Table 3. The density (ind/m²) (mean±SD) of the V. spiralis buds and the plantlets in different lakes between 2011 and 2012.

	Banghu Lake		Shahu Lake		Changhuchi Lake		Dahuchi Lake		Average
year	2012	2011	2012	2011	2012	2011	2012	2011	2012	2011
Density	59.5±39.1	24±13.9	15.8±19.7	14.7±5.9	59.7±47.3	25.6±10.8	17.1±19.3	0.4±0.8	38.6±38.8	18.2±13.6
sampling size	160	147	80	102	40	90	110	66	390	315
chi-squared	104.437***		5.593*		19.721***		48.164***		51.682***

^***p<0.001;

^**p<0.01;

^*p<0.05.