Responses of leaf morphology, NSCs contents and C:N:P stoichiometry of Cunninghamia lanceolata and Schima superba to shading

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 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.

Correlation of Leaf and Root Traits of Two Angiosperm Tree Species in Northeast China under Contrasting Light and Nitrogen Availabilities

“…Despite the contrast to many previous studies, the results of Saldaña-Acosta et al [13] and others illustrated that light effects on SLA/LMA were highly species-specific. As the least mean, the leaf area was in both species also observed under low light conditions; the greater LMA under L− could be interpreted as an indicator of shade intolerance [59]. Our findings also aligned with the C gain hypothesis indicating the least leaf area was observed in shade-intolerant seedlings [59,65].…”

“…As the least mean, the leaf area was in both species also observed under low light conditions; the greater LMA under L− could be interpreted as an indicator of shade intolerance [59]. Our findings also aligned with the C gain hypothesis indicating the least leaf area was observed in shade-intolerant seedlings [59,65]. This implied that both studied species possessed a strategy that did not aim to maximize C assimilation under low light conditions but to invest the available C in stem and root growth-as indicated by the lower LMFs compared to L+.…”

“…The significant variations in the leaf structure and morphology reflect the organ's phenotypic plasticity [59]. Therefore, leaf traits are often used to indicate plant adaptation mechanisms and acclimation potential [59,60].…”

“…The significant variations in the leaf structure and morphology reflect the organ's phenotypic plasticity [59]. Therefore, leaf traits are often used to indicate plant adaptation mechanisms and acclimation potential [59,60]. Excessive irradiance has a detrimental impact on the photosynthetic rate; thus plants, including temperate tree species, often produce smaller and thicker leaves with a higher LMA within large forest gaps [38,59,60].…”

“…Therefore, leaf traits are often used to indicate plant adaptation mechanisms and acclimation potential [59,60]. Excessive irradiance has a detrimental impact on the photosynthetic rate; thus plants, including temperate tree species, often produce smaller and thicker leaves with a higher LMA within large forest gaps [38,59,60]. Vice versa, a decreasing LMA is a frequent phenotypic response of seedlings growing in small, less irradiated forest gaps [61].…”