Abstract:

With the development of functional ecology, it is more and more important in research on functional plant ecology. The functional plant ecology of grassland in Songnen plain was studied in this dissertation. The plant functional traits and vegetation properties of Songnen grassland were investigated, then, the variations of Leymus chinensis traits and L. chinensis community characteristics were analyzed after the controlled experiments by the treatments of defoliation, nitrogen fertilization, vegetation shortness and sparseness, and last, the relationships between the aboveground biomass and species richness, functional group richness, species diversity as well as functional trait diversity of both natural and disturbed grasslands were discussed.
The leaf traits of 66 herbaceous plants were measured. The variation coefficient of leaf thickness (LT) was the highest among the 7 traits of leaf. Pearson correlation showed that specific leaf area (SLA), leaf nitrogen concentration (LNC), leaf phosphorus concentration (LPC), leaf chlorophyll (a+b) content (Chl) and leaf carotenoid content (Cd) were significantly positive correlated with each other. There was no significant correlation between LDMC and LPC, however, LDMC was significantly negative correlated with other leaf traits. LT was only significantly negative correlated to LDMC and SLA. LDMC, SLA, LT, LNC, LPC were significantly different among the 4 plant functional groups (perennial rhizome grass, perennial bunchgrasses, perennial forbs, and annuals/biannuals) analyzed by one-way ANOVA (P <0.05). There was no difference in Chl and Cd among the 4 plant functional groups. Perennial rhizome grass and perennial bunchgrasses had higher LDMC and lower SLA, LT, LNC and LPC than perennial forbs and annuals/biannuals. Leaf N and P concentrations were 22.7±0.9 mg·g^-1 and 1.8±0.0 mg·g^-1, respectively, the N:P ratio was 13.0. The growth of plant was limited by nitrogen in Songnen grassland.
The plant community productivity and the proportion of the dominant species were high, and the community saturation was low in Songnen grassland. For the four functional group communities, the species richness of perennial rhizome grass and perennial forbs was the highest, and there was no significant difference in the functional group richness, and the aboveground biomass of annuals/biannuals was the highest. The relationships between aboveground biomass and diversity showed that the aggregated traits of plant height (H), leaf area (LA), and LNC were better than other indices to predict the variation of the productivity. These results were in agreement with the biomass ratio hypothesis. And the grassland management for the maintenance of ecosystem functioning should focus on the dominant species.
There were no significant difference in species richness and functional group richness after defoliation in both autumn and spring. However, there was significantly positive relationship between aggregated H and aboveground biomass, and there was no significant relationship between species richness, functional group richness, functional diversity and aboveground biomass.
Nitrogen addition had significant effect on the Cha, Chb, Cd, LNC, LDMC and SRL of L. chinensis. There were significant correlations between leaf photosynthetic traits, stem specific density (SSD), and SRL. The relationships between Cha, Chb, Cd, LNC, LDMC, SSD, PH and aboveground biomass of L. chinensis were significant. N addition had no significant effect on species richness and functional group richness. The aboveground biomass decreased as the increases of species richness and functional group richness, but there was no significant tendency.
The different heights and densities of reed stalks had significant effects on the SLA, SSD, H, leaf number (LN), Cha, Chb, Cd, LNC of L. chinensis. Both of species richness and functional group richness decreased as vegetation becoming short and sparse. The effects of vegetation height on L. chinensis traits and community were greater than those of vegetation density.

Key words: Diversity, Functional trait, N addition, Defoliation, Litter

摘要：

随着功能生态学的发展,植物功能生态学研究越来越受到重视.以松嫩草地为对象,调查该区域植被状况及功能性状特征,通过控制试验研究刈割、施氮、植被低矮稀疏化等干扰条件下羊草(Leymus chinensis)性状和羊草群落特征的变化,探讨在自然和干扰条件下物种丰富度、功能群丰富度、物种多样性指数、功能性状多样性与群落地上生物量的关系.
松嫩草地66种草本植物7个叶片性状特征表明:叶片厚度变异系数最大,比叶面积、叶片氮含量、叶片磷含量、叶绿素含量和类胡萝卜素含量之间存在显著的正相关关系;叶片干物质含量与叶片磷含量没有显著的相关关系,但是与其他叶片性状成显著的负相关关系;叶片厚度与叶片干物质含量和比叶面积成显著的负相关关系,但是与其他叶片性状不相关.方差分析表明,叶片干物质含量、比叶面积、叶片厚度、叶片氮、叶片磷含量在4个功能群(多年生根茎禾草、多年生丛生禾草、多年生杂类草、1年生或2年生植物)间差异显著,叶绿素含量和类胡萝卜素含量在各个功能群间差异不显著.多年生根茎禾草和多年生丛生禾草有较高的叶片干物质含量和较低的比叶面积、叶片厚度和叶片氮和磷含量.松嫩草地草本植物叶片氮和磷含量分别为22.7±0.9 mg·g^-1和1.8 ±0.0 mg·g^-1,氮磷比为13.0,氮相对缺乏.
松嫩草地植物群落生产力高,群落饱和度低,优势种在群落中占的比例大.多年生根茎禾草和多年生杂类草群落物种丰富度最高,各群落间功能群丰富度没有显著差异,1年生或2年生植物群落地上生物量最高.地上生物量与多样性关系表明,株高、叶面积和叶片氮含量等功能性状多样性比物种丰富度、功能群丰富度、均匀度和辛普森指数等多样性指标能更好的预测生产力的变化,支持质量比假说,草地管理中应集中于优势种的管理.
秋季或春季不同时间刈割,对群落植物物种丰富度和功能群丰富度都没有显著影响.群落高度性状与地上生物量有显著的正相关关系,物种丰富度、功能群丰富度和功能群多样性与地上生物量关系不显著.
氮添加对羊草的叶绿素a和b含量、类胡萝卜素含量、叶片氮含量、叶片干物质含量、比根长都有显著的作用;羊草的叶绿素a和b含量、类胡萝卜素含量、叶片氮磷含量、叶片干物质含量、比茎重、株高与羊草的地上生物量都有显著的相关性.氮添加处理对羊草群落的物种丰富度和功能群丰富度均没有显著的影响.氮添加当年,地上生物量随着物种丰富度和功能群丰富度的增加有减少的趋势,但是不显著.
不同高度和密度立枯物处理间羊草的比叶面积、比茎重、植株高度、叶片数、叶绿素a和b含量、类胡萝卜素含量及叶片氮含量都有显著的差异.随着植被低矮稀疏化,群落物种丰富度和地上生物量均有降低趋势.植被高度变化对羊草性状、群落特征的影响要大于植被密度.

关键词: 多样性, 功能性状, 氮添加, 刈割, 枯落物