Persistence of old soil carbon under changing climate: The role of mineral-organic matter interactions
Persistence of old soil carbon under changing climate: The role of mineral-organic matter interactions
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DOI：
10.1016/j.chemgeo.2021.120629
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发表时间：
2021-11
期刊：
影响因子：
3.9
通讯作者：
Katherine E. Grant;V. Galy;N. Haghipour;T. Eglinton;L. Derry
中科院分区：
文献类型：
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作者：
Katherine E. Grant;V. Galy;N. Haghipour;T. Eglinton;L. Derry
在全球范围内，土壤储存1500至2800 Pg的有机碳（OC）。在合理的气候变化情景下，这些陆地土壤碳储存的物理和化学稳定性尚不清楚。土壤有机碳（SOC），特别是在火山岩土壤中，是通过矿物基质相互作用而稳定的。这些矿物-有机物相互作用对环境变化的敏感程度如何？在这里，我们提出了一个研究的SOC年龄沿着气候梯度从夏威夷岛上的科哈拉火山的土壤。我们测量了大量样品中的碳同位素组成（14 C/12 C，13 C/12 C），并提取了15个土壤剖面的4-8个层位的生物标志物，以了解SOC年龄的变化和平均年降水量增量差异的持续性。底土中的大量有机碳的放射性碳分数现代（Fm）值低至0.28至0.16（约10，160至约14，630常规放射性碳年）。共存的植物源性长链脂肪酸（LCFA）更古老，超过22，500年。(Fm= 0.060），这意味着这些是最稳定的化合物在土壤中，而相应的短链（C16）脂肪酸是年轻得多，从活跃的微生物群落同化年轻的OC从表层分解的起源一致。有显着的铁损失在较高的平均年降水量（MAP）（>2200毫米yr-1）的网站与情节土壤饱和度和微生物铁减少。在这些地点，%OC较高，与饱和条件促进SOC储存的预期一致。然而，在这些较高的MAP网站铁贫化与更年轻的散装SOC和LCFAs 14 C年龄（~ 290014 C年）比在相同的样品深度的网站，保留最铁（~14，20014 C年）。剩余的矿物基质主要由Si、Al和Ti作为SRO矿物组成。这些数据意味着，在附近的潜在饱和或氧化还原阈值的位置，由环境变化引起的降水适度增加可能会导致Fe-SOC复合物的不稳定，使以前稳定的碳可用于快速降解，可能不可逆地减少旧SOC水库的大小。一个老的，持久的Fe-SOC水库的不稳定性可以减少SOC存储，并最终增加释放到大气中的CO2的量。
Globally, soils store between 1500 and 2800 Pg of organic carbon (OC). The physical and chemical stability of these terrestrial soil carbon stores under plausible climate change scenarios is unclear. Soil organic carbon (SOC), especially in volcanic soils, is stabilized through mineral matrix interactions. How susceptible are these mineral-organic matter interactions to environmental change? Here we present a study of SOC age along a climate gradient of andisols from Kohala volcano on the Island of Hawai'i. We measure carbon isotope composition (14C/12C,13C/12C) in bulk samples and extracted biomarkers for 4–8 horizons of 15 soil profiles to understand variability in SOC age and persistence across incremental differences in mean annual precipitation. Bulk OC in the subsoil has radiocarbon fraction modern (Fm) values as low as 0.28 to 0.16 (~10,160 to ~14,630 conventional radiocarbon years). Coexisting plant-derived long chain fatty acids (LCFAs) are older, over 22,500 yrs. (Fm = 0.060), implying that these are among the most stable compounds in the soil, while corresponding shorter-chain (C16) fatty acids are much younger, consistent with an origin from active microbial communities assimilating young OC percolating from surface horizons. There is significant Fe loss at higher mean annual precipitation (MAP) (>2200 mm yr−1) sites associated with episodic soil saturation and microbial Fe reduction. %OC is higher at these sites, consistent with the expectation that saturated conditions promote SOC storage. However, in these higher MAP sites iron depletion is associated with much younger bulk SOC and LCFAs14C ages (~290014C years) than at equivalent sample depths in sites that retain most Fe (~14,20014C years). The remaining mineral matrix consists primarily of Si, Al, and Ti as SRO minerals. The data imply that modest increases in precipitation resulting from environmental change at locations near a potential saturation or redox threshold could result in destabilization of Fe-SOC complexes, rendering previously stabilized carbon available for rapid degradation, potentially irreversibly decreasing the size of the old SOC reservoir. The destabilization of an old, persistent Fe-SOC reservoir can decrease SOC storage and ultimately increase the amount of CO2released to the atmosphere.