The effects of simulated acid rain on internal nutrient cycling and the ratios of Mg, Al, Ca, N, and P in tea plants of a subtropical plantation

Acid rain alters nutrient cycling in tea plantations. However, the acquisition of Mg and Ca by plants and their nutrient interactions with Al, N, and P in response to acid rain are poorly understood. Experimental treatments simulating acid rain at various acidities (pH 4.5, 3.5, and 2.5) were performed within a red soil tea plantation in China. The available Mg, Al, Ca, N, and P were analyzed in the rhizosphere and bulk soils. Further, these elements were measured in absorptive, transportive, and storative roots in addition to twigs, tea, and mature leaves. Available soil Mg and Ca exhibited negative and positive rhizosphere effects, respectively, but the levels of both decreased due to acid rain treatment. In addition, average Mg and Ca concentrations generally decreased in plant tissues with increasing acidity. In contrast, average Al concentration increased across all plant tissues with increasing acidity treatment. Meanwhile, the ratios of Al/Mg and Al/Ca increased with increasing acidity but that of N/Al decreased in twigs and roots. Lastly, the ratios of N/Al, P/Ca, and N/P were all altered by acid treatment in tea and/or mature leaves. Taken together, these results indicated that elevated acidity increased the internal cycling of Al in plants but decreased Mg and Ca fluxes between soils and roots. Further, the response of interactions among the five measured elements to different acidities varied with tea plant tissue. Our findings may advance our understanding of plant adaptation to increasing soil acidification and atmospheric acid deposition around the world.