This is somewhat incorrect I'm afraid. While your partially correct...the scale at which your thinking is incorrect. Things don't work that way so much.

Some pure stands of one tree species can be vitally important to numerous wildlife species. Wildlife typically do not use one type of habitat for everything and they certainly do not use one stand of trees for everything. Many species mate in one type of cover, feed in an entirely different type of cover and den in yet another.

So saying that increased plant diversity is an indicator of wildlife diversity is not entirely true. Some species for example REQUIRE single species stands of old growth white pine for breeding and they may prefer a regenerating clear cut or multi storied shrub/tree mix for feeding.

So what you should be looking at is the types of cover you have at the forest scale, not the number of species within a stand of trees. The ideal for most types of wildlife habitat would be a mosaic of many different types of cover/stands in a natural layout (ie. not square blocks of one type etc).

More often than not the critical factor which determines if a wildilfe species uses a certain area has much more to do with the AGE of the stand rather than the species composition or a combination of AGE and SPECIES COMPOSITION. So making your land entirely of one cover type is a bad idea, you should want to promote many different timber stands, boggy areas, a few old fields etc...diversity of form/age not neccesarily diversity of species within a stand though often a land with many cover/stand types WILL have more species diversity at the landscape scale. There may be a few stands of nothing but oak, but next door may be a marsh or a shelterwood cut with many different shrub species.

Does this make sense? Maybe you were saying this and I totally misunderstood.

I also take isse with your statement that tree diversity is a sign of timber health. Not true. Pure stands of old growth are arguably some of the most resiliant, disturbance resistant stands in existance. Also, many many forests in the west are almost complete monocultures of lodgepole pine. Those types of forests function normally in natural cycles without much species diversity and are quite healthy until the cycle nears an end and the disturbances that drive forest sucession come into play.

I'm not trying to lecture just stating some things that I feel need to be said. It's great that people are thinking about these things in the context of wildlife management.

Another thing you hit on that is vitally important: the need to manage for WILDLIFE rather than just managing for one or two species. Many people fall into this trap by managing for only one species to the detriment of numerous other species.