The Nam Co , situated within the south-central Tibetan Plateau ( 30 ° – 35 ° N ) , is located at the transitional region between the Indian summer monsoon and westerlies in the growing season .This area with an elevation above 4700 m a . s . l . is characterized by extremely cold and dry treeless environment .Among alpine shrubs , Wilson juniper ( Juniperus pingii var . wilsonii ) is widespread throughout the south-central Tibetan Plateau . ？.