There is growing evidence that plants effect soil biota in ways that have consequences for their own performance. However, we know less about how plant-soil feedbacks vary among habitat types. We tested whether species from high elevations differ from species from low elevations in their susceptibility to plant-soil feedbacks, and whether alpine soils are less inhibitory, via negative feedbacks, than low elevation soils.
We performed a two-step plant-soil feedback experiment. Soil was collected from three alpine and three lowland habitats and used four alpine and four lowland plant species. We first cultured aliquots of soils from each site with each alpine and lowland species independently. In the second round we used an aliquot of the cultured soil and either sterilized the sample or not. Afterwards we grew alpine and lowland species with live or sterile inocula from the cultured alpine and lowland soils.
Results/Conclusions
Plants growing in alpine soil were 25% larger than those growing in lowland soil. There was also a significant interaction between soil origin and culturing (F1,1422=9.95, P=0.002). Culturing of alpine soil did not affect plant growth (F1,674=1.30, P=0.254), but culturing lowland soil reduced plant total biomass by 13% and 18% for alpine and grassland species, respectively. The interaction between soil origin and sterilization was significant (F1,1422=5.58, P=0.018). For alpine soil, sterilization inhibited plant growth in soil that had not been cultured but improved plant growth in cultured soil (interaction between training and sterilization of alpine soil: F1,674=9.72, P=0.002).
For lowland soil, plants were larger in sterile soil than in non-sterile soil (F1,738=4.09, P=0.044). Sterilization did not differ between alpine species and lowland species, but there was a significant interaction between species origin and sterilization (F1,1422=3.88, P=0.049). Sterilization improved the growth of alpine species in lowland soil but had no effect on the growth of alpine species in alpine soil (soil origin and sterilization interaction: F1,597=5.15, P=0.024). The interaction between training and sterilization was significant across soil origin and species origin (F1,1422=16.90, P<0.001).
We found that alpine soils were less inhibitory, via negative plant soil feedbacks, than low elevation soils. Furthermore, alpine species experienced stronger negative feedbacks when grown in low elevation soils than in alpine soils. These results are consistent with the idea that, in the alpine, plant species that are relatively sensitive to negative plant-soil feedbacks escape the strong inhibitory effects of soil biota that occur at lower elevations.