Effect of the shrub Dasiphora fruticosa on regeneration of Picea crassifolia from seeds in the Qilian Mountains of China

As the constructive species of subalpine forest ecosystems in the Qilian Mountains of northwest China, regeneration of Picea crassifolia (Pinaceae) from seeds plays a crucial role in maintaining forest functionality. We investigated the function of Dasiphora fruticosa (Rosaceae), a dominant shrub species in the Qilian Mountains, as a nurse plant for establishment and growth of P. crassifolia saplings. A comprehensive monitoring program was conducted to assess the effect of D. fruticosa on the establishment and growth of P. crassifolia saplings. Our results indicate that D. fruticosa shrubs positively facilitate the occurrence of P. crassifolia saplings. The linear mixed-effects model showed that P. crassifolia saplings had a significantly higher growth rate inside the D. fruticosa shrub canopy than outside, and D. fruticosa shrubs did not significantly affect the mortality percentage of P. crassifolia saplings. The height of dead P. crassifolia saplings was significantly lower than that of the surrounding D. fruticosa shrubs, indicating that these saplings died before growing above the shrub canopy. Soil moisture content under D. fruticosa shrubs was significantly higher than that outside the shrubs. In conclusion, D. fruticosa shrubs facilitate seed germination and sapling establishment of P. crassifolia and promote sapling growth, although their shading effect suggests potential competitive pressure on sapling survival as they develop.