Harvard University is trying to sell some of its timberland investments in South America to investors who will share management of the portfolio as the endowment retreats from bets on natural resources. Harvard Management Co. has approached investors to buy minority or majority stakes in as much as $700 million of property in Brazil, Uruguay and Argentina, and become strategic partners at the same time in an effort to reduce the endowment’s risk, according to people familiar with the matter. The $37 billion…