By Jessica Toonkel

NEW YORK (Reuters) - In the summer Mark Martiak usually spends four days a week at his home office in his Southampton, New York beach house.

But not this year. Martiak, a senior wealth strategist at Premier Financial Advisers, says he isn't sure if he will leave is Manhattan office.

"I don't feel comfortable leaving the office with everything going on," he said. Martiak, whose firm has $300 million in assets under management, this week also cut a 10-day trip to Europe with his family to four nights.

While only a minority of financial advisers and mutual fund managers interviewed by Reuters are completely cancelling their plans, many are scaling back. And those who are doing so say that since the 2008 financial crisis, their summer vacations have not been the same. Now, they are hesitant to leave the office because of the potential for a third summer in a row of volatile markets.

"Wouldn't it really be nice to have a boring summer. But I don't think it will happen this year," said Michael Hasenstab Wednesday at Morningstar Inc.'s annual investment conference in Chicago. Hasenstab oversees $160 billion in bond funds at Franklin Templeton Investments.

Markets have seen two volatile summers in a row. In August 2011, the Dow Jones Industrial Average swung more than 400 points four days in a row - a record - as worries about the European debt crisis and a credit rating downgrade in the U.S. roiled markets.

Now, with concerns about Europe and a slowing U.S. economy back again, advisers and portfolio managers say that if the past two summers are a guide, even more clients will want to be able to quickly schedule face to face meetings.

"Yes, I can be on the phone and available over e-mail but it's not the same," said Michael Pomerantz, president of Pomerantz Financial Associates, a Cherry Hill, New Jersey-based financial adviser. "People still want to know you are in the office if things are going down."

Pomerantz, whose firm has $50 million in assets under management, began cancelling and shortening his summer vacations last month. In May, for example, he turned a week-long trip to Mexico, into a long weekend instead.

Pomerantz has also canceled plans to take a week off for a beach vacation this summer and doesn't expect to take as many long weekends away from work as he would have otherwise.

"I am too scared to leave my office any day of the week," he said. His clients are panicking, he said, and Pomerantz feels like he cannot leave them. "They believe the whole market is going to crash and we are going to be back to 2008."

Some portfolio managers say they are also staying close to the office for the next few weeks.

Phil Orlando, chief equity strategist at Federated Investors, said that the next two weeks will be a "critical inflection point in the economy and the markets," with the Federal Open Market Committee policy meeting earlier this week, the Supreme Court decision on healthcare expected soon, the late June EU Summit and the July 1 Iranian oil embargo by EU countries.

As a result, no one in the firm is taking vacation time until at least July 4.

Dan Fuss, vice chairman and portfolio manager at Loomis Sayles, which oversees more than $172 billion, said his firm is monitoring vacation time.

"Traders have to be very, very coordinated. We don't want two out of four in any one area to be out of the office," Fuss said.

Of course, not everyone is cancelling their summer plans, partly because time off isn't what it used to be. Azim Nahkooda, managing principal and chief executive of Cedar Brook Financial Partners LLC, said he is still plans to take at least a week off at the end of August for a family trip to North Carolina.

"Vacation? What's a vacation," said Nahkooda, whose clients have $2 million to $5 million in investable assets. "With technology today, people can still reach me."

(Reporting By Jessica Toonkel; Additional reporting by David Randall, Jennifer Ablan and Tim McLaughlin)