Advantage of mixed trees in the trade-off between soil water storage and tree biomass: A meta-analysis from artificially planted forests in Chinese Loess Plateau

Abstract

Afforestation is an effective measure to combat land degradation and mitigate climate change. However, afforestation tends to consume a tremendous amount of soil moisture while increasing vegetation biomass and coverage. Although convincing evidence indicates that mixed trees have higher resistance and resilience to climate change and natural disturbance than pure trees, it is unclear how tree mixtures affect the relationship between soil water storage and tree biomass. By conducting a meta-analysis of 86 observations from 27 studies, we showed that there was a trade-off between soil water storage and tree biomass in artificially planted trees on the Loess Plateau, with an average root mean square deviation (RMSD) value of 0.22. The RMSD value between soil water storage and tree biomass for mixed trees was significantly lower than that for pure trees, and the relative benefits of the trade-off were biased toward soil water storage. In dry areas (aridity index (AI) < 0.3), the RMSD value between soil water storage and tree biomass of artificially planted trees was the highest, and this value of mixed trees was significantly lower than that of pure trees. In terms of different plantation ages, the RMSD value between soil water storage and tree biomass for mixed trees was significantly lower than that for pure trees in plantations aged >20 years. Additionally, RMSD values between soil water storage and tree biomass under different afforestation patterns were negatively correlated with the initial water storage and soil organic carbon content. Our results show that tree mixtures optimize the trade-off between soil water storage and tree biomass in arid and semiarid areas.