高寒退化草地星毛委陵菜叶大小与数量的权衡关系

Trade-off between leaf size and leaf number of Potentilla acaulis in degraded alpine grassland

植物叶大小和数量的权衡关系反映了植物对环境的高度适应性及其在复杂生境下的自我调控能力。采用标准化主轴估计(standardized major axis estimation,SMA)方法,在祁连山北坡选择未退化(Ⅰ)、轻度退化(Ⅱ)、中度退化(Ⅲ)和重度退化(Ⅳ)4种高寒草地,研究了星毛委陵菜(Potentilla acaulis)叶大小-数量的关系。结果表明:随着天然草地退化程度的加剧,草地群落的高度、盖度和土壤含水量逐渐下降,星毛委陵菜种群的高度逐渐下降、盖度逐渐上升,星毛委陵菜叶大小呈逐渐减小的趋势,而叶数量增加;各退化草地星毛委陵菜叶大小与叶数量均呈显著负相关(P<0.05),星毛委陵菜分配给叶大小与叶数量的资源间存在着"此消彼长"的关系;不同退化草地间的比较显示,未退化和重度退化草地星毛委陵菜叶大小与叶数量呈显著异速生长关系(P<0.05),轻度和中度退化草地二者呈近似等速生长关系。高寒退化草地星毛委陵菜植株合理权衡叶大小-数量的资源配置模式,体现了植物茎叶构型的表型可塑性机制。

The trade-off between leaf size and leaf number reflects the highly adaptable and selfregulatory abilities of plants in response to complex environmental conditions. With the method of the standardized major axis estimation,the relationships between individual leaf area and leafing intensity of Potentilla acaulis were studied in alpine grasslands at four levels of degradation（ Ⅰ,Ⅱ,Ⅲ,Ⅳ ） on the northern slope of Qilian Mountains in northwest China. The results showed that,with the aggravation of the extent of grassland degradation,the height,coverage,soil water content of the grassland communities decreased,and the height,single leaf area and petiole length of P. acaulis decreased,while its leaf number,leaf thickness and coverage increased. A significant negative relationship between the individual leaf area and the leafing intensity was found in the four alpine grasslands（ P〈0.05）,which reflected a trade-off between the leaf size and number. Meanwhile,an isometric relationship was found between individual leaf area and leafing intensity in lightly and moderately degraded grasslands（ P0.05）,whereas an allometric relationship was found between individual leaf area and leafing intensity in non-degraded and severely degraded grasslands. In brief,the configuration mode of trade-off between leaf size and leaf number of P. acaulis reflects its plasticity mechanism of phenotype in degraded alpine grassland.