Souza-Alonso P, Prats S A, Merino A, Guiomar N, Guijarro M, Madrigal J
Department of Soil Science and Agricultural Chemistry, Higher Polytechnic Engineering School, University of Santiago de Compostela, 27002, Lugo, Spain.
MED - Mediterranean Institute for Agriculture, Environment and Development & CHANGE - Global Change and Sustainability Institute, Instituto de Investigação e Formação Avançada, Universidade de Évora, Pólo da Mitra, Ap. 94, 7006-554, Évora, Portugal.
Sci Rep. 2024 Sep 17;14(1):21718. doi: 10.1038/s41598-024-72361-8.
Soil phosphorus (P), which is essential for ecosystem functioning, undergoes notable changes after fire. However, the extent to which fire characteristics affect P dynamics remains largely unknown. This study investigated the impact of type of fire (prescribed burning and natural wildfires) of different levels of severity on P dynamics in Mediterranean soils. Soil P concentrations in the organic layers were strongly affected by fire severity but not fire type. Low severity fire did not have any observable effect, while moderate fire increased soil P levels by 62% and high severity decreased soil P concentration by 19%. After one year, the soil P concentration remained unchanged in the low severity fires, while rather complex recovery was observed after moderate and high severity fires. In the mineral layers, P concentration was reduced (by 25%) immediately after the fires and maintained for one year (at 42%). P-NMR spectroscopy revealed almost complete post-fire mineralization of organic P forms (mono- and diesters), large increases in inorganic orthophosphate and a decrease in the organic:inorganic P ratio (P:P). After one year, di-esters and orthophosphate recovered to pre-fire levels at all sites, except those where parent material composition (high pH and Fe concentration) had an enduring effect on orthophosphate retention, and thus, on the total soil P. We showed that fire severity and soil pH (and hence, soil mineralogy) played an essential role in soil P dynamics. These findings are important for reliable assessment of the effects of fire on soil P conservation and for improving the understanding the impact of prescribed burning.
土壤磷（P）对生态系统功能至关重要，火灾后会发生显著变化。然而，火灾特征对磷动态的影响程度在很大程度上仍不为人知。本研究调查了不同严重程度的火灾类型（规定燃烧和自然野火）对地中海土壤中磷动态的影响。有机层中的土壤磷浓度受火灾严重程度的强烈影响，但不受火灾类型的影响。低严重程度火灾没有任何可观察到的影响，而中等严重程度火灾使土壤磷水平增加了62%，高严重程度火灾使土壤磷浓度降低了19%。一年后，低严重程度火灾中的土壤磷浓度保持不变，而中等和高严重程度火灾后观察到相当复杂的恢复情况。在矿质层中，火灾后磷浓度立即降低（降低了25%）并维持了一年（为42%）。磷核磁共振光谱显示，火灾后有机磷形态（单酯和二酯）几乎完全矿化，无机正磷酸盐大幅增加，有机磷与无机磷的比例（P:P）降低。一年后，除了母质组成（高pH值和铁浓度）对正磷酸盐保留并因此对土壤总磷有持久影响的地点外，所有地点的二酯和正磷酸盐都恢复到了火灾前的水平。我们表明，火灾严重程度和土壤pH值（以及土壤矿物学）在土壤磷动态中起着至关重要的作用。这些发现对于可靠评估火灾对土壤磷保护的影响以及增进对规定燃烧影响的理解具有重要意义。
