Fig 4. Correlations between plant functional groups and micro-topography and climate
Note: A, F, and K represent the biomass, coverage, and importance value of Gramineae, respectively; B, G, and L represent the biomass, coverage, and importance value of Cyperaceae, respectively; C, H, and M represent the biomass, coverage, and importance value of Leguminosae, respectively; D, I, and N represent the biomass, coverage, and importance value of forbs, respectively; E, J, and O represent the biomass, coverage, and importance values of shrubs, respectively; and P, Q, R, S, and T represent the accumulated temperature above 0°C, the accumulation of precipitation, and latitude, longitude, and altitude, respectively.
2.3 Relationships between micro-topographic factors and steady stages
The characteristics of mini-patches investigated in our research show that 11.1% could be classified to Gramineae–K. humilis and Gramineae–K. humilis to K. pygmaeatransitional mini-patches, 16.3% could be classified to healthy and thickening mattic epipedon in K. pygmaea meadow, 36.2% could be classified to cracking mattic epipedon in K. pygmaea meadow, 16.6% could be classified to eroded mattic epipedon in K. pygmaea meadow, and 19.8% could be classified to black-soil beach meadow (Table 2).
Most of the mini-patches were located on sunny or semi-sunny slopes with angles of less than 10° or in valleys between hills. Livestock grazing intensities affected mini-patches differently and the K. pygmaeamini-patches were more degraded if they were located in the middle of slopes than if they were located elsewhere. Herders typically use pastures located lower on slopes or in valleys as reserve forage production areas because their superior climate conditions facilitate the growth of forage for use in cases of natural disasters or other emergencies. Therefore, more than 90 % of the Gramineae and Gramineae–K. humilis mini-patches occurred in such areas (Table 2).
Our findings indicate that as grazing intensity increased, total plant community coverage decreased. In addition, the total plant community coverage in eroded mattic epipedon K. pygmaea meadows and black-soil beach meadows were not significantly different but were lower than that in other types of meadow. In addition, our findings confirm the generally accepted belief that healthy alpine meadows invariably maintain a certain thickness of mattic epipedon (typically 4-5 cm) (Table 2).
Table 2. Micromorphology in alpine meadows under different grazing intensities