Abstract
AbstractForest fires generate large amounts of ash and biochar, or black carbon (BC), that cover the soil surface, interacting with the soil’s constituents and its seedbank. This study concerns reproductive ecology assessments supported by molecular characterisation to improve our understanding of the effects of fire and fire residues on the germination behaviour of 12 arboreal species with a wide geographic distribution. For this purpose, we analysed the effects of three ash and one BC concentration on the germination of Acacia dealbata Link, A. longifolia (Andrews) Willd., A. mearnsii De Wild., A. melanoxylon R. Br., Pinus nigra Arnold, P. pinaster Aiton, P. radiata D. Don, P. sylvestris L., Quercus ilex L., Q. pyrenaica Willd., Q. robur L., and Q. rubra L. Each tree species was exposed to ash and BC created from its foliage or twigs (except for Q. rubra, which was exposed to ash and BC of Ulex europaeus L.). We monitored germination percentage, the T50 parameter, and tracked the development of germination over time (up to 1 yr). The BC of A. dealbata, P. pinaster, and Q. robur was analysed by pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS) to assess the molecular composition. In six species, ash inhibited the germination, while in another five species, germination was not affected by ash or by BC. In Q. rubra, ash and BC stimulated its germination. This stimulating effect of the BC on Q. rubra is likely to be related to the chemical composition of the ash and BC obtained from Ulex feedstock. The BC of U. europaeus has a very different molecular composition than the other BC samples analysed, which, together with other factors, probably allowed for its germination stimulating effects.
Highlights
Fire is and has been an important ecological and evolutionary factor in world ecosystems for millions of years, perhaps since terrestrial vegetation existed (Trabaud 1981, Pausas 2004)
From the molecular properties of the black carbon (BC) samples, the results suggested that thermal impact was strongest for the Quercus BC, followed by Pinus, Acacia, and Ulex
In the species studied of the Acacia and Pinus genera, ash and BC either do not modify germination, or they inhibit it
Summary
Fire is and has been an important ecological and evolutionary factor in world ecosystems for millions of years, perhaps since terrestrial vegetation existed (Trabaud 1981, Pausas 2004). Among the direct consequences of wildfires is the formation of ash and black carbon (BC) layers that (1) contribute to the modification of the aforementioned physical and chemical soil properties, and (2) alter germination behaviour (rate, time, etc.) of the seeds of many species (Reyes and Casal 1998). These seeds can be present in the soil’s pre-fire seedbank or can originate from the seed rain after the fire. These seeds can be present in the soil’s pre-fire seedbank or can originate from the seed rain after the fire. Kemball et al (2010) demonstrated that the type of ash influences the germination percentage of tree species, and Solaiman et al (2012) showed that the type and quantity of BC influences the germination rate
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