Abstract: Understanding the distribution pattern and spatial correlation of plant population is important for revealing the relationships between plant population and environmental factors, its own characteristics, and interspecific interaction. In this study, three plots were set up along an elevation gradient (2900, 3500, 3800 m). The population spatial distribution pattern and interspecific correlation of Kobresia humilis and Leontopodium nanum at different elevations were analyzed by Ripley K function. The results showed that: (1) The importance value, coverage and abundance of K.humilis showed an increasing trend, while that of L. nanum decreased with increasing altitude. (2) At different altitudes, K.humilis showed aggregated distribution at all the studied scales, with different degrees of aggregation among altitudes. L. nanum showed aggregated distribution at 2900 m and at the scale of 0-2.8 m, but its aggregation intensity gradually decreased with increasing scale, and finally changed to random distribution at 3500 m. At 3800 m, L. nanum showed an aggregated distribution at the 0-2 m scale and a random distribution at the 2-5 m scale. (3) K.humilis and L. nanum showed a positive correlation each other at the 0-1.1 m scale, but no correlation at larger scales at 2900 m, and a negative correlation at all the studies scales of 3500 m. At 3800 m, there was no correlation between the two species at the scale of 0-1.4 m and a negative correlation at larger scales, with the correlation increased with increasing scale.

Key words: pmoA gene., typical steppe, mowing, CH₄ uptake rate, grazing