John C. Malone, a media mogul who is on the verge of buying nearly one million acres of timberland in Maine, could soon become the largest private landowner in the United States, catapulting him ahead of Ted Turner on the list of those who accumulate earth the way others accumulate, say, bison.

Mr. Malone, who lives in Colorado, is chairman of Liberty Media and has extensive holdings in QVC, the cable channel; Expedia.com, the travel Web site; and Sirius XM satellite radio. Liberty Media also owns the Atlanta Braves, which Mr. Turner once owned. Last year, Forbes ranked Mr. Malone as the 110th richest person in America, and though he has been an aggressive media player for decades, he has operated largely out of the limelight.

He intends to keep the land as a working forest, aides said, and will continue to supply timber to local paper mills and keep the land open to the public for recreation. Environmentalists are “cautiously optimistic” that Mr. Malone will not develop the land, said Cathy Johnson of the Natural Resources Council of Maine.

Mr. Malone owns various parcels of land around the country, including more than 68,000 undeveloped acres in Maine and the 290,000-acre Bell Ranch in New Mexico. Once he buys roughly 980,000 acres in Maine’s North Woods and about 20,000 acres in neighboring New Hampshire, under a deal to be completed by Tuesday, he will own 2.1 million acres nationwide.