Looks to be a White Oak.
White oak prefers full sun and moist, well-drained, acidic soil (pH 5.5
to 6.5). It is tolerant of drought once established, but will not
tolerate alkaline or poorly drained soil. Most white oaks develop
chlorosis, or yellowing of leaves, when grown under high pH conditions.
White oak will decline slowly if subjected to root disturbances such as
soil compaction, cutting surface roots, decreases in leaf litter, or
changes in soil drainage conditions. As little as 1 inch of fill soil
can kill an oak.

Found this info online. Might be best to contact a local nursery and ask their opinion.

Hang on to your hat Kic948 , it gets hotter!!! If that's new construction and they are fairly recently planted, perhaps they are still adjusting. Good idea to take a small branch to a nursery..Plants for all Seasons..if you have one nearby, together with a picture of how they are planted at the base. . The builder should replace them if they actually die, which is unlikely.

Doesn't look like a lack of water problem to me. Usually the leaves of trees under water stress begin to look droopy, dull, and limp. Because the brown area has a specific pattern and isn't affecting the entire tree I would suspect some sort of pathogen.

If the crown of the tree is not covered by soil (if the soil is level to the top of the root area, it should be fine. (Although they would look better on the same plane as the lawn and not mounded up, I think) As far as the circled area, the roots don't stop at the edge(unless perhaps the tree is planted in crappy hard soil) they continue to grow out beyond that area. Oaks usually don't like that much water - think California foothills etc. - so perhaps it's getting too much water because of the lawn.

This could be an entirely different Oak variety though, I don't usually see Oaks used as lawn trees.

Lefty has it right, talk to a tree specialist.

I agree with taking a clipping to a local nursery. Better yet, have an arborist come to your house. We live in Southern CA and are home is surrounded by California Live Oaks...very old ones. We had an arborist come to advise us on some issues. Not sure but am wondering if the variety of oaks you have require different care than ours. Too much water is NOT good for our oaks since it can encourage root rot/fungus...especially in warm weather. Get advice from someone who knows oak trees well.

I tend to agree with bellburgmaggie regarding the small, piled dirt mounds. The arborist told us the area below ours should be clear of other plantings and fairly large. Again, it could depend on the variety and/or age. Our oaks are old, huge and beautiful! They're also protected.

Get the dirt away from the trunk. A tree should only be planted at its original depth. I didn't know oaks could grow in hot climates like Houston. We use oaks in PA for lawn trees. They are a strong tree and hold up to wind and snow. Just have to have enough space, because they get large.

Oak trees cover Texas. I'm more central Texas and have 5 different Oaks on my property.

This is what happened to part of one of our trees due to root fungus. :-( The second pic shows a neighbor's tree and what the arborist said NOT to do with plantings and stones right up against the base of the trunk.

I'm near chloe and also surrounded by 100+ year old oak trees. huge. all over the hills. Since we get very little rain here, they obviously don't need a lot of water to thrive. They are all protected here in the state. Big, Gnarly oaks. can't believe they'd plant the same type in your front yard!

there's black oak, red oak, white oak, English oak,,,+ 55 others in the US!

this is one of those in the surrounding hills. you really want these roots next to your plumbing and foundation?

We seem to have mostly Live Oaks and Water Oaks in Houston. In our neighborhood we have two in every front yard, one on each side of the path...they get pretty big!

@Beth, when our house was built (1956) the builders did everything possible to save as many of the old oaks as they could. At that time lots for homes were kept larger so that probably helped with enough space for these beauties. Not something you see today here in SoCal where newer homes can be on top of each other!

When leaves yellow, tree is telling you that the it needs to be fertilized. Ask at your nursery…something like this:

Chloe, exactly. across the street from our homes, was a new tract they built back in the '90s. the city said they could only cut down 80 of the oaks. Homes are still on top of each other though, with no back yards. At least there is a large expanse of untouched hills where all these trees grow. You've prob driven through my 'hood,,,,,57 fwy, just north of the Brea mall. As you drive through the canyon, all those hills have the oaks

Judy, if those trees were just planted, it doesn't need fertilizer. it's stressed. doesn't need anything to help it grow, it just needs to settle in.

Beth, any new planting needs help along the way. Particularly if there isn’t enough rain/watering.

Judy- not a newly transplanted tree. It's always recommended the tree (or plant) settle in and adjust to it's new setting. And we don't know if the nursery had already applied some sort of fertilization to the pot or the soil when it was transplanted. over doing it would not be good at this point. Especially in mid-summer.

Fertilization at the time of planting is generally not recommended. It is ineffective until the root system has a chance to reestablish. It is usually advisable to wait two or three years before applying fertilizer, and then it is recommended to get a soil test first.

But again, I guess it would be ok if the soil was lacking in any sort of nutrients or if the pH was too low. then a small amount might help it acclimate.

http://www.mortonarb.org/trees-plants/tree-and-plant-advice/horticulture-care/caring-new-transplants

this arbor link also has some other helpful tips.

Beth, please address the O P. I am just commenting to share my experiences. This is not a contest of who knows what.

First question - is this a neighborhood problem or limited to your trees?

I suggest the local county extension office for good information about trees and landscape care that is suitable for your climate. A botanical garden or arboretum in the Houston area may have a plant health clinic or volunteer experts to answer questions.

wow judy. alrighty then. just hate for the OP to get erroneous info and possibly kill the tree. Pardon me.

btw,,the leaves are brown, not yellow.

Here is the correct forum for your oak tree question.

http://forums2.gardenweb.com/forums/trees

They might be able to help you as well. good luck :)

klc948,,,Perhaps reading this post would be of help. it was also a newly planted oak tree whose leaves were turning brown.

http://forums2.gardenweb.com/discussions/1686599/please-help-newly-planted-oak-sapling

No Beth H our oaks don't look like the gnarly oak you pictured. Never knew there was so many different types of oak. I guess that is why they call it the mighty oak. I use to have 4 in a row in our back yard of our past house. I use to like watching squirrels leaping tree to tree collect the acorns in the fall.

Beth, yes I know that area. Are you actually in Brea? My husband was just there today on the very sloooooooow and totally jammed 57. But then, what fwy here isn't?

functionthenlook, our oaks are all gnarly with squirrels everywhere. They keep their leaves year round but will drop some when new leaves sprout. The dropped leaves are prickly!

chloebud,, (Send me a PM on here if you get a chance),that fwy is ridiculous. i'm 2 exits north of the mall. he prob went right by me, as the freeway is directly behind my yard!

Beth, not sure why I'm having trouble with the PM function here. It's usually so easy...I'll figure it out. I'm thinking two exits north of the mall might be Diamond Bar...? We're north of there (Glendora) in an area commonly called "The Oaks." Pretty much the main reason this topic caught my eye!

chloe,,,yes I do! that pic of the oak tree I posted, above, was from San Dimas Canyon, near the reservoir.

send me an email and I'll respond back. u should be able to do it w/clicking on my name. I can't send you one.

San Dimas...of course! We're on our way out...will try the email when I get a chance!

I can't help as to why the leaves are turning brown, but you should look at removing the mulch from around the base of the tree. Mulch should not come into contact with the tree trunk and shouldn't have a dome as it can be unhealthy for the tree.

http://www.mortonarb.org/trees-plants/tree-and-plant-advice/horticulture-care/mulching-trees-and-shrubs

I brought a small branch and photos to a nearby nursery and was told there was most likely some issues with the roots due to the (dead) flowers and mulch surrounding the trunk of the tree. We had been intending to take out the flowers the builder put in anyways but removed them and dug out the dirt and soil closest to the trunk. Also watered the tree with microlife and will do some remulching once the rain stops. Hopefully this will help out our trees - thanks for the input!

You need to get rid of the extra soil... make the whole area all one level. Put the soil around some bushes as mulch or just fling it over lawn with a shovel and water it in. It will look much better if those mounds are gone. "...issue with roots"... who knows?, sounds pretty vague. If you still have a problem, call an arborist. Good luck.

Get rid of the mulch and supports. Volcano mulching kills and supports cause weak trunks. Oak leaves are a good mulch, they turn the ph to what oaks like. The browning looks like scalding from UV. It is much worse in recent years and even full sun plants fry up in summer in a lot of places. (If they were in my area I'd make a bed around them with understory shrubs and plantings, this makes a microclimate with humidity and helps with stress and nutrient deficiencies, the plants serve as a mulch.)

That is why they call what has been done to those trees “circles of death.” They kill trees. On large oaks the mulch area should be to the tree drip line. I would also check the soil pH to make sure it is tree hospitalable if the problem continues. Oaks are notorious for not liking their roots disturbed. I lost two large oaks on my property within 3 years when I moved a driveway and thought it wouldn’t be that much of a disturbance as it was 20 feet way from trunk - I was wrong, both died.