Immediate response of soil nitrogen cycling-related enzyme activities to typhoon disturbance along a gap size gradient

Abstract

Although heavy rainfall and the input of unsenescent litter produced by tropical cyclones can profoundly affect the activities of soil nitrogen (N) cycling-related enzymes in coastal mountain forest ecosystems in the short term, the immediate responses of these enzymes to typhoon disturbances and the underlying mechanism remain unknown. To address this knowledge gap, we measured the absolute and biomass-specific activities of urease (URE), acid protease (ACP), glutaminase (GLS), nitrate reductase (NR), and nitrite reductase (NIR) in surface (0–10 cm) and subsurface (10–30 cm) soils from the closed canopy to large canopy gaps in a subtropical broadleaf forest in eastern China before and after the Super Typhoon Doksuri. One day after the typhoon, absolute and biomass-specific enzyme activities of the five enzymes decreased by 2.65%–89.9% and 9.0%–91.8%, respectively. However, biomass-specific enzyme activities recovered within 1 week, increasing by 35.1%–167.3%, whereas absolute enzyme activities exhibited limited recovery. Larger canopy gaps had negligible effects on the immediate response of absolute enzyme activities but significantly amplified the responses of biomass-specific activities. These immediate enzymatic responses were primarily driven by changes in soil carbon and nitrogen fractions, as well as microbial biomass, with distinct pathways of influence among enzyme types. In conclusion, typhoon disturbances can immediately suppress soil N cycling-related enzyme activities, whereas the recovery of biomass-specific enzyme activities is more sensitive to canopy gap size than that of absolute enzyme activities. These findings highlight the critical role of canopy structure in modulating microbial functional recovery following extreme weather events.