Effects of two-century land use changes on soil iron crystallinity and accumulation in Southeastern Piedmont region, USA
Effects of two-century land use changes on soil iron crystallinity and accumulation in Southeastern Piedmont region, USA
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DOI：
10.1016/j.geoderma.2011.12.021
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发表时间：
2012-03
期刊：
影响因子：
6.1
通讯作者：
Jianwei Li;D. Richter
中科院分区：
文献类型：
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作者：
Jianwei Li;D. Richter
为了评估土地利用变化对矿质土壤铁结晶度的影响，本研究量化了美国南山前高地土地利用历史的共同轨迹——老阔叶林、耕地和老田松林上部矿质土壤中不稳定、短程有序和相对结晶的铁池。特别是在具有不同侵蚀历史的可比老田松林中，我们索引了它们的表面矿物-土壤铁结晶度，并比较了各种不同森林生态系统中铁循环（森林地面和矿物土壤层的增加）。结果表明：(1)三种土地利用方式下的耕地土壤铁结晶度显著高于支持老硬木的土壤或支持50年松林更新的原耕地土壤；（ii） 5种松林土壤的铁结晶度随侵蚀程度的增加而增加；（iii）在各种森林中，有机土壤和表层矿物土壤层的铁增生普遍存在，非针状物质的铁增生高于针状物质。考虑到皮埃蒙特地区持续的土壤侵蚀和技术密集型耕作，我们认为农业活动加速了表层土壤中有机复合铁的流失，并导致深度的结晶氧化铁暴露在地表。此外，几十年来森林再生过程中的大量有机输入重建了土壤剖面中氧化铁的反应性和显著增加，这表明生物活动在介导土壤氧化铁和碳化合物转化方面的主要影响，特别是在有机土壤水平层。该研究表明，土地利用变化（农业和再造林）对改变生物活性土壤和凋落物层中铁结晶度及其与有机质分解的相互作用起着深远的作用。目前尚不清楚这些层中的生物活动（通过动物或微生物）如何驱动陆地森林生态系统中的铁生物地球化学转化和再分配。
To evaluate effects of land use changes on iron (Fe) crystallinity in mineral soil, this study quantified labile, short-range ordered and relatively crystalline iron pools in upper mineral soils of old hardwood forests, cultivated agricultural fields, and old-field pine forests, a common trajectory of land-use history in the upland of the Southern Piedmont, USA. Particularly in comparable old-field pine forest but with varying erosion histories, we indexed their surface mineral-soil iron crystallinity and compared iron cycling (accretion in forest floor and mineral soil horizons) in a variety of different forest ecosystems. Our results indicate that: (i) comparable sites with three land uses showed a significantly higher iron crystallinity in cultivated soil than soils supporting old hardwoods or in formerly cultivated soils that have supported 50years of pine forest regeneration; (ii) five selected pine forest soils showed increasing iron crystallinity with elevated erosion; and (iii) iron accretion in organic and surface mineral soils horizons are ubiquitous across a variety of forests with a higher accretion in non-needle materials than needles. Given the continued soil erosion and more technologically intensive plowing across the Piedmont region, we attribute that agriculture activities accelerate loss of organic complexed Fe in the surface soil and resulted in the crystalline iron oxide at depth exposed to surface. Also, large organic input during forest regrowth for decades reestablished the reactivity and significant accretion of iron oxides in soil profiles suggesting major influence of biological activities in mediating the transformation of soil iron oxides and carbon compounds particularly in organic soil horizon. This study suggests that land use changes (agriculture and reforestation) play a profound role in transforming the iron crystallinity and its interaction with organic matter decomposition in biologically active soil and litter layers. It remains unclear how biological activities (via animal or microbes) in these layers have driven the iron biogeochemical transformation and redistribution in terrestrial forest ecosystems.