distribution. The results showed that M. fordiana mainly distributed in the southern and southwestern mountains of China (such as Daiyun Mountain, Nanling Mountain, Luoxiao Mountain, Wuyi Mountain, etc.), extending northward to the southern slope of Dabie Mountain and westward to Hengduan Mountain. This potential distribution was mainly contributed by these variables:precipitation of driest month (bio14, contribution rate 34.6%), altitude (19.2%), and temperature seasonality (bio4, 15.6%), precipitation of warmest quarter (bio18, 12.0%), as well as min-temperature of the coldest month (bio6, 7.0%). The niche, indicated by 60% suitable probability, was 30-55 mm in bio14400-1500 m in altitude, 500-800 mm in bio18 etc.. With the suitable distribution, the priority area of M. fordiana was determined associating the distribution of broad-leaved forests and the preferred altitude (> 700m). Using superposition analysis and existing nature reserves, the gaps were identified. Results showed that the protection coverage of priority area was 4.1%-6.0%, and it was also less than 10% (8.03%) in high-suitable areas. Along the altitude gradients of<400m, 400-700 m and > 700 m, the proportion of protection was significantly higher in > 700 m area (8.7%) than that in 400-700m (4.4%) and < 400 (2.3%) groups, which indicated that the early reserve design basically followed the principle of priority area protection and could effectively protect the high priority area of M. fordiana. Similarly, the case of Jiulian Mountain Nature Reserve showed that 51.4% of the high suitable habitats were strictly protected by the core area. Our results suggested that it was still necessary to improve the protection coverage in Huangshan-Tianmu Mountains, Eastern Miaoling Mountains, northern and southern Gaoligong Mountains, border mountain area between China and Vietnam and southwest mountain area of Guangdong Province. Through the establishment of new nature reserves and optimization of current protection network, the overall protection level of broad-leaved forest in mountainous area can be improved.