First assessment of root biomass and root carbon and nitrogen stocks in Turkish floodplain forests

Estimation of whole root biomass including coarse and larger roots and root balls can provide better understanding of carbon and nitrogen stocks in floodplain forests. Whole root systems of nine ash trees (Fraxinus angustifolia Vahl.) and six alder trees (Alnus glutinosa L.) trees ranging in diameter breast height (dbh) from 29.1 to 72.0 cm for ash and from 29.1 to 44.3 cm for alder were excavated, and their small < 1 cm, medium 1-4 cm, larger > 4 cm and root-ball biomass, and root carbon and nitrogen stocks were determined in Karacabey floodplain forest in Bursa, Turkey. In addition, for the method comparison, small root biomass (< 1 cm) was also determined using soil-core method. The whole root biomass of ash trees varied from 167.7 to 186.8 Mg ha^-1. Alder trees had lower whole root biomass than ash trees ranging from 49.0 to 63.6 Mg ha^-1. The determination of small root biomass by soil excavation method was nearly two-fold higher than by soil core method. Both root carbon and nitrogen stocks showed an increase with increasing root diameter. Among the tree characteristics (dbh, age, height, and volume), the dbh showed the highest correlation with whole root biomass and root carbon and nitrogen stocks for both tree species. It is concluded that young trees can have higher small, medium, and large root biomass and store more C and N in those roots, whereas older trees can have higher root-ball biomass and root-ball carbon and nitrogen stocks in Karacabey floodplain forests.