Figure.6 Transition of different oasis types in Tuha Basin
during 1990 and 2020 (a), and area of oasis transition statistic (b)
4.3 Identification of key land
type
Betweenness centrality was calculated for all nodes in the oasis
transition network (Figure 7) to reveal the importance of nodes and
identify the key land types in the oasis transition network. During the
six sub-periods, grassland had the highest betweenness centrality with
value 17.67, 11.33, 10.67, 12.17, 7.33, and 3.18, respectively, proving
the most important type in the oasis transition process. Grassland was
transferred in mostly from cropland and bare land, and transferred out
to shrubland. However, the betweenness centrality showed descend
tendency as the oasis expansion and more complicated topological
relationship among the land types. The second highest betweenness
centrality was cropland, with the values of 2.67, 3.83, 4.67, 3.33, 4.83
and 2.78, respectively during the six sub-periods. Betweenness
centrality of cropland was close to grassland in 2015-2020, becoming the
key land types in oasis transition network. Furthermore, the betweenness
centrality of bare land was 5.50 in 2015-2020, revealing that it was
also a key land type.