Abstract:

Net photosynthetic rates (Pn), transpiration rates (E) and water se efficiencies (WUE) of 97 species among different habitats of Hunshandak Sand Area in Inner Mongolia were investigated. The results showed that some species such as Salsola collina, Setaria viridis, Agriophyllum pungens, Artemisia ordosica, Caragana microphylla and some other species which possess the C4 photosynthe

tic pathway or with nitrogen fixation ability had higher net photosynthesis rates > 30 μmol

CO2·m-2·s-1), while most of the species which possess the C3 photosyntheti

c pathway or lacked nitrogen fixation ability had lower photosynthesis rates (1.

29-10 μmol CO2·m-2·s-1). Species with transpiration rates between 2-10 mmol

H2O·CO2·m-2·s-1 comprised 71% of the species studied. The selected species which

have high photosynthetic capability should be preferentially used in rehabilitating

degraded grassland. Of the plants measured, C4 species are mainly distributed on

fixed sand dunes. The differences between C4 and C3 species decreased graduall

y with increasing soil moisture. Of the habitats studied, the values of both Pn

and E of grasses and shrubs were found to be in the order of wetland > lowla

nd > fixed dunes, whereas those of trees were in the order of fixed dune > lowland.

The order of WU was opposite to those of Pn and E. Gas exchange traits

of three growth forms growing in different habitats were widely different.

In fixed dunes, Pn of three growth forms were not greatly different,

while the highest E and WUE were found in grasses and trees, respectively.