Biomass allocation and prediction in Nitraria nabkhas

Shrub nabkhas (sand dunes) are widely distributed in the arid region of northwest China. Using the common Nitraria shrub nabkha in the arid region as the research object, this study obtained the morphological and biomass data of 45 Nitraria tangutorum and 21 Nitraria sphaerocarpa shrub nabkhas through sample plot collection and literature data collection and established a biomass prediction model for Nitraria shrub nabkhas. It was found that the biomass of the surface, inner, and lower parts of the nabkha and that of the branch and leaf, and root increased by 0.31, 0.57, 0.12, 0.44, and 0.56 kg, respectively, as the total biomass increased by 1 kg. The change in plant height could explain 76%～88% of the total biomass and that of each component of the nabkha. The change in nabkha length could explain 76%～92% variation in the total biomass and that of each component of the nabkha. The combination of plant height and nabkha length could account for 89%～94% of variation in the total biomass and that of each component of the nabkha. With an increase in nabkha height, the proportion of plant biomass above the sand dune decreased and that inside the nabkha increased, however, there was no significant change under the sand dune. In addition, the proportional increase in root biomass was attributed to the increase in roots inside the sand dune. There were significant correlations between each part of the biomass and the total biomass of Nitraria (P < 0.01). This relationship can be used to predict each component using the other, thus achieving a field-tracking monitor.