3.2 Neighborhood eco-effect
We derived the spatial distributions of both the largest correlation
coefficients for quantitatively characterizing the optimal EP responses
of the LEP, AEP, and HEP ecosystems to the snow-onset SP (Supplementary
Fig. 4A, in the form of trends) over the NH (Fig. 3) and their related
response directions (Fig. 4). For the case of snow-end SP, the spatial
maps of both the largest correlation coefficients (Fig. 5) and the
related response directions (Fig. 6) were also derived. In both of these
two scenarios, the 0.5°×0.5° geo-grids performing with statistically
significant EP-SP correlations, somehow, were locally clustered but
globally scattered across the continents.
-Insert Fig. 3 here-
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-Insert Fig. 5 here-
-Insert Fig. 6 here-
The statistics of area ratios for the geo-grids, which performed with
the statistically strongest EP responses of the LEP, AEP, and HEP
ecosystems to the snow-onset and -end SP of both the same geo-grid and
all of the surrounding geo-grids, compared to the whole NH were obtained
(Fig. 2d–f, respectively). For the EP of any kind of the ecosystems,
the ratio of their responses to the SP of the same geo-grids could not
compare with the ratio sum for the geo-grids around, even could not
compete with that for any of the geo-grids around. The same inference
was available for the NA (Supplementary Fig. 5) and NE (Supplementary
Fig. 6) as well. This eco-effect suggested that the productivity of the
Arctic circumpolar ecosystems was more sensitive to the SP anomalies of
their neighboring sites. As regards to the ratios of the EP responses to
the snow-onset and -end SP, the statistics (Supplementary Fig. 7) showed
that for the three kinds of ecosystems, snow-onset rather than -end SP
decided their productivity for all of the NH, NA, and NE study areas.
This inference is consistent with the previous finding (Vaganov et
al., 1999), albeit the NA area showed a minor difference.