Can direct seeding or natural regeneration be used to establish a buffer?

Yes.

There is no reason that these two methods of establishment couldn't be successful if done correctly. Both methods create a more natural stand of woody plants. This may better meet the objectives of the landowner. However, it may create problems because buffers are managed systems whose major function is to intercept and reduce NPS pollutants. As a result they require more maintenance than a native stand and random spacing may create problems for access during more frequent harvesting, etc. Natural regeneration may be difficult to obtain in many agricultural areas because the natural source of seed or propagules may be miles from the buffer site.