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So SHERBURNE COUNTY TREE BOARD • d 26401 180th St. Big Lake, MN 55309 (612) 263-8522 BOPsO TO: Steve Ach, Elk River City Planner FROM: Tim Edgeton, County Forest Resource Specialist DATE: January 22, 1996 RE: Forest Health Assessment for Oak Creek Estates - Preliminary Plat On January 16, i st3 I mel on-site with Steve Johnston, Engineer tor !-andtorrn Engineering Company to review the Oak Creek Estates development. In making the assessment, I used data from the field inspection, from aerial photographs, from our oak wilt inventory maps (produced by the DNR), and from the survey maps supplied by Landform Engineering showing topography and proposed grading plans. Below is a summary of that inspection. Attached is a map outlining the approximate location of dead areas and the oak wilt sites (according to inventory). The land is heavily forested with a few small clearings. The primary forest cover type • consists of northern pin oak arid bur oak. Other species present include elm, cherry, birch, aspen, and boxelder. Understory vegetation consists mostly of hazel and prickly ash. The health and condition of trees varies with species and location. The higher elevation areas are comprised mostly of bur oak. These trees appear to be in good condition. Both mature and younger age classes are present. The lower elevation areas seem to have much more mortality. Roth pin oak and bur oak are found in the lower areas, but much of the pin oak is dead and either still standing or already on the ground. Of the 2 or 3 large dead forest areas in the development, they all seem to be in low elevations. Because of this, there is a good indication, that the dieback was due in part to droughth. Although the oak wilt inventory maps show 2 distinct oak wilt infection centers present, I could not confirm any oak wilt during the inspE chat i. i vitouiit strongly recommend ttov4e er, tn«i it be checked again for oak wilt sometime this spring or early summer. There is no charge for this and if oak wilt is diagnosed, the County Cost-Share Program is still available. Overall, the south 1/2 of the development is where much of the standing dead trees are found. The far east 1/3 of the development seems to be in excellent condition and the north 1/2 is in good condition. Again, the dead areas seem to be found in the low elevations. The terrain is quite rolling with hills located throughout development. The rolling topography will definitely make grade changes near trees more likely than a flat area would. Generally, the more grade changes that occur near trees, the more mortality will occur. Unfortunately, the dieback usually doesn't show up until 2 to 4 years later, so there is no easy or immediate way to tell if damage; was done. 'I herefore, in areas where trees wish to be saved or preserved, minimizing the grade changes near them will be very important. Because pin oak are especially intolerant to grade change, be aware of their locations. For assistance with tree preservation techniques, please foci free to contact me. If you have any further questions, call me at 263.8522.. Thank you.