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compaction, and soil chemical changes. <br /> 1. Positive grade changes from fill and sedimentation <br /> causes a decrease in soil oxygen levels. An increase in soil <br /> carbon dioxide and other toxic gases can also occur, leading <br /> to large areas of anaerobic conditions. Anaerobic soil <br /> conditions cause a decrease in the root respiration process <br /> which is essential for the uptake and transport of minerals <br /> and nutrients. <br /> 2. Anaerobic soil conditions are also produced by soil <br /> compaction, the increase in soil bulk density with a decrease <br /> in soil pore space. Compacted soil is also impervious to <br /> root penetration, and thus inhibits root development. Soil <br /> compaction is generally caused by the weight and vibrations <br /> of heavy machinery, vehicle parking, and the storage of fill <br /> and/or construction materials within the critical root zones <br /> of trees. <br /> 3. Changes in soil chemistry will adversely affect tree <br /> survival. The most frequent occurrence is the change <br /> (decrease) in soil acidity by concrete washout. Most trees <br /> native to the Anoka County are prefer slightly acid soils; <br /> concrete residues are highly basic. The leakage or spillage <br /> of toxic materials such as fuels or paints can be fatal for <br /> trees. <br /> D. Trunk and crown disturbances are generally mechanical in <br /> nature and are either caused directly by clearing and grading <br /> �. machinery, or indirectly by debris being cleared and falling <br /> into trees marked for protection. <br /> 1. Common forms of damages include stripped bark and <br /> cambium, split trunks, and broken limbs. <br /> 2 . Damage also occurs from the posting of signs such as <br /> building permits, or survey markers on trees. <br /> 3 . Indirect damage can be caused by the placement of <br /> burn holes or debris fires too close to trees. The possible <br /> range of damages include scorched trunks with some cambial <br /> dieback, the loss of foliage due to evaporative heat stress <br /> (leaf desiccation) , and completely burned trunks and crowns. <br /> SECTION VI METHODS OF TREE PROTECTION <br /> A. Planning and considerations. Tree space is the most <br /> critical factor in tree protection throughout the development <br /> process. The root system of trees can easily extend beyond <br /> the dripline of the tree canopy (Figure 3) . The root system <br /> within the dripline region is generally considered to be the <br /> critical root zone. Disturbance within this zone can <br /> directly affect a tree's chances root zones the following <br /> standards shall apply: <br /> 1. The use of tree save islands and stands is <br /> encouraged rather than the protection of individual (non- <br /> specimen) trees scattered throughout a site. This will <br /> facilitate ease in overall site organization as related to <br /> tree protection. <br /> 2 . The protective zone of specimen trees or stands of <br /> trees or otherwise designated tree save areas shall include <br />