Usufruct and or Usufructuary

If the father dies and leaves a will giving his spouse usufruct until her
death ( no mention of remarriage in will)of the dwelling he owned prior to
the second marriage with no specifics for expenses, is that spouse
responsible for expenses such as taxes, property insurance, any annual
maintenance to property, or does his children who now own the property have
to incur the expense of the list of expenses above. If you have any example
I would be very interested in viewing same.

Normally the life tenant is responsible for part or all.

Check your local law and have the document carefully reviewed as it also normally addresses that issue.