Distribution of shrub-herb community biomass and its relationship with soil factors in middle and low mountainous areas of northwest Hebei Province

The distribution of aboveground and belowground biomass (Belowground / Aboveground, BA) is an important parameter associated with shrubby grassland communities. It is of great significance for estimating carbon storage and studying the growth strategy of shrubby grassland communities. The shrubby grassland communities at altitudes of 1 630 – 2 030 m in the middle and low mountainous areas of Northwest Hebei Province were chosen as the research objects. This study compared and analyzed the distribution of shrub-herb community biomass and its response to soil factors through field investigation, sampling and indoor analysis. The results showed the following: 1) the relationship between the aboveground biomass and altitude is a “single peak curve”, reaching a maximum at altitudes of 1 830 – 1 930 m, with an average value of 293.90 g·m^–2, and the relationship between belowground biomass and altitude is defined by a “U-shaped curve”, with a minimum at altitudes of 1 830 – 1 930 m, and an average value of 620.07 g·m^–2; 2) the belowground biomass has an “inverted pyramid” distribution, and the belowground biomass of 0 – 10 cm soil layer is more different (P < 0.1) in the 1 830 – 1 930 m and 1 930 – 2 030 m altitude gradients; 3) the biomass of shrub-herb communities is mainly distributed underground, and the belowground biomass is 6.16 times that of the aboveground biomass, and the aboveground biomass is negatively correlated with the belowground biomass of 0 – 20 and 0 – 40 cm at 0.05 level; 4) the belowground biomass is negatively correlated with soil pH and bulk density at 0.05 level, and positively correlated with available phosphorus at 0.01 level, and the aboveground biomass is negatively correlated with the pH value at 0.05 level, while the ratio of belowground biomass to aboveground biomass is positively correlated with soil organic matter at 0.01 level. Overall, there was a negative correlation between the aboveground and belowground biomass of shrub-herb communities in the study area (P < 0.05), and the belowground biomass was greater than the aboveground biomass. The results of this study provide a scientific basis for improving the ecological services and ecological restoration of shrub-herb communities in the middle and low mountainous areas of the northwest Hebei Province.