兰州北山刺槐枝叶性状的坡向差异性

Slope-related variations in twig and leaf traits of Robinia pseudoacacia in the northern mountains of Lanzhou

枝叶生长关系是植物在环境胁迫条件下提高空间资源利用能力的一种策略,弄清枝叶生长关系对理解植物应对环境异质性的表型可塑性具有重要意义。该文利用Arc GIS建立研究区域的数字高程模型,研究了兰州市北山不同坡向人工林刺槐(Robinia pseudoacacia)小枝茎截面积-总叶面积和出叶强度-单叶面积的生长关系。结果表明:随着坡向由北坡向东坡、南坡和西坡转变,刺槐林群落的郁闭度、高度和土壤含水量呈现先减小后增大的趋势,刺槐小枝茎截面积、总叶面积和单叶面积呈现先减小后增大的趋势,出叶强度呈现先增大后减小的趋势;北坡、东坡、南坡和西坡4个坡向的刺槐小枝的茎截面积和总叶面积均呈显著的正相关关系(p<0.05),并存在显著大于1的共同斜率,刺槐的出叶强度与单叶面积均呈显著的负相关关系(p<0.05),并存在接近于–1的共同斜率;随着坡向由北坡向东坡、南坡和西坡转变,茎截面积-总叶面积和出叶强度-单叶面积两组关系的回归方程截距呈现先减小后增大的趋势。刺槐枝叶在不同坡向上的异速生长关系反映了植物功能性状对生长环境的响应和适应,以及植物构型构建的投资权衡机制。

Aims The growth relationship between twigs and leaves is a strategy that plants enhance the ability to use space resources under environmental stresses, and elucidation of this characteristics is important for understanding the phenotypic plasticity of plants in coping with environmental heterogeneity. Our objective was to examine how Robiniapseudoacacia would vary in twig and leaf configuration in response to changes in slope aspect. Methods In the northern mountains of Lanzhou in Gansu Province, China, 20 transects were laid out horizon- tally along the contour at intervals of 50 m from an elevation of 1 550 m upward in four different slope aspects, and 12 plots were set up along each transect at intervals of 5 m. A handheld GPS was used to measure latitude, longitude and altitude of each plot. Community traits were investigated and all individuals of R. pseudoacacia were used for measurements of the cross-sectional area of twigs, total leaf area, leafing intensity, and average area of a single leaf on each twig. ArcGIS was used to construct the digital elevation model （DEM）. The 240 plots were categorized into groups of northern, eastern, western and southern aspects, and the standardized major axis （SMA） estimation method was then used to examine the allometric relationship between the cross-sectional area of twigs, total leaf area, leafing intensity and average area of a single leaf. Important findings With changes in the slope aspect from north to east, south and west, the crown density, av- erage tree height and soil moisture of the plant community displayed a pattern of decrease--increase, and the cross-sectional area of twigs, total leaf area and average area of a single leaf of R. pseudoacacia displayed a pat- tern of decrease--increase and the leafing intensity displayed a pattern of increase---decrease. Significant positive relationships between the cross-sectional area of twigs and total leaf area were found in R. pseudoacacia in all slope aspects （p 〈 0.05）, and the common slope of the regressions was significantly greater than 1; significant negative relationships between leafing intensity and average area of a single leaf were found in all slope aspects （p 〈 0.05）, and the common slope of the regressions was significantly close to -1. In addition, when the slope as- pect changed from north to east, south and west, the y-intercepts in the scaling relationships of the cross-sectional area of twigs vs. total leaf area and the leafing intensity vs. individual leaf area both displayed a pattern of de- crease--increase. The allometric relationship between twig and leaf with changes in slope aspect of the habitat reflected the response and adaption of plant functional traits to their biotic and abiotic environments and the in- vestment balance mechanism of plant architecture construction_