Shrub is an important vegetation type for maintaining ecosystem stability in arid and semiarid zones. We investigated typical shrub species in grassland of northern Xinjiang, and analyzed their carbon (C) and nitrogen (N) contents in leaves, branches and stems, in order to accurately estimate the C and N pools in shrubland, and to obtain basic data for C and N cycling study.
Methods Leaf, branch and stem samples of 13 shrub species were collected in northern Xinjiang, and determined for C and N contents.
Important findings In northern Xinjiang, the typical shrub species include Nitraria spp., Convolvulus tragacanthoides, Reaumuria songarica, Anabasis spp., Caragana spp., Ephedra spp., Calligonum mongolicum, Haloxylon spp., Spiraea hypericifolia, Krascheninnikovia spp., Nanophyton erinaceum, Kalidium spp., and Salsola spp. These shrubs belong to the families of Rosaceae, Leguminosae, Ephedraceae, Tamaricaceae, Zygophyllaceae, Polygonaceae, Convolvulaceae, and Chenopodiaceae, respectively. The C contents in different organs ranked in the order of stems (45.76 ± 3.43)% > branches (44.27 ± 4.51)% > leaves (39.15 ± 5.91)%, and the N contents ranked in the order of leaves (2.21 ± 0.59)% > branches (1.55 ± 0.44)% > stems (1.34 ± 0.35)%; the C:N followed the order of stems (36.74 ± 10.80) > branches (31.07 ± 10.43) > leaves (18.94 ± 5.82). The contents of C and N as well as C:N within organs were significantly different among shrub species of different families (p < 0.05); the C contents in different organs in the species of Rosaceae were significantly greater (p < 0.05); the N contents in leaves and stems in the species of Leguminosae were significantly greater (p < 0.05); the N content in branches in the species of Ephedraceae was significantly greater (p < 0.05); the values of C:N in leaves and branches in Convolvulus tragacanthoides were significantly greater (p < 0.05); the value of C:N in stems in the species of Rosaceae was significantly greater (p < 0.05), those in those of other families. The average values in the aboveground tissues across the shrub species studied was (43.77 ± 4.43)% for the C content, (1.56 ± 0.45)% for the N content, and 31.78 ± 10.12 for C:N. The degree of variation was low for the C content, with average coefficient of variation of only 10%, in contrast to the average coefficient of variation of 27% for the N content and 32% for C:N.