川西云杉人工林与天然林群落空间分布格局及种间关联性

Spatial distribution pattern and interspecific correlation between plantation and natural forest of Picea likiangensis var.rubescens in western Sichuan,China

【目的】随着国家退耕还林工程的实施,川西云杉Picea likiangensis var.rubescens人工林面积和蓄积量不断增长,已成为川西地区森林资源的重要组成部分。本研究分析道孚县川西云杉人工林与天然林活立木空间分布格局特征及种间关联性差异,以揭示人工林群落动态变化及演替规律。【方法】采用典型样方法设置12块固定样地,测量每株活立木中心位置坐标、胸径、树高和冠幅等,运用点格局分析中的单变量Ripley’s L(t)函数和双变量Ripley’s L12(t)函数分别分析人工林与天然林群落的空间分布格局和群落中树种间的空间关联性。【结果】①随着恢复年限的增加,人工林群落内川西云杉种群密度呈下降趋势,而群落物种数逐渐增加;②人工林群落中活立木空间分布格局总体上表现为随机分布,而天然林内活立木空间分布以聚集分布为主;③人工林中川西云杉与其他阔叶树种无空间关联性,而天然林群落内主要树种间关联性在小尺度范围上呈不相关,在大尺度上表现为负相关。【结论】经过50 a人工恢复后,川西云杉人工林与天然林在群落空间分布格局和种间关联性方面仍然存在一定的差异,生态恢复进程较慢。建议采取适当间伐与种植天然林优势树种相结合的方式,优化改造人工林结构,从而加快人工林向天然林群落演替进程。

[Objective]As an important component of forest resources in western Sichuan,the area and standing volume of Picea likiangensis var.rubescens(PL)plantations are increasing with the implementation of the national project Converting Farmland to Forest.This study aims to analyze the spatial distribution pattern and interspecific correlation between natural forest and plantation in Daofu County,so as to reveal community dynamic change and succession law of plantation community.[Method]The typical sampling method used to set up 12 fixed plots to measure the central position coordinates,diameter at breast height(DBH),height and crown width of each living tree.The univariate Ripley’s L(t)function and bivariate Ripley’s L12(t)function in point pattern analysis were used to analyze the spatial distribution pattern of plantation and natural forest colony,and the spatial correlation between tree species in the community.[Result](1)With the increase of restoration years,the population density of PL gradually decreased,while the number of community species gradually increased.(2)The spatial distribution pattern of living trees was generally random in plantations but was aggregated in natural forests.(3)The spatial correlation between PL and other broad-leaved tree species was not significant in plantations,while the main tree species in the natural forest community were not correlated on a small scale but negatively correlated on a large scale.[Conclusion]After 50 years of artificial restoration,there are still distinct differences between PL plantations and natural forests in community spatial distribution pattern and interspecific correlation,and the process of ecological restoration is slow.It is suggested that the structure of plantations could be optimized and improved by combining thinning measures and planting dominant tree species of natural forests,so as to accelerate the succession process from plantations to natural forests.