Despite this wide range of treatments, our meta-analysis confirms that there is a highly significant overall effect of drought on the amount of total biomass (dry weight) of riparian wetland plants (random-effects model, P < 0.001; Table 1 ), which becomes critical when droughts last longer than approximately 30 days (Fig. 1 ).
If we look at these genera specifically, response ratios of the survival of seedlings of both Populus and Salix show a negative relationship with drought duration, while seedling survival of Tamarix does not show a significant trend and seems hardly affected by drought.
The cases with a 1–2 cm water table decline per day reveal a relatively mild negative relationship, which is almost significant.