RENO -- Sierra Nevada ski resorts are starting to shut down lifts for the season after what some operators are calling a "very challenging year" because of the economy's downhill slide.

The Boreal, Soda Springs and Homewood resorts around Lake Tahoe closed on Sunday, a week before the nearby Alpine Meadows, Heavenly, Northstar-at-Tahoe and Diamond Peak ski areas plan to halt operations.

In a message on their resort's Web site, Alpine Meadows executives said the economy is prompting an earlier-than-usual shutdown of their slopes. Last year, the resort closed May 4.

Art Chapman, president of JMA Ventures, and Jim Kercher, chief operating officer and general manager of Alpine Meadows, said it was "a very challenging year" for the industry as skier counts and revenue were down sharply at all Tahoe resorts.

"Our decision to close April 19 was driven by the unfortunate fact that we are not seeing the number of skiers necessary to cover our operating costs on weekdays or weekends," they wrote.

Other resorts said skier numbers were down but for different reasons such as a later start of snow and a snowy Presidents Day weekend that kept crowds away. Most Sierra resorts plan to close by late this month despite storms in recent days that dropped up to 20 inches of snow.

"We weren't significantly down because our prices are cheaper than other resorts," Boreal spokesman Jon Slaughter said Sunday.

Corporate communications at Vail Resorts, which owns Heavenly on Tahoe's south shore and four ski resorts in Colorado, did not return a voice message and an e-mail requesting comment.

But at an April 1 conference in Keystone, Colo., Vail Resorts Chief Executive Officer Rob Katz said his company has faced a decline in ski school participation and high-end retail spending this season.

"We've seen such huge declines, especially during some of the key weeks," said Katz, whose company is the nation's largest ski operator.