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To explore the physiological and ecological adaptability of different dominant species during grassland community succession, we measured soil nutrients, plant biomass and C, N and P contents of two dominant species using the method of spatial sequences instead of chronosequences in the successive series of Agropyron michnoi community - A. michnoi + A. cristatam community - A. cristatam community in Hulunbuir Grassland. During the succession progress, the contents of soil total C, total C, available N and available P increased significantly. The N and P contents and N/P of leaves, stems and roots of A. michnoi and A. cristatam increased significantly, while the C/N showed opposite response. The leaf C content of A. michnoi and the C contents of leaves, stems and roots of A. cristatam significantly increased. The leaf C/P of A. michnoi and the C/P of leaves and roots of A. cristatem increased significantly, while the C/P of stems and roots of A. michnoi and the stem C/P of A. cristatem decreased significantly. In the community co-dominated by A. michnoi and A. cristatam, A. michnoi improved its interspecific competitiveness by reducing C content in stems and roots and increasing the C content in leaves, while A. cristatem adapted to environmental changes by reducing root to shoot ratio and reproductive ratio. A. michnoi was limited by N availability (N/P14) in different communities, while A. cristatem was limited by P availability in single dominant community(N/P16)and by both N and P in co-dominant community (14N/P16). The index of stoichiometric homoeostasis of foliar N of A. michnoi in the single dominant community and the co-dominant community were 5.92 and 2.94, respectively, indicating higher N stability, while the index of stoichiometric homoeostasis plant of foliar P of A. cristatem in the single dominant community and the co-dominant community were 4.12 and 3.37, respectively, which indicated higher P stability.为了探究草地群落演替过程中不同优势种的生理生态适应性,本研究采用空间代替时间序列的方法,分析呼伦贝尔草地米氏冰草群落—米氏冰草+冰草群落—冰草群落演替系列的土壤养分、两优势种的生物量及C、N和P含量。结果表明: 随着米氏冰草群落—米氏冰草+冰草群落—冰草群落的演替,土壤全碳、全氮、速效氮及速效磷含量均显著升高;米氏冰草和冰草叶、茎和根的N、P含量及N/P均显著升高,而各构件的C/N降低;米氏冰草叶的C含量及冰草叶、茎和根的C含量均显著升高。米氏冰草叶C/P及冰草根和叶C/P均显著升高,而米氏冰草根和茎C/P及冰草茎C/P均显著下降。在米氏冰草+冰草共优势种群落中,米氏冰草通过降低茎和根C含量,增加叶C的积累,提高其种间竞争力, 而冰草通过降低根冠比和生殖比来适应环境变化。米氏冰草在不同群落中均受N限制(N/P14);而冰草在单优势种群落中受P限制(N/P16),在共优势种群落中受N和P限制(14N/P16)。在单优势种群落和共优势种群落中,米氏冰草叶N化学计量内稳性指数分别为5.92和2.94,具有较高的氮内稳性,冰草叶P化学计量内稳性指数分别为4.12和3.37,具有较高的磷内稳性。. |
