Root architecture characteristics of four dominant annual herbs in Tengger Desert, China

To investigate the adaptability of annual herbaceous species in deserts, we collected root samples of four common annual herbaceous plants in the sand-fixing vegetation area on the southeastern edge of the Tengger Desert, namely Agriophyllum squarrosum, Stilpnolepis centiflora, Corispermum hyssopifolium, and Grubovia dasyphylla, through the traditional excavation approach. Based on the quantification of root morphology indicators, we analyzed root characteristics using geometric topology and fractal theory, and compared the diversity of root characteristics and the differences in adaptation mechanisms among the four species. The results showed that root-shoot ratio and root depth-width ratio of the four species followed an order of A. squarrosum > S. centiflora > C. hyssopifolium > G. dasyphylla. The specific root length and specific surface area followed an order of A. squarrosum < S. centiflora < C. hyssopifolium < G. dasyphylla. The root topology index TI and the modified topology indices q_a and q_b exhibited the same trend, with an order of A. squarrosum > S. centiflora > C. hyssopifolium > G. dasyphylla. The root fractal dimensions of A. squarrosum, S. centiflora, C. hyssopifolium, and G. dasyphylla were 1.215, 1.278, 1.387 and 1.631, and the root fractal abundances were 3.528, 3.248, 2.479 and 2.451, respectively. A. squarrosum and S. centiflora adopted a high growth resource strategy, featuring simple root structure, tending towards the fish-tail-shaped branching structure, and possessing strong abilities of vertical resource acquisition and spatial expansion, while C. hyssopifolium and G. dasyphylla adopted a high-quality resource strategy, having more complex root structure, with forked branching and higher resource utilization efficiency.