Estimation of n 1 echanical resistance of lakeside Phragmites stands Wolfgang

The power of resistance of reed stands against mechanical impact by waves and drifting matter is assessed using the mechanical properties of the stem wall (modulus of elasticity, breaking stress), the dimensions of the stem's cross section (diameter, momentum of inertia), and the culm density. The power of resistance of an individual stem (pmr) was found to be proportional to the bending stiffness (ME) and to the breaking strength (Ms) in the internode position where maximum deflection or breaking occurs. The power of mechanical resistance of reed stands (PMR) was found to be proportional to the sum of individual ME values (or Ms values, respectively) per unit surface (I m ). Two predictive models, based on the pmr and the PMR values were tested using mechanically damaged stands in the field; the pmr model fits observed values in 70-90% of all cases (damaged culms), the PMR model explains 53-67% of the variability in percentage of damaged biomass.