Plants emerging in late spring (ET2) had the greatest total mass at the second and third stages (LSD, P < 0.05; Appendix Fig. 8). Plants emerging in spring (ET1) and late spring (ET2) also had greater stem mass and allocation and stem length than others (P < 0.05), while late-emerging plants (ET3 and ET4) showed higher petiole and lamina mass allocation than others (P < 0.05), and ET2 and ET3 had the greatest reproductive mass and allocation (P < 0.05; Appendix Figs. 9, 10).
For the modular mass per layer, effects of emergence time, growth stage, modular type and layer and their interactions were significant in most cases (Table 3; Appendix Table 5). Generally for plants in all treatments at all stages, stem mass decreased with higher layers, and main root mass and lateral root mass decreased with lower layers (Fig. 1–4). For those emerged in spring (ET1), they had the greatest petiole and lamina mass, with the greatest total layer mass in the top layer (at the height of 40 cm) than in other layers at day 50 (ANOVA, P < 0.001), but had the greatest petiole, lamina and reproductive mass, with the greatest total layer mass in the layer of 60 cm at day 80 (P < 0.05), and the layer with greatest total layer mass (also with greater branch leaf mass than layer of 60 cm) became 80 cm at day 110 (P < 0.05; Fig. 1). For plants that emerged in late spring (ET2), compared to that in other layers, they had higher total layer mass in layers of 40–50 cm at day 50 (P < 0.05), in layers of 40–60 cm at day 70 (P < 0.05), and in layers of 60 and 80 at day 90 (P < 0.05; Fig. 2). The plants that emerged in summer (ET3) had the highest lamina mass and total layer mass in the layer of 30 cm at day 50 (P < 0.05), had higher total layer mass from 20 to 40 cm at day 70 (P < 0.05; Fig. 3). The plants that emerged in late summer (ET4) had the highest total layer mass in the layer of 20 cm at day 40 (P < 0.05), and in the layer of 30 cm at day 50 (P < 0.05; Fig. 4).
Table 3
Four-way ANOVA on modular mass per layer of plants, with emergence time (ET), growth stage (GS), module component (MC), and layer (LA) as effects.
Source of variation | df | F | p |
ET | 3 | 46.523 | < 0.001 |
GS | 2 | 80.945 | < 0.001 |
MC | 8 | 45.109 | < 0.001 |
LA | 4 | 9.650 | < 0.001 |
ET × GS | 3 | 3.264 | 0.021 |
ET × MC | 21 | 11.287 | < 0.001 |
ET × LA | 9 | 3.948 | < 0.001 |
GS × MC | 13 | 29.435 | < 0.001 |
GS × LA | 6 | 15.463 | < 0.001 |
MC × LA | 21 | 4.387 | < 0.001 |
ET × GS × MC | 15 | 5.001 | < 0.001 |
ET × GS × LA | 9 | 0.573 | 0.820 |
ET × MC × LA | 27 | 2.459 | < 0.001 |
GS × MC × LA | 14 | 2.709 | 0.001 |
ET × GS × MC × LA | 14 | 0.596 | 0.870 |
For the morphological traits per layer, effects of emergence time, growth stage and layer and their interactions were mostly significant for stem diameter, petiole length and angle (Table 4; Appendix Table 5). Generally across all treatments, stem diameter of plants decreased with higher layers, and this trend became more pronounced at later stages (P < 0.05; Fig. 5). They also had petiole length decreasing with higher layers at the second stage (P < 0.05; Fig. 6b, g, l, o), but not at the first stage (Fig. 6a, f, k), or had even increasing petiole length with higher layers at the third stage (P < 0.05; Fig. 6c, h, m, p). The petiole angle did not differ among different layers for all ET treatments and stages (data not shown).
Table 4
F-values for three-way ANOVA on all morphological modular traits per layer, with growth stage (GS), population density (PD), and layer (LA) as effects. Abbreviations: SD stem diameter; PL petiole length; PA petiole angle; BL branch length; BA branch angle. * p < 0.05, ** p < 0.01, *** p < 0.001.
Source of variation | df | SD (mm) | PL (cm) | PA (o) | BL (cm) | BA (o) |
ET | 3 | 54.533*** | 28.703*** | 28.919*** | 0.063 | 0.585 |
GS | 2 | 21.259*** | 22.908*** | 123.798*** | | |
LA | 4 | 72.572*** | 2.156 | 7.723*** | 0.451 | 0.478 |
ET × GS | 3 | 11.687*** | 9.831*** | 13.578*** | | |
ET × LA | 8 | 5.715*** | 18.995*** | 1.355 | 0.556 | 1.749 |
GS × LA | 6 | 15.047*** | 7.958*** | 2.270 | | |
ET × GS × LA | 9 | 0.895 | 3.398* | 1.273 | | |
Comparing the distributions of traits among layers of plants that emerged in different periods, we found that at day 50, plants tended to allocate greater mass to leaf and reproductive mass in higher layers (30–50 cm for ET1, 2 and 20–30 cm for ET3, 4), with later emergence (Fig. 1a, Fig. 2a, Fig. 3b, Fig. 4c). However, at day 70–80, plants of ET2 and ET3 had greater mass allocated to leaves, reproductive organs and branches in lower layers (40 cm for ET1 and ET2, and 20–40 cm for ET3), compared to those of ET1 (Fig. 1b, Fig. 2b. Figure 3c). In addition, plants of ET1 and ET2 had thicker stems in layers of 10–30 cm than those of ET3 and ET4 (Fig. 5), while plants of ET3 and ET4 at day 50 had similar distribution of petiole length among layers as ET1 and ET2 at day 70–80 (Fig. 6b, g, l, p). At the third stage, plants of ET2 had branches mainly in layers of 60-80cm, but those of ET1 and ET3 had branches distributed over more layers (Fig. 1c, d, Fig. 2c, d, Fig. 3c, d, Fig. 6e, j, n).