The amelioration of degraded larch (Larix olgensis) soil depends on the proportion of Aralia elata litter in larch-A. elata agroforestry systems

Research has indicated that introducing Aralia elata into larch plantations forms an agroforestry system which could provide economic benefits for local farmers and improve degraded soils. However, the impact of litter mixtures on soil chemical and microbial properties in this agroforestry system are unclear, which limits efficient management of the agroforestry system. A 365-d incubation experiment examined the effect of litter mixtures of different proportions of larch (L) and A. elata (A) on soil chemical and microbial properties. The results show that levels of mineral N, available P, microbial biomass carbon and nitrogen, cumulative C mineralization, and activities of hydrolases and oxidases increased with an increase of A. elata in the litter mixtures. Concentration of total soil carbon, nitrogen, and phosphorous did not change (except for total nitrogen). Compared with larch litter alone, levels of mineral N, available P, microbial biomass carbon and nitrogen, cumulative C mineralization, and the activities of hydrolases and oxidases increased by 7.6–433.5%. Most chemical and microbial properties were positively correlated with mixed litter proportions and the initial levels of N, P, K, Ca, Mg, Mn, Zn and Cu in the litter, while negatively correlated with the initial concentrations of C, Fe and lignin, C/N and lignin/N ratios. The results indicate that A. elata litter can improve degraded larch soil and the degree depends on the proportion of A. elata litter in the litter mixtures.