Potlatchdeltic Corp., a real-estate investment trust focused on owning timberland, has agreed to buy rival CatchMark Timber Trust Inc. in an all-stock deal that values CatchMark at more than $600 million.  The combined company is expected to have a market valuation of more than $4 billion. It will own about 2.2 million acres of timberlands, including 626,000 acres in Idaho and over 1.5 million acres in the U.S. South.   PotlatchDeltic shareholders will own about 86% of the combined company, the two REITs said. CatchMark shareholders will receive ...