Regeneration failure of lakeshore plants under an artificially altered water regime

Abstract

To reveal the effects of artificial alteration of water level regime on the regeneration of lakeshore plants from seeds, we examined the factors causing regeneration failure in Lake Kasumigaura, Japan. A survey of microtopography within and around a remnant fragment of lakeshore vegetation revealed that, over a large range, the habitat is frequently inundated in spring under the current water regime, although it was rarely inundated under past water regimes. Analysis of the patterns of seedling emergence and establishment at microsites at various elevations revealed a significant negative correlation between number of inundation days and abundance or species-richness of seedlings that emerged in the spring. Most seedling deaths occurred when the study site was inundated. We suggest that regeneration failure caused by the artificial raising of the lake's water level is one of the principal mechanisms of the recent vegetational decline in the lake.

Relationship between seed and clonal growth in the reproduction of Carex rugulosa Kük. in riverside meadows

“…This suggests that seedling deaths might be induced by submergence. It has been recognized that the young seedlings of many marsh plant species are very sensitive to submergence and either die or stop growing if they are submerged (Armstrong et al 1999;Mauchamp et al 2001;Nishihiro et al 2004b). In C. rugulosa, it is considered that seedlings can survive if the rainfall is not enough to cause inundation of marsh ground during the juvenile period or if seeds germinate in relatively high areas where seedlings are not submerged during rainy days.…”

“…The survival rate of seedlings can be reduced by physical conditions of the habitat or other biological factors. Inundation or wave action can severely suppress seedling growth and increase mortality (Armstrong et al 1999;Mauchamp et al 2001;Budelsky & Galatowitsch 2004;Nishihiro et al 2004b). If clonal ramets grow densely, seedling growth will be affected through competition with clonal rivals (Eckert et al 2003).…”

Developing water level regulation strategies for macrophytes restoration of a large river-disconnected lake, China

“…Second, after shifted to higher elevation, floating and submerged macrophyte seedlings germinated in shallow water areas would be exposed to air in April-June because of the gradually decreased water level during that time. Seedling stage is usually accompanied by extremely high mortality due to the lower resistance to external interference (Silvertown and Dickie, 1980;Mauchamp et al, 2001;Nishihiro et al, 2004). The drought caused by low water level in April-June would be destructive to the floating and submerged macrophyte seedlings.…”

Quantitative evaluation of water-level effects on “regeneration safe-sites” for lakeshore plants in Lake Kasumigaura, Japan

“…Our previous studies in the remnant lakeshore reedmarsh suggest that although species rich soil seed banks are still retaining in the soil, the opportunity for seed germination and/or seedling establishment is largely reduced by the inundation (Nishihiro et al 2004a(Nishihiro et al , 2004b. The reduction in regeneration safe-sites is suspected as a major cause of the recent decline of the species diversity.…”

“…Marsh plants are highly sensitive to changes in water regime: overly high water levels have caused declines in or the extermination of their populations (van der Valk 1981, Galinato and van der Valk 1986, Schneider 1994, Lenssen et al 1998, Baldwin et al 2001, Budelsky and Galatowitsch 2004. Furthermore, germination and seedling establishment stages of marsh plants can be severely inhibited by inundation (Galinato and van der Valk 1986, Baldwin et al 1996, Lenssen et al 1998, Seabloom et al 1998, Nishihiro et al 2004a). Inhibition of regeneration by seeds can lead not only to the immediate disappearance of above-ground populations of annual plants, but also to decreases in the size and genetic diversity of perennial plant populations (Watkinson and Powell 1993).…”