Variability analysis of litter quality, mineral nitrogen, soil respiration and microbial biomass under afforested tree stands

In order to identify and sustainable management of afforested tree stands, the effects of Alnus subcordata, Acer insigne, Sequoia sempervirens and Acer insigne - Sequoia sempervirens stands on quality of litter and soil were investigated in Salmanshahr areas of Mazandaran Province. Samplings were done from the litter and 0-10cm depth of topsoil using randomly systematic method with 15 replicates for each stand. Organic carbon (C) and total nitrogen (N) content of litter, soil water content, pH, organic C, total N, nitrate and ammonium concentration, microbial respiration, microbial biomass of C and N were measured. Results showed that the highest values of soil water content, litter and soil N, nitrate and ammonium concentration, microbial respiration, microbial biomass of C and N belonged to Alnus subcordata compared with Acer insigne > Acer insigne - Sequoia sempervirens > Sequoia sempervirens pure and mixed stands. Whereas greater amounts of C/N of litter and soil organic C were found under Sequoia sempervirens stand. Generally, Acer insigne - Sequoia sempervirens mixed stand presented intermediate mode viewpoint of litter quality and soil fertility. According to our data, afforestation with broad-leaved species, especially N-fixing trees of Alnus subcordata, improved the litter and soil quality, whereas the Sequoia sempervirens species created the inappropriate condition.