Hello, Mrs.Camille.There is no direct train/bus to Jiuzhaigu and Huanglong, you need to transfer at Chengdu .It takes 16 hours by train/12hours by bus from xi'an to Chengdu,10 hours from Chengdu to Jiuzhaiguo and two hours from Jiuzhaiguo to Huanglong. let me know if you have further questions.
Hello. Dear Jason.Thanks for your question.
The scenery in Jiuzhaigou varies with seasons.Best time to visit Jiuzhaigou is in autumn .If you come over in spring ( March to the end of May.),There is strong sunlight in Jiuzhaigou because of the plateau landscape there. It is not cold in Jiuzhaigou spring, but the ultraviolet radiation is strong.