Growth of Phragmites japonica on a sandbar of regulated river: morphological adaptation of the plant to low water and nutrient availability in the substrate

Abstract

The construction of upstream dams regulates flood magnitudes, reduces the inundation frequency of the riparian zones and curtails the discharge of sediments to the downstream. Adaptation of a Phragmites japonica colony growing at a rarely flooded sandbar (1.4 Â 0.25 km) was investigated. Above-and belowground biomass was sampled, together with litters on the ground surface of a quadrat and soil in the rhizosphere. Five sampling locations were selected with three locations located in sandy and two in stony areas. The results showed the total biomass and the ratio of above-to belowground biomasses were larger at the sandy sites than the stony sites. However, the fraction of root biomass (i.e. root to rhizome ratio) in the belowground biomass at the stony sites was higher than that at the sandy sites. Higher aboveground and total plant biomass in the sandy areas was because the plants had better access to water and nutrients than plants growing in stony beds. A higher proportion of root biomass, at the expense of rhizome biomass, in the belowground biomass of plant growing in stony sites was due to the difficulty in accessing water and inorganic nutrients. The ratios of nitrogen (N) to phosphorus (P) in the plant tissues were mostly between 5 and 10, indicating that plant growth was N limited. Low ratios of total N (TN) to total P (TP) were also recorded in soil samples, where TN was 300-700 mg/kg and TP was 300-350 mg/kg. A wide phenotypic plasticity observed in P. japonica was an importance factor to maximize the plant survival and fitness in frequently disturbed habitats, and this plasticity was the result of both true adjustment and ontogenetic drift. A mitigation effort, aimed to prevent coarsening of the riverbed by supplying sand to the downstream, can actually advance the development of P. japonica colonies.

Spatial and temporal tree colonization in a midstream sediment bar and the mechanisms governing tree mortality during a flood event

“…This reduces the magnitude of the drag force and reduces the probability that an individual tree will be displaced R. pseudoacacia colonized fine sediment and this species had a high level of mortality due to washing away. According to our results, R. pseudoacacia extends roots horizontally, probably to acquire space quickly and derive nutrients in the relatively sterile soil of the sediment bar, against competition from other species (Asaeda et al, 2009). The vertical propagation of R. pseudoacacia was observed to be not more than 50 cm deep, and it has been noted elsewhere that R. pseudoacacia is a shallow rooted species (Peng et al, 2004;Wisconsin Department of Natural Resources, 2009).…”

“…The Arakawa River has been subject to gradual forestation in its flood plains as a result of river regulation. The largest flood on record took place on 7 September 2007 (Asaeda et al, 2009), and resulted in the desertification of a substantial area downstream.…”

“…Floods are also major disturbances for submersed, emergent or riparian plant communities (Nilsson, 1987;Giller and Malmqvist, 1998). Both sandy and stony habitats in highly disturbed, steep and frequently flooded rivers are colonized by pioneering plant species that commonly display physiological and/or morphological attributes that enable them to tolerate such disturbances (Capon, 2005;Asaeda et al, 2009).…”

Nanometer-scale elongation rate fluctuations in theMyriophyllum aquaticum(Parrot feather) stem were altered by radio-frequency electromagnetic radiation

“…[46][47][48] Plants may thus have adapted to EMR exposure as they are continuously exposed to EMR in the natural environment due to the continuous operation of communication transmitters. Therefore, it is important to study plants exposed to EMR for long periods of time to understand any mechanisms used by plants to adapt to EMR exposure.…”

Effects of water turbulence on plant, sediment and water quality in reed (Phragmites australis) community

“…size and the fine particles content of the bottom sediments, the same relationship for coarse sediments was negative, i.e correlation coefficients for sediment particle sizes of 1000, 500, 250, 125 and 62.5 µm were -0.193, -0.092, 0.119, 0.394 and 0.355, respectively. Fine particles would provide better growth and ease of penetration for rhizomes compared to coarse sandy sediments because of mechanical obstruction of sandy beds (Asaeda et al, 2009).…”