Spruce Feller

local YPos = 0

function refuel()
    print( "Refueling..." )

  turnAround()
    turtle.select(1)
    turtle.suck(64)
    turtle.refuel(64)
  turnAround()
end

function getSapplings()
    print( "Getting sapplings..." )

    turtle.select(2)
    turtle.suckDown(4)
end

function turnAround()
    turn( "r" )
    turn( "r" )
end

function turn( direction )
    if direction == "r" then
        turtle.turnRight()

        return true
    elseif direction == "l" then
        turtle.turnLeft()

        return true
    else
        return false
    end
end

function dump()
  turn("r")
  for n=3,16 do
        local itemCount = turtle.getItemCount(n)
        if itemCount > 0 then
            turtle.select(n)
            turtle.drop(64)
        end
    end
  turn("l")
end

function plantSapplings()
  turtle.select(2)
  turtle.forward()
  turtle.forward()
  turn("l")
  turtle.place()
  turn("r")
  turtle.back()
  turtle.place()
  turn("l")
  turtle.place()
  turn("r")
  turtle.back()
  turtle.place()
end

function compareLoop()
  local tree = false
  while tree == false do
    if not turtle.compare() then
      tree = true
    end
    sleep(5)
  end
end

function mainLoop()
  while true do
    compareLoop()
    local topFound = false

    if turtle.getFuelLevel() < 1000 then
      refuel()
    end
    getSapplings()
    turtle.dig()
    turtle.forward()

    while topFound == false do
      if YPos > 200 then
        turtle.dig()
        turtle.up()
        turtle.dig()
        YPos = YPos + 1
        topFound = true
        print("Reached max height...")
      elseif turtle.up() then
        turtle.dig()
        YPos = YPos + 1
        topFound = true
        print("Top found...")
      else
        turtle.dig()
        turtle.digUp()
        turtle.up()
        turtle.dig()
        YPos = YPos + 1
        print("Going up... YPos: "..YPos)
      end
    end

    turn("l")
    turtle.dig()
    turtle.forward()
    turn("r")

    while YPos > 0 do
      turtle.dig()
      turtle.digDown()
      turtle.down()
      YPos = YPos - 1
    end

    turtle.dig()
    turn("r")
    turtle.forward()
    turn("l")
    turtle.back()

    dump()
    plantSapplings()
  end
end

mainLoop()