Synergistic aboveground-belowground growth of Bidens pilosa L. in heterogeneous karst habitats

Based on simulation of heterogeneous karst habitats, the aboveground and belowground growth relationship of Bidens pilosa L. and biomass distribution patterns under two soil habitats (SW: shallow and wide; DN: deep and narrow) and three water treatments (W100%: control; W50%: water reduction by 50%; W30%: water reduction by 70%) were investigated through a randomized block group experiment. Results showed that: (1) Aboveground growth (plant height, ground diameter, leaf area, leaf biomass) and root growth (root length, root surface area, root volume, root biomass) in both habitats decreased with the decrease in applied water; the leaf area ratio increased with the decrease in applied water; and the root-to-mass ratio increased at first and then decreased in the SW soil habitat, but increased in the DN soil habitat. (2) Aboveground biomass and root biomass, leaf area and root length, and leaf area and root growth in each layer of the two habitats showed significant positive correlations. In SW soil habitats, the aboveground biomass of B. pilosa showed a significant positive correlation with the root biomass in each soil layer, whereas in the DN soil habitat, the aboveground biomass was only significantly positively correlated with the middle and upper soil layer root biomass. Studies have shown that B. pilosa exhibited good synergistic aboveground and belowground growth strategies in different habitats. When enhancing the acquisition of belowground resources, B. pilosa also enhanced the acquisition of aboveground resources. In SW soil habitats, B. pilosa coped with rapid drought and water shortages by coordinating the lateral expansion ability of the root system and growth of plant leaves; in DN soil habitats, plants coordinated the downward expansion ability of the root system and expansion of the leaf area to better utilize deep water resources in the soil.