PS 22-20 - Effects of open-field experimental extreme climate events on soil extracellular enzyme activity and microbial biomass under Pinus densiflora and Larix kaempferi seedlings

Background/Question/Methods

Soil microbes play major roles in the terrestrial ecosystem by exchanging nutrients with plants. However, it is unclear how the interaction between soil microbes and plants is influenced by climate change. The present study investigated the effects of extreme climate events (extreme warming and precipitation pattern) on the soil extracellular enzyme activities and microbial biomass in the soil covered with 0-year-old Pinus densiflora and Larix kaempferi seedlings. Open-field treatments of two-week extreme warming (+3°C and +6°C) and the two-week precipitation manipulation including drought (100% rainfall interception) and heavy rainfall (43mm per day) were applied from April 12^th to June 6^th, 2021. Soil microbial biomass carbon and nitrogen and extracellular enzyme (acid phosphatase, β-glucosidase, N-acetyl-glucosaminidase, and leucine aminopeptidase) activities were measured after the completion of all treatments.

Results/Conclusions

The activities of acid phosphatase and N-acetyl-glucosaminidase under the L. kaempferi seedlings were higher than those under P. densiflora seedlings by 28.00% (p< 0.05) and 75.95% (p< 0.01), respectively. It appeared that the notable enzyme activities under the Larix kaempferi seedlings are due to the difference in carbon emissions from the roots and substrate provision by the deciduous layer. The interactive effects of warming and precipitation manipulation significantly affected the β-glucosidase activity, showing a different activity variance from -42.98% to +49.78%. Compared to the precipitation control, microbial biomass carbon and nitrogen increased 9.62% and 8.63% in the heavy rainfall treatments and decreased 9.85% and 15.36% in the drought treatments, respectively (p< 0.01, p< 0.01). The varied responses of microbial biomass were strongly influenced by soil water content by precipitation manipulation, while the extracellular enzyme activities showed little response to the drought or heavy rainfall treatments. The overall results indicate the microbial sensitivity to environmental variables as well as interactions with the planted species. Since this study confirmed only the measurements shortly after the extreme climate events manipulation, further investigation is needed to address the mechanisms of soil microbe-plant interactions response to future climate changes.