Root decomposition and nutrient flux following whole-tree harvest of northern hardwood forest

Decomposition of roots of Acer saccharum, Betula alleghaniensis, Fagus grandifolia and Picea rubens in a northern hardwood ecosystem was measured following whole-tree harvest of watershed 5 at Hubbard Brook Experimental Forest, New Hampshire. Decay of fine roots was initially rapid but declined abruptly after the 1st summer. Ash-free weight loss from small woody roots decreased with increasing root diameter and was much slower than decay rates for corresponding aboveground tissues. Weight loss rates among species generally were not significantly different, but large woody roots (10-100 mm diameter) of sugar maple decayed much more rapidly than the other species. Rapid release of K and Mg was observed for all roots. Initially high rates of N and P release were observed for fine roots, whereas these nutrients were effectively retained in decaying woody roots. Retention of Ca was observed for all roots; significant accumulation of Ca was observed in the larger size classes of woody roots. Particularly for N and K, release from decaying roots was an important nutrient flux pathway supplying stream outflow and vegetation regrowth in the first two years following forest harvest. -from Authors