Chemical properties and distribution of phytotoxic Al species in intensively cultivated soils of Phyllostachys praecox stands

Abstract

The influence of intensively cultivated Phyllostachys praecox on soil chemical properties such as soil acidity,the distribution of phytotoxic aluminum (Al)species that theoretically contribute to Al toxicity,and the contribution of Al toxicity to Ph. praecox bamboo forest damage and soil degradation were determined using a correlation analysis. We set eight stands:rice paddy field(Os) and juvenile Taxus chinensis foresty field (Tw) as controls,Ph. praecox stands that has been planted for 2,6,8,11,16 and 20 a in the town of Taihu headstream,Lin'an,China. Results indicated that due to Ph. praecox cultivation,soil pH declined from 6.53 (Os) and 5.57 (Tw) to 3.55 (Pp20) in the surface (0-10 cm) and subsurface (10-20 cm) layers,soil organic matters and cation exchange capacity (CEC) increased after organic matter mulching,and soil humus quality decreased; however,soil electrical conductivity rose in the earlier cultivation period and droped in the final phrase due to the intensity of cultivation and fertilization. The concentration of 8-hydroxyquinoline (HQN) extractable Al in the 0-10 and 10-20 cm soil layers also increased over time. The concentration of HQN extractable Al in forest soils of 16 a was 108.01 mgkg－1，which compared to the controls,was 5 times higher than Os (22.94 mgkg－1) and 10 times higher than Tw (10.08 mgkg－1). The concentration of acetic acid extractable Al had a consistent trend with the concentration of HQN extractable Al showing a highly significant positive correlation(r = 0.831 7,P 0.000 1,adjusted R2 = 0.687 4). These results suggested that Al toxicity risk in soils of intensively cultivated P. praecox stands was increasing as a result of sustained acidification. [Ch,2 fig. 4 tab. 26 ref.]