Growth Response of Potamogeton crispus to Lime Application in Experimental Mesocosms; Technical note

摘要

The objectives of the research were to examine Potamogeton crispus shoot, root, and propagule (i.e., turions) growth response to lime application in experimental outdoor mesocosms. Potamogeton crispus is a nonnative species that has become widespread in temperate regions of North America (Bolduan et al. 1994). Because densities are often high and senescence occurs in mid-summer, P. crispus also represents an important source of internal nutrient loading for algal assimilation (James et al. 2002). Its life cycle is unusual in that it propagates primarily via vegetative structures called turions. P. crispus grows rapidly in early spring and develops a thick canopy by early to late May in northern climates. Turion development is believed to be triggered by water temperatures greater than 20 degrees C and a photoperiod greater than 12 hours (Chambers et al. 1985). Shortly after turion production, the population senesces in late June through early July and turions settle to the sediment for germination and over wintering as small plantlets. Dense plant populations can produce greater than 1000 turions .m(-2 exp.), thereby ensuring a large turion bank for production of next year's cohort (Woolf and Madsen 2003). Thus, P. crispus management plans need to target turion production versus peak biomass in order to achieve long-term population reduction (Poovey et al. 2002; Woolf and Madsen 2003). One of the management concerns is specifically targeting P. crispus propagation with minimal impact to the native macrophyte community. Its rapid growth cycle in early spring while native species are still dormant provides a window for control prior to turion formation. Herbicide application (Diquat and Endothall) during this period can be very effective in reducing both biomass and turion formation (Netherland et al. 2000).