秦巴山地垂直带谱结构的空间分异与暖温带—亚热带界线问题

秦巴山地垂直带谱结构的空间分异对于揭示秦巴山地地域结构复杂性和过渡性、探索中国复杂的生态地理格局具有重要的意义。本文从文献中搜集了秦巴山地33个山地垂直带谱,建立了秦巴山地数字垂直带谱体系,从纬向、经向和坡向3个维度分析了山地垂直带谱的结构、特征、数量、高度以及分布模式。结果表明:①纬向上从南向北基带由亚热带常绿阔叶林带逐渐转变为暖温带落叶阔叶林带;垂直带结构由复杂逐渐变得简单;优势带由山地针阔混交林和山地常绿落叶阔叶混交林转变为山地落叶阔叶林带;②经向上山地垂直带结构呈现复杂—简单—复杂的特征;常绿落叶阔叶混交林带和山地落叶阔叶林带的海拔呈现了二次曲线分布模式;山地针阔混交林带的海拔则呈现显著的线性降低趋势;③坡向方面,秦岭北坡和南坡基带均为暖温带落叶阔叶林带,但南坡含有常绿成分;大巴山北坡为亚热带常绿落叶阔叶混交林带,大巴山南坡为亚热带常绿阔叶林带;秦岭和大巴山北坡优势带类似,均为山地针阔混交林带或山地落叶阔叶林带,但大巴山南坡具有独特的山地常绿落叶阔叶混交林优势带,这表明了大巴山比秦岭更适合作为暖温带和北亚热带的分界线,但是未来还需使用土壤和气候指标进行系统的分析。

Spectra structures of altitudinal belts and their significance for determining the boundary between warm temperate and subtropical zones in the Qinling-Daba Mountains

The Qinling-Daba Mountains, as the north-south transition zone of China and the watershed between the Yellow River and the Yangtze River, are characterized by multi-dimensional and high-degree heterogeneity and variations in climate and landscape. Especially, the spectra of altitudinal belts show outstanding areal differentiation in the study region and could be considered to serve as a criterion for determining the boundary between warm temperate and subtropical zones in the Qinling-Daba Mountains. This paper designs a digital integrated system for 33 spectra of altitudinal belts in the study region and analyzes their structures and the spatial patterns of the main altitudinal belts from north-south, from west-east and with exposures. The results show that: (1) From south to north, the basal belt gradually transfers from subtropical evergreen broadleaved forest to warm temperate deciduous broadleaved forest; the spectra of altitudinal belts change from complex to simple; the dominant belt changes from mixed broadleaf-conifer forest and evergreen-deciduous broadleaved mixed forest, and then to deciduous broadleaved forest belt; and the upper limit of the evergreen-deciduous broadleaved mixed forest decreases from 1600-2000 m in the Daba Mountains to 700-800 m in the Xunhe Basin of the Qinling Mountains. (2) From west to east, the structures of altitudinal belt spectra show a complex pattern in the eastern and western sections but a simple one in the middle section; the upper limits of both evergreen-deciduous broadleaved mixed forest belt and mountain deciduous broadleaved forest belt present a quadratic curve distribution pattern in longitude direction; however, the upper limit of mountain broadleaf-conifer mixed forest belt exhibits a nearly linear decrease in west-east direction from 2700 m to 2000 m in the Qinling Mountains and from 3300 m to 1600 m in the Daba Mountains. (3) In the Qinling Mts., the basal belt is just warm temperate deciduous broadleaved forest both in the northern and southern flanks, with only some evergreen trees mixed in the basal belt in the southern flank; while in the Daba Mts., the basal belt is evergreen-deciduous broadleaved mixed forest in the northern flank and evergreen broadleaved forest belt in the southern flank. The north flanks of the Qinling and Daba Mountains have similar dominant belts, namely, mountain broadleaf-conifer mixed forest belt or mountain deciduous broadleaved forest belt. However, the southern flank of the Daba Mountains has its own unique dominant belt, i.e., evergreen-deciduous broadleaved mixed forest belt. This implies that the Daba Mountains are more appropriate than the Qinling Mountains to act as the boundary between subtropical and warm-temperate zones in central China.