Patterns of Hydroclimatic Variability in Proxy: Tree-Rings from the Khangai Mountains of Mongolia

Abstract:

The sparse water resources of semi-arid regions such as Mongolia are important for sustaining traditional livelihoods and supporting modern development. Nomadic pastoralists of the Khangai Mountain region rely on surface water supplies for their livestock. Increasing agricultural and industrial development, particularly mining, will place strain on already limited water resources. The large amounts of spatial and temporal hydroclimatic variability inherent to this region can be assessed through dendrohydrology, or the application of tree-ring research to study long-term past hydrologic phenomena. The Larix sibirica, and Pinus sibirica trees of the region provide records of the persistence of moisture limitation over the last several hundred years. We analyze a network of ten tree-ring sites, two of which are newly developed and examine correlations of ring width to monthly and seasonal streamflow in four river basins across the region to inform the selection of tree-ring predictor sites for use in streamflow reconstruction. Precipitation correlations were also assessed using data from the Global Precipitation Climatology Centre as previous research suggests gridded precipitation data correlates as strongly with the selected tree-ring sites as station-based data, yet have no missing data. The streamflow data had fewer missing values than station-based precipitation data, but were also not complete. Missing monthly mean flow values from five gages were filled using Predictive Mean Matching methods. Moderate (r=0.35-0.54) to strong (r=0.55-0.74) significant positive correlations were found for previous year’s (PY) and current year’s (CY) summer precipitation, mainly in June, July, and August. More strong and moderate correlations were observed with streamflow in PY and CY summer months than with precipitation; some spring months were also well correlated. Northern river gages correlated with more tree ring sites and had overall higher correlation values than southern sites. The most southerly streamflow sites however, were not significantly correlated to tree-ring widths in CY June or July. The results suggest distinct spatial patterns of proxy relations to hydroclimate in each basin necessitating careful selection of tree-ring predictors for modeling past moisture conditions.