• Journal of Korean Society of Forest Science
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• v.84 no.2
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• pp.198-206
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• 1995

The objective of this study was to determine the rate of nitrogen mineralization at clearcut and uncut in oak(Quercus rubra L.) and pine(Pinus resinosa Ait.) stands. The study sites were located in northern Lower Michigan, U.S.A. Nitrogen mineralization rates in the top 15cm of mineral soil were examined during the 1991 and 1992 growing seasons(May-October) using an in situ buried tag technique. diet nitrogen mineralization in oak stands over the course of both growing seasons was 67kg/ha in the clearcut and 30kg/ha in the uncut stands. In contrast, net nitrogen mineralization in pine stands was 27kg/ha and 13kg/ha for the same treatments. Total net nitrogen mineralization rates were always higher in oak stands than in pine stands. Extractable $NO_3^-$ before and after one month soil incubation in both oak and pine stands was generally not detectable in the uncut stands, but in the pine clearcut treatment(nitrification over the course of both growing seasons : 3.3kg/ha). The results indicated that : 1) substantial increases in the amount of available soil nitrogen occurred following clearcuts in both stands : and 2) the loin rates of nitrification may be an important mechanism for retention of nitrogen in both oak and pine stands.

• International Journal of Oral Biology
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• v.36 no.2
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• pp.65-70
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• 2011

Recently, mini-implant is popular in the orthodontic treatment due to its simplicity and convenient surgical procedure. The objective of this study is to provide the anatomical guideline for mini-implant placement by analysing the cortical bone thickness in Korean. Hemi-sections of sixteen maxillae and twenty-two mandibles with normal teeth were used. Interdental areas between the 1st premolar and the 2nd premolar (Group 1), the 2nd premolar and the 1st molar (Gruop 2), and the 1st molar and the 2nd molar (Group 3) were sectioned and then scanned. After setting the axis of teeth, the cortical bone thickness was measured at the distance of 2 mm, 4mm, 6 mm, and 8 mm from alveolar crest. The mean thickness of cortical bone in the maxilla according to distance from alveolar crest was $1.30\;{\pm}\;0.63\; mm$ (2 mm), $1.49\;{\pm}\;0.62\; mm$ (4mm), $1.72\;{\pm}\;0.64\; mm$ (6mm), and $1.90\;{\pm}\;0.90\; mm$ (8 mm) at the buccal side and $1.33\;{\pm}\;0.47 \;mm$, $1.31\;{\pm}\;0.45\; mm$, $1.37\;{\pm}\;0.55\; mm$, and $1.39\;{\pm}\;0.58 \;mm$ at the palatal side. In the mandible, that was $3.14\;{\pm}\;1.71 \;mm$, $4.31\;{\pm}\;2.22 \;mm$, $4.23\;{\pm}\;1.94 \;mm$, and $4.30\;{\pm}\;1.57\; mm$ at the buccal side and $1.98\;{\pm}\;0.88 \;mm$, $2.79\;{\pm}\;1.01\; mm$, $3.35\;{\pm}\;1.27$ mm, and $3.93\;{\pm}\;1.38\; mm$ at the lingual side. The buccal cortical bone thickness in the maxilla was decreased from Group 1 to Group 3, while the thickness of palatal side was no change. In the mandible, it did not show a tendency at the buccal side and it was decreased from Group 1 to Group 3 without significant difference at the lingual side. Therefore, the buccal side of the Group 1 and Group 2 in both the maxilla and mandible seems to be the most appropriate site for a mini-implant placement with taking the stability and retention.