Dry-wet cycling area enhances soil ecosystem multifunctionality in the aquatic-terrestrial ecotones of the Caohai Lake in China

The microbial need for nutrient resources can be assessed by soil extracellular enzymes and their stoichiometry. Changes in lake water levels affect land use and nutrient management in the aquatic-terrestrial ecotones of the lakeshore. However, the drivers of changes in microbial nutrient limitation under different inundation gradients in the lake’s aquatic-terrestrial ecotones remain unclear. Here, based on vector analysis, we assessed microbial nutrient limitation by studying soil enzyme activities in four different inundation zones (heavy, moderate, mild, and non-inundation) in the aquatic-terrestrial ecotones of Caohai Lake. The findings indicate that inundation conditions significantly influenced the soil properties and enzyme activities. The mean nitrogen and phosphorus acquisition enzymes were higher in both moderate inundation (Mod-inu) and mild inundation (Mil-inu) zone soils, indicating rapid N and P turnover rates in these two zones. However, microorganisms had higher carbon requirements and higher enzyme C:N and vector lengths in heavily inundated compared to lightly inundated. Compared to the non-inundation zone, the microbial phosphorus limitation was found to be most severe in heavy inundation (Hea-inu) and Mod-inu zones. Decreased phosphorus limitation following the inundation weakens could be contributed to improving soil ecosystem multifunctionality. The alterations in the soil extracellular enzymes and stoichiometric characteristics in various inundation zones were primarily influenced by factors such as soil moisture content, available phosphorus, and nitrate nitrogen. Overall, the Mod-inu and Mil-inu zones can better maintain the multifunctionality of the aquatic and terrestrial ecosystems; special attention should be given to the microbial phosphorus limitation in the Hea-inu zone in order to effectively manage nutrients and restore soil ecosystems in the aquatic-terrestrial ecotones.