Abstract: Studies of the spatial distribution of plant populations are an important means to reveal the alteration of plant population, community, and ecosystem with environmental changes. In this study, we investigated the spatial pattern of two dominant species Ligularia virgaurea and Potentilla fragarioides in alpine meadow of Gannan under different groundwater depths of 0.1, 0.5 and 1.0 m, using Ripley K function. The results showed that: (1) with increasing groundwater depth, the contents of soil water and soil nutrients (SOC, STN, STP) decreased gradually; the individual abundance, plant height, biomass and coverage of L. virgaureapopulation decreased first and then increased, while these parameters of P. fragarioides population showed gradual decrease patterns. (2) When the groundwater depth was 0.1 m, the whole L. virgaurea population showed an aggregation distribution, while the P. fragarioides population showed a random distribution. When the groundwater depth was 0.5 m, L. virgaureapopulation showed an aggregation distribution at a large scale. With increasing scale, the aggregation degree gradually reduced, and finally reached a random distribution. At the scale of 0-2.9 m, the population of P. fragarioides showed an aggregation distribution, while at the scale of 2.9-3.6 m and 3.6-5 m, it showed a random distribution and an uniform distribution, respectively. When the groundwater depth was 1.0 m, L. virgaurea population showed an aggregation distribution and a random distribution in the range of 0-2.3 m and 2.3-5 m, respectively. P. fragarioides population showed an aggregation distribution in the range of 0-4.4 m, and tended to be a random distribution in the range of 4.4-5 m. (3) When the groundwater depth was 0.1 m, the two populations were negatively correlated at the whole scale. When the groundwater depth was 0.5 m, the two populations were uncorrelated. When the groundwater depth was 1.0 m, the two populations were positively correlated at small scale, and gradually became uncorrelated with increasing scale.

Key words: alpine meadow, groundwater depth, Ligularia virgaurea, Potentilla fragarioides, spatial distribution pattern.