We investigated how different degrees of shading affected growth, morphology, and biomass allocation in seedlings from two coniferous and three broadleaved species. The experiment was conducted in a shade house over a 1-year period. Our results showed that under increasing shade, seedlings from most species exhibited lower total biomass, net assimilation rates, relative growth rates, root mass ratios, and root/shoot ratios. In contrast, the slenderness quotients, leaf area ratios, and specific leaf areas increased with increasing shade. For coniferous species, growth traits were relatively more plastic (responsive to shade) than morphology or biomass allocation traits, whereas for broadleaved species, growth and biomass allocation were the mostshade-sensitive traits. When comparing coniferous versus broadleaved species, the former had a higher growth plasticity index and lower allocation plasticity than the latter. Root biomass and stem mass ratio were the most and least plastic traits in response to shading. Our results indicate that shade differentially affects coniferous and broadleaved species in terms of their growth, morphology, and biomass allocation. These findings have important implications for the establishment and maintenance of mixed-species stands.

Abstract Background: The non-structural carbohydrates (NSCs), carbon (C), nitrogen (N), and phosphorus (P) are important energy source or nutrients for all plant growth and metabolism. To persist in shaded understory, saplings have to maintain the dynamic balance of carbon and nutrients, such as leaf NSCs, C, N and P. To improve understanding of the nutrient utilization strategies between shade-tolerant and shade-intolerant species, we therefore compared the leaf NSCs, C, N, P in respond to shade between seedlings of shade-tolerant Schima superba and shade-intolerant Cunninghamia lanceolate. Shading treatments were created with five levels (0%, 40%, 60%, 85%, 95% shading degree) to determine the effect of shade on leaf NSCs contents and C:N:P stoichiometry characteristics.Results: Mean leaf area was significantly larger under 60% shading degree for C. lanceolata while maximum mean leaf area was observed under 85% shading degree for S. superba seedlings, whereas leaf mass per area decreased consistently with increasing shading degree in both species. In general, both species showed decreasing NSC, soluble sugar and starch contents with increasing shading degree. However shade-tolerant S. superba seedlings exhibited higher NSC, soluble sugar and starch content than shade-intolerant C. lanceolate. The soluble sugar/starch ratio of C. lanceolate decreased with increasing shading degree, whereas that of S. superb remained stable. Leaf C:N ratio decreased while N:P ratio increased with increasing shading degree; leaf C:P ratio was highest in 60% shading degree for C. lanceolata and in 40% shading degree for S. superba. Conclusion: S. superba is better adapted to low light condition than C. lanceolata through enlarged leaf area and increased carbohydrate reserves that allow the plant to cope with low light stress. From mixed plantation viewpoint, it would be advisable to plant S. superba later once the canopy of C. lanceolata is well developed but allowing enough sunlight.

Background: An understanding of the light requirement of tree species has paramount importance in management of mixed species forests. Here, we examined changes in leaf morphological traits, non-structural carbohydrate contents and C:N:P stoichiometry in Cunninghamia lanceolata and Schima superba seedlings that were grown under five light intensity levels (5%, 15%, 40%, 60%, and 100% sunlight) in a shade house. Results: Mean leaf area was significantly larger under 40% light intensity for C. lanceolata while maximum mean leaf area was observed under 15% light intensity for S. superba seedlings, whereas leaf mass per area decreased consistently with decreasing light intensity in S. superba; Non-structural carbohydrate content was higher for S. superba than C. lanceolata when seedlings were exposed to 100%, 15% and 5% light intensity; Leaf C:N ratio decreased while N:P ratio increased with decreasing light intensity; leaf C:P ratio was highest in 40% light intensity for C. lanceolata and in 60% light intensity for S. superba. Conclusion: S. superba is better adapted to low light intensity than C. lanceolata through enlarged leaf area and increased carbohydrate reserves that allow the plant to better maintain C balance. From mixed species planting viewpoint, it would be advisable to plant S. superba later once the canopy of C. lanceolata is well developed but allowing enough sunlight (up to 15%-60%).