Heterogeneous distribution of a floating‐leaved plant, Trapa japonica, in Lake Mikata, Japan, is determined by limitations on seed dispersal and harmful salinity levels. Issue 5 (25th July 2014)

• Record Type: Journal Article
• Authors: Nishihiro, Jun; Kato, Yoshikazu; Yoshida, Takehito; Washitani, Izumi
• Is Part Of: Ecological research. Volume 29:Issue 5(2014)
• Page Start: 981
• Page End: 989
• Publication Date: 2014-07-25
• Subjects: Macrophyte -- Ramsar Convention wetlands -- Salinity -- Seed germination -- Seed dispersal; Ecology -- Periodicals; Ecology -- Japan -- Periodicals; Écologie; Japon; Ecology; Japan; Ressource Internet (Descripteur de forme); Périodique électronique (Descripteur de forme); Periodicals; 577.05
• DOI: 10.1007/s11284-014-1186-6
• Languages: English
• ISSNs: 0912-3814

Abstract

Abstract: Factors affecting the within‐lake distribution of Trapa japonica were analysed in Lake Mikata, Japan, by integrating remote sensing analyses, field surveys, and laboratory experiments. The T . japonica bed has been expanding since 2006 and covered more than 60 % of the lake's area from 2008 to 2010. However, two parts of the lake, the upper and lower areas, retained open water, even during recent years. A survey of lake‐bottom sediments revealed a heterogeneous seed distribution. Although seed density exceeded 13 seeds/m 2 in the lake's central area, no seeds were observed in the upper and lower areas. A seed‐bag retrieval experiment showed that 75.6 % of seeds at the upper site germinated when seeds were artificially introduced, whereas 6.7 % of seeds germinated at the lower site. These results suggest that seed dispersal opportunities are the primary limitation on the distribution of T . japonica in the upper area. Brackish water was found in springs in the lower area, reflecting an adverse inflow of water from a downstream brackish lake. Laboratory experiments revealed significant adverse effects of water salinity on germination and early growth of T. japonica . Based on these results, we concluded that the heterogeneous distribution of T. japonica within the lake was determined by a combination of two factors: limitations on seed dispersal determined by the inflowing river and harmful salinity levels caused by inflows of seawater from the Sea of Japan via a downstream brackish lake.