title: Does prescribed burning affect leaf secondary metabolites in pine stands?
abstract: Prescribed burning (PB) is gaining popularity as a low-cost forest protection measure that efficiently reduces fuel build-up, but its effects on tree health and growth are poorly understood. Here, we evaluated the impact of PB on plant defenses in Mediterranean pine forests (Pinus halepensis and P. nigra ssp. laricio). These chemical defenses were estimated based on needle secondary metabolites (terpenes and phenolics including flavonoids) and discussed in terms of chlorophyll fluorescence and soil nutrients. Three treatments were applied: absence of burning (control plots); single burns (plots burned once); and repeated burns (plots burned twice). For single burns, we also explored changes over time. In P. laricio, PB tended to trigger only minor modifications consisting exclusively of short-lived increases (observed within 3 months after PB) in flavonoid index, possibly due to the leaf temperature increase during PB. In P. halepensis, PB had detrimental effects on physiological performance, consisting of (i) significant decreases in actual PSII efficiency (ΦPSII) in light-adapted conditions after repeated PB, and (ii) short-lived decreases in variable-to-maximum fluorescence ratio (Fv/Fm) after single PB, indicating that PB actually stressed P. halepensis trees. Repeated PB also promoted terpene-like metabolite production, which increased 2 to 3-fold compared to control trees. Correlations between terpene metabolites and soil chemistry were found. These results suggest that PB impacts needle secondary metabolism both directly (via a temperature impact) and indirectly (via soil nutrients), and that these impacts vary according to species/site location, frequency and time elapsed since last fire. Our findings are discussed with regard to the use of PB as a forest management technique and its consequences on plant investment in chemical defenses.
authors.affiliation: ISA (Institut Sophia Agrobiotech: UMR Université de Nice - INRA - CNRS). Centre INRA-PACA Sophia Antipolis, 400 Rte des Chappes, 06903, Sophia-Antipolis Cedex, France.
authors.forename: A V
authors.initials: AV
authors.lastname: Lavoir
authors.forename: E
authors.initials: E
authors.lastname: Ormeño
authors.forename: V
authors.initials: V
authors.lastname: Pasqualini
authors.forename: L
authors.initials: L
authors.lastname: Ferrat
authors.forename: S
authors.initials: S
authors.lastname: Greff
authors.forename: C
authors.initials: C
authors.lastname: Lecareux
authors.forename: B
authors.initials: B
authors.lastname: Vila
authors.forename: J P
authors.initials: JP
authors.lastname: Mévy
authors.forename: C
authors.initials: C
authors.lastname: Fernandez
mesh_terms: D003247:Conservation of Natural Resources / Q000379:methods*; D005390:Fires; D028223:Pinus / Q000254:growth & development / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism*; D064210:Secondary Metabolism; D012987:Soil / Q000737:chemistry; D013729:Terpenes / Q000378:metabolism; D014197:Trees / Q000254:growth & development
chemical_list: D012987:Soil; D013729:Terpenes