Secondary forest ecosystems have become major forest resources worldwide, compared with the primary forests, the tree species composition of secondary forest ecosystems have been changed, particularly, they become mono tree species composition when replaced by a large area of larch (Larix olgensis or L. kaempferi) timber plantations. The change of these tree species affects the quantity and quality of litter input and root activity in the soil, thus changing the soil properties, affecting the nutrient supply of plants and the sustainability of ecological services in the secondary forest ecosystem.  

Previous studies of the effects of tree species on soil properties are inconsistent, and even contrary. This may be induced by the sample methods that only a single tree species stand was considered, while ignoring the differences of tree species in the mixed forest stands, which limits foresters to select appropriate tree species to improved soil properties.  

In order to find out the differences in the effects of tree species in mixed forests on soil properties, a research team led by Dr. ZHU Jiaojun from the Institute of Applied Ecology (IAE) of the Chinese Academy of Sciences (CAS) has examined the difference of five common native tree species: Acer mono, Quercus mongolica, Juglans mandschurica, Fraxinus rhynchophylla, and Fraxinus mandschurica on soil chemical and microbial properties in four independent and randomly distributed secondary mixed forest sites, which have been built up 10 years, in Qingyuan Forest CERN, CAS (China Ecosystem Research Network).  

The researchers found that the native tree species were significant different in the studied soil properties in 0-10 and 10-20 cm soil depths. Especially in 0-10 cm, F. mandschurica had higher soil mineral N and available P, microbial biomass C (MBC) and microbial biomass N (MBN), and higher activities of phenol oxidase, exoglucanase, and β-glucosidase than F. rhynchophylla and Q. mongolica, while J. mandschurica and A. mono were not significant different from the others.  

It is notable that these five native tree species exhibited improving soil chemical and microbial properties, compared with the adjacent larch plantation soils in secondary forest ecosystems.  

According to Dr. ZHU, introduction of F. mandschurica followed by that of A. mono and J. mandshurica, and then Q. mongolica and F. rhynchophylla into larch plantations would benefit for restoring the degraded plantation soils. 

This work entitled "Native broad-leaved tree species play key roles on maintaining soil chemical and microbial properties in a temperate secondary forest, Northeast China" has been published in the journal Forest Ecology and Management. 

The study was funded by the National Natural Science Foundation of China.