内蒙古锡林河流域植物功能群组成及其水分利用效率的变化——依水分生态类群划分

依照植物水分生态类群,将锡林河流域主要植物种划分为6个植物功能群:旱生植物、中旱生植物、旱中生植物、中生植物、湿中生植物和湿生植物。沿土壤水分梯度,我们调查了8个植物群落的功能群组成及其d13C值。结果表明:1)在水分状况不同的8个群落中,植物功能群的组成有很大差异。在较湿润生境中(沼泽化草甸和盐化草甸),湿中生和湿生植物成为优势种并构成地上生物量的主要部分;在干旱生境中(草甸草原、典型草原和退化草原),旱生和中旱生植物占绝对优势并构成群落生物量的90%以上;2)不同功能群d13C值表现为:旱生植物(-26.38) = 中旱生植物(-26.51) > 旱中生植物(-27.02) > 中生植物(-27.56) = 湿中生和湿生植物(-27.80),表明随着不同水分生态类群所适应生境从干旱到湿润逐渐转变,植物的水分利用效率显著降低;3)在土壤水分状况不同的生境下,旱生植物始终维持相对较高的d13C值和水分利用效率;而中旱生植物的d13C值表现出较大的变化幅度,表明其对土壤水分的改变更敏感;4)旱生植物叶片脯氨酸含量最高;旱中生、中旱生和中生植物次之;湿中生和湿生植物脯氨酸含量最低。不同水分生态类群脯氨酸含量与其d13C值和地上生物量呈显著正相关关系。

Variations in Composition and Water Use Efficiency of Plant Functional Groups Based on Their Water Ecological Groups in the Xilin River Basin

Major plant species in the Xilin River Basin were grouped into six plant functional groups(PFGs) based on their water ecological groups: xerophytes, mesoxerophytes, xeromesophytes, mesophytes,hygromesophytes and hygrophytes. We surveyed the composition, d13C values and proline concentrationof PFGs in eight different plant communities along a soil moisture gradient. Results show that: (1) PFGsoccurred variously in eight steppe communities with different soil moisture status. In wetter habitats,hygromesophytes and hygrophytes were more abundant and accounted for the majority of abovegroundbiomass, whereas xerophytes and mesoxerophytes became more conspicuous in dryer habitats; (2) thenumerical order of the mean d13C values of PFGs is as follows: xerophytes (-26.38? = mesoxerophytes(-26.51? > xeromesophytes (-27.02? > mesophytes (-27.56? = hygromesophytes and hygro-phytes (-27.80?; (3) xerophytes maintained relative higher d13C values and water use efficiency (WUE) inhabitats of different water availability, whereas d13C values of xeromesophytes were more sensitive tochange in soil water availability; (4) From xerophytes to hygrophytes, their proline content markedly increased.Significantly positive correlations existed between proline and biomass or d13C values of different waterecological groups.