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Objective This study investigates the effects of drought stress on soil reinforcement performance of root systems in the water-level fluctuation zone of the Three Gorges Reservoir area， providing a theoretical basis for vegetation restoration， soil and water conservation， and ecological protection in this area. Methods Taking the root-soil composite of Cynodon dactylon as the research object， samples were collected from the field and subjected to adaptive maintenance. Drought conditions were simulated through controlled water supply in pot experiments. The experiment established treatments of different drought intensities （CK for control， moderate drought MD， and severe drought SD）， drought durations （0， 5， 10， 15， 30， and 60 days）， and root contents （0% for bare soil， 0.1%， 0.2%， and 0.3%）. Direct shear tests were conducted on the remolded samples to analyze the effects of drought intensity and drought duration on the shear resistance of the Cynodon dactylon root-soil composite. In addition， the microscopic mechanisms of the effects of drought stress on the soil reinforcement performance were revealed through microscopic tests of roots. Results 1） Samples under all conditions exhibited distinct strain-hardening failure characteristics， and drought stress and root incorporation had little effect on the variation patterns of stress-strain curves. 2） Short-term moderate drought improved the shear strength of the Cynodon dactylon root-soil composite， while long-term severe drought significantly reduced the shear strength （p<0.05）. Root incorporation significantly increased the soil shear strength， and the enhancement performance increased with the increase of root content. Compared with the bare soil treatment， the shear strength of the root-soil composite in CK， MD， and SD groups increased by 8.70%-51.52%， 4.35%-63.64%， and -13.04%-39.39%， respectively. 3） The response patterns of cohesion to drought stress and root incorporation were consistent with those of shear strength， while the internal friction angle remained relatively stable with slight fluctuations. Compared to bare soil treatments， the cohesion of the root-soil composite for CK， MD， and SD groups increased by 42.46%-63.99%， 15.08%-67.50%， and 15.08%-48.49%， respectively， while the internal friction angle increased by 1.55%-1.83%， -1.61%-1.68%， and -1.16%-1.43%， respectively. Conclusion Short-term moderate drought stress can improve the shear resistance of the Cynodon dactylon root-soil compositeto a certain extent， but excessive stress severely damages the root structure and reduces the shear strength of the root-soil composite.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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