Biological, chemical and thermal indices of soil organic matter stability in four grassland soils
Biological, chemical and thermal indices of soil organic matter stability in four grassland soils
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DOI：
10.1016/j.soilbio.2011.01.024
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发表时间：
2011-05
影响因子：
9.7
通讯作者：
A. Plante;José M. Fernández;M. Haddix;J. Steinweg;R. Conant
中科院分区：
文献类型：
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作者：
A. Plante;José M. Fernández;M. Haddix;J. Steinweg;R. Conant
土壤有机质的各种生态系统功能取决于其数量和稳定性。许多分馏技术已经开发出来表征SOM的稳定性，热分析技术已经显示出有希望的结果来描述整个土壤样品中SOM的完整连续体。然而，SOM热稳定性与生物或化学稳定性之间的潜在联系尚未得到充分探讨。本研究的目的是比较用于表征SOM稳定性的传统化学和生物方法与热分析技术获得的结果。研究人员沿大陆年平均温度梯度收集了四个北美草地的表层土壤样本，每个草地都有原生和耕地利用。土壤有机碳浓度在6.8 ~ 33 g C kg - 1soil之间。在35℃条件下培养588 d，利用红外气体分析仪（IRGA）测量co2浓度，周期性测定土壤的C矿化率，计算SOM稳定性的生物指标。以培养前后热水可萃取有机C （HWEOC）含量为化学指标。最后，对孵育前后的样品进行同步热分析（即热重法（TG）和差示扫描量热法（DSC）），以确定SOM稳定性的热指标。长期孵育导致高达33%的初始土壤c矿化。呼吸5%的初始土壤有机碳（SOC）所需的天数范围为27至115天，被提出作为SOM稳定性的标准化生物学指标。与天然植被下的土壤相比，栽培土壤的日数更多，并且随着站点年平均温度的升高而减少。HWEOC（占初始SOC的百分比）对土地利用没有一致的响应，但在长期孵育后显著降低。原生植被下土壤的能量密度（J mg−1OM）高于栽培土壤，长期孵育也会降低土壤的能量密度。发生一半质量损失或能量释放的温度对土地利用变化的响应通常大于对孵化的响应。强相关性表明SOM的热稳定性和生物地球化学稳定性之间存在联系，但由于矿物成分和有机矿物相互作用的作用，对大块土壤样品中SOM的热行为的解释仍然模棱两可。
The various ecosystem functions of soil organic matter (SOM) depend on both its quantity and stability. Numerous fractionation techniques have been developed to characterize SOM stability, and thermal analysis techniques have shown promising results to describe the complete continuum of SOM in whole soil samples. However, the potential link between SOM thermal stability and biological or chemical stability has not yet been adequately explored. The objective of this study was to compare conventional chemical and biological methods used to characterize SOM stability with results obtained by thermal analysis techniques. Surface soil samples were collected from four North American grassland sites along a continental mean annual temperature gradient, each with a native and cultivated land use. Soil organic C concentrations ranged from 6.8 to 33 g C kg−1soil. Soils were incubated for 588 days at 35 °C, and C mineralization rates were determined periodically throughout the incubation by measuring CO2concentration using an infrared gas analyzer (IRGA) to calculate biological indices of SOM stability. Hot-water extractable organic C (HWEOC) contents were determined before and after incubation as chemical indices. Finally, samples from before and after incubation were analyzed by simultaneous thermal analysis (i.e., thermogravimetry (TG) and differential scanning calorimetry (DSC)) to determine thermal indices of SOM stability. Long-term incubation resulted in the mineralization of up to 33% of initial soil C. The number of days required to respire 5% of initial soil organic carbon (SOC), ranged from 27 to 115 days, and is proposed as a standardized biological index of SOM stability. The number of days was greater for cultivated soils compared to soils under native vegetation, and generally decreased with increasing site mean annual temperature. HWEOC (as % of initial SOC) did not show consistent responses to land use, but was significantly lower after long-term incubation. Energy density (J mg−1OM) was greater for soils under native vegetation compared to cultivated soils, and long-term incubation also decreased energy density. The temperatures at which half of the mass loss or energy release occurred typically showed larger responses to land use change than to incubation. Strong correlations demonstrated a link between the thermal and biogeochemical stability of SOM, but the interpretation of the thermal behavior of SOM in bulk soil samples remains equivocal because of the role the mineral component and organo-mineral interactions.