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• W53238785 abstract "Els incendis forestals han esdevingut una de les principals problematiques ambientals a larea mediterrania. En les darreres decades, el nombre de focs i darea cremada han augmentat notablement. A mes dels factors de risc associats a les condicions climatologiques i topografiques, el comportament del foc ve condicionat per lestructura de la vegetacio i, per tant, dels patrons successionals dacumulacio de fitomassa aeria. La tesi descriu el proces de desenvolupament i aplicacio dun model semimecanistic de la dinamica de combustible en ecosistemes arbustius mediterranis. Aquest proces ha constat de les seguents fases:Revisio de treballs previsSha dut a terme una revisio dels estudis que aborden la dinamica de diferents formacions arbustives presents a larea mediterrania iberica i, amb aquesta, de les principals caracteristiques estructurals de la vegetacio relacionades amb el risc dincendi. La taxa d'acumulacio de combustible varia d'acord amb diferents factors vinculats al creixement de la vegetacio. Malgrat aixo, es poden establir uns patrons comuns per a diferents formacions arbustives mediterranies. Aquesta compilacio ha posat de manifest que un indret cremat pot tenir un elevat risc dincendi en un temps relativament curt, pero molt variable, despres del foc. Aquest rang de temps se situa en 5-10 anys per a molts matollars, i de 1-2 anys per als herbassars densos. Aquesta informacio, que es escassa per aquest tipus de vegetacio i en aquesta area destudi, es una eina valuosa en el camp de la prediccio del comportament del foc i de la gestio preventiva del risc.Estudi experimental en brolles mediterraniesSha estudiat la dinamica de combustible en brolles mediterranies a partir duna cronosequencia de tres incendis de 3, 10 i 17 anys al Baix Camp (Tarragona). Sha recol·lectat la biomassa aeria en 8 quadrats de 9 m2 per incendi, distribuits en vessants nord i sud. Al laboratori shan determinat diferents parametres estructurals (mort/viu i classes de gruixaria) i funcionals (produccio de brots) de la comunitat. Els resultats han mostrat les tendencies principals en la dinamica daquestes comunitats en relacio al risc dincendi. No shan observat diferencies significatives entre les carregues de combustible recollides en diferents orientacions per a un mateix incendi. La taxa dacumulacio de combustible es mes elevada en els periodes inicials de la successio i satenua en els periodes posteriors, coincidint amb la presencia dun nombre major despecies arbustives pero amb clara dominancia del garric (Quercus coccifera). Tambe sha observat una estabilitzacio de la biomassa foliar de la comunitat. Lincrement de les diferents fraccions de material arbustiu viu i mort i del combustible herbaci condiciona laugment del risc dincendi amb ledat regenerativa de la brolla. Finalment, sha utilitzat el sistema BEHAVE de simulacio de propagacio dincendis forestals per avaluar quantitativament el risc associat a cada escenari regeneratiu.Desenvolupament, calibratge i validacio dun model de la dinamica de combustible en ecosistemes arbustius mediterranisLa gestio del foc a larea mediterrania requereix de noves eines metodologiques que abordin la complexitat de funcionament dels sistemes i la seva aplicabilitat. Aquest apartat descriu laproximacio aportada pel modul arbustiu de GOTILWA+, un model funcional que simula el creixement duna coberta arbustiva a partir de processos de base i que vincula les seves sortides a variables estructurals rellevants en la gestio del foc. El model incorpora els plantejaments de base del model forestal GOTILWA+ que es fonamenten en els fluxos daigua i carboni en el sistema. La descripcio conceptual del model es complementa amb una analisi de sensibilitat i un exercici de calibratge. Posteriorment, shan desenvolupat un seguit dexercicis de validacio del model a partir de dades d'estudis de camp en garrigues a Catalunya i al Baix Llenguadoc. El model reprodueix de forma realista la dinamica successional de la biomassa vegetal, segons els objectius del model (base mecanistica i aplicabilitat de les sortides) i atenent al nivell de simplificacions assumides.Aplicacio en escenaris de canvi climaticLa major part dels models de circulacio atmosferica GCMs prediuen un augment de la temperatura i una disminucio de la precipitacio a larea mediterrania en aquest segle, tot i la incertesa en la prediccio del regim futur de precipitacions. Els ecosistemes mediterranis es poden veure seriosament afectats per aquests canvis pel que fa al seu funcionament, estructura i distribucio. A larea mediterrania, els ecosistemes arbustius presenten un especial interes perque han protagonitzat una notable expansio en les darreres decades a causa del creixent impacte del foc i dels canvis dusos del sol. A fi davaluar les respostes daquests ecosistemes a diferents escenaris de canvi climatic shan dissenyat un seguit dexperiments de simulacio amb el modul arbustiu de GOTILWA+. El model sha fet correr sota diferents escenaris de GCMs generats a partir de les darreres prediccions demissions de lIPCC. Els resultats apunten cap a una disminucio de la disponibilitat daigua al sol i a un creixement notable de la necromassa i el combustible fi en aquest tipus de comunitats. Aquestes tendencies, en cas de confirmar-se, podrien tenir uns efectes evidents en el regim de pertorbacions.--------------------------------------------------Wildland fires are one of the most important environmental problems in Mediterranean regions. In the last decades, the number of fires and burnt surface has increased remarkably. Phytomass successional patterns determine structural characteristics of the vegetation and, hence, fire risk. This thesis describes the modelling process of the fuel dynamics in Mediterranean shrublands. This process involves the following phases:A review of previous studiesThis chapter reviews studies on fuel dynamics in different Mediterranean shrublands, specially located in Iberian coastal area. The fuel accumulation rate varies depending on different factors involved in vegetation growth. In spite of this, it is possible to establish common patterns for different Mediterranean vegetation-types. This compilation remarks that a burned place shows a high fire risk in a relatively short time after fire. This time lapse is 5-10 years for shrublands and 1-2 years for grasslands. This information, which is scarce for this kind of vegetation in the study area, is useful for fire risk management and fire behaviour prediction.An experimental study of the successional fuel dynamics in a Mediterranean shrublandSuccessional changes of vegetation structural properties related to fire behaviour in a Mediterranean shrubland were studied through a wildfire chronosequence, which comprises fires of 3, 10 and 17 years of regenerative age in southern Catalonia. Aerial biomass was collected from 8 plots of 9 m2 for each fire. Plots were located on south- and north-facing slopes. Laboratory processing of plant material allowed us to determine structural (diameter classes and dead to live ratio) and functional (leaves and twigs production) community parameters. No significant differences between fuel loads in opposite slopes for the same fire were found. The fuel accumulation rate was higher in the early successional stages than in the later ones. Dominance of kermes oak (Quercus coccifera) in mature successional stages was also observed. Leaves biomass reaches a steady state in the intermediate successional period, earlier than total biomass. The increase in the different components of fuel complex (fine materials and dead fuel) determines the increase of fire hazard with the regenerative age of the shrubland. Finally, the BEHAVE fire simulation system has been used to evaluate, in a quantitative way, the fire risk related to fuel dynamics.Mediterranean shrublands dynamics modellingFire management in the Mediterranean area requires of new methodological tools that link the functional system complexity and their applicability. This paper describes the approach contributed by the shrubland module of GOTILWA+, a functional model that simulates the growth of a shrubland cover from basic processes and that tie model outputs to relevant structural variables in fuel management. The model incorporates GOTILWA+ forest model layouts, which are based on ecosystem water and carbon fluxes. The model conceptual framework description is complemented by sensitivity analysis and a calibration exercise. The last phase constitutes a validation exercise using field data from studies in garrigues dominated by Quercus coccifera (kermes oak) in Catalonia and southern France. The model is able to reproduce realistically the successional dynamics of plant biomass according to the model purposes (mechanistic based framework and output applicability) and considering the level of assumed simplifications.A model application: climatic change and Mediterranean shrublandsMost atmospheric Global Circulation Models GCMs predict a temperature increase and a precipitation decrease in the Mediterranean area during this century, though predictions of future precipitation regimes are uncertain. Mediterranean ecosystems would be seriously affected by these changes at functional, structural and distributional levels. Shrubland ecosystems are significant components of the Mediterranean landscapes. A set of simulation experiments with the GOTILWA+ shrubland module were designed to evaluate ecosystem responses to different GCMs climate change scenarios derived from the last IPCC emission scenarios. Results predict a decrease in soil water availability and an increase in fine fuel growth and standing necromass. These structural changes would affect the future disturbance regime." @default.
• W53238785 created "2016-06-24" @default.
• W53238785 creator A5084307922 @default.
• W53238785 date "2002-12-04" @default.
• W53238785 modified "2023-09-24" @default.
• W53238785 title "Modelització de la dinàmica de combustible en ecosistemes arbustius mediterranis" @default.
• W53238785 hasPublicationYear "2002" @default.
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