Restoration of woody vegetation after a disturbance can be jeopardized by the harsh conditions characteristic of these sites. Transplants of tree seedlings often desiccate within the first few weeks. Management options to increase survival, such as supplemental watering or shading, are costly--and in some cases not even feasible. However, there are some low-cost techniques with the potential to improve seedling survival by increasing water availability to plants. Biochar, which is charcoal applied as a soil amendment, may be used to increase the moisture retention of the soil and perhaps enhance mycorrhizal fungi colonization of the roots. Additionally, inoculating transplanted seedlings with beneficial microbiota by using soil collected from nearby forests could introduce and accelerate mycorrhizal fungi colonization, further increasing the availability of water to the seedlings.
To test the potential effects of biochar and forest soil inoculation on tree seedling establishment in a restoration setting, we conducted a field experiment in which bare-root seedlings of Quercus rubra were transplanted into a degraded area in a former pine plantation. Seedlings were planted under four treatments: biochar and soil inoculum (B+S), only biochar (B), only soil inoculum (S), and control (C). We then monitored seedling growth and survival.
Results/Conclusions
At the end of the growing season, seedlings were harvested to assess mycorrhizal fungi colonization of the roots and total biomass. Mortality was high in all treatments, but survival was highest in seedlings that received the soil inoculum (16%), followed by the biochar treatment (15%). Lowest survival took place under control conditions (6%), and unexpectedly under the combined biochar and soil inoculum treatment (5%). Analysis of root colonization by mycorrhizal fungi shows that neither soil inoculum or biochar application had an impact. Soil transfer and biochar application may need to occur on different scales or at different times in the seedling germination and growth process.