Species good in windbreaks and thickening out bottoms of hedges:

Worcesterberry
Blackberry - good at filling out both top and bottom of windbreaks
Ramanas rose
Gooseberry (where only moderate winds are expected)
Elaeagnus (various kinds, Autumn Olive sounds great)
Damson (apparently Myrobalan (vigorous) is indeed alkaline tolerant, 6-7m high and wide)
Crab apple
Mulberry (marginally more wind tolerant, like Hazel, due to being wind- and not insect-pollinated)
Siberian Pea - windbreak