Chemical parameters of aboveground plant biomass
Plant species differed significantly in all parameters which were measured in aboveground biomass (Table 1). Acantholimon sp. andAndrosace sp. had the lowest N (2.70 ± 0.31% and 1.99 ± 0.30%, respectively) and P (0.09 ± 0.03% and 0.07 ± 0.02%, respectively) content, and the highest N:P ratios (32.46 ± 11.94 and 31.38 ± 6.43, respectively). Erysimum altaicum had the highest content of both N (4.98 ± 0.88%) and P (0.28 ± 0.12%). The high and low cluster varied in several measured parameters, depending on the plant species (Appendix 1). Most notably, Braya pamirica and Oxytropis sp. had higher N and P content in the high cluster than in the low cluster. Most parameters in most species were not significantly correlated with the distance from the burrow entrance (Table 2). We found significant correlations in Erysimum altaicum with total N (rho= -0.64, S = 1872.6, p < 0.05), total P (rho = -0.61, S = 1839.6, p < 0.05) content and N:P ratio (rho = 0.54, S = 521.46, p < 0.05) (Fig. 4).
Faeces from burrows from the high cluster had higher content of N (4.2% ± 0.28) and lower δ15N values (0.07‰ ± 0.42) than faeces from the low cluster (3.03% ± 0.71 and 1.54‰ ± 1.22, respectively). The content of P was similar in both locations (0.7% ± 0.17 and 0.65 ± 0.19 on the high and low cluster, respectively). Out of 20 faeces – plant species pairs, the δ15N values differed in 7. In three cases plants had higher values than faeces and in four cases lower (Fig. 5.)