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复层林对闽楠幼树生长、叶片形态和光合特性的影响

Effects of unevenly aged two-layer mixed forest on growth, leaf morphology, and photosynthetic characteristics of Phoebe bournei (Hemsl.) Yang saplings

  • 摘要: 以杉木(Cunninghamia lanceolata (Lamb.) Hook.)、闽楠(Phoebe bournei (Hemsl.) Yang)异龄复层混交林(简称杉楠复层林)和檫木(Sassafras tzumu (Hemsl.) Hemsl.)、闽楠异龄复层混交林(简称檫楠复层林)中的7年生闽楠幼树为研究对象,以纯林中的7年生闽楠幼树为对照,研究3种林分中闽楠幼树的生长量、叶片表型、叶片显微结构、光合色素含量、光合参数日变化和光合-光响应曲线的变化规律,分析复层林和纯林中闽楠幼树生长、叶片形态和光合特性的差异。结果显示:(1)与闽楠纯林相比,杉楠复层林中闽楠幼树的胸径增量和树高增量分别高46.61%和43.87%;檫楠复层林中闽楠幼树的胸径增量和树高增量分别低20.75%和26.53%;(2)与闽楠纯林相比,两种复层林中闽楠幼树的叶片鲜重和含水率减小,叶片变薄变“细长”,同时其中脉厚度、上表皮厚度、下表皮厚度、栅栏组织厚度和海绵组织厚度显著降低;(3)两种复层林中闽楠幼树的叶绿素ab、总叶绿素和类胡萝卜素含量显著高于纯林中的闽楠;(4)纯林和杉楠复层林中闽楠幼树的净光合速率除上午8∶00外差异不大,檫楠复层林中闽楠的净光合速率在10∶00和14∶00时均显著小于前两者。研究结果表明杉楠复层林下闽楠幼树的生长状况更优,檫楠复层林因为遮阴程度高等原因,对闽楠幼树的生长造成抑制。

     

    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.

     

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