The value of pines to deer? Here is how I look at it - pine trees generate revenue. Land is an asset, and in order for many landowners to continue owning and maintaining their land, the asset needs to generate revenue. There are a number of different options for generating revenue, but you asked about "pine plantations".
When a pine plantation is young, it does provide early-successional habitat which benefits deer in the form of quality bedding and escape cover as well as browse. I don't know about your area, but in the southeast browse production on the order of 1-1.5 tons per acre is a ballpark estimate given variation in site prep techniques and site index. Once the canopy of the pines closes, that browse production goes to nearly zero. At that point, pines don't benefit deer other than to provide thermal cover.
You mentioned thinning - in order for pines to grow, they need resources (sunlight, moisture and nutrients). When there are more trees than available resources, the trees stop growing. So thinning a plantation reduces competition between the remaining trees and allows them to utilize more resources and thus continue to grow. There is a time following a thinning operation when there are more resources on the site than the trees are able to utilize. During that time, other vegetation takes advantage of excess sunlight, moisture and nutrients and produces the early successional habitat that existed in the early years of the plantation.
Things change over time, and the plantation is no different. As the pines grow, they utilize more of the available resources until once again nearly zero early-successional habitat exists and the remaining trees are once again competing with each other for available resources. Now it is time to thin again, and the process repeats itself.
So - is there value in thinning your pines to release the oaks? That depends. Would the oaks produce if they were not crowded by the pines? That depends on the age of the oaks and how much of the available resources they can utilize. Keep in mind, oaks are beneficial to deer when they are producing acorns. Even in the best situation, oaks benefit deer for a few months out of the year. What is a deer going to eat and live in the rest of the year?
When I think of oaks, and where I want them - I want them where they belong - where they would have traditionally been. In my area that is the low areas, river bottoms, drainages and transitional zones between these features where fire historically limited their existence. When oaks start creeping out of those areas and occupying space elsewhere, I start to question their value. Is there something else that would provide more / better for a deer in that space. A couple oaks that produce a few hundred pounds of acorns per acre for 2-4 months, or early-successional vegetation that produces 1-1.5 tons of browse that is available for 12 months in addition to quality cover? Oaks are not bad, in fact they are a very valuable part of the equation, but a forest of all mature oaks is not the answer either. Once again, where I am, I have no hesitation cutting oaks or any other hardwood out of a pine plantation if I have other options that would be a better fit.
So back to the pines you asked about - manage the pines how you need to in order to generate revenue. If you are one of the lucky ones that doesn't need to consider the revenue produced by the pines, manage them as a component of a healthy system, which means opening up the canopy to promote species that help benefit deer all year. Understand that a healthy forest is comprised of all stages of growth for as wide a variety of species as possible.
My long-winded $.02 on pine plantations.
