氮沉降对杉木人工林土壤铝形态分布和盐基离子含量的影响

Increasing nitrogen deposition leads to changes in the aluminum fraction profiles of soil, which have a negative influence on plant growth and soil microorganisms. However, there have been limited studies on the characteristics and mechanism of aluminum speciation under nitrogen deposition. To explore the transformation mechanism of aluminum and the antagonism of exchangeable aluminum with base cations under nitrogen deposition, the present study used the sequential extraction method to extract three aluminum fractions and determine the base cation contents in Cunninghamia lanceolata plantations, following two years of a nitrogen deposition simulation experiment. The results indicated that short-term nitrogen deposition did not cause significant changes in soil total carbon, total nitrogen，pHH2O and pHKCl. The low-nitrogen (LN) treatment led to decreased exchangeable Al content; however, there was no significant effect on the base cation. The high-nitrogen (HN) treatment led to increased content of exchangeable aluminum in the soil, resulting in the leaching of large amounts of Ca2+ and Mg2+ into the soil, which in turn reduced the Ca/Al and Mg/Al ratios. In the HN treatment, the content of weak organic bound aluminum in the soil increased, whereas the content of strong organic bound aluminum increased in order to buffer soil acidification. This study indicated that the LN will alleviate the effects of aluminum toxicity in the forest, whereas HN will aggravate the effects of aluminum toxicity during initial nitrogen deposition. This study provides a theoretical basis for the assessment of aluminum toxicity in subtropical forests in the future.