Nitrogen deposition effects on soil organic matter chemistry are linked to variation in enzymes, ecosystems and size fractions
Nitrogen deposition effects on soil organic matter chemistry are linked to variation in enzymes, ecosystems and size fractions
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DOI：
10.1007/s10533-008-9257-9
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发表时间：
2008-10-01
期刊：
影响因子：
4
通讯作者：
Zak, Donald R.
中科院分区：
文献类型：
--
作者：
Grandy, A. Stuart;Sinsabaugh, Robert L.;Zak, Donald R.
最近的研究大大提高了我们对土壤有机质化学和N在某些有机质转化中的作用的认识，但N沉降对土壤C动态的影响仍然难以预测。在模拟大气氮沉降6年后，研究了两种生态系统（糖枫、糖槭-枫木、美洲椴和黑栎、绒栎-白栎、紫椴-白栎）中3个粒径级（> 250 μ m、63-250 μ m和< 63 μ m）土壤有机质化学和酶动力学。alba）。在每个生态系统中的三个复制林分中研究了环境和模拟（80-kg NO3--N ha（-1）年（-1））大气氮沉降。我们发现显着的，生态系统特定的影响，氮沉降对土壤有机质化学裂解气相色谱/质谱。首先，糠醛，多糖的主要热解产物，显着减少模拟N沉积在糖枫-杉木生态系统（15.9比5.0%），但增加了N沉积在黑橡树-白橡树生态系统（8.8比24.0%）。第二，模拟大气氮沉降增加的比例总木质素衍生物，总多糖在> 250 μ m级的糖枫-杉木生态系统从0.9到3.3，但没有变化，在其他大小类或在黑橡树-白橡树生态系统。第三，模拟氮沉降增加了两种生态系统中63-250和> 250 μ m组分中木质素衍生物与含氮化合物的比例，但在< 63 μ m组分中没有增加。酶动力学和有机物化学之间的关系是最强的颗粒级分（> 63 μ m），其中有氧化酶活性和浓度的木质素衍生物和聚糖酶活性和碳水化合物的浓度之间的多重相关性。在粉质粘土组分（< 63 μ m），这些酶-底物的相关性减弱与颗粒表面的相互作用。我们的研究结果表明，大气氮沉降导致的酶活性的变化直接关系到土壤有机质化学的变化，特别是那些发生在粗糙的土壤粒度级。
Recent research has dramatically advanced our understanding of soil organic matter chemistry and the role of N in some organic matter transformations, but the effects of N deposition on soil C dynamics remain difficult to anticipate. We examined soil organic matter chemistry and enzyme kinetics in three size fractions (> 250 mu m, 63-250 mu m, and < 63 mu m) following 6 years of simulated atmospheric N deposition in two ecosystems with contrasting litter biochemistry (sugar maple, Acer saccharum-basswood, Tilia americana and black oak, Quercus velutina-white oak, Q. alba). Ambient and simulated (80-kg NO3--N ha(-1) year(-1)) atmospheric N deposition were studied in three replicate stands in each ecosystem. We found striking, ecosystem-specific effects of N deposition on soil organic matter chemistry using pyrolysis gas chromatography/mass spectrometry. First, furfural, the dominant pyrolysis product of polysaccharides, was significantly decreased by simulated N deposition in the sugar maple-basswood ecosystem (15.9 vs. 5.0%) but was increased by N deposition in the black oak-white oak ecosystem (8.8 vs. 24.0%). Second, simulated atmospheric N deposition increased the ratio of total lignin derivatives to total polysaccharides in the > 250 mu m fraction of the sugar maple-basswood ecosystem from 0.9 to 3.3 but there were no changes in other size classes or in the black oak-white oak ecosystem. Third, simulated N deposition increased the ratio of lignin derivatives to N-bearing compounds in the 63-250 and > 250 mu m fractions in both ecosystems but not in the < 63 mu m fraction. Relationships between enzyme kinetics and organic matter chemistry were strongest in the particulate fractions (> 63 mu m) where there were multiple correlations between oxidative enzyme activities and concentrations of lignin derivatives and between glycanolytic enzyme activities and concentrations of carbohydrates. Within silt-clay fractions (< 63 mu m), these enzyme-substrate correlations were attenuated by interactions with particle surfaces. Our results demonstrate that variation in enzyme activity resulting from atmospheric N deposition is directly linked to changes in soil organic matter chemistry, particularly those that occur within coarse soil size fractions.