Effects of slope aspect on growth and photosynthetic characteristics of three cultivated grass species in the Three-River-Source Region

The slope aspect is a main terrain factor and affects plant growth and photosynthetic characteristics. We studied the effect of different slope aspects on the growth characteristics and photosynthesis of Poa pratensis ‘Qinghai’, Elymus nutans, and Deschampsia cespitosa in the degraded grassland of “Black Soil Mountain”. By monitoring and analyzing the two characteristics of all three plants on each slope, suitable habitats were screened out, providing a scientific basis for vegetation restoration of Black Soil Mountain in the Three-River-Source region. The results showed that 1) The growth characteristics of D. cespitosa (plant height, leaf length, stem diameter, leaf area, and aboveground biomass) in shady slopes were significantly higher than those on sunny slopes (P < 0.05), and the specific leaf area and underground biomass in E. nutans on sunny slopes were significantly higher than those on the shady slope (P < 0.05). No significant differences were found between the slopes for any of the growth indices of P. pratensis ‘Qinghai’ (P > 0.05). 2) Transpiration rate (T_r) and stomatal conductance (G_s) of P. pratensis ‘Qinghai’ on the sunny slopes was significantly higher than those on the shady slopes (P < 0.05), and the intercellular CO₂ concentration (C_i) of E. nutans was significantly higher on the shady slopes than on the sunny slopes (P < 0.05). The C_i and G_s of D. cespitosa on sunny slopes were significantly higher than those on shady slopes (P < 0.05). D. cespitosa was suitable for growth on shady slopes, whereas sunny slopes promoted photosynthesis in P. pratensis ‘Qinghai’ and E. nutans.