Quantifying the effect of shading and watering on seed germination in translocated forest topsoil at a subtropical karst of China

Abstract

Soil translocation is recognized as a promising method to recover degraded ecosystems and save regionally threatened species, however, the diversity and density of woody species, and the similarity of germinated seedlings between translocated site and donor forest are always low, and few studies have paid attention to the manageable environmental factors for seed germination when forest topsoil exposed to strong light condition. In this study, we tested how shading treatment (ST) and watering treatments (WT) affect the germination of species in translocated forest topsoil and whether different life forms respond differently to different ST and WT following soil translocation. We found that the richness of shrub species had a positive linear relationship with WT, and increased by 0.8 species when additional 10 L m−2 water was added. The richness of trees species was positively linearly correlated with ST and increased by 0.5 species when 10 units of shade degrees was increased. The effect of ST on richness was greatest for total species, followed by herb and tree species, while the effect of WT affected these in the order total > herb > shrub species. The densities of shrub and tree species had a positive linear relationship with ST and increased by 1.0 and 1.2 seedlings m−2 when 10 units of shade degrees were increased respectively. Whereas, the densities of total species, herb species, and liana species had a parabolic relation with ST, reaching maximum densities of 79.8, 39.8, and 5.3 seedlings m−2 at shade degrees of 70%, 45%, and 27.5%, respectively. Moreover, the similarity between germinated communities and donor forest had positive linear relationship with ST and WT, except for herb species. Therefore, in theory, ST and WT significantly improved the diversity, density, and similarity of woody seedlings in translocated forest soil, but the density of herb and liana species decreased respectively when shade degrees exceeded 45% and 27.5% respectively. In practice, putting soil under moderate or heavy shade (shade degrees range from 45% to 70%) is a promising method to duplicate a diverse and similar forest if translocation process coincides with the rainy season. This finding can be incorporated into the practice and management of natural forest restoration and accelerate the early stage of forest restoration and succession.