3.1 EP development mode
The histograms of the statistically significant short-term LEP, AEP, and HEP trends (1999–2013) over the NH (Supplementary Fig. 1) were derived (Fig. 2A–C, respectively). In the study period, for the whole NH the EP of the three kinds of ecosystems all were increasing, wherein the LEP and HEP ecosystems both showed weaker tendencies than the whole ecosystems (the average LEP trend = 0.28 year-1, the average AEP trend = 0.31 year-1, and the average HEP trend = 0.29 year-1). Then, the histograms of the statistically significant LEP, AEP, and HEP trends across the NA (Supplementary Fig. 2) and NE (Supplementary Fig. 3) were also generated. The EP strengthening tendencies over the NE were quite approximate to those of the NH, merely being a little stronger for all the three kinds of ecosystems (the average LEP trend = 0.32 year-1, the average AEP trend = 0.35 year-1, and the average HEP trend = 0.32 year-1); but for the NA, the EP strengthening tendencies were much slighter and of a little difference in their relative relation, i.e., the HEP ecosystems showed stronger tendencies than the whole ecosystems (the average LEP trend = 0.13 year-1, the average AEP trend = 0.15 year-1, and the average HEP trend = 0.16 year-1). The results suggested that in the last decade the terrestrial ecosystems over the NE were more prosperous than those over the NA, in terms of productivity capacity increasing, and this inference was briefly consistent with the findings in the earlier studies (Piao et al., 2007; Kim et al., 2012). In addition, the statistically significant snow-onset and -end SP trends (2001–2014) over the NH were also derived (Supplementary Fig. 4), with their characteristics quantitatively characterized.
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