More than 400 bright yellow signs with white centers have sprung up in Fairfax County this week.

Unlike the daffodils that surround many of the signs, the notices are generating interest in land use rather than excitement about the coming of spring.

The signs are public notices of a possible land-use change on the sites where the signs are posted.

This week the Fairfax County Planning Commission began holding hearings on more than 300 challenges to the county's comprehensive land-use plan. That plan is considered the Bible of land-use planning and zoning in Fairfax.

Overflow crowds have jammed hearing rooms and forced Fairfax Planning Commission Chairman George Lilly to rule that no hearing will be started after midnight. Many hearings will be rescheduled to Saturdays later this month.

The bright yellow signs are seen as symbols of the continuing boom in residential and commercial growth in Fairfax. To some, those signs are ominous threats to the stability of their neighborhoods. To others, they mean increased tax revenue and money for current land owners. Efforts to change the land-use plan in some of the more densely populated neighborhoods have united residents in an attempt to preserve what they have and divided other areas where residents would like to sell their land for more intense development.

The possible changes are part of the 1985 annual review of the county master plan. Since this is a third year in the planning cycle, every application filed automatically is heard by the planning commission. In other years, only items meeting strict criteria can be heard.

When the number of proposed changes hit an all-time record this year, the board of supervisors told the county staff to post signs on the sites in the same way land involved in rezoning actions is flagged.

"We had to order 400 more signs at a cost of just over $6,000," according to Sidney R. Steele, acting director of the Office of Comprehensive Planning. Those signs will be stored for future use after hearings before the planning commission are completed and action by the board of supervisors is taken on the various proposals this summer.

The signs have easily tripled the number of phone calls the county's planning office expected to get concerning the changes, Steele said. He said the county has had to hire a temporary staff person to help handle the calls.

Several weeks ago, Fairfax officials mailed a tabloid newspaper listing all the plan amendment changes to every household. In the past this has been the only method of notification of possible changes.

"When you see a sign in your neighborhood, it is more relevant than seeing a complicated number on a long list of changes that you really do not know anything about," said one county staff member.

Wayne Pumphrey, head of the land-use division, said he thinks the signs have helped "people who were unaware of the process. There is a lack of knowledge about these amendments," he said.

Pumphrey, Steele and Lilly agreed there is confusion over the difference in the land-use plan amendment process and the rezoning process.

Lilly this week reminded those attending public hearings on possible changes in the Annandale and Seven Corners areas that the items being heard by the planning commission were not rezonings. "These are proposals to change the land-use plan," Lilly said. Changing the land plan is just the first step in getting a project built. Lilly said this stage deals with the merits of land use, not with the particulars of a specific building or project.

Lilly said he thinks the yellow signs may have confused people. "I think the posting has tended to throw people off because they have been put up just like standard rezoning signs," he said.

The signs that indicate land is being considered for a plan change are yellow with white centers. Descriptions of the proposed changes are written on the white portion, but "you take your life in your hands" if you stop your car to read them, Lilly said.

Yellow signboards also are used to post other possible land changes. The center portions are color coded, Steele said. White means it is a plan amendment proposal. Orange means a scheduled public hearing before the planning commission on a special exception or rezoning. Yellow means a board of supervisors' hearing on a rezoning or special exception. Blue signals a hearing before the board of zoning appeals and green means a proposed public facility, such as a trail or park, is being proposed.