On a recent trip to Japan I visited Katsura Rikyu, the Imperial villa. Our equivalent may be Chequers. This was my second visit to the garden and it has to be one of the best in world.
I cannot say what the material is made from as the translation did not come across clearly enough to understand. They use this construction to protect Cycads (Cycas revoluta). Cycads are a bit at odds with the concept that Japanese gardens are trying convey. Yet they valued the plants as gifts from and as a inference to, their more southerly islands so that in a few very traditional Japanese gardens you get these wonderful installations during the winter.