Fluctuations of element concentrations during the growing season of Polytrichum formosum (Hedw.)

Abstract

Fourteen elements (Al, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Ni, Pb, Sr, Ti, and Zn) were quantitatively determined by AES/ICP in aboveground parts of the endohydric moss Polytrichum formosum (Hedw.) after sampling over regular intervals from 1985 to 1987. With the exception of K, Mg, and Zn all elements showed a large continuous fluctuation (> 30%) during the growing season. Four different patterns of seasonal variation were found: (1) large seasonal variations of element concentrations (∼80%) with maximum concentrations in winter and lowest concentrations in the summer months (Al, Fe, Cr, Mg, Pb, and Ti), (2) smaller seasonal variations (∼50%) with maximum concentrations in winter and lowest concentrations in summer (Ba, Ca, Cd, Cu, Sr), (3) slight seasonal variations (∼30%) with maximum concentrations in the summer (K), and (4) slight seasonal changes (∼30%) with maximum concentrations in the winter (Mg and Zn). The relative biological variance of element concentrations between 9 different stands of Polytrichum formosum decreases in the following sequence: Ti, Al, Pb, Fe, Cr, Ni, Ba, Ca, Cu, Cd, K, Mg, Sr, Zn. The relative biological variance of individual elements is generally lower than the variance in element concentrations caused by seasonal changes. Because of its high biological variance for most elements investigated (seasonal as well as between different stands of Polytrichum formosum) this moss should only be used as a passive bioindicator, if all other environmental parameters are standardized.