为给遭受酸化危害的重庆马尾松(Pinus massoniana)纯林的恢复与管理提供科学依据, 在属于酸雨区的重庆市江北区铁山坪林场, 调查了马尾松香樟(Cinnamomum camphora)混交林的土壤化学性质和林木生长状况, 并与毗邻的马尾松纯林和香樟纯林进行了比较。结果表明, 与马尾松纯林相比, 混交林腐殖质层和土壤酸度降低, 交换性盐基离子Ca²⁺和Mg²⁺含量增加, 酸性阳离子Al³⁺和H⁺含量明显减少(p < 0.05)。混交林马尾松树冠下腐殖质层和0-60 cm土层马尾松细根的干重、长度、表面积、体积和根尖数的总密度都显著低于马尾松纯林(p < 0.05), 比值分别为0.44、0.71、0.59、0.46和0.71, 马尾松树高显著低于马尾松纯林(p < 0.05), 其针叶变色率为15%, 显著高于马尾松纯林(p < 0.05), 香樟的生长特征与香樟纯林相似。结果说明, 尽管混交林的土壤化学性质优于马尾松纯林, 但林中马尾松的生长状况表现出了明显的恶化迹象, 而香樟依然比较健康, 这可能与香樟具有明显的竞争优势有关。因此, 在利用香樟营造与马尾松的混交林来改善遭受酸化危害的马尾松纯林的生长状况时, 应注意调控香樟的竞争优势。

Aims Acid rain has led to Pinus massoniana forest decline in Chongqing, Southwestern China. Cinnamomum camphora, an acid-resistant broadleaved tree species, has been widely distributed in the region. Cinnamomum camphora is thought to improve soil properties and health condition of P. massoniana; however, little information is available from mixed plantations of P. massoniana and C. camphora exposed to acid rain. Our objective was to examine soil chemical properties and growth traits of these two species in mixed plantations in the region.

Methods We investigated soil chemical properties and above- and below-ground growth condition of a mixed plantation of P. massoniana and C. camphora in the Tieshanping Forest Farm of Chongqing City. We compared results with those from adjacent pure plantations of P. massoniana and C. camphora, which were planted at the same time as the mixed plantation.

Important findings Compared with the pure P. massoniana plantation, pH values were greater in the humus and soil of the mixed plantation, contents of exchangeable Ca²⁺ and Mg²⁺ were higher, contents of exchangeable Al³⁺ and H⁺ were significantly lower (p < 0.05), the amount of fine roots of P. massoniana in the humus and soil was smaller (p < 0.05), height of dominant trees of P. massoniana was significantly lower (p < 0.05) and needle discoloration percentage of dominant trees of P. massoniana was higher (p < 0.05). Growth characteristics of C. camphora were similar to those of the pure C. camphora plantation. This study suggested that although C. camphora ameliorated soil chemical properties, health of P. massoniana of the mixed plantation worsened, which might be caused by stronger competitive abilities of C. camphora. Therefore, the competitive advantage of C. camphora against P. massoniana should be properly controlled when establishing mixed plantations of P. massoniana and C. camphora for improving the health of pure P. massoniana plantations in the region.