Friday, August 10, 2018
ESA Exhibit Hall, New Orleans Ernest N. Morial Convention Center
Background/Question/Methods
In western North America, mountain pine beetle (Dendroctonus ponderosae) has killed large regions of lodgepole pine (Pinus contorta) forests. Pines form mutualisms with fungi known as mycorrhizas, which improve plant uptake of nutrients from soils through specialized fungal structures on pine root tips. Previous research indicates that in some pine stands, the community composition of mycorrhizal fungi shifts after high mortality of pine by mountain pine beetle, with subsequent decreases in lodgepole pine seedling survival and growth. While previous research explored the effects on seedling performance of soil inocula sourced from beetle-killed or non- attacked pine stands, it did so over a relatively narrow range of pine stands on the landscape. In consequence, the generality of these previous findings were somewhat limited given the large geographic expanse of forest disturbed by these beetles. Here, our objective is to assess pine seedling growth and survival when inoculated with soil from beetle-killed or non-attacked stands, and importantly, across beetle-killed stands that substantially vary in edaphic properties. We established 15 sites in pine forests with high levels of tree mortality across a wide geographic range in western Alberta, Canada. We collected soil from each of these sites, which we then assessed for texture and nutrients (NH4+, NO3-, and PO43-); there were substantial difference among sites in these soil characteristics. In a growth chamber, we grew pine seedlings in three treatments; soil inoculum sourced from beetle-killed stands, non-attacked stands, and without inoculum. After four months in the growth chamber, we assessed seedling survival and transplanted the seedlings into the 15 field sites.
Results/Conclusions
After four months in the growth chamber, seedling survival was significantly greater in those grown with soil inoculum sourced from beetle-killed stands than those grown with soil inoculum from non-attacked stands and those receiving no inoculum. Seedling survival was not significantly greater between those grown with soil inoculum sourced from non-attacked, and those receiving no inoculum. Six weeks after transplanting, seedling survival and heights did not differ significantly by origin of soil inoculation. Additionally, the most variance explained in survival and heights of seedlings after transplanting was by soil edaphic properties, rather than by origin of soil inoculation. In conclusion, these results suggest environmental filters (physical edaphic properties) may have a greater pronounced influence than biotic factors (soil inoculum) on seedling success. This study may provide insight to novel methods of rehabilitating beetle-killed pine stands with poor regeneration.
In western North America, mountain pine beetle (Dendroctonus ponderosae) has killed large regions of lodgepole pine (Pinus contorta) forests. Pines form mutualisms with fungi known as mycorrhizas, which improve plant uptake of nutrients from soils through specialized fungal structures on pine root tips. Previous research indicates that in some pine stands, the community composition of mycorrhizal fungi shifts after high mortality of pine by mountain pine beetle, with subsequent decreases in lodgepole pine seedling survival and growth. While previous research explored the effects on seedling performance of soil inocula sourced from beetle-killed or non- attacked pine stands, it did so over a relatively narrow range of pine stands on the landscape. In consequence, the generality of these previous findings were somewhat limited given the large geographic expanse of forest disturbed by these beetles. Here, our objective is to assess pine seedling growth and survival when inoculated with soil from beetle-killed or non-attacked stands, and importantly, across beetle-killed stands that substantially vary in edaphic properties. We established 15 sites in pine forests with high levels of tree mortality across a wide geographic range in western Alberta, Canada. We collected soil from each of these sites, which we then assessed for texture and nutrients (NH4+, NO3-, and PO43-); there were substantial difference among sites in these soil characteristics. In a growth chamber, we grew pine seedlings in three treatments; soil inoculum sourced from beetle-killed stands, non-attacked stands, and without inoculum. After four months in the growth chamber, we assessed seedling survival and transplanted the seedlings into the 15 field sites.
Results/Conclusions
After four months in the growth chamber, seedling survival was significantly greater in those grown with soil inoculum sourced from beetle-killed stands than those grown with soil inoculum from non-attacked stands and those receiving no inoculum. Seedling survival was not significantly greater between those grown with soil inoculum sourced from non-attacked, and those receiving no inoculum. Six weeks after transplanting, seedling survival and heights did not differ significantly by origin of soil inoculation. Additionally, the most variance explained in survival and heights of seedlings after transplanting was by soil edaphic properties, rather than by origin of soil inoculation. In conclusion, these results suggest environmental filters (physical edaphic properties) may have a greater pronounced influence than biotic factors (soil inoculum) on seedling success. This study may provide insight to novel methods of rehabilitating beetle-killed pine stands with poor regeneration.