Warming, nitrogen deposition, and provenance shift above–belowground insect interactions and host compensatory growth

Above–belowground insect herbivore interactions and plant compensatory growth are crucial for reshaping the fitness of invasive plants, and it is likely that climate warming, nitrogen (N) deposition, and plant provenance influence this interaction and growth in a complex way. We performed an experiment with Solidago canadensis from home and introduced ranges, leaf-chewing Spodoptera litura, and root-feeding Protaetia brevitarsis under climate warming and N deposition, and addressed how these abiotic stressors and plant provenance jointly shaped the reciprocal effects between S. litura and P. brevitarsis and the compensatory growth of S. canadensis after herbivory. Under ambient conditions, S. litura and P. brevitarsis inhibited each other on the basis of growth; warming, N addition or warming plus N addition shifted or even reversed this competition depending on provenance. While the survival-based above–belowground interactions differed from growth-based ones, warming or warming plus N addition also shifted or even reversed the neutralism or amensalism detected under ambient conditions depending on provenance. S. canadensis from its home range was more tolerant of herbivory than from its introduced range under ambient conditions; warming, N addition or warming plus N addition decreased the plant compensatory growth of native S. canadensis, but increased that of invasive S. canadensis relative to ambient conditions. These findings suggest that climate warming and N deposition could enhance positive above–belowground insect interactions, increasing insect pressures on S. canadensis, and that plant provenance might be important in mediating climate change effects on insect interactions and host compensatory growth under plant invasions.