Everything on earth evolved around changing seasons and the different versions of resources they bring with them, so I'm curious, how did natural processes take advantage of winter qualities to shape earth as we know it? It seems like the advantages captured from other seasons are more obvious, specifically to plant life (spring- showers, summer- direct sunlight) so what's the unique aspect of winter that helps continue the process?
I don't know if one answer can list all the positives, but one I can think of is this: In many (not all) places of the world winter produces the most violent storms. Because deciduous trees lose their leaves during winter, they thus have less wind resistance, which in turn lessens--but does not eliminate--their vulnerability to being toppled over by severe winds.
And of course, hibernating species take advantage of winter by sleeping through it and pretty much staying awake for the rest of the year. (I sometimes wish we humans could do the same.)
There is nothing "necessary" in winter, as much as nothing is "necessary" in any other seasons or natural phenomena. It's not like there's an all powerful being (God) that decided we needed a winter. Winter is a fact of life that occurs because of Earth's rotation tilt. It's there whether we want it or not and whether we're even here to contemplate it's "necessity".
That said, things have evolved around the existence of winter, and the occurrence of winter has become necessary for their life. For example, some cherry cultivars taste better when exposed to cold. Winter causes fish, mammals, insects, birds, etc to migrate and subsequently breed. Ski resorts are open in winter and without it people who work there will be unemployed.
Seems to me the creation of soil may be largely due to the effects of winter. If not for the seasonal death and decay of part of plants exposed to winter conditions, soils would be less rich. Look at the soils in the tropical rain forest areas, which area relatively poor in nutrients, in comparisons to the rich dark soils of the great plains, where winter temperatures kill the surface plants, but reintroduce that vegetation into the soil to aid the growth of the soil for the next seasons growth.
Another important aspect for winter is the snow, which, besides providing skiers with entertainment, provides moisture which, being retained in the snowpack late into the spring and summer, and allows life to flourish into regions which would otherwise receive little or no precipitation in the summer months.