Growth Of Phragmites Research Articles

CLONAL INTEGRATION AND THE EXPANSION OFPHRAGMITES AUSTRALIS

The recent expansion of the reed Phragmites australis in western Atlantic salt marshes has become a conservation concern. Historically, Phragmites was restricted to the terrestrial border of marshes, but now it aggressively invades lower elevations. To explore factors influencing this expansion, we examined (1) the effects of physical factors and competitive interactions on the performance of Phragmites and (2) the role of clonal integration on the ability of Phragmites to invade low marsh habitats. We transplanted Phragmites into vegetation along an elevation gradient, with and with- out neighboring plants. Phragmites died when transplanted to the lowest marsh zone but survived and expanded in higher marsh zones. This suggests that the low oxygen availability characteristic of waterlogged soils limits Phragmites growth in the low marsh. Neighboring vegetation reduced Phragmites growth in all zones, and severing Phragmites rhizomes invading the low marsh reduced the survivorship and photosynthetic rate of ramets. These results suggest that Phragmites may invade low marsh habitats by initially es- tablishing itself in the high marsh and then expanding into lower, less favorable habitats using clonal integration. This has important implications for understanding the changing dynamics of New England salt marsh plant communities and developing management strat- egies for the control of Phragmites.

Clonal Integration and the Expansion of Phragmites australis

The recent expansion of the reed Phragmites australis in western Atlantic salt marshes has become a conservation concern. Historically, Phragmites was restricted to the terrestrial border of marshes, but now it aggressively invades lower elevations. To explore factors influencing this expansion, we examined (1) the effects of physical factors and competitive interactions on the performance of Phragmites and (2) the role of clonal integration on the ability of Phragmites to invade low marsh habitats. We transplanted Phragmites into vegetation along an elevation gradient, with and without neighboring plants. Phragmites died when transplanted to the lowest marsh zone but survived and expanded in higher marsh zones. This suggests that the low oxygen availability characteristic of waterlogged soils limits Phragmites growth in the low marsh. Neighboring vegetation reduced Phragmites growth in all zones, and severing Phragmites rhizomes invading the low marsh reduced the survivorship and photosynthetic rate of ramets. These results suggest that Phragmites may invade low marsh habitats by initially establishing itself in the high marsh and then expanding into lower, less favorable habitats using clonal integration. This has important implications for understanding the changing dynamics of New England salt marsh plant communities and developing management strategies for the control of Phragmites.

Shading by Phragmites australis: a threat for species‐rich fen meadows?

Abstract. Common reed (Phragmites australis Trin.) has spread in fen meadows on the Swiss Plateau during the last decades. An increased dominance of this tall grass may reduce the plant species richness and displace rare or endangered species because of the additional shade. To investigate whether this has actually happened and whether shading by Phragmites was likely to be responsible for the reduction, the plant species composition was surveyed in 241 plots (4 m2) with differing above‐ground biomass of Phragmites (ABP). Species richness and the occurrence of characteristic fen species were negatively related to site productivity (total above‐ground biomass), but correlations with ABP were generally weaker. The main change associated with increasing ABP within species‐rich fens (alliances Molinion and Caricion davallianae) was an increase of species characteristic of the more species‐poor alliance Filipendulion. Thus, Phragmites did apparently not play a disproportionate role in the reduction of species richness in the plant communities studied. Selective clipping experiments and light measurements also indicated that shading by Phragmites does not have a strong effect upon the performance of other species in the community, at least in the short term. The reason appeared to lie in the later seasonal growth of Phragmites compared with the other species. These results suggest that the direct impact of shading by Phragmites on the species richness of fen meadows is probably lower than has been assumed. However, possible long‐term or indirect effects still need to be investigated.

Dynamic Modeling of growth of Phragmites, as a Functional Tool in Water Quality Management

Recently, much attention has been drawn on experimental analysis of production potential and nutrient composition of the emergent macrophyte, Phragmites. But very few has attempted to analysis the phenomena using numerical simulation models. A dynamic growth model has been developed with the objective to simulate the seasonal variation of above and below ground biomass of Phragmites and it has been extended to simulate the nutrient composition of above ground organs. Basically, this model comprised of two sub models, biomassub and model nutrient sub model to simulate seasonal variation of biomass and nutrients. Given the initial rhizome biomass prier to growth commencement together with total global radiation (μE/m2/d) and daily mean air temperature (0C) for the intended simulation period, the model allows a reliable evaluation of production potential and mineral nutrient composition. This paper will discuss two applications made for seasonal variation of nutrient composition of Phragmites.

Underground organs ofPhragmites communis, their growth, biomass and net production

The present paper sums up the knowledge obtained from the study of growth periodicity in the underground organs ofPhragmites communisTrin. and from the analyses of differentPhragmites stands in three regions of Czechoslovakia. A period of intense growth ofPhragmites rhizomes was recorded in summer. Spring (end of April and beginning of May) and autumn (mainly September) seem to be the periods of most active root growth. During July and August, accumulation of reserve material takes place both in new and old rhizomes. In the stands investigated, the biomass ofPhragmites rhizomes varied from 2 kg/m2 to 5 kg/m2, and root dry weight from 0.08 kg/m2 to 3.6 kg/m2. The ratio of underground to total aboveground dry weight was highly variable (1.0 to 9.9). The estimated annual net rhizome production ofPhragmites, in two different stand, was 30% (Sakvický fishpond) and 60% (Nesyt fishpond) of the seasonal maximum above-ground biomass.