三峡库区消落带狗牙根群落生物量和物种多样性对刈割的响应

Effects of Mowing on Biomass and Species Diversity of Cynodon dact ylon Community in the Riparian Zone of the Three Gorges Reservoir Area

【目的】探究三峡库区消落带不同高程狗牙根(Cynodon dactylon)群落的生物量和物种多样性对刈割的响应。【方法】在三峡库区汝溪河消落带160 m和170 m高程选择狗牙根群落,设置不刈割、留茬30 cm、留茬20 cm和留茬10 cm共4种刈割强度处理,研究刈割处理后不同高程狗牙根群落生物量和物种多样性的变化。【结果】刈割明显降低了狗牙根的盖度、密度、重要值和地上生物量,且170 m高程处生长的狗牙根生物量下降幅度更大;除了生长在170 m高程经留茬30 cm处理的狗牙根群落以外不同刈割强度处理下的狗牙根群落生物量无统计学意义上的差异,160 m高程处狗牙根群落生物量明显高于170 m高程处狗牙根群落生物量;生长在170 m高程处狗牙根生物量占比与生长在160 m高程处的狗牙根相比下降幅度更大,而狗牙根群落中其他物种的生物量占比随刈割强度增加逐渐上升;刈割处理明显增加了狗牙根群落的丰富度指数、Simpson指数、Shannon-Wiener指数和Pielou均匀度指数;群落生物量与物种多样性之间无统计学意义上的相关性,但狗牙根生物量与物种多样性呈统计学意义上的负相关关系(p<0.05)。【结论】三峡库区消落带160 m高程处生长的狗牙根比170 m高程处生长的狗牙根更能耐受刈割胁迫,一定程度的刈割可以明显提高狗牙根群落的物种多样性。

[Purposes]To investigate the effect of mowing on the species diversity and biomass of Cynodon dactylon communities growing at different elevations in the riparian zone of the Three Gorges Reservoir Area(TGRA).[MethodsJC.dactylon communities in the riparian zones of 160 m and 170 m in the Ruxi River were selected.The effects of elevation and mowing on community biomass and species diversity were studied by using no mowing control,stubble 30 cm,stubble 20 cm,and stubble 10 cm mowing treatments.[Findings]Mowing significantly reduced the coverage,density,important value,and aboveground biomass of C.dactylon,and the biomass of C.dactylon decreased more at 170 m elevation.There was an insignificant difference in C.dactylon community biomass under different mowing intensities(except for C.dactylon communities grown at 170 m elevation treated with stubble 30 cm),and the C.dactylon community biomass at 160 m elevation was significantly higher than that at 170 m elevation.The proportion of C.dactylon biomass at 170 m elevation decreased more than that at 160 m elevation,mowing significantly increased the biomass of other species in the community.The mowing treatment significantly increased the Species richness,the Simpson index,the Shannon-Wiener index,and the Pielou evenness index.There was no significant correlation between community biomass and species diversity,but there was a significantly negative correlation between C.dactylon community biomass and species diversity.[Conclusions]C.dactylon grown at 160 m elevation were more tolerant of mowing stress than at 170 m elevation in the TGRA,a certain degree of mowing can significantly increase the species diversity of the C.dactylon community.