Cumulative ET for each year of 2003–2010 respectively (panel a); cumulative ET averaged over the observation periods and its standard deviation (black line) and monthly variations in standard deviation (red line and the axis on right) (panel b).

<p>Cumulative ET for each year of 2003–2010 respectively (panel a); cumulative ET averaged over the observation periods and its standard deviation (black line) and monthly variations in standard deviation (red line and the axis on right) (panel b).</p

Cumulative precipitation versus average air temperature of the whole year and the growing season (April–October) during the period 1989–2010.

<p>For the period of 2003–2010, the size of black dot is approximately proportional to the ET amount. The two-digit numbers (YY) denote the years from 2003 to 2010 (20YY). Dotted lines represent the averages over the 20 year period.</p

Coefficient of variation (CV) of ET at flux sites with over 3 years' observations.

<p>Coefficient of variation (CV) of ET at flux sites with over 3 years' observations.</p

Air temperature (T_a °C) and growing season length (GSL, in days T_a≥5°C) during 2003–2010.

<p>Air temperature (T_a °C) and growing season length (GSL, in days T_a≥5°C) during 2003–2010.</p

Yearly values of cumulative ET calculated through different approaches: V_cli-eco (for variable climate and variable ecosystem responses); V_cli (for variable climate); V_eco (for variable ecosystem responses).

<p>The correlation coefficients of the cumulative values calculated with the three approaches are also reported.</p

Annual accumulated ET, R_n, P and annual averaged T_a during 2003–2010.

<p>Annual accumulated ET, R_n, P and annual averaged T_a during 2003–2010.</p

Correlation coefficients between annual ET and climatic drivers (R_n, T_a, P, SW and VPD).

<p>Correlograms were calculated by shifting the climatic driver backward one month at a time. The open signs represent that the coefficients are not significant while the closed signs mean significant (p<0.05).</p

Correlation coefficients (R) between ET and some of the climatic drivers (R_n, T_a and VPD) at monthly and annual scale (p represents the probability-value).

<p>Correlation coefficients (R) between ET and some of the climatic drivers (R_n, T_a and VPD) at monthly and annual scale (p represents the probability-value).</p

The IKONOS image (Nov. 7, 2003) around the QYZ flux tower (red point).

<p>The interval between buffer circles is 200<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0085593#pone.0085593-Zhang1" target="_blank">[43]</a>.</p

Multi-year (2003–2010) environmental conditions accumulated or averaged monthly: (a) net radiation (R_n); (b) precipitation (P); (c) air temperature (T_a); (d) soil water contents (SW) at 5 cm; (e) vapor pressure deficit (VPD) and (f) ET.

<p>The error bars represent the standard deviation.</p