The Mystery of the Dying Cedar Trees

As I travel across Nebraska this year, I keep seeing dead and dying eastern red cedar trees.  Some are big, some are small, but they’re definitely dead.  Since cedar trees are a major invader of grasslands across the state, I’m not complaining about all the dead ones, but I do wonder what’s killing them.

Why are cedar trees dying around Nebraska?

Why are cedar trees like these dying around Nebraska?

Interestingly, the trees seem to be dying in clusters, rather than as random or scattered individuals.  To me, that indicates at least two possible causes of death.  One possibility is that some kind of disease or insect is killing trees and then spreading to others nearby.  The second is that trees are dying from last year’s drought conditions and that local variation in soil texture means that cedars in some places were more vulnerable to drought than others.

the

Not all cedar trees are dying.  Sometimes it appears that random trees are dying and others right next to them are not.  Upon closer inspection, however, there are usually clusters of trees that are dying (note the right side of this photo).  Disease?  Or drought/soils?

Since my experience with trees is mostly limited to attempts to keep them out of my prairies, I thought I’d contact someone who has a broader range of expertise on the subject.  I emailed Scott Josiah, the state forester with the Nebraska Forest Service and asked him why cedar trees are dying.  Scott said he thought the drought hypothesis made the most sense, and that trees growing in soils with coarse sands and low levels of organic matter, for example, would be stressed more than those in soils that hold more moisture.

It was good to hear from an expert on the subject, but I’ll admit to a little skepticism.  I really like Scott, and as I said above, I’m no expert on trees, but cedar trees sure seem like they’d be tough enough to survive a one year drought…  Heck, I’ve seen them growing out of ROCKS!  I took Scott’s answer and filed it away, but continued to wonder about the possibility of a disease or insect outbreak that foresters and others just hadn’t yet identified.

And then last week, I found some pretty convincing evidence that I think has solved the mystery.

We were at our Kelly Tract on the North Platte River, working on some vegetation sampling and Canada thistle control when I noticed some dead cedar trees in some old shelterbelts on the property.  As I got closer, I realized this was a perfect site to test Scott’s idea that drought was killing cedar trees.  The Kelly Tract is a floodplain prairie with strong patterns of alluvial (river deposited) soils across the site.  That means there are lots of different soil types all mixed together – a naturally-occurring experimental design.

soil patterns

From this angle, you can clearly see some of the alluvial soil patterns that intersect with the line of cedar trees at The Nature Conservancy’s Kelly Tract along the North Platte River by Sutherland, Nebraska.

While conducting my vegetation surveys, I noticed that last year’s drought had definitely affected the grasses and wildflowers much more severely in some places than others.  Broad streaks of green and brown wound across the prairie, tracing the old channels and sandbars formed when the river had long ago flowed across the site.  When we’ve done soil sampling elsewhere along the Platte, we’ve found that soils with coarse sand and low organic matter are quickest to dry up in drought conditions – I assume the same is true at the Kelly Tract.  I figured that if drought, combined with soil texture, was killing cedar trees, I’d be able to see whether the dead trees were in the same “streaks” that contained dried up grasses and wildflowers.

They were.  In fact, every brown tree I saw was located along a streak of brown grass, and every green tree was in a streak of green grass.  It was as perfect a pattern as you could hope for.

The outlined area in this aerial photo.

This aerial photo from several years ago shows the alluvial soil patterns more clearly than in the earlier photo.  The red outline is approximately the same location the earlier photo was taken from.  I haven’t yet been able to find any aerial photography from this year (this older photo doesn’t show this year’s brown trees) but when I do, I’ll bet the brown trees will be in the brown streaks…

While cedar trees are certainly tough, it sure looks as if Scott was right – last year’s drought was just too much for those trees to handle, at least in some soils.  Mystery solved!

Way to go, Scott!   Now I have a new problem…  Do I hope for a wet year to help our prairies recover?  Or a dry year to kill more cedars??

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About Chris Helzer

Chris Helzer is an ecologist and Eastern Nebraska Program Director for The Nature Conservancy. He supervises the management and restoration of approximately 4,000 acres of land in central and eastern Nebraska - primarily along the central Platte River. Chris is also the author of "The Ecology and Management of Prairies in the Central United States", published by the University of Iowa Press.
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18 Responses to The Mystery of the Dying Cedar Trees

  1. Dunwiddie says:

    Hi Chris-
    Very interesting post. You and Scott may well be correct here, but you might still keep an eye out for pathogens. Pretty often what kills trees is a combination of interacting factors. Bugs will stress trees, which then may succumb to droughts they would otherwise survive. Or vice versa. I’ve been fooled enough times over my career by accepting a seemingly obvious explanation for something, only to be later corrected by someone who looked a little more closely.

    • Chris Helzer says:

      Peter, it’s a very good point. As you say, very few things in nature can be linked to a single cause! I’m pretty comfortable with drought being a major contributor, but would not be surprised to find extenuating circumstances such as those you suggest…

  2. Lisa says:

    We have been seeing this is Kansas as well. Drought is definately a major factor. Often the dead trees are in a tree row or shelterbelt and they are spaced close enough together that they are competing for moisture. Those that are spaced out in rangeland are experiencing less competition and they are surviving. At least in our part of the state, this has been a three year drought which has been intensified by very high temperatures.

  3. Randy Hyden says:

    No mystery, The drought in `11 in Texas killed millions of them. It was odd how one would survive right next to another that died.

  4. timupham says:

    They are dying all throughout the Midwest, from Texas to Ontario.

  5. Patrick says:

    It also seems from the pictures that the dying trees showed more stunted growth than their healthy neighbors, suggesting that they were not growing in optimal locations. I believe this would further support the hypothesis that the soil conditions dictated whether the drought pushed them over the edge.

  6. Rex says:

    The 2002 to 2007 drought killed a row of old cedar trees at our ranch near Gordon. No spread to trees in the yard or newer trees. This drought has killed a number of trees in windbreaks. Lisa’s observation suggests that drought will not significantly affect the invasive trees in prairies but will have a disproportionate affect on the deliberately planted trees.

  7. dhillis2013 says:

    @timupham says that “These cedar trees survived drought in past centuries.” In Texas, at least, most of the millions of Ashe junipers (“cedars”) that died in 2011 were relatively young (<60 years), which means that they were not around during our last major drought (in the early 1950s). We've had lots of droughts since the 1950s, but they have been the regular droughts that we experience every three to five years with La Niña cycles (even though each time the media report them as "the drought of the century"). The 1950s drought was remarkable in its duration (at least five years of significantly low rain…it was actually three droughts in close succession). But the 2011 drought in Texas actually saw far less rain than any one year of the 1950s drought, and far less than in any year ever previously recorded. It also appears (from tree ring records) to have been a remarkably dry year compared to any in the past five centuries. So the fact that millions of junipers (and oaks) died in the drought of 2011 is not surprising. The worst of the drought moved north in 2012; now it has returned to Texas. We are still no where near the duration of the 1950s drought, but at least the first year of the current drought (actually starting in fall of 2010) was significantly worse. See rainfall data for the past century plus and a discussion of rainfall patterns in Texas at http://doublehelixranch.com/FlyGapRainTrends.html

    • timupham says:

      How does this compare to the 1930′s Dust Bowl?

      • dhillis2013 says:

        The 1930s Dust Bowl was actually not a terribly remarkable drought (at least over most of Texas and Oklahoma). It was largely a problem caused by inappropriate agricultural procedures, coupled with a moderately severe but typical La Niña drought. But it was not nearly as severe as the early 1950s drought, or as bad in any one year as 2011 was over most of Texas. Take a look at the rainfall record at the link above (if you scroll down, there is a graph of rainfall in central Texas from 1895-2012), and you’ll see that the Dust Bowl was a pretty typical La Niña drought. The droughts that stand out are the early 1950s drought (for its duration) and the 2011 drought (for its short-term severity).

        • timupham says:

          Also, there was an economic factor involved in the 1930′s Dust Bowl. During World War I, the United States vastly overly produced, and exported it off to war-torn Europe. During the 1920′s, European countries put up high tariffs, to keep American exports out. Farmers were shut out of the Roaring Twenties. Then in 1929, the Great Depression set in.

          • dhillis2013 says:

            Yes, absolutely, and it certainly resulted in a lot of hardship for the farmers who were trying to do dry-land farming in the Texas and Oklahoma Panhandles. They gave up and moved away, and few people try to dry-land farm there anymore. But as a drought, the Dust Bowl was not remarkable.

  8. Charlotte Reemts says:

    We’ve had some Ashe juniper mortality on The Nature Conservancy’s preserves in the Hill Country of Texas. Most of the trees that died were smaller, understory trees (possibly due to competition from larger, more established trees), so the overall effect is a thinning out of the subcanopy.

  9. Mary says:

    In the years preceding the Dust Bowl, there was plenty of rain. Farmers increased their yields too much. So when the drought hit, disaster. Too bad the Pine beetle doesn’t like cedars.

  10. Pingback: Wildlife & Conservation Link Round-up | Rebecca in the Woods

  11. Tammy says:

    I am no expert, however, we have been seeing this in Texas for years because of the drought. The radio talk show experts were alerted to this (back when it started) said that the cedars would not be the first to die because of drought, but they were. Now we have millions of dying and dead trees of all species. In eastern Travis County, which is known for being the green area of the county, you will see wooded expanses with a large number of dead trees.

  12. John says:

    Several months ago I saw lots of dead cedars on my place. I seen several around one of my ponds and some out in the field. Today I went back and seen those that were green and alive now are dead. Some a few feet from water (pond never dries up) and it rained several times since then. I don’t see any dead grass. I don’t think its a water problem. I’m not saying its gas drilling but I’ve lost a lot of trees (oak and some others) for no apparent reason after they started fracking gas wells.

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