Tree colonization trends on a sediment bar after a major flood

Abstract

Tree mortality and regeneration in riparian areas are greatly influenced by flooding. The elevational distribution of Salix spp. and Robinia pseudoacacia were investigated by observing densities and standing conditions before and after a major flood on a sediment bar in the middle reaches of the Arakawa River in Kumagaya, Japan. The subsequent tree recruitment was also examined. R. pseudoacacia was easily washed away with the eroded sediment, whereas Salix spp. was found to be more tolerant. Both species were able to survive even after collapsing, provided that their roots were fully or partially embedded in the sediment. Re-shooting of collapsed trees, rather than emergence from saplings (either by seeds or vegetative fragments), was observed to be the major method of recruitment after the flood. Therefore, tree density before the flood was unchanged, unless the trees were subject to washing away. Salix spp. recruitment was mainly observed in low-lying areas and R. pseudoacacia in elevated areas. Recruitment from saplings was species-specific. Salix spp. at high elevations originated mainly from shoot fragments as they need high levels of moisture for seed germination and at higher elevations, sediment moisture content is very low. R. pseudoacacia, on other hand, originated mainly from roots and seeds. At a given elevation, past recruitment patterns indicated that the annual recruitment of trees increased with tree density up to a particular threshold of recruitment density. Further increases in tree density beyond that optimum value resulted in a decline in recruitment. Furthermore, threshold density was observed to increase along with elevation for R. pseudoacacia while declining with Salix spp.

Modelling of nutrient dynamics and vegetation succession in midstream sediment bars of a regulated river

“…Therefore, while the flushing of vegetation is one of the most important processes that is used to produce these vegetative structures, its succession is based on an alteration of sediment characteristics, such as its nutrient condition in the basic process. Asaeda et al (2010) and Asaeda et al (2011b) reported that the colonization of two dominant tree species in the Ara River floodplain of Japan, namely Salix spp. and R. pseudoacacia, is determined by a difference in the tolerance of each species to flooding-induced sediment mobilization.…”

Development of a simulation model considering vegetation growth and flushing in Arakawa River

“…Robinia pseudoacacia and Albizia julibrissin. Details are given in Asaeda et al (2009Asaeda et al ( , 2011. Figure 2 were taken before and after the flood that the great flood caused by Typhoon No.…”

“…From the field observation by Asaeda et al (2011), the criteria was obtained for the surviving trees after the 2007 flood and the scouring depth of the ground surface. It is obtained such that 50% of the trees are lost if the scour depth is 0.5 m, and all trees are washed away if the scour depth is 1.0 m or more, as is shown in Fig.…”

Assessing the Effects of Periodic Flooding on the Population Structure and Recruitment Rates of Riparian Tree Forests

“…One of the major disruptions that needs to be considered in fluvial environments is the successive effect of floods on forest stands. Frequent floods and heavy flooding are dominant factors in the dynamics and structure of riparian stands [20,21]. It is known that heavy floods can cause considerable destruction of trees.…”

“…Furthermore, it is recognized that the flood regime and sediment mobility are responsible for the configuration of channels, floodplains and riparian vegetation [22,23]. Furthermore, the physiological characteristics of forest communities may indeed vary depending on soil and sediment properties, as well as the microtopography of the riverbanks, which are gradually shaped by successive floods [18,21,24].…”