What significant change occurred on Earth between the Carboniferous period and the Permian period that most likely contributed to the success of the gymnosperms?

rise in temperature and drier climate

Explanation:

The most significant changes that occurred were the rose of the temperatures and the dying of the climate and this lasted for about the period of  299 to 251 million years and was followed by the Carboniferous period and it contributes to the success of the plants and the growth of the gymnosperms.

Bwould be my guess |-/