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Nitrogen and carbon dynamics in prairie vegetation strips across topographical gradients in mixed Central Iowa agroecosystems

机译:爱荷华州中部混合生态系统中草原植被带跨地形梯度的氮和碳动态

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摘要

Reductions of nitrogen (N) export from agricultural lands because of changes in specific N stocks and fluxes by incorporation of small amounts of prairie vegetation strips (PVS) are poorly understood. The primary objective of this study was to evaluate the effect of the presence and topographical position of PVS on soil and plant carbon (C) and N stocks relative to annual crop and native prairie vegetation. The study was implemented within three small adjacent watersheds, treated with one of the following cover types: (1) 100% row-crop agriculture (CROP); (2) 20% prairie vegetation (PVS) distributed along the contour across three topographical positions: upslope, sideslope and footslope position; and (3) 100% 17-year old reconstructed native prairie (RNP) as the control condition. Total soil organic C (SOC), total soil N (TN), inorganic N availability as indexed by ion exchange resins, N stocks in plant biomass and litter, and the ratio of C3:C4 plant species were measured during the 2010 growing season. Results showed that over five years of treatment, PVS footslope improved soil quality by increasing TN by almost 100% and SOC by 37%; while CROP footslope TN decreased by 31% and SOC decreased by 28%. Overall, N stocks in plant biomass and litter were higher in PVS compared with RNP, except in the footslope where the lower N plant stocks was associated with higher C3 abundance in RNP. Nitrogen availability was higher in CROP (25.4 ± 1.4), followed by PVS (10.2 ± 1.3), and RNP (2.2 ± 1.4); with the highest values recorded in the upslope position for PVS and RNP, and the footslope for CROP. These findings are important for designing watersheds with PVS to reduce N accumulation in the footslope position and promote additional N retention in soil organic matter and plant biomass, thereby minimizing N losses to streams.
机译:由于掺入少量的草原植被带(PVS),由于特定氮素储量和通量的变化,减少了从农业土地中输出的氮(N),人们对此知之甚少。这项研究的主要目的是评估相对于一年生作物和大草原植被而言,PVS的存在和地形位置对土壤和植物碳(C)和N储量的影响。该研究是在三个相邻的小流域内进行的,并用以下其中一种覆盖物进行了处理:(1)100%行间农业(CROP); (2)20%的草原植被(PVS)沿着等高线分布在三个地形位置:上坡,侧坡和山坡位置; (3)以100%17岁的当地自然草原(RNP)作为控制条件。在2010年生长季节期间,测量了土壤有机碳总量(SOC),土壤总氮(TN),离子交换树脂索引的无机氮有效性,植物生物量和凋落物中的氮储量以及C3:C4植物物种的比率。结果表明,经过5年的处理,PVS山坡通过使TN增加近100%和SOC增加37%改善了土壤质量。而CROP山坡TN下降了31%,SOC下降了28%。总体而言,PVS的植物生物量和凋落物中的N储量均高于RNP,但山麓地区除外,其中较低的N植物储量与RNP中的C3丰度较高相关。 CROP(25.4±1.4),PVS(10.2±1.3)和RNP(2.2±1.4)其次是氮的可利用性。对于PVS和RNP,最高值记录在上坡位置,对于CROP,值记录在山坡上。这些发现对于设计具有PVS的流域非常重要,以减少山坡位置上的N积累并促进土壤有机质和植物生物量中氮的额外保留,从而最大程度地减少溪流中的N损失。

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