淀山湖沉水植物——苦草群落恢复影响因子研究

Effects of environmental factors on Vallisneria natans restoration in Lake Dianshan

在淀山湖0.5、1.0、1.5、2.0 m水层进行苦草(Vallisneria natans)现场生长实验,试图找出淀山湖苦草植被恢复的适宜环境条件。试验期间每天测量光照强度和水体溶解氧等环境因子,每隔10 d监测苦草的根长、株高、鲜重等生长指标的变化情况。结果表明:水深对苦草的生长具较显著影响,光照强度、溶氧分别和苦草日相对生长率具显著相关性;苦草的株高、叶片数、根长等生物学生长指标在0.5、1.0 m水层生长良好,1.5 m与2.0 m均出现不同程度的负增长状况。光照强度与苦草日相对生长率之间具有显著相关性(r=0.905),0.5、1.0 m水层的光照强度下苦草的相对生长率分别为0.14和0.11,而1.5、2.0 m水层的光照强度下苦草出现负增长的情况。水中的溶解氧含量与苦草成活率之间具有显著相关性(r=0.935)。随着水深的增加,溶氧逐渐降低,苦草的成活率也逐渐下降。在2.0 m水层处,溶氧均值为2.76 mg.L-1,苦草的成活率为46.5%,在1.0 m水层处,溶氧为5.66 mg.L-1,苦草成活率为86.5%,因此,淀山湖苦草群落恢复宜先在1.0 m以浅的沿岸带开展。

We conducted an experiment in Lake Dianshan to investigate the optimal environmental factors for the survival and regrowth of Vallisneria natans.Light intensity and DO were measured daily from August 12,2010 to September 22,2010 at four different depths（0.5,1.0,1.5 and 2.0 m） in Lake Dianshan.Plant growth indices,e.g.,plant height,shoot length,and fresh weight were also measured every 10 days during the same period at each water depth.Statistical results showed that growth rate of Vallisneria natans was positively related to light intensity（r=0.905） and negatively related to depth.The relative growth rates were 0.14 and 0.11 in 0.5 and 1.0 m,respectively.Plant height,leaf number,and root length were higher in waters with depths of 0.5 and 1.0 m than in waters with depths of 1.5 and 2.0 m.Dissolved oxygen was greatly related to the survival rate of Vallisneria natans（r=0.935）.About 86.5% of Vallisneria natans survived in depth of 1.0 m where DO was 5.66 mg·L-1,while only 46.5% survived in depth of 2.0 m where DO was 2.76 mg·L-1.We suggest to begin the restoration of Vallisneria natans in littoral zone,where depth is less than 1.0 m.