水位变化对三峡库区低位消落带狗牙根种群的影响

[目的]研究三峡库区水位变化对狗牙根种群的影响,为库区低位消落带植被恢复的物种选择提供依据。[方法]分别于2008和2009年调查了三峡库区长寿段156m消落带的狗牙根（Cynodon dactylon L.）种群,研究了狗牙根种群地上分株与地下茎的生长发育,以及生物量的变化。[结果]2009年狗牙根地下茎的总茎长和总茎节数显著增长,分别比2008年增长了303.5%（P〈0.01）、411.1%（P〈0.01）;而分株的茎长、茎节数、叶宽、叶片数均显著被抑制,分别比2008年下降了60.1%（P〈0.01）、55.1%（P〈0.01）、28.6%（P〈0.01）、33.8%（P〈0.01）。同时,地下茎的总芽数、萌发芽数和芽数/茎长显著升高,分别比2008年增加了500.7%（P〈0.01）、228.5%（P〈0.01）和50.9%（P〈0.01）,而萌发率比2008年低45.3%（P〈0.01）。2009年狗牙根植株的分株、地下茎和根的生物量均显著下降,与2008年相比,其单位面积上分株、地下茎和根的鲜质量分别降低了65.6%、23.4%和70.8%,干质量分别降低了65.9%、18.8%和64.5%,差异达极显著水平（P〈0.01）;但其地下茎的鲜质量/总鲜质量和干质量/总干质量比2008年分别高64.6%（P〈0.01）、64.7%（P〈0.01）。[结论]库区水位调节显著促进了低位消落带狗牙根种群地下茎的茎长生长、芽和分株形成,而抑制了分株的生长发育。

Influence of the Water Level Change on the Cynodon dactylon Population in the Low Water-fluctuating Zone in Three Gorges Reservoir

[Objective] The reference for the selection of the species for the vegetation recovery in the low water-fluctuating zone of Three Gorges reservoir through the research on the influence of water level change on Cynodon dactylon population.[Method] The variation of the Cynodon dactylon population in the Changshou area—water-fluctuating zone(156 m) of Three Gorges reservoir in 2008 and 2009 was investigated and the growth and development of the plantlet and rhizome of C.dactylon population,and its variation of biomass were studied.[Result] The result showed that total length of the stem and total number of the node of C.dactylon rhizome were significantly increased in 2009,which were 303.5%(P<0.01) and 411.1%(P<0.01) more than those in 2008,respectively.The length and number of node,the width and number of the leaf were remarkably inhibited in 2009,which were 60.1%(P<0.01),55.1%(P<0.01),28.6%(P<0.01) and 33.8%(P<0.01) less than those in 2008,respectively.The total number of bud,the germinated bud and the ratio of bud number to stem length of rhizome were remarkably enhanced in 2009,which were 500.7%(P<0.01),228.5%(P<0.01) and 50.9%(P<0.01) more than those in 2008,respectively.The germination rate of the rhizome was 45.3% in 2009 compared with that in 2008(P<0.01).The biomass of plantlet,rhizome and root of C.dactylon were significantly decreased in 2009 and compared with those in 2008,65.6%(P<0.01) of the plantlet,23.4% of the rhizome and 70.8% of the root in unit-area were reduced respectively,which difference were at the level of P<0.01.The mass of the dry material of plantlet,rhizome and root were 65.9%(P<0.01),18.8%(P<0.01) and 64.5%(P<0.01) in 2009 less than those in 2008,respectively.The ratio of the fresh weight to total fresh weight of rhizome and the dry weight to total dry weight of rhizome in 2009 were 64.6%(P<0.01) and 64.7%(P<0.01) more than those in 2008,respectively.[Conclusion] The control of water level of the Three Gorges reservoir could accelerate the growth of rhizome and stem,the formation of bud and plantlet.