草原沙漠化过程中植物叶面积的变化及其与土壤因子的关系

Changes of plant leaf area and its relationships with soil factors in the process of grassland desertification

在自然状态下,对沙质草原沙漠化过程中主要植物叶面积变化及其与土壤因子的关系进行了研究。结果表明:随着沙漠化加剧,羊草和糙隐子草的比叶面积在沙漠化初期(梯度Ⅰ)下降显著(P<0.01),菊叶萎陵菜和冰草的比叶面积在沙漠化后期(梯度Ⅲ)下降显著(P<0.05),寸草苔比叶面积下降不显著(P>0.05),冷蒿比叶面积从沙漠化中、后期开始显著增加(P<0.05),扁蓿豆比叶面积从沙漠化初期开始显著增大(P<0.01);羊草、糙隐子草和冷蒿的叶面积指数总体上呈显著下降趋势(P<0.01),扁蓿豆叶面积指数显著增加(P<0.01);羊草、糙隐子草叶面积指数与土壤粘粒、C、N含量、土壤含水量呈显著正相关(P<0.01),与土壤C/N比呈显著负相关(P<0.01);冷蒿和扁蓿豆叶面积指数与土壤因子的相关性和上述二者正好相反(P<0.05);在叶面积指数与土壤因子线性拟合中,糙隐子草叶面积指数与土壤C/N拟合最高(R2=1),其次是羊草叶面积指数与土壤含水量的拟合(R2=0.992),扁蓿豆叶面积指数与土壤C/N拟合最低(R2=0.268)。土壤C/N是影响草原沙漠化过程中共有种叶面积的关键因子(P<0.05),其影响大小为糙隐子草>羊草>冷蒿>扁蓿豆。

This paper studied the changes of the main plant species leaf area and their relationships with soil factors in the process of grassland desertification under natural conditions. With the intensification of desertification, the specific leaf area （SLA） of Leymus chinensis and Cleistogenes squarrosa decreased significantly （P〈0.01） at early desertification stage （gradient Ⅰ）, and that of Potentilla tanacetifolia and Agrostis cristatum decreased significantly （P〈0.05） at late desertification stage （gradient Ⅲ）. The SLA of Carex duriuscula had no significant change （P〈0.05）, but that of Artemisia frigida and Melilotoides ruthenica decreased significantly from mid-and late desertification stage （P〈0.05） and from early desertification stage （P〈0.01）, respectively. The leaf area index （LAI） of M. ruthenica increased significantly （P〈0.01）, while that of the others decreased significantly （P〈0.01）. The LAI of L. chinensis and C. squarrosa was significantly positively correlated with soil clay, C, N, and moisture contents （P〈0.01）, and significantly negatively correlated with soil C/N ratio （P〈0.01）; while the correlations of the LAI of A. frigida and M. ruthenica with the soil factors were quite opposite （P〈0.05） from those for L. chinensis and C. squarrosa. The linear fitting between the LAI of C. squarrosa and soil C/N was the highest （R2=1）, followed by that between the LAI of L. chinensis and soil moisture content （R2=0.992）, and between the LAI of M. ruthenica and soil C/N （R2=0.268）. Our results suggested that in the process of grassland desertification, soil C/N was the key factor affecting the leaf area of common species （P〈0.05）, with the order of the effect being C. squarrosa L. chinensis A. frigida M. ruthenica.