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Earlywood, latewood, and adjusted latewood correlations to precipitation: a test case from the Khangai Mountains, Mongolia




Wolf, J. Marshall, author
Venable, Niah B. H., author
Nutag Action and Research Institute, publisher

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The Khangai Mountains of central Mongolia provide important ecosystem services to the surrounding region as the headwaters for a number of river systems and critical pasture for the animal herds of nomadic pastoralists. The mountains also provide a long-term record of regional moisture variability preserved within the tree-rings of Siberian larch (Larix sibirica) forests. Ring width measurements are commonly used to statistically reconstruct the hydroclimatology of a region based on the correlation of ring widths to precipitation and/or streamflow. Tree cores were collected, cross-dated, and the ring widths were measured from a site near Jargalant bagh in northern Bayankhongor aimag. Seasonal precipitation totals for the period from 1962 to 2012 were compiled from several meteorological stations surrounding the site. These historical precipitation values were compared to indices of total (TW), earlywood (EW), and latewood (LW) ring widths generated from a series of 16 cores. Nearly 70% of the annual precipitation in the Khangai region falls during the summer season (June, July, August), resulting in stronger correlations of ring widths (TW, EW and LW) to the previous year's summer precipitation than to the current year's spring or previous year's fall precipitation. The dependence of LW widths on antecedent EW ring widths masks any correlation to spring and fall precipitation. This dependence was removed using linear regression, resulting in the discovery of a negative relationship between the adjusted latewood (LWa) ring widths and precipitation in both spring of the current year and fall of the previous year. This indicates that LWa captures a different climate signal not detectable when working with the original LW, EW or TW measurements. Correlations of EW with (previous year's) summer precipitation were similar in value to correlations of TW with (previous year's) summer precipitation, suggesting that additional measurements of ring width may not be needed for use in reconstructing long-term summer precipitation variability. However, LWa and the associated measurements required for its calculation may be potentially useful for reconstructing spring and fall precipitation patterns in summer precipitation-dominated hydroclimate systems.


Includes bibliographical references.
Presented at the Building resilience of Mongolian rangelands: a trans-disciplinary research conference held on June 9-10, 2015 in Ulaanbaatar, Mongolia.

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adjusted latewood


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