Effects of shading on early growth of Cyclobalanopsis glauca (Fagaceae) in subtropical abandoned fields: Implications for vegetation restoration

In order to restore natural ecosystems and improve the environment, the restoration of abandoned agricultural lands to their native vegetation is urgent and challenging work. In response to a new initiative in China, the National Engineering Program on Converting Abandoned Agriculture Land to Forest Stands, this study was undertaken to seek novel approaches for accelerating forest restoration efforts. We tested the hypothesis that the late-successional tree species, Cyclobalanopsis glauca, is not able to establish and grow in full-sun environments on abandoned lands due to inhibited early growth of C. glauca seedlings. We carried out a 2-year field experiment on early growth of C. glauca in subtropical abandoned fields under three different shade treatments (no shade, fully exposed to ambient sunlight; medium shade and heavy shade, about 40% and 22% of full ambient sunlight, respectively) and compared their growth and biomass to 2-year old C. glauca seedlings growing in a natural forest environment. Our results showed that: 1) both medium shade and heavy shade treatments enhanced the establishment and early growth of C. glauca seedlings as compared to no shade, and that growth and survivorship was greatest in the heavy shade treatment; and 2) the growth and biomass of C. glauca seedlings on abandoned fields (in the cleared and prepared plots in this study) were equal to or greater than the growth and biomass of seedlings growing in nearby forests. This study supports the viewpoint that consideration of species shade tolerance is important when developing restoration management strategies.