水位变化对三峡库区低位狗牙根种群的影响

2009年调查研究了三峡库区长寿段消落带的狗牙根（Cynodon dactylon L．）种群，探讨了库区水位变化对低位狗牙根种群的影响。结果表明，156m处狗牙根地下茎的总茎长、总茎节数和总茎节数／总茎长大于150m处的狗牙根，分别比后者多20．3％、30．1％、11．3％；而其地下茎的总芽数／总茎长、萌芽数和萌芽率分别比后者低7．5％、34．3％、74．9％。同时，156m处狗牙根分株的株数、茎长、叶宽、叶长低于150m处的狗牙根，分别比后者少了26．2％、10．8％、19．0％、37．9％；其茎节数、茎节数／茎长、叶片数、根长较大，分别比后者增加了18．7％、34．2％、10．0％、22．6％。156m处狗牙根植株分株的鲜质量、干质量、鲜质量／总鲜质量、干质量／总干质量分别比150m处的狗牙根低32．5％、13．2％、18．2％和14．2％；其地下茎的鲜质量、干质量、鲜质量／总鲜质量、干质量／总干质量分别比后者高5．8％、17．5％、27．2％、15．2％；且前者的分株、地下茎和根的干鲜质量比均分别比后者高29．6％、12．5％和17．6％。表明，库区水位变化显著促进了150m处狗牙根地下茎茎节伸长、芽形成、芽萌发和分株的生长。因而，低位狗牙根对库区水位变化具有较强的适应能力。

Influence of water level fluctuating on Cynodon dactylon population of low water level zone in Three Gorges Reservoir

To investigate influence of water level fluctuating of Three Gorges reservoir on Cynodon dactylon population in low water level zone, C. dactylon population in Changshou area were studied in 2009. Results showed that total stem length, total node number and the ratio (total node number to total stem length) ofC. dactylon rhizomes in 156 m water level zone were more than those in 150 m water level zone, which increased 20.3%, 30.1% and 11.3%, respectively. And total buds number to total stem length ratio, ger-minated buds number and germination rate of the former rhizomes were 7.5%, 34.3% and 74.9% lower than those of the latter, re-spectively. At the same time, plant number, stem length, leaf width and leaf length of the former ramets were lower than those of the latter, decreased 26.2%, 10.8%, 19.0% and 37.9%, respectively. And node number, node number to node length rate, leaf number and root length of the former ramets were more than those of the latter, with the increase of 18.7%, 34.2%, 10.0% and 22.6%, respec-tively. Furthermore, fresh mass, dry mass, fresh mass to total fresh mass ratio and dry mass to total dry mass ratio of the former ramets decreased 32.5%, 13.2%, 18.2% and 14.2% respectively compared with the latter. Instead, the promotion of the former rhi-zomes correspond to 5.8%, 17.5%, 27.2% and 15.2% respectively. Moreover, the former ratio of dry-to-fresh mass of the former ramets, rhizomes and roots were 29.6%, 12.5% and 17.6% more than those of the latter, respectively. It indicated that water level fluctuating enhanced rhizomes' nodes elongation, buds formation and germination, and ramets growth of C. dactylon in 150m water level zone. So, C. dactylon has a strong adaptability to water level fluctuating in Three Gorges reservoir.