Abstract:
Differences in growth characteristics, leaf morphologies, and photosynthetic characteristics of
Phoebe bournei (Hemsl.) Yang saplings in unevenly aged two-layer mixed (UATLM) forest and pure forest were explored to provide a scientific basis for the construction of UATLM forest and cultivation of precious tree species. We investigated 7-year-old
P. bournei saplings in
Cunninghamia lanceolata (Lamb.) Hook. +
P. bournei UATLM forest (CP forest),
Sassafras tzumu (Hemsl.) Hemsl. +
P. bournei UATLM forest (SP forest), and pure
P. bournei forest. We measured the growth, leaf phenotype, leaf structure, photosynthetic pigment content, changes in photosynthetic parameters, and photosynthetic-light response curves in the three forests. Results showed that: (1) Compared with the pure forest, the DBH and height of increments saplings in the CP forest were 46.61% and 43.87% higher, respectively, while those in the SP forest were 20.75% and 26.53% lower, respectively. (2) Compared with the pure forest, the fresh weight and water content of leaves of the
P. bournei saplings in the two UATLM forests were lower, leaves were thinner and slenderer, and midrib, upper epidermis, lower epidermis, palisade tissue, and spongy tissue thickness was significantly reduced. (3) Chlorophyll
a, chlorophyll
b, total chlorophyll, and carotenoid contents in
P. bournei saplings from the two UATLM forests were significantly higher than levels in the pure forest. (4) The net photosynthetic rate (
Pn) of the saplings did not significantly differ between the pure forest and CP forest, except at 8∶00 am, while the
Pn of saplings in the SP forest was significantly lower than that of the other two forests at 10∶00 am and 2∶00 pm. This study showed that the growth conditions of
P. bournei saplings were better in the CP forest, while
P. bournei sapling growth was inhibited in the SP forest due to shading.