Firefighters were attacked with golf balls while they tried to put out a blaze which was started deliberately.
Seven appliances from Mansfield were called to Oak Tree Nature Reserve at 7pm on Friday (15 July), where they spent three hours stopping the fire from spreading to a nearby leisure centre.
The crews were hit with golf balls as they tackled the blaze and they are now working with police to find who is responsible.
Area manager Andy Macey of Nottinghamshire Fire and Rescue Service said: "Deliberate fires put lives at risk and take our fire engines away from dealing with other life-threatening incidents.
"With the extreme weather we are already dealing with more incidents than normal, and deliberate fire starting needlessly ties up our resources.
"Attacks on our crews as they go about their job are completely unacceptable and we will be working with our police colleagues to identify those responsible.
"I ask anyone with information to come forward to the police."