Litter decomposition in southern Appalachian black locust and pine-hardwood stands: litter quality and nitrogen dynamics

Litter decomposition in southern Appalachian black locust and pine-hardwood stands: litter quality and nitrogen dynamics. Can. J. For. Res. 18: 54-63. To compare litter decomposition and nitrogen (N) dynamics in 16-year-old black locust and pine-hardwood forest stands, weight loss, N concentration, and litter quality of the dominant species in each stand were monitored for 863 days, using litterbags. The species studied were Robinia pseudo-acacia L. (leaflets and rachises), Liriodendron tulipzfera L., and Rubus spp. (leaves and stems) in the black locust stand and Kalmia latifolia L., Pinus rigida Mill., and L. tulipifera in the pine-hardwood stand. Between-stand comparison of L. tulipifera leaf litter indicated a significant stand effect on weight loss during the first 8 months but no significant stand effects on N concentration and net immobilization. Initial lignin content was highly correlated to percent weight remaining and net N immobilization after 33 1 and 863 days. All litter types exhibited an absolute increase in " lignin " that appeared to originate from the more soluble litter fraction. Robinia pseudo-acacia leaflets, P. rigida, K. latifolia, and Rubus stems decomposed slowly, but only the latter two species were in the net N immobilization phase at day 863. Rubus leaf litter decomposed rapidly, releasing 70% of its original N by day 33 1. The role of Rubus and other understory species in influencing organic matter and N accretion in these early successional systems is discussed. Robinia pseudo-acacia leaflets contained 8 1% of their original N at day 863. This retention of N, coupled with its greater potential to form recalcitrant material during decomposition, suggests a mechanism to explain the long-term effects of Robinia pseudo-acacia on N storage in the forest floor and soil. Litter decomposition in southern Appalachian black locust 1 and pine-hardwood stands: litter quality and nitrogen dynamics. Can. J. For. Introduction The chemical quality of litter, through its interaction with macroclimate and the litter biota, largely regulates the rate