I'm assuming you're talking about ALY (Al Nozha Airport) in which case the trees aren't the only problem. The vertical expansion of buildings in the surround area is becoming a mater of concern for approaching aircraft and the facilities are quite small. This summer SV will have a daily ALY service (4 from JED, 3 from RUH).
I doubt any major refirbishments will haapen at ALY as the authorities are planning to close it down (in 2008) and move all operations to HBE (Borg Al Arab airport) which is currently served by Air Arabia, British Airways, TUI Belgium and Emirates. Hopefully by then the authorities would have improved transportation links between HBE and Alex city centre which has been the main reason airlines have avoided HBE till now even though its facilities are better than ALY's
Besides it seems strange an MD-90 would face 'severe' payload restriction on a relatively short flight even if the runway is short/restricted.