The Bonn Cabinet today nominated Karl Otto Poehl as the next president of West Germany's federal Bundesbank, or central bank, an institution that has grown into one of the most important international centers of monetary policy-making.

Poehl, 49, who has been the Bundesbank vice president for the past two years, is the youngest man to hold the prestiqious top job, and his appointment for an eight-year term means he could be a major figure on the world economic scene for many years to come.

Government spokesmen say they expect no major shifts in Bundesbank policy under Poehl, who will take over on Jan. 1, 1980, from Otmar Emminger, 68, who is stepping down as president of the bank.

Nevertheless, Poehl is a distinctly different personality from the type of person most Germans are used to as head of the bank, which is the equivalent of the Federal Reserve Board, and his background is also more political.

Poehl, for example, has been a member for 30 years of the Social Democratic Party, which rules in Bonn in coalition with the smaller Free Democratic Party.His political as well as his economic skills were so highly regarded that he was brought into the federal chancellery as chief economic adviser by former Social Democrat chancellor Willy Brandt in 1971 and then made a state secretary in Bonn's finance ministry by the current chancellor, Social Democrate Helmut Schmidt.

Schmidt's economic spokesman, Armin Gruenewald; said today that the cabinet had no doubts about the continued independence of action of the Bundesbank under Poehl.

But there has been speculation for some time that Poehl's expected appointment, coming about one year before federal elections, might somehow allow the current government additional flexibility in control of the money supply which the bank, under Emminger, has kept extremely tight to hold down inflation.

Government officials deny this, saying they see few if any differences in policy between Poehl and Emminger and that, whenever necessary, Poehl, too, will go for the tight monetary policy to fight inflation.

Conservative opposition party spokesmen, however, have criticized the appointment as "politicizing" the bank.

Hansjoers Haefele, a Parliamentary financial spokesman for the joint conservative parties, said Poehl was "polititcally tied to and dependent on the government" and the the appointment would "poison" public trust in the bank's independence. Opposition chancellor candidate Franz Josef Strauss claimed Poehl was within "the smokey circle around Brandt" and would diminish the "power and sovereignty" of the bank.

Poehl's credentials as an experienced specialist in international monetary affairs are not under attack. What will be different for traditionally more officious Germans, and some international bankers, will be Poehl's relative youth, his more relaxed manner and the certainty that he is a man with powerful political connections.

Poehl, who is well known in the United States, is an economist and also worked as a journalist for several years before entering economic research and then government.

By American standards, the Bundesbank has been extremely conservative with monetary and interst-rate policies that sometimes have aggravated the federal government here. More recently, the bank has annoyed the United States and other European governments who felt that the bank was endangering general economic growth by its ultra-conservative stance against inflation

The bank, therefore, has shown its independence. But in comparison to the U.S., there is also a special closeness to the federal government. In recent years, as domestic and international economic policy became so intertwined, top Bundesbank officials began attending more than a dozen federal cabinet meetings here each year and are certain to be on hand for any discussions of the federal budget.