Complex effects of different types of acid rain on root growth of Quercus acutissima and Cunninghamia lanceolata saplings

Abstract

Background: Soil acidification caused by acid rain (AR) can damage plant roots, which in turn negatively impacts plant health. In response to changing AR types, research efforts to elucidate their specific impacts on plants have become intense. Methods: For this study, we investigated the effects of simulated sulfuric, nitric, and mixed AR on the root systems of Quercus acutissima Carr. and Cunninghamia lanceolata (Lamb.) Hook. under different acidity levels. Results: As the AR S/N ratio and pH decreased, the height growth rate (HGR), basal diameter growth rate (DGR), total root length (TRL) and total root surface area (TRS) of C. lanceolata decreased, whereas the TRL and TRS of Q. acutissima remained the same. When the NO3− concentration in AR was increased, the root activity, superoxide dismutase (SOD) and catalase (CAT) activities of C. lanceolata roots revealed a downward trend; however, the root activity of Q. acutissima and the peroxidase (POD) activity of C. lanceolata roots revealed an upward trend. Further, redundant analysis and structural equation models indicated that AR pH had a greater impact on the HGR of Q. acutissima than that of C. lanceolata, while the impact of the AR S/N ratio on C. lanceolata growth rates was greater than that of Q. acutissima. Conclusions: Our results suggested that the root systems of different tree species had variable responses to AR, and the AR S/N ratio was an important factor affecting plant root growth. This might facilitate new strategies for the cultivation and protection of plantations in the future.