It could be a cat spraying urine to mark its territory. How high does the brown extend? If its more than four foot, I would lock the doors at night! Lol

Lol, Fractal, but I want to know which side has gone brown, the one facing the sun, or the one in the dark, say against a fence or wall. Or is it standing in an open area, so all sides are equal. If its close to a fence or wall and you don't turn it periodically, that could cause browning on one side.

thanks lol, I dont think its a cat....the side that has turned brown is facing the sun its standing in the open,but the brown side gets the sun most of the day.as that side faces east.

its not a dog either i guess ie a male dog to be precise lol ?

well we've had some very, very hot sun in recent weeks -if the pot was a bit dry, the growth on that side could have gone brown quite easily - the needles on a conifer transpire all the time, losing moisture, so its quite possible that's what happened.