Morphological functional types and photosynthetic pathway types were identified for the forage species from steppe communities in Inner Mongolia, China, using the data of both field survey and published papers. Seven typical steppe communities were selected to investigate the morphological functional type and photosynthetic pathway type compositions and plant functional type (PFT) diversity in steppe communities at regional scale. Morphological functional types, based on plant height and leaf type combined with life span, were optimal for comparing the community differences in the region, while photosynthetic pathway types were fairly coarse for such studies. Of the seven morphological functional types in the steppe communities, perennial forbs (PEF) were the dominant type, and 60 % of species belonged to this type. Each of the high perennial grass (HPG), short perennial grass (SPG), and annual grass (ANG) types represented less than 10 % of the total, even though the grass species were dominant in the seven steppe communities. The differences of PFTs between the steppe communities were remarkable, and the PFT richness and diversity increased from the communities with moist conditions to the ones with dry environments.
Photosynthetic pathway types, based on δ13C measurements, were determined for 125 species in 95 genera and 32 families growing in rangelands from Inner Mongolia. Of the total species, 4 species from 3 genera and 2 families had C4 photosynthesis (2 species in Gramineae and 2 in Chenopodiaceae) and 118 species from 90 genera and 31 families had C3 photosynthesis. The number of C4 species differed significantly among four rangeland sites, 4 species in desert, 3 species in steppe, but no C4 species were identified in meadow and dune. Six species [e.g. Agriophyllum arenarium Bieb., Bassia dasyphylla O. Kuntze, Saussurea japonica (Thunb.) DC.] earlier identified as C4 species using the enzyme ratio method were found as C3 species using the carbon isotope ratios (δ13C). Hence the enzyme ratio method for C3 and C4 identification may not always be reliable. The δ13C values of 3 species of Crassulaceae, which had been considered as CAM species, differed remarkably [-25.79 ‰ for Sedum aizoon L., -24.42 ‰ for Osostachys fimbriatus (Turcz.) Berger, and -16.97 ‰ for O. malacophyllus (Pall.) Fisch], suggesting that the use of δ13C method as a diagnosis for CAM photosynthetic pathway type may not always be reliable and supplementary measurements are needed. and X. Q. Liu, R. Z. Wang, Y. Z. Li.
Photosynthetic pathway Types (C3, C4, and CAM) and life forms of native species from Hulunbeier rangelands, north China were studied. Of the total 258 species, 216 species in 132 genera and 42 families had C3 photosynthetic pathway, including dominant herbs, e.g. Stipa baicalensis Roshev. and Leymus chinensis (Trin.) Tzvel., Filifolium sibiricum Kitam. and Arudinella hirta (Thunb.) Koidz. 38 species in 28 genera and 10 families were found with C4 photosynthesis, and 4 species in 2 genera and 1 family had CAM photosynthetic pathway. The occurrence of C4 species was common in Gramineae and Chenopodiaceae, and the two families were leading ones within C4 plants. More than 52 % of the total 258 species were in H form, 21 % in Th form, 19 % in G form; the other life form Types, e.g. Ch, M, N, and HH, formed less than 3 %. 68 % of C4 species were in Th form and 24 % in H form, indicating that these Types were the dominant life forms for C4 species in the rangeland region. The occurrence of C4 species was closely related with plant habitats, disturbed lands had the highest C4 abundance (55 % of the total C4 species), followed by grasslands and sandy soil, and forests had the lowest C4 abundance (8 %). Hence the occurrence of C4 species could be efficient indicator for rangeland dynamics in Hulunbeier rangelands.