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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 response 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.

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Litter plays an important role in seedling establishment (emergence, survival, and early growth). Here, we performed a meta-analysis on 404 datasets from 33 independent studies to analyze the effects of litter cover on seedling emergence, survival, height, and biomass (root, stem, leaf, and total). Each dataset was stratified according to experimental conditions, litter type (broadleaf versus needle litter), litter amount (thickness), and seed size. The results showed that litter cover had an overall negative effect on seedling emergence and survival, a neutral effect on root, leaf, total biomass, and a positive effect on stem biomass and seedling height than the no-litter cover control. Compared to thin (<250 g m−2) and medium (250–500 g m−2) litter layers, thick litter (>500 g m−2) was more detrimental for seedling emergence, survival, and total biomass, which could be an adaptation mechanism to prevent the growth of young seedling among high densities of other plants (trees). Broadleaf litter cover had a stronger negative effect on seedling emergence and total biomass than needle litter. Litter cover had a stronger negative effect on emergence of small seeds than on emergence of larger seeds. Similarly, litter cover had a stronger overall negative effect on seedling emergence than on seedling survival. In field and common garden experiments, litter effects were negative for emergence and positive for total biomass. In glasshouse and germination chamber experiments, litter effects were negative for emergence, survival and total biomass. These findings would contribute to advancements in forest management, improving conservation and restoration efforts.

Effects of light quality on phenotypic plasticity in Cunninghamialanceolata (Lamb.) Hook. seedlings during growth and development, and the underlying mechanisms, were investigated. The seedlings showed distinct morphological adjustments when exposed to an equal photosynthetic photon flux density (400 μmol·m−2·s−1) of different light qualities: monochromatic blue (BL), monochromatic red (RL), monochromatic far-red (FrL), mixed RL and FrL at 1:1 (RFr1:1L), mixed RL and FrL at 1:2 (RFr1:2L), and multi-wavelength white (WL, control). Compared with WL, FrL and BL significantly promoted height increment. However, BL was unfavorable for root growth. The seedling biomass was lower and the root-to-shoot ratio was smaller under BL. RL promoted leaf area enlargement, root growth, axillary bud number, and increased the root-to-shoot ratio, but inhibited stem elongation. Low R/Fr ratios or increased FrL proportion increased seedling stem elongation. The seedling growth under RFr1:1L treatment was poorer than that under other treatments; however, the number of axillary buds was the highest. The plasticity of leaf morphology traits was lower in different treatments, and that of axillary bud traits was crucial in the adaptation of C. lanceolata to light quality. Precise management of light quality and wavelength in controlled environments may maximize the economic efficiency of forest production and enhance its quality.

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.

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This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.