Figure.5 Oasis transition network principal components in
different periods
Table 1 showed the results of node ratios, out-degree and in-degree from
the oasis transition network to quantify the conversions among various
oasis types. A ratio less than 1 indicated a transfer-in oasis type in
the sub-period; if the ratio declined during 1990 and 2020, the
transfer-in area of the oasis type accelerated. A ratio greater than 1
showed a transfer-out oasis type; if the ratio grew during 1990 and
2020, the transfer-out area of the oasis type sped up.
Natural oasis and artificial oasis were expressed as transfer-in types
from 1990 to 2020, with ratios of 0.46 and 0.52, respectively.
Throughout the study periods, grassland had the highest out-degree and
in-degree values and the ratios were steadily round 1, implying the most
active land type in the oasis transition network. Shrubland had a low
ratio and increasing tendency in out-degree and in-degree throughout the
study period. The ratio of shrubland dramatically dropped from 1.10 to
0.19 from 2015 to 2020, indicating the shift from transfer-out to
transfer-in. The ratio of forest varied during the study period and it
peaked at 0.23 during 2015 to 2020. Generally, water body was a
transfer-out type, and the ratio fluctuated during 1990 and 2020. The
ratio of cropland was a transfer-in type with the ratio smaller than 1
after 1995. The out-degree and in-degree maintained in a high level and
changed slightly from 1990 to 2020. Built-up had the lowest ratio
(0.00-0.02), suggesting that the area of built-up was fixed, and it was
difficult to be converted into other land types.
Tab.1 Node ratio, out-degree and in-degree in oasis transition
network