The trails at Lost Valley are lined with pine, maple and oak trees.

Come Sunday, the ski area in Auburn will be helping redwoods and sequoias grow as well.

Tree Street Youth will host a challenge to see how many vertical feet one can climb in one afternoon.

Two groups from Tree Street’s empowerment programs — the Redwoods and the Sequoias — hiked up and down Lost Valley on Friday to see what’s in store come Sunday.

“I now get what this is all about,” said Alli Nolan. “This is going to be so much fun.”

The Maine Summit Trek for Tree will challenge participants to climb to the top of Lost Valley as many times as they can to raise funds for the Tree Street Youth program.

The goal for some will be to see how much elevation they can gain in comparison to all 14 of Maine’s 4,000-foot peaks combined.

“We are training for Katahdin — the big one. That’s eight hours of this,” said Julia Sleeper as she hiked up Lost Valley with two van loads of redwood and sequoia teenagers. Katahdin is Maine’s highest mountain at 5,269 feet.

Participants can hike up the short, but steep Big Buck ski trail during the Big Buck Fun Run Challenge with the opportunity to enter raffles at each stop along the trail. There is no cost to hike up Big Buck. Or, participants can enter the Endurance Hiking Challenge along the half-mile access road for $25.

The Maine Summit Trek for Tree will be held from 11 a.m. to 3 p.m. Sunday. The event will be held during Lost Valley’s Fall Fest, a free event to attend.

Nolan, the leader of the Tree Street pre-k program, said staff are receiving more requests for outdoor field trips. “We have been getting more and more requests for nature outings,” said Nolan.

“It’s been really cool to see the youth asking and getting excited about it,” said Nolan.

“This is nice over here,” Abdul Yonis said about the view from the top.

“It’s like freedom. I love this,” 14-year-old Masud Matan said after hiking to the summit of Lost Valley.