MOE Key Laboratory of Western China's Environmental Systems and Gansu Key Laboratory for Environmental Pollution Prediction and Control, College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China.
MOE Key Laboratory of Western China's Environmental Systems and Gansu Key Laboratory for Environmental Pollution Prediction and Control, College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China.
Sci Total Environ. 2018 May 1;622-623:1056-1066. doi: 10.1016/j.scitotenv.2017.12.027. Epub 2017 Dec 13.
Metal bioavailability and extracellular enzyme activity are two important indicators of soil quality in metal-contaminated soil. However, it is unclear how the chronosequence effect modifies these two factors in highly contaminated calcareous soils undergoing afforestation. We used Populus simonii Carr. and the calciphilous Ulmus macrocarpa Hance as contrasting tree species to study the chronosequence effect. We found that afforestation significantly increased soil total nitrogen (N) content as well as soil carbon (C)/phosphorus (P) and N/P ratios, but decreased soil total P content and soil C/N ratio, regardless of the tree species and stand age, suggesting strong P limitation. However, available P did not change significantly with stand age. In both tree species, P mobilization depleted soil organic matter through the priming effect of dissolved organic carbon, whereas the decrease in soil pH in the U. macrocarpa stands enhanced CaCO dissolution, collectively reducing the capacity of the soil to immobilize metals, resulting in increased metal bioavailability with stand age. The activity of oxidase (dehydrogenase) was positively correlated with bioavailable zinc concentration, soil electrical conductivity, and soil total N content. Hydrolase activities (alkaline phosphatase, β-glucosidase, and urease) were significantly positively correlated with the ratios of soil C/N and C/P, soil pH, and CaCO, but negatively correlated with soil N/P ratio and bioavailable cadmium concentration. Increasing stand age was associated with the gradual recovery of oxidase activity and remarkable inhibition of hydrolase activity. Our results suggest that the combination of soil hydrolase activity and metal bioavailability can predict soil quality in the afforestation of highly contaminated soils.
金属生物有效性和胞外酶活性是受金属污染土壤质量的两个重要指标。然而，在经历造林的高度污染的石灰性土壤中，时序列效应如何调节这两个因素尚不清楚。我们使用了泡桐和麻栎作为对比树种来研究时序列效应。我们发现，造林显著增加了土壤全氮（N）含量以及土壤碳（C）/磷（P）和 N/P 比，但降低了土壤全磷（P）含量和土壤 C/N 比，无论树种和林龄如何，这表明存在强烈的磷限制。然而，有效磷含量随林龄的变化并不明显。在这两个树种中，磷的动员通过溶解有机碳的激发效应消耗了土壤有机质，而麻栎林土壤 pH 值的降低则促进了碳酸钙的溶解，这共同降低了土壤固定金属的能力，导致生物有效性金属随林龄的增加而增加。氧化酶（脱氢酶）的活性与可利用锌浓度、土壤电导率和土壤全氮含量呈正相关。水解酶活性（碱性磷酸酶、β-葡萄糖苷酶和脲酶）与土壤 C/N 和 C/P 比、土壤 pH 值和 CaCO3 呈显著正相关，与土壤 N/P 比和可利用镉浓度呈负相关。林龄的增加与氧化酶活性的逐渐恢复和水解酶活性的显著抑制有关。我们的研究结果表明，土壤水解酶活性和金属生物有效性的结合可以预测高度污染土壤造林后的土壤质量。
