Secondary forest ecosystems have become major forest resources worldwide, especially in Northeast China, secondary forests account more than 70%. However, 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. These changes of tree species affect the quantity and quality of litter inputs and root activities in soil, further alter the soil properties (generally lead to soil degeneration).

Subsequently, these changes of tree species influence the nutrient supply of plants, and affect the sustainability of ecological services of the secondary forest ecosystems. 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 know the differences in the effects of tree species in mixed forests on soil properties, recently, a research team, led by Dr. ZHU Jiaojun from the Institute of Applied Ecology (IAE), Chinese Academy of Sciences(CAS), 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.

The implication from this study: 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 recently published in the journal Forest Ecology and Management, 462 (2020) 117971 by DIAO Mengmeng, YANG Kai, LI Mingcai and XU Shuang.

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

Email: yueqian@iae.ac.cn