Chair of Agroecology, Bayreuth Center of Ecology and Environmental Research, University of Bayreuth, Bayreuth, Germany.
Environment, Natural Resources and Desertification Research Institute, National Center for Research, Khartoum, Sudan.
Glob Chang Biol. 2021 Dec;27(24):6436-6453. doi: 10.1111/gcb.15918. Epub 2021 Oct 11.
Burning has commonly been used to increase forage production and nutrients cycling in grasslands. However, its long-term effects on soil organic carbon (SOC) and nitrogen (N) pools within the aggregates and the relation between aggregates-associated SOC and soil CO emissions need further appraisal. This study evaluated the effects of 64 years of annual burning on SOC and N dynamics compared to annual mowing and undisturbed treatments in a grassland experiment established in 1950. Soils were sampled from four depths representing the upper 30 cm layer and fractionated into macroaggregates, microaggregates and silt + clay fractions. The macroaggregates were further fractionated into three occluded fractions. The SOC in the bulk soil and aggregates were correlated to soil CO effluxes measured under field conditions. Compared to the undisturbed treatment, annual burning decreased aggregates stability, SOC and N in the upper 30 cm layer by 8%, 5% and 12%, respectively. Grassland mowing induced greater aggregates stability than burning only in the upper 5 cm. Burning also decreased SOC in the large macroaggregates (e.g., 0-5 cm) compared to mowing and the undisturbed grasslands but proportionally increased the microaggregates and their associated SOC. Soil N associated with aggregates decreased largely following grassland burning, for example, by 8.8-fold in the microaggregates within the large macroaggregates at 20-30 cm compared to the undisturbed grassland. Burning also increased soil CO emissions by 33 and 16% compared to undisturbed and mowing, respectively. The combustion of fresh C and soil organic matter by fire is likely responsible for the low soil aggregation, high SOC and N losses under burned grassland. These results suggested a direct link between grass burning and SOC losses, a key component for escalating climate change severity. Therefore, less frequent burning or a rotation of burning and mowing should be investigated for sustainable grasslands management.
燃烧通常被用于增加草原的草料产量和养分循环。然而，它对土壤有机碳（SOC）和氮（N）在团聚体中的长期影响以及与团聚体相关的 SOC 和土壤 CO 排放之间的关系仍需要进一步评估。本研究评估了与每年刈割和未扰动处理相比，在 1950 年建立的草原实验中，64 年的每年燃烧对 SOC 和 N 动态的影响。从代表上层 30cm 层的四个深度采集土壤样本，并分为大团聚体、微团聚体和粉粒+粘粒。大团聚体进一步分为三个闭塞部分。在田间条件下测量土壤 CO 通量后，将原状土壤和团聚体中的 SOC 与土壤 CO 通量进行了相关分析。与未扰动处理相比，每年燃烧使上层 30cm 层的团聚体稳定性、SOC 和 N 分别降低了 8%、5%和 12%。与燃烧相比，每年刈割仅在上层 5cm 处诱导更大的团聚体稳定性。燃烧还降低了大团聚体（例如，0-5cm）中的 SOC，与刈割和未扰动草地相比，但相应地增加了微团聚体及其相关的 SOC。与团聚体相关的土壤 N 大量减少，例如，与未扰动草地相比，在 20-30cm 处大团聚体中的微团聚体中的土壤 N 减少了 8.8 倍。与未扰动和刈割相比，燃烧分别使土壤 CO 排放增加了 33%和 16%。火灾对新鲜 C 和土壤有机质的燃烧可能是燃烧草地土壤团聚体减少、SOC 和 N 损失高的原因。这些结果表明，草地燃烧与 SOC 损失之间存在直接联系，而 SOC 损失是加剧气候变化严重程度的关键因素。因此，应研究减少燃烧频率或燃烧和刈割交替进行，以实现可持续的草地管理。
