Increased N deposition retards mineralization of old soil organic matter
Increased N deposition retards mineralization of old soil organic matter
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DOI：
10.1016/j.soilbio.2003.08.015
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发表时间：
2003-12-01
影响因子：
9.7
通讯作者：
Siegwolf, R
中科院分区：
文献类型：
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作者：
Hagedorn, F;Spinnler, D;Siegwolf, R
本研究旨在探讨氮素沉积增加对新老土壤有机质(SOM)库的影响。我们利用了一个为期4年的实验，在这个实验中，生长在酸性壤土和钙质沙地上的云杉和山毛榉暴露在增加的N沉积(7vs.70kgN ha(-1)yr(-1))和大气中增加的二氧化碳中。添加的二氧化碳在C-13中被耗尽，这使我们能够区分SOM中的新旧碳-按颗粒大小划分的池。施氮量增加4年后，酸性壤土0~10 cm土层土壤有机质总量显著增加(+9%)，而石灰性砂土的土壤有机质含量增加不明显。在25 cm土层以下，高氮条件下酸性壤土的碳贮量比低氮条件下大100~300gCm(-2)。但与试验期间土壤扰动造成的石灰性砂土600~700g Cg C0.25m(-1)m(-2)相比，这一增加幅度较小。在高氮沉积条件下，两种土壤沙粒中小于4年生的新有机质的数量都较多，表明树木对土壤的碳输入增加。施氮量(+25%)时，酸性壤土的根系生物量较大。两种土壤粘粒和粉质组分中老碳、4年以上老碳的含量在高氮下显著高于低氮下。由于粘粒和淤泥结合的有机质由腐殖化的化合物组成，这表明N的添加延缓了陈旧和腐殖化的有机质的矿化。粘土和粉砂组分对碳矿化的阻挡作用为60~80gCm(-2)4a，相当于这些组分老有机质矿化总量的40%左右。因此，在氮沉积增加的情况下保存腐殖化的老有机质可能是一个长期导致土壤碳储量增加的过程。(C)2003爱思唯尔有限公司。保留所有权利。
The aim of this study was to investigate the effects of increased N deposition on new and old pools of soil organic matter (SOM). We made use of a 4-yr experiment, where spruce and beech growing on an acidic loam and a calcareous sand were exposed to increased N deposition (7 vs. 70 kg N ha(-1) yr(-1)) and to elevated atmospheric CO2. The added CO2 was depleted in C-13, which enabled us to distinguish between old and new C in SOM-pools fractionated into particle sizes. Elevated N deposition for 4 yr increased significantly the contents of total SOM in 0-10 cm depth of the acidic loam (+ 9%), but not in the calcareous sand. Down to 25 cm soil depth, C storage in the acidic loam was between 100 and 300 g C m(-2) larger under high than under low N additions. However, this increase was small as compared with the SOM losses of 600-700 g C g C 0.25 m(-1) m(-2) from the calcareous sand resulting from the disturbance of soils during setting up of the experiment. The amounts of new, less than 4 yr old SOM in the sand fractions of both soils were greater under high N deposition, showing that C inputs from trees into soils increased. Root biomass in the acidic loam was larger under N additions (+25%). Contents of old, more than 4 yr old C in the clay and silt fractions of both soils were significantly greater under high than under low N deposition. Since clay- and silt-bound SOM consists of humified compounds, this indicates that N additions retarded mineralization of old and humified SOM. The retardation of C mineralization in the clay and silt fraction accounted for 60-80 g C m(-2) 4 yr(-1), which corresponds to about 40% of the old SOM mineralized in these fraction. As a consequence, preservation of old and humified SOM under elevated N deposition might be a process that could lead to an increased soil C storage in the long-term. (C) 2003 Elsevier Ltd. All rights reserved.