The presence of specific trees has been connected with morel habitat. However, proof of habitat causation has not been officially determined. Morels have been found around apple, elm and oak trees among many others. The commonality is that the trees are dead or dying when the morels have been spotted. Research suggests that the presence of competitive species like other fungi or microbial activity changes the composition of soil. It has been observed that the rate of hyphal development in morels is slower at lower temperatures and in a habitat with competitive species! I have done extensive research on the issue and would love to talk to you more about this!