Publication Date:
2013-08-03
Description:
Riparian vegetation influences hydraulic and morphodynamic river processes and may contribute to sediment stabilization. In turn, vegetation recruitment and growth on non-cohesive fluvial deposits, strongly depends on river hydrology and the ability of roots to develop and anchor efficiently in order to resist flow erosion. In this paper, we examine the above and the below ground seasonal growth dynamics of Salix cuttings in relation to local river hydro- and morphodynamics, based on a detailed and unique data set. During two season-long campaigns in 2009 and 2010, 1188 and 1152 cuttings respectively were organized in square plots and planted on a gravel island of the restored reach of the River Thur (Neunforn, Thurgau, Switzerland). Each year, all cuttings were monitored almost regularly from the beginning until the end of the growing season (April-September). Root development statistics were also obtained from high-resolution scanner analysis of carefully uprooted samples from selected plots. Our results show how cutting survival as well as the nature and strength of correlations between island topography and cutting growth statistics depend on river hydrology. An empirical functional form that links root development on the basis of measured main stem length is then proposed for predictive purposes. Cutting mortality following flood events is shown to depend nonlinearly on both erosion and deposition processes, whereas it appears more linearly related to the magnitude of the bed shear stress distribution generated by the maximum seasonal flood. This analysis allows an identification of an important threshold for plant survival within different erosion and deposition regimes, which explains the spatial and temporal distribution of the surviving cuttings within the plots. These results have practical implications, for instance for evaluating, planning and managing the use of riparian trees in restoration projects. This article is protected by copyright. All rights reserved.
Print ISSN:
0885-6087
Electronic ISSN:
1099-1085
Topics:
Architecture, Civil Engineering, Surveying
,
Geography
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