围栏措施对青藏高原高寒草甸群落结构和稳定性的影响

人工条件下高寒脆弱生态系统群落结构及其稳定性的变化是研究其生态功能的重要内容。本研究以乌玛塘高寒草甸示范区为例,对研究区植被进行植物群落学调查,对植物群落功能群和稳定性进行分析,研究了高寒草甸植物群落在围栏4年和8年后,围栏内外群落的结构变化和稳定性差异。结果表明,1)围栏内物种多样性大于围栏外;围栏4年后群落内一年生、二年生植物重要值明显高于围栏外;围栏8年后,群落优势种发生变化,高山嵩草(Kobresia pygmaea)优势度降低,一年生、二年生植物甘肃马先蒿(Pedicularis kansuensis)成为优势物种之一;多年生禾草,杂类草以及一年生、二年生植物3个功能群所含物种数显著多于围栏外(P0.05);2)围栏4年后群落稳定性表现为围栏内围栏外,8年后表现为围栏内围栏外。短期围栏使得群落稳定性高于未围栏的群落,但是群落结构差异并不明显,随着围栏时间增加,群落结构发生明显变化,且群落稳定性降低,围栏外群落则趋向于稳定。

Effect of fences on functional groups and stability of the alpine meadow plant community in the Qinghai-Tibet Plateau

The changes in community structure and stability of the alpine meadow ecosystem under artificial conditions are an important way to study its ecological function.To explore this kind of change in the Qinghai-Tibet Plateau,field investigations within and outside of fences in a permanent sample plot (established in 2005) in Wumatang were conducted in August of 2009 and 2013.Species richness(R),differences in functional groups,and M.Godron stability index were analysed to explore the differences between fenced and unfenced communities.The results showed that 1) the species richness of the fenced community was greater than unfenced;the number of annual and biennial plants in the fenced community was significantly greater than in the unfenced one in 2009;the dominant species of the fenced community changed from Kobresia pygmaea to Pedicularis kansuensis by 2013,and species belonging to perennial grasses,forbs,and annuals and biennials meant the fenced community was obviously richer than the unfenced community;and 2) the M.Godron stability index showed that the fenced community was more stable than the unfenced one in 2009,but less stable than the unfenced community in 2013.The fenced community structure showed an obvious change and the stability presented a downtrend as the time went by,whereas the stability of the unfenced community presented an uptrend.