This is the name of a wood, where, presumably, there are or used to be bears.
presumably 是副词“大概;也许”。分析句子为了排除干扰,暂且去掉:
This is the name of a wood, where there are or used to be bears.
where there are or used to be bears 是关系副词 where 引导的非限制性定语从句,修饰 a wood(wood 指“小树林”是可数名词)。
定语从句中 or 表示选择意义。分别是下面的意思:
there are bears 现在有熊出没。
or there used to be bears 或者过去有熊出没。