冀北山地不同坡向白桦枝叶异速生长关系研究OACSTPCD

Current year twig is an independent component unit for plant growth,it is important to study the quantitative relationships that are relative to the twig growth for understanding the survival and adaptation strategies of a plant.In this study,we took the current year twigs of Betula platyphylla growing on differ-ent slopes in mountainous areas of Northern Hebei as the research objects,growth parameters of different parts of a twig were measured to analyze the relationship between the twig growth and slope aspect,and to reveal ecological strategies and adaption of B.platyphylla,parameters included the dry weight(DW)of the twig stem,DW of the leaves of a twig,leaf area,DW of the petioles of a twig,and DW of a whole twig.The results showed that 1)except for the DW of the twig stem,other dry weigh parameters of the twig of B.platyphylla growing on semi-sunny slope were significantly higher than those on shady slope,and there was no significant difference in leaf area between different slopes.2)The standardized major axis estima-tion(SMA)showed that at the twig level,the relationships of DW of the twig stem & DW of a whole twig,DW of the total leaves of a twig &DW of a whole twig,total leaf area of a twig &DW of a whole twig,among different slopes were isokinetic,while the relationship between DW of the total petiole of a twig and DW of a whole twig was allometry.Moreover,the common slopes of the twig stem DW &whole twig DW,and total petiole DW & whole twig DW were 1.12 and 1.22,which were greater than the com-mon slope of whole leaves DW of a twig &the whole twig DW(1.04).3)At the leaf level,the relationship between total leaf DW of a twig & total petiole DW of a twig was allometry on shady and semi-sunny slope,and isokinetic on semi-shady slope.The relationship between the total leaf area of a twig &total pet-iole DW of a twig was isokinetic on the shady slope,and allometry on other slopes.4)The leaf size in each aspect had a negative isokinetic relationship with the leaf intensity.When the leaf was expressed by DW,the normalization constant was the smallest(-0.18)on shady slope.When the leaf was expressed by are-a,the normalization constant was the smallest(2.01)on semi-sunny slope.The results indicate that in or-der to adapt to the change of slope aspect,plant will give priority to allocating resources to stems and peti-oles,and more leaves with large area and small mass will be planted on the twigs of B.platyphylla on the shady slope to expand its growth space,obtain more light and facilitate the growth.