WASHINGTON — The roads to the national forests could get bumpier. Trails could get messier. Maintenance on bridges, dams and recreation sites could become tougher under President Donald Trump’s proposed budget for fiscal 2018, which begins Oct. 1.

The White House is seeking only about $100 million in funding for capital improvement and maintenance by the National Forest Service, down from $363 million this year.

That 73 percent cut could have a huge impact on recreation,…