More likely to be aspen (Populus tremula) than it is poplar. They are native to Iceland although not very widespread in their distribution. These look to be intentionally planted rather than wildlings.

One of the most planted trees in Iceland is populus trichocarpa, the wester balsam-poplar but identifying poplars is not easy. Aspen might be native to Iceland but not as widely planted as some Alaskan trees.

Shoots too thick, buds too big for aspen.

Thanks everybody. Taking all suggestion into account I am leaning towards the Black Cottonwood or Western Balsam-Poplar Populus trichocarpa.

Btw, would not Aspen spread already by suckering beyond the row ?

Just in case if someone wanted to chime in with more info I sharpened the picture in hope it can help. Here it is:

More info on poplars in Iceland (in english):

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