Background Magnoliaceae plants resources is rich in China, which have widely been used in making landscape to demonstrate gardens and cultural connotation by making full use of its aesthetic functions such as posture, culture and good views, and which was introduced in Hainan Tianxiang Magnolia Plant Conservation Research Center in Danzhou county of Hainan province, but lack of understanding the ecological service functions such as soil and water conservation of Magnoliaceae plants in this region. It is of great significance for rational introduction based on the water-holding capacity of each Magnoliaceae plants to render the Magnoliaceae plants configuration more reasonable in garden application.

Methods Seven common Magnoliaceae plants (Michelia shiluensis, Michelia crassipes, Michelia foveolata, Michelia maudiae, Michelia odora, Manglietiastrum sinicum, Manglietia lucida) in Hainan were selected as the research objects, and the water-holding function of litter layer and soil layer of different Magnoliaceae plants were determined by quantitatively research with immersion method and cutting-ring method.

Results 1) The litter volume of the seven plants was about 5.24-25.11 t/hm², which followed the order of M. shiluensis > M. crassipes > M. foveolata > M. sinicum > M. maudiae > M. odora > M. lucida. The decomposition degree of dead branches and leaves of Manglietia lucida was high. 2) The maximum water-holding capacity of litter layer varied from 14.32 to 25.45 t/hm². The modified interception amount was 15.88-53.85 t/hm², which followed the order of M. shiluensis > M. crassipes > M. foveolata > M. sinicum > M. odora > M. lucida > M. maudiae. The water-holding function of M. shiluensis and M. crassipes litter layer was good. 3) Semi-decomposed litter could be saturated in 8 h and undecomposed litter reached saturation in 10 h, the water-holding capacity had logarithmic relationship with soaking time (R² > 0.92); the absorption rate changed the most within the first 2 h of soaking and there was a power function relationship between water absorption rate and soaking time (R² > 0.94). 4) The mean soil bulk density of different plants varied from 1.22 g/cm³ to 1.55 g/cm³, and the total porosity varied from 40.03% to 49.89%. The saturate soil water holding capacity was about 400.34-498.95 t/hm², and the effective soil water-holding capacity was about 26.23-70.33 t/hm². The water-holding capacity of the soil layer was in the order of M. foveolata > M. crassipes > M. lucida > M. shiluensis > M. odora > M. sinicum > M. maudiae. A significant power function relation between infiltration rate and infiltration fitting time was found (R² > 0.90).

Conclusions The water conservation capacity of soil layer is higher than that of litter layer, which is the main part for hydrological effect of forest land. The water conservation capacity of M. shiluensis, M. crassipes and M. foveolata is better than those of other Magnoliaceae plants, which suggested to give priority to the mixed planting of M. shiluensis, M. crassipes and M. foveolata in the application of landscape.