Be there for them. Not necessarily tell them "don't be suicidal" But more of telling them "if you ever need someone to talk, I'm here", Or even asking them about their life could get them to open up to you about why they are feeling suicidal, you could be the person they need to open up to.
Because the tree moves the water and food around through the cambium. If it cannot go through the cambium, they tree will have nothing to eat and slowly, die.
