Forest Sciences Centre of Catalonia, CEMFOR-CTFC, Ctra St Llorenç de Morunys, km 2, 25280 Solsona, Spain.
Aix Marseille Univ, Univ Avignon, CNRS, IRD, IMBE, Marseille, France.
Tree Physiol. 2017 Dec 1;37(12):1622-1636. doi: 10.1093/treephys/tpx069.
Prescribed burning is used to reduce fuel hazard but underburning can damage standing trees. The effect of burning on needle terpene storage, a proxy for secondary metabolism, in fire-damaged pines is poorly understood despite the protection terpenes confer against biotic and abiotic stressors. We investigated variation in needle terpene storage after burning in three Mediterranean pine species featuring different adaptations to fire regimes. In two pure-stands of Pinus halepensis Mill. and two mixed-stands of Pinus sylvestris L. and Pinus nigra ssp. salzmanni (Dunal) Franco, we compared 24 h and 1 year post-burning concentrations with pre-burning concentrations in 20 trees per species, and evaluated the relative contribution of tree fire severity and physiological condition (δ13C and N concentration) on temporal terpene dynamics (for mono- sesqui- and diterpenes). Twenty-four hours post-burning, monoterpene concentrations were slightly higher in P. halepensis than at pre-burning, while values were similar in P. sylvestris. Differently, in the more fire-resistant P. nigra monoterpene concentrations were lower at 24 h, compared with pre-burning. One year post-burning, concentrations were always lower compared with pre- or 24 h post-burning, regardless of the terpene group. Mono- and sesquiterpene variations were negatively related to pre-burning δ13C, while diterpene variations were associated with fire-induced changes in needle δ13C and N concentration. At both post-burning times, mono- and diterpene concentrations increased significantly with crown scorch volume in all species. Differences in post-burning terpene contents as a function of the pine species' sensitivity to fire suggest that terpenic metabolites could have adaptive importance in fire-prone ecosystems in terms of flammability or defence against biotic agents post-burning. One year post-burning, our results suggest that in a context of fire-induced resource availability, pines likely prioritize primary rather than secondary metabolism. Overall, this study contributes to the assessment of the direct and indirect effects of fire on pine terpene storage, providing valuable information about their vulnerability to biotic and abiotic stressors throughout time.
规定的燃烧用于减少燃料的危险，但不完全燃烧会损坏立木。尽管萜类化合物可以为生物和非生物胁迫提供保护，但燃烧对受损松树中针叶萜烯储存（次生代谢的替代物）的影响知之甚少。我们研究了在三种具有不同火灾模式适应能力的地中海松树中，燃烧后针叶萜烯储存的变化。在两种纯林的地中海柏木（Pinus halepensis Mill.）和两种混合林的欧洲赤松（Pinus sylvestris L.）和欧洲黑松（Pinus nigra ssp. salzmanni （Dunal） Franco）中，我们比较了 20 棵树每一种物种在燃烧后 24 小时和 1 年时的浓度与燃烧前的浓度，并评估了树火严重程度和生理状况（δ13C 和 N 浓度）对时间萜烯动态（单萜、倍半萜和二萜）的相对贡献。燃烧后 24 小时，地中海柏木的单萜浓度略高于燃烧前，而欧洲赤松的浓度则相似。相反，在更耐火的欧洲黑松中，24 小时的单萜浓度则低于燃烧前。1 年后，无论萜烯组如何，浓度都始终低于燃烧前或 24 小时后。在所有物种中，单萜和倍半萜的变化与燃烧前的 δ13C 呈负相关，而二萜的变化与燃烧后针叶 δ13C 和 N 浓度的变化有关。在两个燃烧后时间点，所有物种的冠层灼伤体积都与单萜和二萜浓度呈显著正相关。不同松树物种对火灾敏感性的燃烧后萜烯含量差异表明，萜类代谢物在易燃或燃烧后防御生物因子方面可能对火灾频发生态系统具有适应性重要性。1 年后，我们的结果表明，在资源可用性因火灾而引起的情况下，松树可能更倾向于优先进行初级代谢，而不是次级代谢。总的来说，这项研究有助于评估火灾对松树萜烯储存的直接和间接影响，为它们在时间上对生物和非生物胁迫的脆弱性提供了有价值的信息。
