黄土丘陵区撂荒农耕地土壤有效态微量元素演变特征

【目的】探索农耕地撂荒对土壤微量元素演变特征的影响，为该地区植被恢复中土壤质量评价和生态恢复的持续健康发展提供科学依据。【方法】以黄土丘陵区不同撂荒年限的坡耕地为研究对象，分析农耕地撂荒后不同坡向土壤4种有效态微量元素的变化趋势。【结果】黄土丘陵区坡耕地撂荒后，阴坡由于土壤温度较低，含水量较大，植被生长旺盛。有机碳、全氮、有效锰、有效铁、有效锌含量变化规律性较强，表现为在演替前期变化较小，而后期随撂荒年限的延长而显著增加，有效铜则随撂荒年限呈降低趋势。阳坡土壤有机碳、全氮及4种有效态微量元素含量则随年限呈波动变化。不同演替阶段土壤微量元素密度变化不同，阳坡土壤有效铁和有效锌密度在演替前10年明显高于阴坡，而在10年后显著低于阴坡；有效铜密度在前5年略低于阴坡，5年后明显高于阴坡。【结论】黄土丘陵区坡耕地撂荒20年后，虽然4种土壤有效态微量元素含量有所提高，但仍处于低或极低水平，因此黄土丘陵区通过自然演替来改善土壤微量元素状况还需要较长的时间。

Characteristic of Soil Available Trace Elements on Abandoned Cropland in the Loess Hilly Region

【Objective】 The research was made to provide a scientific guidance for the sustainable development of ecological restoration and the evaluation of soil quality by studying the effect of abandoned cropland on soil trace elements in the hilly-gully region of the Loess Plateau. 【Method】 The present study investigated the changes of four available trace elements at different slope aspects during succession on abandoned cropland in the loess hilly region. 【Result】 The results showed that during the vegetation succession on abandoned cropland, the content of organic C, total N, available Mn, available Fe, available Zn in this shady slope presented a significant regular variation due to the high soil moisture favorable vegetation conditions, showing no significant difference at the early stage of succession while increased with the increasing years at the later stage. Available Cu exhibited a decrease trend with years. Organic C, total N, and four available trace elements in the sunny slope fluctuated with the increasing years. The density of four trace elements differed significantly at different succession stages. Compared with the shady slope, available Fe and Zn density in the sunny slope was higher in the first 10 years while was lower 10 years later, available Cu density was slightly lower in the first 5 years and was higher thereafter. 【Conclusion】Although the content of four soil trace elements in the cropland increased after abandoned for 20 years, it is still in the extremely lower level, thus natural recovery to improve the status of trace elements in this region probably need more time.