Internal heterogeneity of ramet and flower densities of Typha angustifolia near the boundary of the stand

Abstract

Fifteen relatively narrow stands of Typha angustifolia, including both stands bounded to open water and ridged boundary, were investigated in terms of the distributions of ramet density as well as the fraction of flowering ramets. The ramet density, fraction of flowering ramet and morphological characteristics of ramets were measured continuously from one side of the stand to the other, together with depth and the nutrient concentration of pore water. The rhizome biomass was also measured at the periphery and at the center of the stand. The results indicated that the shoot density declined gradually from the edge to the center, however, the fraction of the flowering ramets were significantly higher at the edge while it rapidly declined away from the edge. Statistical analyses indicate that the ramet density depends on either depth or nutrient level of the pore water; however, the distance from the edge was the most probable factor to reduce the fraction of the flowering ramets. The rhizome biomass was mostly larger at the periphery than at the center, likely because the accumulation of the horizontal rhizomes as extension was blocked by the boundary. High flowering fraction near the periphery was probably induced by the hormonal change caused by the blockage. However, a large fraction of ramets flowered simultaneously with large rhizome biomass at the periphery, likely because of the preferable light climates compared with inside the stand.