A man in his 60s has been arrested by police investigating the felling of the Sycamore Gap tree in Northumberland.
He is the second person arrested over the incident.
Northumbria Police said the man was held on Friday evening in connection with the felling of the tree and he remains in police custody assisting officers with inquiries.
A 16-year-old boy was arrested on Thursday on suspicion of criminal damage and has since been released on bail pending further inquiries.
Detective Chief Inspector Rebecca Fenney-Menzies, of Northumbria Police, said: "The senseless destruction of what is undoubtedly a world-renowned landmark - and a local treasure - has quite rightly resulted in an outpour of shock, horror and anger throughout the North East and further afield.
"I hope this second arrest demonstrates just how seriously we're taking this situation, and our ongoing commitment to find those responsible and bring them to justice.
"Although another arrest has been made, this investigation is still in the early stages, and we would continue to encourage any members of the public with information which may assist to get in touch.
"If you've seen or heard anything suspicious that may be of interest to us - I'd implore you to contact us.
"I'd also like to remind the public that this remains a live investigation so, for that reason, please avoid any speculation both in the community and on social media.
"Any information - no matter how small or insignificant you think it may be - could prove absolutely crucial to our enquiries."
National Trust general manager Andrew Poad told BBC Breakfast the stump was "healthy" and staff might be able to coppice the tree, a technique allowing new shoots to grow from the base of a trunk.
He said: "It's a very healthy tree, we can see that now, because of the condition of the stump, it may well regrow a coppice from the stump, and if we could nurture that then that might be one of the best outcomes, and then we keep the tree."
Rob Ternent, head gardener at The Alnwick Garden in Northumberland, said the tree will start growing again but "won't ever be the same shape or as good of a tree as it was".
He told the PA news agency: "It's worth a try but I think livestock and wildlife will potentially damage it as well. It'll be very difficult to get it back to the original tree.
"The growing season's coming to an end now but by spring next year it will have some life in it. It'll probably be about eight foot tall, but it'll be lots of singular branches, more bushy.
"It was about 300 years old so it'll take a long time to get back to that size. It's a massive shame."