One of the most important parts of managing a property for wild game is being able to produce a diverse amount of food sources. The more plant species your property has on it, especially highly palatable species, the more game animals you will be able to support. With a diverse amount of food sources the game animals on your property will be able to meet all their nutritional requirements through the seasons and allow them to grow and reproduce more effectively. However managing for a high amount of plant diversity can be somewhat complicated and there are many different factors that could come into play one of the major ones being how to manage invasive and overabundant plants.
Managing invasive woody plant species is somewhat straightforward. Basically you need to selectively cut anything that is outcompeting other tree and shrub species especially if it is not producing any real food source. For example if your property is covered in Tree-of-Heaven trees which are a pretty useless tree for wildlife as well as highly invasive, than you should continuously cut them back and plant other species until they either die out or are shaded out by other species. On the contrary if your property is covered in apple trees and nothing else then you should likely keep a large percentage of them, but still cut some out to allow room for other species as well. We want to aim away from any type of monoculture even if it is a productive one that provides a good food source for wild game. While apples are a great food, they are available only seasonally and will not give wild game their full nutritional requirements leading to fewer game over time.
Dealing with invasive trees and shrubs is relatively simple, however when it comes to grass and forb dominated habitats it can become quite difficult to manage them for a high diversity especially if it is already being overtaken by aggressive weedy species. There are both native and nonnative grasses and forbs that can completely take over open meadow type areas and can prevent plant species diversity. Many people know the common "weeds" in their areas. Out west a very common one and one that I am faced with on my property is yellow star thistle. This annual forb can completely take over some areas, especially in disturbed and degraded soils, preventing the establishment of any other plants as well as providing practically no food value to wild game. This is a type of plant I would like to be without, however it has essentially become naturalized in my area so it is best to learn how to manage it. Without using herbicides, which would also kill the plants I want, I will need to learn more about the plant and it's life cycle to determine the best way to manage it. After doing some research I figured out that if you can prevent it from going to seed then you can control it long enough to establish more desirable plants that will prevent it from taking over. To do this you need to cut it back to the ground such as with a weedeater right around the time it is beginning to flower which is usually around late spring and early summer. Once the first flowers start opening I will aggressively cut it back with the weedeater once and then again a few weeks later as new sprouts come back. This will essentially kill that years seed and help prevent future infestations. This will need to be done several years in a row due to seed stored in the soil, but eventually it will greatly reduce this plant almost to the point of elimination. During this time it will also be necessary to spread desirable seed to establish and help provide a barrier to possible future infestations. This type of management is labor intensive for a few years, but once the right plants are growing, ideally a diverse mix of palatable forage species, then anymore starthistle that invades that area will have a hard time reestablishing itself to those high levels. Every plant will have it's weaknesses, whether it be frequent mowing, targeted seasonal weedeating, grazing patterns of livestock, plowing, shading out etc. But it will be up to you to research and figure out how to remove the invasive plants on your property.
One of the best things to prevent invasive species from taking over your property is to already have a healthy diverse amount of species established. This means you will need to plant and spread seed of many different plant species to not only give more food options to wild game, but to also provide that healthy barrier against aggressive monoculture forming plant species. There are many factors that will determine how successful you will be at establishing desirable forage plants, but it will likely take lots of trial and error to find something that works specifically for your property. Like always research is key and knowing the biology and ecology of your chosen plants will be important to figuring out the best method of establishment and management once established.
One more point I'd like to make is that just because a plant is not native does not mean it will be bad for your property. A good example of this is the bienneal forb Salsify. This is a nonnative "invasive" weed that has become common in the west. In some instances on disturbed and degraded soils it can take over and become an unwanted weed. However in much of the west it has naturalized and become a part of the balanced ecosystem of the open grassland regions. This plant also happens to be excellent deer and elk forage and some studies have shown that some deer and elk preferred to eat this forb in spring and summer more than any other plant in that particular region. So I just wanted to point out that not all nonnative "weeds" are necessarily bad for your property and there are in fact many that are an excellent food source for wild game. And at the same time many natives are practically useless for wild game habitat and some will need to be managed so they don't take the real estate of more desirable species.
Many species of plants that have come from other countries are here to stay. Some of them are bad for wild game habitat and some are good. It is practically impossible to get rid of them at this point. But if one is able to manage their property carefully then they can make sure to have a wide variety of both natives and nonnatives that will lead to better habitat for the game on their property.