Dynamic changes of soil aggregate-associated phosphorus adsorption-desorption characteristics in a chronosequence of Chinese fir plantations

Abstract

Successive cultivation of Chinese fir affects soil phosphorus (P) adsorption-desorption characteristics by altering both abiotic and biotic factors, such as soil aggregate size and microbial activities. However, previous studies have predominantly focused on individual factors (abiotic or biotic factors) without considering their combined effects on soil P adsorption-desorption characteristics. To address the research gaps, this study was conducted to investigate the response of abiotic factors (P forms, soil organic matters (SOM), iron and aluminum oxides (Fe₂O₃ and Al₂O₃) concentrations, and aggregate sizes) and biotic factors (microbial activities) to Chinese fir stand ages (control, 9-yr, 17-yr, and 26-yr) and how the combined relationship affect P adsorption-desorption characteristics in Chinese fir plantations. The results showed that under the same initial P concentration (0.0, 0.3, 1.5, 3.0, 10.0, 20.0, and 50.0 mg L⁻¹), parameters of P adsorption-desorption characteristics including the quantity of stable adsorption P, quantity of stable desorption P, adsorption P rate, and desorption P rate in macro-aggregates (> 0.25 mm) were significantly higher than that in the micro-aggregates (< 0.25 mm). However, in 26-yr of Chinese fir plantations, parameters of P adsorption-desorption characteristics within almost all aggregate fractions significantly decreased, driven by declines in inorganic P, SOM, amorphous Fe₂O₃ and Al₂O₃, macro-aggregates, and microbial biomass (as indicated by PLFAs). The order of factors affecting P adsorption-desorption characteristics variation is P forms, SOM, microbial biomass, and Fe₂O₃ and Al₂O₃. The results of this study indicate crucial factors affecting the P adsorption-desorption process, with a combined effect of abiotic factors within the culture of Chinese fir. Therefore, to prevent significant soil P losses and promote P utilization efficiency, it is crucial to consider the combined impacts of abiotic and biotic factors on soil P cycling characteristics across different stand ages during Chinese fir cultivation.