河西走廊绿洲-荒漠过渡带湿生与盐生生态型芦苇种群空间分布格局分析

河西走廊绿洲-荒漠过渡带植被生长与健康状况对绿洲的稳定性起决定性作用.本研究选取有芦苇(Phragmites australis)天然分布的湿地和盐碱生境设置样地,调查湿生芦苇和盐生芦苇种群空间分布格局,采用6种聚集指标和Iwao模型,综合分析不同取样尺度及不同高度级芦苇种群的分布格局与聚集强度,为研究种群个体行为、种群扩散型提供一定信息.结果表明:湿生芦苇和盐生芦苇种群在取样面积为4、8、16、20、40和100 m2的6个尺度上均为集群分布,其中湿生芦苇聚集程度大于盐生芦苇,盐生芦苇有一定的随机分布趋势,表明湿生生境较盐碱生境更有利于增加芦苇种群聚集强度.湿生芦苇和盐生芦苇各自在不同取样尺度间聚集程度相当.湿生芦苇种群各高度级聚集程度均大于盐生芦苇,且尤以Ⅴ级和Ⅵ级湿生芦苇老龄阶段聚集强度最大.盐生芦苇Ⅱ、Ⅲ、Ⅳ、Ⅵ高度级有一定的随机趋势,但在Ⅰ、Ⅴ高度级无随机趋势.湿生生境水分不再是芦苇生长的限制因子,种群聚集度比较高;盐生生境由于水盐胁迫,土壤水分亏缺和较高的含盐量成为芦苇种群发展的限制因子,芦苇为了满足自身对水分、养分的需求,有随机分布的倾向,进而获得较大的空间及资源来维持其生存和发展.

Analysis of the population spatial distribution patterns of wet and saline ecotype Phragmites australis in the oasis-desert transition zone of the Hexi Corridor

The vegetation growth and health status in the oasis-desert transition zone of the Hexi Corridor plays a decisive role in the stability of the oasis. The experimental plots used in this study were set up at wetland and saline habitats with a natural distribution of Phragmites australis population. The spatial distribution patterns of wet P. australis and saline ecotype P. australis population were subsequently investigated. Six kinds of aggregation indexes and Iwao model were used to comprehensively analyze the distribution pattern and aggregation intensity of P. australis populations in different sampling scales and height grades, to obtain information for the investigation of the population behavior and population diffusion type. Our results showed that: both the wet P. australis and saline P. australis population spatial distribution patterns were measured by cluster distribution on six scales, with sampling areas of 4, 8, 16, 20, 40 and 100 m2, and saline P. australis showed a random distribution trend. The aggregation intensity of wet P. australis was higher than that of saline P. australis, which meant that the wet habitat was more beneficial to improve aggregation intensity than saline habitats. The aggregation intensity of wet P. australis and saline P. australis were similar in different sampling scales. At all height classes, the aggregation intensity of wet P. australis was higher than that of saline P. australis, especially at the Ⅴ and Ⅵ grades, where the wet P. australis aggregation intensity was the highest. There was a certain random trend at the Ⅱ, Ⅲ, Ⅳ, and Ⅵ height classes of the saline P. australis but no random trend at the Ⅰ and Ⅴ height classes. As water was not the limiting factor for the growth of P. australis in the wet habitat, the population aggregation intensity of P. australis was higher than that in the saline habitat. Owing to the saline stress and water deficit in the saline habitat, the development of the P. australis population in the saline habitat was limited; in order to acquire more water and nutrients, the P. australis population in the saline habitat showed random distribution trend, so as to get more space and resources for its survival and expansion.