The above- and below-ground biomass of alpine meadow on eastern margin of the Tibetan Plateau and their relationships with abiotic and biotic factors

Our knowledge of grassland biomass and its relationships with abiotic and biotic factors on eastern margin of the Tibetan Plateau is extremely limited. Here, we measured above-ground biomass (AGB), below-ground biomass (BGB) and root/shoot ratio (R/S) of alpine meadow, and explored their driving factors, including abiotic factors (altitude and slope properties, and climate) and biotic factors (plant community properties) based on field survey from 53 sites on eastern margin of the Tibetan Plateau. The results showed that the median values of AGB, BGB and R/S of alpine meadow in this region were 284.44 g m- 2, 2232.98 g m- 2 and 7.31, respectively. 85.42% of total biomass allocated to below-ground and 87.13% of BGB distributed in top soil (i.e. 0-20 cm). There was no significant correlation between AGB and BGB. AGB did not change, while BGB and R/S related downward quadratically with increasing altitude; AGB significantly linearly decreased, but BGB and R/S changed upward quadratically along slope gradient. Temperature and precipitation had no effect on AGB but significantly influenced BGB and R/S. AGB was positively linearly correlated with community height and coverage, and BGB was negatively linearly correlated with community height, while R/S was negatively linearly correlated with community height and coverage. There was no relationship between plant biodiversity and grassland biomass. The contribution of biotic factors on grassland biomass was higher than abiotic factors at the present scale. This study highlighted the importance of belowground parts in alpine grasslands, and could provide useful information for understanding the determining factors for grassland biomass in the Tibetan Plateau.