Aridity and soil properties drive the shrub-herb interactions along drought gradient in desert grassland in Inner Mongolia

Abstract

Purpose Environmental conditions can control the structure and composition of plant communities by changing the direction and intensity of plant-plant interactions. However, how drought and soil properties drive the change of shrub-herb interaction in the shrub-encroachment desert steppe in Inner Mongolia remains unclear. Methods We explored the changes of shrub-herb interaction along the aridity gradient, and analyzed how the aridity index and soil properties affect the shrub-herb interaction. Field collection of plant samples and soils from northeast to southwest desert steppe in Inner Mongolia was undertaken and the samples were analyzed for biomass, diversity, soil PH, soil organic matter and other elements. Results The results show that the positive shrub-herb interaction (RII > 0) increased at first and then decreased in the range of aridity index 0.54 to 1.85 (drought degree decreased gradually). Aridity index (AI), soil organic matter (SOM) and soil total phosphorus (TP) were the main factors driving shrub-herb interaction. AI indirectly affected shrub-herb interaction through TP, and the facilitation of shrubs on herbs coverage and biomass increased with the increase of TP. The SOM can directly affect the shrub-herbs interaction, and the facilitation of shrubs on herb diversity decreases with the increase of SOM. Conclusion Overall, although shrub-herb interactions respond differently to environmental factors. This study underscores the positive effects of shrubs on vegetation restoration in desert steppe, and changing environmental conditions by increasing precipitation, increasing TP content, and reducing SOM content can enhance facilitation of shrub on herbs to accelerate the ecological restoration of degraded desert steppe.