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).