大狼毒+西南委陵菜型退化亚高山草甸优势物种演替及土壤碳、氮时空分异特征对围封的响应

Abstract: Degraded grassland which dominated by poisonous weeds is the main type of degraded subalpine meadow in the southern margin of Qinghai-Tibetan Plateau, but whether the dominant position of poisonous weeds could be weakened through livestock exclosure? To discuss this question, the experiment of livestock exclosure was designed in subalpine meadow which dominated by Euphorbia jolkinii and Potentilla lineata. Through our study we found Euphorbia jolkinii and Potentilla lineata also occupying the leading position after three years of exclosure, and the dominance of Potentilla lineata significantly increased along the prolongation of exclosure period. Which kind of variation of the dominant position of excellent forages and poisonous weeds will be presented along the continually prolongation of exclosure period, and which kind of soil mechanism caused this variation? In order to answer these questions, the quantative characteristics of dominant species and the spatio-temporal distribution of carbon and nitrogen in rhizosphere soil in degraded subalpine meadow would be further studied. Through this research, we want to reveal the successional law of dominant species after livestock exclosure, and to ascertain the spatio-temporal distribution of carbon and nitrogen in rhizosphere soil with the succession of vegetation, and to reveal the soil mechanism which causing the dominant species succession at the same time. Our research will provide guidance for making adaptive management strategy for grassland in ecological fragile area.

摘要："毒害草"型退化草地是青藏高原南缘退化亚高山草甸的主要类型，围封能否消弱毒害草在亚高山草甸中的优势地位？为探讨这一科学问题，我们前期开展了大狼毒+西南委陵菜型退化亚高山草甸的围封实验，发现围封前3年，毒害草西南委陵菜和大狼毒仍为群落的优势物种，且西南委陵菜的优势度随围封年限的延长而增加，大狼毒优势度无显著变化。随着围封年限的继续延长，毒害草和优良牧草的优势地位会呈现怎样的消长动态变化？引起这种变化的土壤学机制是什么？目前尚不清楚。因此，本项目在前期研究的基础上，进一步开展围封后大狼毒+西南委陵菜型退化亚高山草甸优势物种数量特征及土壤碳、氮时空分异特征的研究。通过本研究，探讨围封后大狼毒+西南委陵菜型退化亚高山草甸优势物种演替规律，摸清植被演替过程中优势物种根际土壤碳、氮的时空分异特征，揭示优势物种演替的土壤学机制。研究成果对我国生态脆弱区草地适应性管理策略的制定具有重要的指导意义。

"毒害草"型退化草地是青藏高原南缘退化亚高山草甸的主要类型，围封能否消弱毒害草在亚高山草甸中的优势地位？随着围封年限的继续延长，毒害草和优良牧草的优势地位会呈现怎样的消长动态变化？引起这种变化的土壤学机制是什么？为探讨这一科学问题，本项目在前期研究的基础上，进一步开展了围封后大狼毒+西南委陵菜型退化亚高山草甸优势物种数量特征及土壤碳、氮、磷时空分异特征的研究。研究结果表明：（1）围封后滇西北大狼毒+西南委陵菜型亚高山草甸植被恢复演替，群落中优良牧草的优势地位显著增加，毒害草的优势地位下降。经5年以上的围封管理，大狼毒+西南委陵菜型亚高山草甸的优势物种组成由未围封样地的“大狼毒+西南委陵菜+绶草”演替为“大狼毒+草地早熟禾+西南委陵菜”。（2）围封后大狼毒+西南委陵菜型亚高山草甸0-10、10-30cm土层C、N、P含量显著增加，与未围封样地相比差异显著（P＜0.05），并且随着围封年限的延长，土壤C、N、P含量增加比例上升。同时，就围封过程中主要物种对土壤C、N、P空间分布的影响来看，在同一样地，大狼毒0-10cm根际土壤C、N、P含量显著高于西南委陵菜和草地早熟禾（P＜0.05），10-30cm土层无显著性差异。（3）滇西北大狼毒+西南委陵菜型亚高山草甸在围封恢复过程中，大狼毒种群数量特征与土壤C、N、P含量呈负相关关系，草地早熟禾种群数量特征与土壤C、N、P含量呈正相关关系。围封后滇西北亚高山草甸土壤养分含量提高，土壤结构改善，富足的土壤养分和良好的土壤结构在促进优良牧草生长的同时，间接的“抑制”了大狼毒的生长，这可能是围封后滇西北大狼毒+西南委陵菜亚高山草甸优势物种演替的驱动机制之一。本项目研究成果对我国生态脆弱区草地适应性管理策略的制定具有重要的指导意义。