Trees show higher resilience than herbs under phosphorus deficit induced by 12-year simulated acid rain

Acid rain, with 60% deposition in Asia, may exacerbate plant phosphorus (P) limitation; however, its long-term effects on different plant life-forms remain largely undetermined. Understanding these effects is essential for predicting ecosystem resilience and promoting forest health under environmental change. Herein, we investigated the P status in two tree and two herb species and their rhizosphere soils after 12 years of acid treatment at three pH levels (pH: 4.0, 3.5, and 3.0) in a tropical forest in Southern China. We found that leaf, litter, and root P; leaf N and P resorption efficiency, and their ratios remained stable in trees; however, herb leaf and litter P levels declined. Acid addition reduced inorganic P in tree rhizosphere soil and inorganic and organic P in herb rhizosphere soil. Rhizosphere soil P fractions were more regulated by soil physicochemical properties and less regulated by microbial community in trees than herbs. Under long-term simulated acid rain, stable tree P status benefited from soil inorganic P depletion, and herbs partially met their P requirements via biological mineralization of soil organic P. These distinct P-associated responses and acquisition strategies provide insights into safeguarding forest health among plants of different functional types under long-term acid rain events.