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The extent of canopy openness for each sampling point, defined as the per cent of the upper hemisphere compared of open sky, was quantified using hemispherical photography. For this purpose, we used a 7-mm Nikon f 7.4 fisheye lens (the lens has an orthographic projection of 180�� angle of view), mounted on a Nikon Coolpix 5000 digital camera (Nikon Corporation, Tokyo, Japan) and Gap Light Analyzer (gla ver. 2) software (Frazer, Canham & Lertzman 2000). For each site, cores were prepared following the standard dendrochronological techniques (Stokes & Smiley 1996): cores were dried, mounted and glued firmly in grooved wooden sticks and sanded with successively finer grades of sandpaper until optimal surface resolution http://www.selleck.cn/products/PD-98059.html allowed annual rings to be distinguished under magnification. All samples were dated and visually cross-dated to detect the presence of either false or incomplete rings using marker rings. Following visual cross-dating, tree rings�� width was measured to the nearest 0.001?cm and assigned to calendar years using a microscope mounted on a dendrochronometer with a Velmex sliding stage and Accurite http://www.selleckchem.com/products/Rapamycin.html measuring system. For Patagonian sites, calendar dates were assigned to rings according to the southern hemisphere tree-ring dating convention that assigns an annual ring to the calendar year in which the annual ring formation begins (Schulman 1956). Only cores that either passed through the stem pith or close by (arc of innermost rings was visible) were retained. Among these, we used procedures described by Duncan (1989) to estimate the number of missing rings in cores that missed the pith of the tree. No correction was applied for time required to grow to coring height. Cross-dating was further validated using the program cofecha, which calculates cross-correlations between individual series and a reference chronology (Grissino-Mayer, Holmes & Fritts 1996). We elaborated a master series at each of four altitudes per site. Series showing portions of abnormal growth or low correlation with the reference chronology (i.e. r2? http://www.selleckchem.com/products/Everolimus(RAD001).html there is a geometry effect due to the difference between linear growth (ring widths) and two-dimensional (basal area) or three-dimensional growth, which are better indicators of tree growth, and second, tree vigour shows an ontogenetic increase�Cstabilize�Cdecline growth trend with tree age. To minimize the geometry problem, we converted one-dimensional ring width increment to two-dimensional basal area increment (BAI), assuming perfect concentric circles: where R is the radius of the tree and n is the year of the tree-ring formation.