阿拉善荒漠灌丛群落谱系结构及其影响因子

为探究阿拉善荒漠灌丛群落的构建机制,该研究选取净亲缘关系指数(NRI)作为谱系结构指数,在对阿拉善荒漠灌丛群落野外调查的基础上,以群落物种组成为基础数据,计算各样地群落的NRI,并分析NRI在经纬度梯度上的变化趋势及其与土壤因子和水热因子的关系。结果表明:(1)阿拉善荒漠灌丛群落谱系结构在阿拉善高原东南部以发散状态为主,在阿拉善高原西部和北部地区以聚集状态为主。(2)阿拉善荒漠灌丛群落的NRI随经度的升高而减小,随纬度的升高而增大。(3)阿拉善荒漠土壤质地、土壤容重、土壤pH值和土壤有机碳含量与其群落谱系结构均无显著相关性;在降水因子和温度因子中,与群落谱系结构相关系数最大的分别为年降水量和年温度变化范围(最暖月最高温与最冷月最低温的差值),其中:年降水量与NRI呈显著负相关关系,年温度变化范围与NRI呈显著正相关关系,且最暖月最高温和最冷月最低温与NRI均有显著相关性,推测年温度变化范围对阿拉善灌丛群落谱系结构的影响是通过最暖月最高温和最冷月最低温起作用的。研究发现,阿拉善高原东南部区域的荒漠灌丛群落构成主要受竞争排斥的作用,其西部和北部地区的群落构成主要受环境过滤的影响;阿拉善荒漠灌丛群落的谱系结构主要受年降水量和极端温度的影响。

Phylogenetic Structure of Shrub Community in Alxa Desert and Its Environmental Determinants

To explore the construction mechanism of shrub communities in Alxa Desert, we quantified the phylogenetic structure of each assemblage in Alxa Desert using net relatedness index (NRI) and analyzed the variation pattern of NRI along longitude and latitude gradient and the relationship between NRI and soil factors and hydrothermal factors. The results were as follows: (1) the shrub communities in the southeast of Alxa plateau were mainly phylogenetically overdispersed, and in contrast, the shrub communities in the west and north of Alxa plateau were mainly phylogenetically clustered. (2) NRI of the shrub communities in Alxa Desert decreased with increasing longitude and decreasing latitude. (3) In Alxa Desert, the soil texture, soil bulk density, soil pH value and soil organic carbon content had no significant influence on the phylogenetic structure of the shrub communities. Annual precipitation and temperature annual range (The difference of the extreme maximum temperature and extreme minimum temperature) were the most correlated factors with the phylogenetic structure of shrub communities in Alxa Desert among the precipitation factors and temperature factors, respectively. Annual precipitation was negatively correlated with NRI, and temperature annual range was positively correlated with NRI. The extreme maximum temperature and extreme minimum temperature showed significant correlation with NRI. Based on these analyses, we speculated that temperature annual range influenced the phylogenetic structure of shrub communities through the extreme minimum temperature and extreme maximum temperature. Studies showed the shrub communities in the southeast of Alxa plateau were mainly affected by interspecific competition and the shrub communities in the west and north of Alxa plateau were mainly structured by environmental filtration, and that the phylogenetic structure of shrub communities in Alxa Desert were mainly affected by annual precipitation and the extreme temperatures.