Response of nitrogen mineralization dynamics and biochemical properties to litter amendments to soils of a poplar plantation

Understanding the impact of plant litters on soil nitrogen (N) dynamics could facilitate development of management strategies that promote plantation ecosystem function. Our objective was to evaluate the effects of different litter types on N mineralization and availability, microbial biomass, and activities of l-asparaginase and o-diphenol oxidase (o-DPO) in soils of a poplar (Populus deltoides) plantation through 24 weeks of incubation experiments. The tested litters included foliage (F), branch (B), or root (R) of poplar trees, and understory vegetation (U) or a mixture of F, B, and U (M). Litter amendments led to rapid N immobilization during the first 4 weeks of incubation, while net N mineralization was detected in all tested soils from 6 to 24 weeks of incubation, with zero-order reaction rate constants (k) ranging from 7.7 to 9.6 mg N released kg^?1 soil wk^?1. Moreover, litter addition led to increased microbial biomass carbon (C) 49–128% and increased MBC:MBN ratio by 5–92%, strengthened activities of l-asparaginase and o-DPO by 14–74%; Up to about 37 kg N ha^?1 net increase in mineralized N in litter added soils during 24 weeks of incubation suggests that adequate poplar and understory litter management could lead to reduced inputs while facilitate sustainable and economic viable plantation production.