Preserves: parks or leisure?

In and around Dallas (Texas), there are several county/city-run preserves that are owned by the county in their Open Space Programme that sets aside undeveloped land for, well, preserving nature in a mostly-urban prairie.

Most of the preserves are city-maintained, but there are few located in rare unincorporated areas of the county.

My question is, are these preserves handled as "nature preserves" or "parks"? So far, I've mapped these as nature preserves (except for one). I'd just like to get a precise definition of the tags in this context.

Thanks, AB