TEMPORAL AND DEPTH-RELATED PATTERNS OF FINE-ROOT DYNAMICS IN NORTHERNHARDWOOD FORESTS

1 The dynamics of fine (< 2.0 mm) roots growing in two northern hardwo od forests were quantified to a depth of 1 m in 10-cm increments, We h ypothesized that patterns of root production and mortality would be br oadly synchronous at all depths, but that deep roots would be comparat ively less dynamic than shallow roots, 2 Our data showed that shallow roots were responsible for the majority of total annual fine root prod uction and mortality. Nearly half of all roots growing and dying in th e I-m profile occurred in the upper 20 cm of the soil, while roots loc ated at depths of 75 cm or more accounted for only 11% of annual produ ction and 4% of annual mortality. 3 Fine root production prior to, or coincident with, canopy expansion was significant at all depths. The r elative importance of early fine root growth generally increased with depth, with between 50 and 80% of annual production occurring prior to mid-June at depths exceeding 50 cm. Episodic deep root production dur ing the growing season appeared to be related to periods of high water demand. 4 Patterns of fine root mortality were more variable among de pths. Mortality was distributed rather evenly throughout the year near the soil surface, but mid-season mortality was generally low at depth s greater than 50 cm.