Importance of macroaggregate dynamics in controlling soil carbon stabilization: short-term effects of physical disturbance induced by dry-wet cycles
Importance of macroaggregate dynamics in controlling soil carbon stabilization: short-term effects of physical disturbance induced by dry-wet cycles
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DOI：
10.1016/s0038-0717(01)00153-5
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发表时间：
2001-12-01
影响因子：
9.7
通讯作者：
Merckx, R
中科院分区：
文献类型：
--
作者：
Denef, K;Six, J;Merckx, R
团聚体对土壤有机质的物理保护被认为是土壤碳稳定的重要机制。在这项研究中，我们评估了干燥和潮湿对大团聚体形成和降解(即大团聚体周转)、大团聚体内微团聚体形成和与团聚体相关的碳动态之间的相互关系的影响。用干湿循环模拟了耕作引起的土壤团聚体破坏效应之一。从长期免耕(NT)和常规耕作(CT)田间试验建立的概念模型随后被用来解释我们的结果。从连续耕作的焊接粉壤土(Aridic Paleustoll)中采集了250微米的风干土样。将样品与C-13标记的小麦混合，培养74天。一组土壤样本接受四次DW循环，而另一组保持田间容量(对照)。在第14、44和74天，在大的大团聚体(>；2000 um)中分离到水稳定的微团聚体(53-250um)。在两个DW循环(第44天)后，分离和分析了微团聚体间和微团聚体内颗粒物有机质(POM)组分的总C和小麦C。我们观察到DW大团聚体中水稳定性微团聚体的比例明显低于对照大团聚体(占大团聚体重量的9%和13%)。同时，DW大团聚体的微团聚体内POM-C浓度显著低于对照大团聚体。DW和对照微团聚体内POM-C的这种差异对于天然微团聚体POM-C(0.73比1.03 g kg(-1)大团聚体)(P<；0.05)比小麦来源微团聚体内POM-C(41对49 mg C kg(-1)大团聚体)(P<；0.1)更显著。经过两次干湿循环(第44天)，干燥和润湿不再造成大团聚体的破坏。从第44天到74天，DW大团聚体中微团聚体的比例和微团聚体内POM-C的浓度都显著增加。我们的结论是，大团聚体内新的微团聚体中的POM-C受到增强的大团聚体周转的抑制，而大团聚体的周转仅在短期内通过干燥和潮湿来增强。此外，我们认为，除了大团聚体破裂时释放出总的(即天然和小麦来源的)POM外，干燥和潮湿还会导致大团聚体的快速重组，优先掺入小麦来源的POM，从而导致DW大团聚体中天然POM-C的相对下降。(C)爱思唯尔科学有限公司出版的2001年。
Physical protection of soil organic matter by aggregates is considered to be an important mechanism for soil carbon stabilization. In this study, we evaluated the effect of drying and wetting on the interrelationships between macroaggregate formation and degradation (i.e. macroaggregate turnover), microaggregate formation within macroaggregates, and aggregate-associated carbon dynamics. Dry-wet (DW) cycles were used to simulate one of the soil aggregate disruptive effects induced by tillage. A conceptual model developed from long-term no-till (NT) and conventional tilled (CT) field experiments was then used to interpret our results. Sieved (250 mum) air-dried soil samples were taken from Weld silt loam soil (Aridic Paleustoll) that had been cultivated continuously. The samples were mixed with C-13-labeled wheat and incubated for 74 days. One set of soil samples was subjected to four DW cycles, while the other set was kept at field capacity (control). At days 14, 44 and 74, water-stable microaggregates (53-250 mum) held within large macroaggregates (> 2000 mum) were isolated. Inter-and intra-microaggregate particulate organic matter (POM) fractions were separated and analyzed for total and wheat-derived C. After two DW cycles (day 44). we observed a significantly lower proportion of water-stable microaggregates within DW macroaggregates compared to control macroaggregates (9 versus 13% of the macroaggregate weight). Simultaneously, DW macroaggregates had significantly lower intra-microaggregate POM-C concentrations compared to control macroaggregates. This difference in intra-microaggregate POM-C between DW and control was more significant for native intra-microaggregate POM-C (0.73 versus 1.03 g kg(-1) macroaggregates) (P < 0.05) than for wheat-derived intra-microaggregate POM-C (41 versus 49 mg C kg(-1) macroaggregates) (P < 0.1). After two DW cycles (day 44), drying and wetting no longer caused macroaggregate disruption. From day 44 to day 74, both the proportion of microaggregates and the concentration of intra-microaggregate POM-C significantly increased in DW macroaggregates. We conclude that POM-C in new microaggregates within macroaggregates is inhibited by an enhanced macroaggregate turnover, which is only in the short term enhanced by drying and wetting. Furthermore, we suggest that besides a release of total (i.e. native and wheat-derived) POM upon macroaggregate breakdown, drying and wetting induced a fast reformation of macroaggregates with preferential incorporation of wheat-derived POM, resulting in a relative decline of native POM-C in DW macroaggregates. (C) 2001 Published by Elsevier Science Ltd.