Leaf trait variations and relationships of three Acer species in different tree sizes and canopy conditions in Xiao Hinggan Mountains of Northeast China

doi:10.17521/cjpe.2023.0369

Abstract

Abstract:

Aims Leaf traits are affected not only by plant sizes, but also by different canopy conditions where mature trees and saplings grow. Thus, these trees choose various survival strategies to adapt to different canopy conditions by adjusting their leaf traits. The aim of this study is to investigate the changes of leaf traits of three Acer trees along with the changes of plant size and canopy condition.

Methods In this study, three species (Acer ukurunduense, A. tegmentosumand A. pictumsubsp. mono) in broadleaf Pinus korainesis forest in Xiao Hinggan Mountains of Northeast China were selected. Six leaf economics spectrum traits, specific leaf area (SLA), leaf dry matter content (LDMC), leaf thickness (LT), chlorophyll (Chl) content, net photosynthetic rate per area (A_area) and non-structural carbohydrates (NSC) content, together with two defensive traits, total phenolics (TP) content and flavonoids (FLA) content of adult trees and saplings in gaps and saplings in understory were measured. Whether leaf traits and their relationships varied with plant sizes and canopy conditions was further analyzed to illustrate how gaps influence forest regeneration by altering leaf traits, and to explore the differentiation of survival strategies for plant individuals growing under various habitats.

Important findings Adults in gaps had higher LDMC, Chl content, FLA content and NSC content compared with saplings in gaps, which meant adults had adequate photosynthetic accumulation and they were more capable to defend against herbivory. LDMC, LT, Chl content and A_area of gap saplings were significantly higher than saplings in understory, indicating that canopy condition was a vital source of leaf trait variations. The absolute slope of relationship between SLA and LDMC for adults was significantly higher than that for saplings in gaps, but the absolute slope of understory saplings was significantly lower than that of the gap saplings. The relationship between defensive traits remained stable among different plant sizes and canopy conditions. These evidences showed that, adults invested more in leaf construction such as leaf thickness and defensive substances, so they chose “conservative” strategy. Saplings in understory improved their ability to acquire light by increasing SLA, they therefore tended to choose “acquisitive” strategy. Saplings in gaps however, showed the transition strategy between “conservative” and “acquisitive” strategies. Results further indicated that, when saplings were not limited by light, their photosynthetic rate increased rapidly to be significantly higher than that of adults. In addition, forest gaps can promote the regeneration of forest stand by enhancing the abilities of photosynthesis and resistance to herbivory of saplings.

Key words: leaf traits, defensive traits, non-structural carbohydrates, canopy condition

PENG Zhong-Tao, JIN Guang-Ze, LIU Zhi-Li. Leaf trait variations and relationships of three Acer species in different tree sizes and canopy conditions in Xiao Hinggan Mountains of Northeast China[J]. Chin J Plant Ecol, 2024, 48(6): 730-743.

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Figures/Tables 6

Table 1 Differences in diameter at breast height (DBH), tree height (H) and environmental factors among different canopy conditions and plant sizes of three Acer species in Xiao Hinggan Mountains (mean ± SE)

因子 Factor	林隙成年树 Adults in gaps	林隙幼树 Saplings in gaps	林内幼树 Saplings in understory
DBH (cm)	17.31 ± 1.46^a	5.15 ± 0.23^b	5.20 ± 0.17^b
H (m)	15.02 ± 1.23^a	7.23 ± 1.16^b	7.34 ± 0.92^b
CO (%)	24.63 ± 1.30^a	23.49 ± 1.15^a	15.15 ± 0.79^b
SWC	0.90 ± 0.10^a	1.00 ± 0.09^a	0.77 ± 0.06^a
STN (mg·g^-1)	12.11 ± 1.04^a	12.25 ± 0.97^a	10.53 ± 0.96^a
STP (mg·g^-1)	1.28 ± 0.11^a	1.30 ± 0.09^a	1.07 ± 0.08^a
pH	5.69 ± 0.12^a	5.49 ± 0.10^a	5.59 ± 0.12^a

Fig. 1 Leaf traits variations for three Acer species among different tree sizes and canopy conditions in Xiao Hinggan Mountains. *, p < 0.05; ***, p < 0.001; ns, p ≥ 0.05. Aarea, net photosynthetic rate per area; Chl, chlorophyll; FLA, flavonoids; LDMC, leaf dry matter content; LT, leaf thickness; NSC, non-structural carbohydrates; SLA, specific leaf area; SS, soluble sugar; ST, starch; TP, total phenolics.

Fig. 2 Correlations coefficients between leaf traits of three Acer species in Xiao Hinggan Mountains. *, p < 0.05; **, p < 0.01; ***, p < 0.001. Aarea, net photosynthetic rate per area; Chl, chlorophyll content; FLA, flavonoids content; LDMC, leaf dry matter content; LT, leaf thickness; NSC, non-structural carbohydrates content; SLA, specific leaf area; TP, total phenolics content.

Fig. 3 Variations for trait-trait relationships between different sizes of three Acer species in Xiao Hinggan Mountains. The significant regression relationships between leaf traits were shown as solid lines (p < 0.05), and the regression line was represented by a dashed line if the relationships weren’t significant (p ≥ 0.05). *, p < 0.05; **, p < 0.01; ***, p < 0.001. p1 < 0.05 indicated that the slope of relationship between leaf traits varied significantly with plant sizes; p1 ≥ 0.05 indicated that the slope of relationship between leaf traits didn’t vary significantly with plant sizes; p2 < 0.05 indicated a significant difference in intercept; p2 ≥ 0.05 indicated no significant difference in intercept. Aarea, net photosynthetic rate per area; Chl, chlorophyll content; FLA, flavonoids content; LDMC, leaf dry matter content; LT, leaf thickness; NSC, non-structural carbohydrates content; SLA, specific leaf area; TP, total phenolics content.

Fig. 4 Variations for trait-trait relationships between different canopy conditions of three Acer species in Xiao Hinggan Mountains. The significant regression relationships between leaf traits were shown as solid lines (p < 0.05), and the regression line was represented by a dashed line if the relationships weren’t significant (p ≥ 0.05). *, p < 0.05; **, p < 0.01; ***, p < 0.001. p1 < 0.05 indicated that the slope of relationship between leaf traits varied significantly with canopy conditions; p1 ≥ 0.05 indicated that the slope of relationship between leaf traits didn’t vary significantly with canopy conditions; p2 < 0.05 indicated a significant difference in intercept; p2 ≥ 0.05 indicated no significant difference in intercept. Aarea, net photosynthetic rate per area; Chl, chlorophyll content; FLA, flavonoids content; LDMC, leaf dry matter content; LT, leaf thickness; NSC, non-structural carbohydrates content; SLA, specific leaf area; TP, total phenolics content.

Fig. 5 Principal component analysis (PCA) for leaf traits and defensive traits among different plant sizes and canopy conditions of three Acer species in Xiao Hinggan Mountains. Aarea, net photosynthetic rate per area; Chl, chlorophyll content; FLA, flavonoids content; LDMC, leaf dry matter content; LT, leaf thickness; NSC, non-structural carbohydrates content; SLA, specific leaf area; TP, total phenolics content.

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