When Roosevelt became president，he transformed this love of the West into concrete legislation，setting aside lands for national parks，national forests，initiating a vigorous national debate about conservation.
为何用setting 和 initiating?
When Roosevelt became president，he transformed this love of the West into concrete legislation，setting aside lands for national parks，national forests，initiating a vigorous national debate about conservation.
这个句子说罗斯福当了总统将来，将他对美国西部的热爱转化成了具体的立法行动：马上一些土地规划为国家公园，国家森林，与拓展了全民关于环境保护的辩论。三个动词transform，set和initiante不在一个层次上，set只不过讲解transform的具体的作法，即方法，而initiate为set的结果。因此让transform作谓语，set以分词形式作谓语的方法状语，initiate为目前分词作setting aside的结果状语。如此，三个动词的主次关系就分明了。假如都用谓语形式，则没主次之分了。
另外一种办法就是在setting之前加for example, he set aside。。。，initiating...。如此也能表明后者是对transform的补充说明，仍然突出的是transform这个动作。
When Roosevelt became president，he transformed this love of the West into concrete legislation. For example, he set aside lands for national parks，national forests，which initiated a vigorous national debate about conservation.
