不同群落中米氏冰草和羊草的年龄结构动态

米氏冰草和羊草都是根茎型禾草,是典型的无性系植物。采取单位面积挖掘取样法,对呼伦贝尔沙地植被次生演替过程中的米氏冰草和羊草种群分株年龄结构进行调查。结果表明,在单生和混合群落中,米氏冰草分株分别由3和4个年龄级组成,羊草均由2个年龄级组成;米氏冰草分株数量和生物量年龄结构变化基本一致,即随着生长年限的延长,呈减少低龄级和增加高龄级比例的趋势,使单生群落中始终为增长型,但接近于稳定型,混生群落中由增长型变为稳定型。羊草分株数量和生物量年龄结构在连续2a均为明显的增长型。羊草各龄级平均单株生产力均高于米氏冰草,平均是米氏冰草的5.2倍。米氏冰草和羊草种群分株年龄结构的变化,蕴含着米氏冰草种群的优势地位将被羊草种群取代的趋势。

Dynamics of age structures on Agropyron michnoi and Leymus chinensis in different communities

Agropyron michnoi(short for A.michnoi) and Leymus chinensis (short for L. chinensis) are both rhizome grass in clonal plants. A.michnoi is one of the pioneer species in the secondary succession process showing good adaptivity to the Hulunbeier sandy environment, While L. chinensis is a dominant species of zonal vegetation. The coexistance of A.michnoi and L. chinensis populations in the succession indicated that, the seral process has entered into the transition stage from sandy vegetation to normal grassland plant. To understand its details, the three sample plots were prepared in the mixed dominant population community, ie. A.michnoi solitary plot (P1), L. chinensis solitary plot (P2) and mixed plot (P3). The method of plant reproductive ecology was used in excavation sampling in the elemental area (25cm×25cm, depth 30cm), and it was repeated for 5 times. The mixed dominant population community was investigated and the age class of tillers was identified by the age structure of tillering nodes. The results indicated that ramet modules of A.michnoi consisted of 3 or 4 age classes respectively in 2009 and 2010, in single and mixed communities; While L.chinensis consisted of 2 age classes; As for A.michnoi, the variations of ramet modules numbers were similar to those of biomass age structures.The fact reveals that, with the increase of growing years, there may be a downward trend of low age class and an upward trend of high age class.As a result, the single community always the growth type, but may close to stable type, and the mixed community may chang from growth type to stable type. Additionally, the number of ramet modules and biomass age structures of L.chinensis all showed growth type apparently in 2 years running. The single plant productivity of L.chinensis of all age classes was 5.2 times higher than that of A. michnoi on average. The changes of the tiller's age structures showed the tendency that the superiority of A.michnoi community may be replaced by L.chinensis.