Effects of slope aspects and soil properties on the growth of various strains of balsa trees

The manufacture of large wind turbine blades generally uses composite sandwich panels with balsa wood as the core materials. At present, the balsa wood raw materials in China are completely dependent on imports, and often face the problem of unstable supply or even periodic shortage. In order to ensure the security and stability of the balsa wood supply chain, wind power enterprises have initiated large-scale cultivation work in Xishuangbanna, Yunnan. Xishuangbanna has complex terrain and unique environment. Clarifying the site suitability for balsa cultivation and understanding the growth characteristics of different balsa varieties are urgent issues that need to be addressed for the domestic production of balsa trees. The results showed that shady slopes were more suitable for the cultivation of balsa trees, and the stem wood volume of Indonesian balsa germplasm and Ecuadorian balsa germplasm on shady slopes could reach 2.76 times and 1.93 times of the corresponding germplasm on sunny slopes. At the early stage, soil moisture condition on shady slopes was more conducive to the rapid development of forest stands. Soil total phosphorus, nitrate nitrogen, exchangeable calcium, and various available trace elements (manganese, copper, zinc) promote its growth, while excessive exchangeable aluminum and available iron inhibit it. A comparison between the two provenances indicated that the Ecuadorian balsa exhibited superior branch-free height, whereas its diameter at breast height (DBH) growth rate was slower than that of the Indonesian provenance. Therefore, it is recommended to cultivate balsa trees on shady slopes using Ecuadorian and Indonesian varieties. In order to achieve higher yield, soil improvement measures should be implemented, including the application of calcium fertilizer, pH adjustment to mitigate aluminum toxicity, and supplementation of trace elements such as zinc, copper, and manganese.