>>7689193I previously worked in China and Taiwan so I picked up a general understanding. The goal of bonsai is to recreate nature in miniature form.
The scrolls are used as an accent to help paint certain elements of the nature scene. Different subjects mean different things in this context. Birds typically represent specific seasons. For example, a swan is local during winter where I live.
Other accents include small potted plants like wildflowers to invoke spring or more commonly to accentuate certain features of the tree. A delicate fern makes a thick truck look stronger.