LB 29-288 - Unpredictable growth: The influence of competitive environments and soil biota on the growth of three native grassland species.

Background/Question/Methods:

The emergence of new species in plant communities can change existing soil properties as novel soil organisms may be introduced and existing interactions between plant roots and other soil organisms may be altered. Furthermore, new species may also change soil nutrient dynamics. Together, these changes affect the performance of plant species in a community and ultimately influence community composition and structure. The expansion of shrubs in grasslands is often accompanied by changes to abiotic soil factors which can alter plant performance. However, shifts in vegetation can also cause changes to the soil biota, but it is unclear how plants in these communities respond to these changes. The soil biota exerts a great deal of influence on plant growth and persistence in a community due to the net effect of soil mutualists and antagonists, but this effect can vary with competitive environments. To test plant response to changes in soil biota and whether this is affected by neighbour density, we conducted a 3-month greenhouse experiment. We grew three native species in different neighbour densities with live and sterile soils from areas dominated by a N-fixing shrub, Elaeagnus commutata (Wolf-willow), and shrub-free adjacent areas in a grassland located in central Alberta, Canada.

Results/Conclusions:

Overall, one of three species responded differently to soil biota from the two community types, but two species reported different responses to soil biota with changes in neighbours. A. scabra had a net neutral response to grassland live soil, primarily due to variable responses to neighbour presence; its response to live soil from wolf-willow communities was negative irrespective of neighbours. F.hallii had negative responses to live soils from grassland and wolf-willow communities that were unaffected by changes in neighbour density. G. triflorum responded positively to live soil from grassland and wolf-willow but the effect of wolf-willow soil biota decreased with greater neighbour density. Together, these results indicate great similarity between soil biota of the two plant communities, however, species responses to either soil community may be unpredictable due to the dynamic relationship between a soil’s biotic effect and a plant’s competitive environment.