Since it was recently transplanted, I would think the stress you are seeing is from transplant shock. It takes some time for a recently planted tree to get its roots established and to thrive. This is a critical time to also make sure you are watering the tree so it has the resources to get established.

These articles from MSU Extension and the University of Minnesota have some really helpful tips on maintaining newly planted trees/shrubs that you may also consider: 

• Don't forget about newly planted trees and shrubs
• Planting and transplanting trees and shrubs

Hello. My birch tree has been in the ground for 8 years. Sorry I wasn’t so specific. Please look at the picture again. Help..

I see. Thank you for the clarification. It does seem in a stressed state, but that does not mean it is dying. Watering will still be of upmost importance to help bolster tree health and help it tolerate this stress. More information on watering established trees here: How and When to Water

It is hard for me to tell what may be causing this browning from the photos. Environmental stressors such as drought, improper planting, poor drainage, poor soil can all lead to these symptoms. 

You may also want to inspect the tree for any signs of insect damage or boring insects like the bronze birch borer: Bronze Birch Borer, MSU IPM

I would also check the base of the tree. Look for any areas that appear "soggy" or look abnormal. I would also check the tree roots - do they look white and healthy? Or brown/mushy or brittle? Poor root growth and development can certainly affect water/nutrient uptake and above ground growth. 

Okay, thanks for more info on the soil. Were you able to dig down and inspect the roots? 

Sure, you can send more photos and I will do my best to see if they show any more indicators as to what may have caused this. Another possibility I am thinking about could be heat stress. Do you have information about the exact species and cultivar of this plant so I could investigate a bit further? Some birches do best when it is a bit cooler (soil temps rarely exceeding 75F). 

I also recommend taking a closer look at the trunk for any signs of insects (like holes from borers), which can be a challenge to see in photos. 

I am thinking it may be environmental stress that is causing this browning. Either heat stress or a soil issue. Has there been any sort of construction or anything in this area (new plants, etc.) that may have disturbed the root system? 

For the rest of the season, I would be sure to mindfully water based on the article I listed previously. This will hopefully help the tree tolerate whatever stress it is experiencing, overwinter and come back healthy in the spring. 

One idea is to also get a soil test. This will tell you all about what the current fertility of the soil is as well as the structure (ie. clay, sand, loam), and it will give you fertilizer recommendations based on that. Proper fertilization next spring will also hopefully help this tree recover from this stress. You can get started on a soil test here: MSU Soil Test