Net photosynthetic rate (PN), transpiration rate (E), and stomatal conductance (gs) declined from upper leaves to the lower ones during dry and rainy seasons, indicating that long-term carbon budget should take into account PN variations for different leaf types. Relatively greater PN in the dry season suggested that this species is more able to maintain higher PN under drought, but the relatively higher E in the dry season might reduce water use efficiency (PN/E) for the species. Significant correlations between PN and gs indicated that gs may be the critical factor for PN variability in the desert region. and R. Z. Wang ... [et al.].
Photosynthetic pathways (e.g. C3, C4) and morphological functional types (e.g. trees, shrubs, high perennial grasses, perennial forbs) were identified for the native species from the Saskatchewan mixed prairie, using the data from references published between 1950 and 2003. Of the total 219 identified species in 145 genera and 45 families, 208 species in 137 genera and 44 families were found with C3 photosynthesis, and most of these species are dominants (e.g. Agropyron dasystachyum Hook. and Stipa spartea var. curtiseta Hitchc.). 11 species in 10 genera and 3 families were identified with C4 photosynthesis (e.g. Atriplex argentea Nutt., Andropogon scoparius Michx., Boutelou gracilis Lag., Calamovilfa longifolia Hook.). The amount of total identified C4 species in the region is much less than that from the South Dakota mixed prairie (27 species). Gramineae is the leading family with C4 photosynthesis (8 species), Chenopodiaceae ranks the second (2 species). Relatively less forb types [50 % perennial forbs (PEF) and 12 % annual forbs (ANF)] and more graminoid types (25 %) composition suggested that the rangelands in the region are relatively stable. Lacking of the knowledge on the optimal traits for PFTs classification in the region, further studies (e.g. C3 and C4 plant identification and optimal trait selection) are needed to explore the relationships between PFTs and vegetation variations, as well as land-use and climate changes. and R. Z. Wang, X. Q. Liu, Y. Bai.
Photosynthetic pathways (C3, C4, and CAM) and morphological functional types were identified for the species from vegetation in agro-pastoral ecotone, North Beijing. 792 vascular plant species (nearly half of the total species in the ecotone), in 66 families and 317 genera, were identified with C3, C4, and CAM photosynthesis (Table 1). 710 species (90 % of the identified species in Table 1) in 268 genera and 64 families were found with C3 photosynthesis, 68 species (9 % of the total identified species) in 40 genera and 7 families with C4 photosynthesis, and 14 species in 4 genera and 1 family with CAM photosynthesis. Gramineae is the leading family with C4 photosynthesis (43 species), Cyperaceae ranks the second (16 species) followed by Chenopodiaceae (5 species). The significant increase of C4 proportion (C4/total species) with land deterioration suggested the plants of this type are remarkably responsive to land use in the ecotone. 792 species were classified into nine morphological functional types and the changes of most of these types (e.g. perennial forbs (PEF), annual grasses (ANG), and annual forbs (ANF)) were consistent with habitats and vegetation dynamics in the agro-pastoral ecotone. Hence the photosynthetic pathways, combined with the morphological functional types, are efficient indications for studying the linkage between species and ecosystems in the ecotone. and X. Q. Liu, R. Z. Wang.
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.