FIGURE 1. Distribution patterns of individual cushions (left; in
five replicate 20 × 20 m plot in each community, shown in separate
columns) and age/size structure of populations of the A.
polytrichoides cushion plant (right; individuals are presented in
different size categories of diameter in centimeter) in the four
communities with increasing elevation (in other words, along with
different community successional stages possibly driven by climate
warming) in Pujin pasture. Communities are presented along with
increasing elevation as PJ1 (4384 m; ‘climax community’), PJ2 (4505 m;
‘balance community’), PJ3 (4727 m; ‘primary community’) and PJ4 (4920 m;
‘initial community’). Orange, blue and white squares represent living
individual cushions, dead cushion traces, and cushion-free areas,
respectively. The darkness of the orange and blue colors is positively
related to the size of the cushion patches/individuals and cushion
traces, respectively.
Generally, colder populations are dominated by young and juvenile
individuals (diameter < 25 cm), while warmer populations are
dominated by adult (diameter 25 - 45 cm) and old individuals (diameter
> 45 cm) (Figure 1A-D; Figure S2). Population density
varied among study sites (DF = 7, F = 33.39, P< 0.001), and increases with elevation hence with decreasing
temperature in Pujin pasture; but the recorded densities of CM
populations did not differ (Figure 2A).
Population productivity varied among study sites (DF = 7,F = 17.76, P < 0.001), and was highest for
populations in Pujin pasture (Figure 2B). In Pujin pasture, the warmest
population (PJ1) had significantly higher productivity than the other
three colder populations, which did not significantly differ in this
respect (Figure 2B). No significant differences in productivity between
CM and PY populations was detected either, but the YL population had
extremely low population productivity compared with all other
populations (Figure 2B).