Tree damage from last nights storms   Lee Frelich   Aug 11, 2007 12:26 PDT  ENTS: Many people in the Twin Cities were awakened at 3:30 am this morning by 80 mph winds as a bow echo downburst made its way through town. I have been gathering information on tree damage all day, and so far it looks like there were two east-west oriented strips about 1/2 mile wide of heavier damage where thousands of trees were blown down. One of these made its way through the southern part of St.Paul Campus of the University of MN where I work, through the state fairgrounds and Como Park, where bur oaks, red oaks, sugar maples, green ashes, and white pines lay strewn across the landscape. Because of the severe drought and hard ground conditions, most trees snapped off rather than uprooting. Most streets in the affected areas are closed and power is out to 110,000 homes. I woke up a half hour before the storm hit and noticed that lightning was flashing more than 100 times per minute, a sure indication of a severe storm. The weather channel radar showed a slow moving meso-scale convective complex of thunderstorms perhaps 50 miles in diameter and an associated flash flood watch. Suddenly the thunderstorm cluster re-organized itself into a line and a rear inflow jet stream developed, pushing the lead cell into a bow echo just as the storm was overhead in Minneapolis, resulting in a downburst with no prior warming. The national weather service is rather clueless about derechos and downbursts anyway, so I have learned not to expect any sort of warming of their approach. Unfortunately the fast speed of movement of the storm gave us only 10-15 minutes of heavy rain, which nevertheless amounted to 3/4 inch. Not enough to break the severe drought, but enough to keep it from getting worse for a few days. Most trees have been totally wilted for the last two weeks as we have had 24 days of >90 degree temperatures and very little rain. Today a few trees are perking up, but others remain wilted and are losing their leaves. We are hoping for another round of storms later today with possible drought relief as a cold front approaches that may return us to normal temperatures in the 80s and dewpoints below tropical levels. There was only a light sprinkle in the boreal forests of northern MN, and that place is ready to go up in flames at any moment. Lee Re: storms/Tree damage   Lee Frelich   Aug 13, 2007 19:05 PDT  ENTS: Tree damage from the storms early Saturday was more massive than I thought. Several hundred bur oaks were flattened in Como Park, in addition to the grove of white pine around the statue of Henrik Ibsen. Streets around the St.Paul campus of the University of MN are lined with debris 5 feet high. I will try to get some pictures for the website. In the mean time, word has just come that another bow echo derecho is on its way within the hour with winds >80 mph and baseball sized hail. Two of the remaining old-growth white pine forests in southern MN are potentially in the path of this storm, as well as downtown Minneapolis and St.Paul. I only have a few minutes to get ready for the storm... Lee Re: storms/Tree damage   rayof-@ndws.com   Aug 13, 2007 19:28 PDT  Models took one of those thru MA/NY last week, but fortunately, it didnt quite materialize. A second one raked across PA/NY, with some microburst damage and a couple of tornado's thrown in for good measure. Ray Re: storms/flying trees/drought   Lee E. Frelich   Aug 14, 2007 08:07 PDT  Ray: Last nights storms apparently had winds >100 mph in some areas (although Minneapolis only had 50-60 mph winds), and as a result media coverage is concentrating on demolished homes and other building damage, rather than tree damage. One TV station is examining damage done by flying dinosaurs from the Jurassic Car Wash in Brainerd, MN. A 6 foot long triceratops got detached from its pole during the storm, flew through the air and knocked over a pump at a nearby gas station. There is also plenty of coverage of flying boats that landed upside down in the middle of town, snowplows brought out to plow hail 3 inches deep, etc., etc. Trees can fly just as well as fiberglass dinosaurs and boats. The propensity of mature blue spruce trees to pull out of the ground or snap off and fly through the air, landing 50-100 feet from their point of origin never ceases to amaze me--I see it happen every time we get one of these big storms. No other tree species flies like blue spruce. For those trees that did not blow down the storms of the last two days have been a blessing. 2-3 inches of rain has put a dent in a drought that equals that of 1988 in southern MN, although there are still vast areas in the north that have not had any rain. A lot of trees this morning look much greener than they have for the past 6 weeks. Thousands of lindens, hackberries and maples in town had turned completely brown, and it will be interesting to see if they put out a new set of leaves, or whether they are dead. Lee Re: storms/flying trees/drought   Edward Frank   Aug 14, 2007 13:14 PDT  Lee, Of course that is the lead for the news. How often do triceratops attack a gas pump? Even in Minnesota? Maybe it was mating season. Ed Re: storms/flying trees/drought   Lee E. Frelich   Aug 15, 2007 16:18 PDT  Ray: Yes, we do have some Jurassic trees. This website shows the history of Ginkgo, which has a lineage going back to about 190 million years before present (mybp, the Jurassic Period was 206-144 mybp): http://www.ucmp.berkeley.edu/seedplants/ginkgoales/ginkgofr.html Ginkgo is common on the streets of Minneapolis today, and although not native now, it could have been native to MN 100 mybp. Asian people are commonly seen picking up the fruit of female ginkgo trees in lawns in Minneapolis, and they discard the flesh (which usually rots and produces butyric acid--the same chemical in rancid butter) and roast the seeds which are known as silver almonds. Many of the so-called male ginkgo trees have changed to female over the years, and thus efforts to exclude female trees from the city have failed. Lee Re: Tree mortality/New rainfall record   Lee E. Frelich   Aug 20, 2007 07:02 PDT  Ernie: We may have set a new daily rainfall record for the state of Minnesota yesterday--17 inches, at a station in southeastern MN.  The state climatologist will investigate and let us know today if its the official record. In southern MN we have completed another drought to flood cycle. The floods are unlikely to persist long enough to kill trees by waterlogging the soils in the steep terrain of southeastern MN, although several thousand trees probably went into rivers in flash floods and landslides. Windstorms last week probably killed less than a million trees. The two big tree mortality factors this year are the drought which persists in northern MN, WI and MI, and which by conservative estimate is likely to kill something on the order of 100 million trees by the time its over, and the Ham Lake Fire last May, which by my estimate killed about 7 million trees in MN, and probably 14 million trees in total including the adjacent portions of Canada that burned. By comparison the big blowdown of 1999 killed about 35 million trees in MN in less than an hour, and several blowdowns in 1995 killed about an equal number. Lee Re: Elm trees survived the storm   Lee Frelich   Sep 01, 2007 06:26 PDT  ENTS: Yesterday I went to MN State Fair, the fair grounds having been hit by the storm three weeks ago that damaged 45 buildings, and was worried that most of my favorite trees would only be represented by stumps. It must have taken every carpenter in town to get all the buildings back in shape by the time the fair opened. You would never know that a derecho had trashed the place three weeks ago. Hundreds of trees were damaged on the fairgrounds, but the storm mostly gave them character by deforming their crowns, taking off branches facing towards the west. The trees on the farigrounds are well on their way towards looking like the little trees in the bonsai exhibit--one of the favorite forms bonsai growers use is the windblown form that trees on the seashore, and trees in the middle of the continent have, with all branches pointing in one direction due to relentless daily winds and occasional hurricane force storms. Most ENTS live in the banana belt between the ocean and continental interior, where tree are actually straight (e.g. the Berkshires, interior NC, PA, etc.), so they aren't used to flagged trees with branches pointing one way. Anyway, only a handful of the large elms went down, and the elm cathedral with its 7 massive elms all 4 feet dbh arching over the street still has six trees, a loss of only one from the storm. The black maple (about 30 inches dbh) was totally intact despite its hilltop position. Its many leaves still hang in a pattern where the lobes on the sides are folded up, making the leaves look like turkey feet. Its amazing how well big vase shaped elms in good health on the fairgrounds survived such high winds, while trees in a nearby Como Park went down by the hundreds. I suspect the reason is lawnmower damage in the park. So many trees there had rot at the base from years of lawnmower and weed eater damage, and the fairgrounds does not have any such damage. It just goes to show that good tree care more than pays for itself. Lee RE: lawn mower damage   Lee E. Frelich   Sep 04, 2007 10:38 PDT  Matthew: Lawn mowers that most home owners use usually only injure the bark of younger threes. However, in parks gigantic tractor lawn mowers are used to mow large areas quickly and they are easily capable of knocking off pieces of bark on large trees. Whether a given tree is injured depends on the microtopography around each tree. Some trees are hit repeatedly and large open wounds persist for decades. Such trees are far more likely to blow down in storms. The University of Minnesota maintains an area free of grass around each tree on campus, so that mower operators are not tempted to mow close to trees, to prevent such injuries. Too bad the city parks are unable to do the same. Lee At 04:25 PM 9/3/2007, you wrote:   Well, I am glad to hear that nearly all the trees survived the nasty weather. It sounds like you'll end up with a field full of large bonsai trees; it must be interesting to watch the old trees develop character provided the weather doesn't get too out of hand. While the Midwest storms can be nasty, at least the folks there appreciate their trees. Here in Maryland, a field of old trees would probably be cut down and replaced with a shopping mall (because the nearest mall is almost 5 miles away... I wish I was kidding!) I am surprised that lawnmower and weedwacker damage can be so severe. I thought that only was a threat to young trees with thin bark... Mathew Hanuum   Home