J.P. Morgan Asset Management’s timber-investing arm has acquired about 250,000 acres in the Southern pine belt for more than $500 million. The latest purchase seems made with an eye toward carbon markets.    The wealth manager said its Campbell Global unit, which invests on behalf of pension funds, foundations and other institutional investors, will manage the commercial forests in Mississippi, Oklahoma and Arkansas for wood production as well as carbon capture.      The latter is usually accomplished with less logging. Companies eager to make up for their emissions ...