Studies On Physioecological Traits Of 30 Plant Species In The Subalpine Meadow Of The Qinling Mountains

The Qinling Mountains is one of the hotspots for biodiversity conservation in China, and species in the subalpine environment can be an important indicator of the climate change. To explore the adaptation strategy of meadow species to subalpine environment, 30 species were selected to investigate their gas exchange traits, photosynthetic pathways, content of carbon and nitrogen. The results are following:1. Net photosynthetic rates, transpiration rates, stomatal conductance, water use efficiencies and intercellular carbon dioxide concentration of the 30 selective species were quite different among classes,families and species. The results showed that Ligularia hookeri had the largest net photosynthesis rates (18.75μmol·m^-2·s^-1) ,and Pedicularis verticillata had the lowest photosynthesis rates (0.73μmol·m^-2·s^-1) . Stomatal conductance varied greatly among species and the maximal value was 74.75 times of the minimum one. 86.7% of these species with stomatal conductance ranged from 0.15 to 1.32 mol·m^-2·s^-1, while 70% of these species had water use efficiencies averaged 3.01～5.90μmol·mmol^-1. Pearson correlation analysis indicated that there were significantly positive correlations between net photosynthetic rates, stomatal conductance and transpiration rates(P<0.01). Based on the gas exchange traits, these 30 species were classified into 4 groups by cluster analysis.2. The photosynthetic pathways were identified by using the discriminant analysis model and the anatomy methodology. Of the total 30 species, 7 species in 7 genera and 6 families were C₄ photosynthesis, the rest was C₃ photosynthesis. There was disparity between the two methods, but the results of the anatomy method seems much reasonable. Fragaria orientalis Losinsk. was identified as a C₄ species in this study.3. The order of C and N content in plant tissue were leaves>shoots >root s, and the C/N ratio was shoots > roots > leaves, the One-way ANONA indicated that the distribution of C,N and the C/N ratio in roots, shoots, leaves were significant different (P<0.01) .The distribution of C, N and the C/N ratio in the 30 selective species were species-specific, and the distribution in four groups based on their gas exchange traits were not significant different (P>0.05). The C and N content in soil decreased with soil depth, while the C/N ratio increased with the soil depth.