Optimum water depth for restoration of Bolboschoenus planiculmis in wetlands in semi-arid regions.

Bolboschoenus planiculmis is a key wetland plant in the semi-arid regions of Songnen Plain, China, providing food and habitat for the endangered Siberian crane. B. planiculmis wetlands are being degraded by water shortages caused by anthropogenic activities and climate changes. However, the vegetation dynamics under hydrological fluctuations have been rarely reported. We conducted a two-year field investigation in B. planiculmis wetlands to determine the vegetation response to water level changes, and a comparative control experiment to examine the restoration effect of supplemental water on degraded community. We found that the community biomass was positively related with water depth under natural conditions, whereas plant diversity and richness were negatively related. The population density, biomass, and root/shoot ratio of B. planiculmis exhibited quadratic relationships with water depth. The optimum ecological threshold of water depth determining B. planiculmis populations was 11.2–36.1 cm. The control experiment demonstrated that water depth at 0–10 cm during the early growing season and 10–25 cm at later growing stages can enhance the dominance of B. planiculmis and help it outcompete other macrophyte species. Understanding the water requirement cycles of B. planiculmis is valuable for guiding water management plans for the rehabilitation of degraded natural wetlands. [ABSTRACT FROM AUTHOR]