In order to support the development of optimized adaptive forest management scenarios for the Poblet area, a new forest management decision support tool was constructed. This system integrates the dynamic forest simulation model GOTILWA+, based on physiological processes controlled by climatic and edaphic factors and able to predict forest development under different climate scenarios and management options with a Particle Swarm optimization algorithm that supports in rapidly finding the optimal combination of decision variables (the number, timing and intensity of thinning and the rotation length) to maximise a given management objective under a certain climate – management scenario. Two climate scenarios were applied: current climate and Climate Change (A1FI scenario, IPCC) using daily climate data. Three different management objectives have been tested: (1) timber profitability (soil expectation value, SEV) (€/ha), (2) wood biomass production (WBP) (Mg/ha/year), (3) stand-level water use (WU) (m3 of water/m3 wood produced) and a fourth objective, crucial for the management of Mediterranean forests, a composite index of Fire risk and Damage. The decision variables (i.e. the variables to optimize) are the time between thinnings and the basal area remaining in the forest after each particular thinning (as a measure of the thinning intensity). The age at which the last thinning takes place defines the rotation length. Other variables such as the time of the tending or preparatory thinning, the remaining density of trees after tending, the threshold for DBH size of these remaining trees, as well as the threshold size of the trees cut during the commercial thinning have been kept as constant values. Further exploration of the effect of the changing values of these variables on the final optimized results is to be explored in future steps. The results mentioned in these pages have been obtained with a constant density of 1200 trees/ha after tending with DBH >= 7 cm. The tending has been always applied at the age of 12 years. When the density of trees with a DBH >=7 cm at age 12 is lower than 1200 trees/ha, the remaining density is reduced to this density in order to keep trees with a DBH >= 7 cm. Analogously, at each commercial thinning intervention, all the trees cut have to be trees equal or bigger than 10 cm in DBH. This is a main commercial restriction which has important effects on the final results. An important effort was also undertaken to construct user-friendly interfaces that facilitate the selection of climate scenarios, management objectives, site variables, economic parameters, etc. to the user. These interfaces also provide visual and summarized information on the optimal forest management strategies for the selected variables. It has become a user friendly but rather complex tool integrating in a unique way a mechanistic model and a management optimization algorithm. We do not expect this tool to be used by field managers, but it is an interesting tool for scientific analysis, advanced forestry and ecology students, or consultants preparing forest management plans.
The outcomes of the decision support system were confronted with expert knowledge of the field managers, and with experiences and published results from decades of climate change related research in Poblet area, conducted by CREAF, UB and other institutes. Conversion experiments in holm oak coppice towards high forest showed for example that thinning improves vitality and growth under drought stress.
Some related papers:
Peñuelas J, Gracia C, Filella I, Jump A, Carnicer J, Coll M, Lloret F, Curiel J, Estiarte M, Rutishauser T, Ogaya R, LLusiá J and Sardans J. 2010. Intégration des effets du changement climatique sur les forêts méditerranéennes: observation, expérimentation, modélisation et gestion p. 351. Introducing the climate change effects on Mediterranean forest ecosystems: observation, experimentation, simulation and management p. 357 Forêt Méditerranéenne XXXI, nº 4, december 2010. ISSN 0245-484XKeenan T., Sabate S. and Gracia C. 2010. Soil Water Stress and coupled photosynthesis-conductance models: Bridging the gap between conflicting reports on the relative roles of stomatal, mesophyll conductance and biochemical limitations to photosynthesis. Agricultural and Forest Meteorology. 4203 11 pp.
Lopez B., Gracia C.,Sabate S. and Keenan T. 2009. Assessing the resilience of Mediterranean holm oaks to disturbances using selective thinning. Acta Oecologica, 35 pp:849-854
Keenan T., Niinemets U., Sabaté S., Gracia C., Peñuelas J. 2009. Seasonality of monoterpene emission potentials in Quercus ilex and Pinus pinea: Implications for regional voc emission modeling. Journal of Geophysical Resarch, 114. 11 pp.
Keenan T., Sabaté S., Gracia C. 2009. The importance of mesophyll conductance in regulating forest ecosystem productivity during drought periods. Global Change Biology. 16 pp.
Cotillas M., Sabaté S., Gracia C., Espelta J. 2009. Growth response of mixed mediterranean oak coppices to rainfall reduction. Could selective thinning have any influence on it? Forest Ecology and Management, 258. 1677-1683.
GRACIA C. 2008. Water yield depends on the water and carbon trade-off in forest ecosystems. EXPO-World Zaragoza.
López B., Holmgren M., Sabate S., Gracia C. 2008. Estimating annual rainfall threshold for estabalishment of tree species in water-limited ecosystems using tree-ring data. Journal of Arid Environments, 72. 602-611.
GRACIA C., SABATE S, Keenan T., 2007 Carbon pools in Mediterranean forests: comparing eddy covariance and GOTILWA+ model results. At Carbon dynamics in natural beech forests, Slovenian Forestry Institute (SFI), Ljubljana, Slovenia.
Schröter D., Cramer W., Leemans R., Prentice I.C., Araujo M., Arnell N., Bondeau A., Bugmann H., Carter T., Gracia C., Vega-Leinert A.d.l., Erhard M., Ewert F., Glendining M., House J., Kankaanpaä S., Klein R., Lavorel S., Lindner M., Metzger M., Meyer J., Mitchell T., Reginster I., Rounsevell M., Sabate S., Sitch S., Smith B., Smith J., Smith P., Sykes M., Thonicke K., Thuiller W., Tuck G., Zahele S., Zierl B. 2005. Ecosystem service supply and vulnerability to global change in Europe. Science, . 10 pp.
Morales P., Sykes M.T., Prentice I., Smith P., Smith B., Bugmanns H., Zierl B., friedlingstein P., Viovy N., Sabate S., Sánchez A., Pla E., Gracia C., Sitch S., Arneth A., Ogee J. 2005. Comparing and evaluating process-based ecosystem model predictions of carbon and water fluxes in major European forest biomes. Global Change Biology, 11. 2211-2233.
Gracia C., Pla E., Sánchez A., Sabaté S. 2004. Gotilwa+: Un modelo de crecimiento forestal basado en procesos ecofisiológicos. Cuad. Soc. Esp. Cienc. For., ?
Sabaté S., Gracia C., Pla E., Sánchez A., Vayreda J. 2004. Aplicación del modelo GOTILWA+ al análisis de los efectos del cambio climático y la gestión forestal en el balance de carbono y agua en los bosques. Cuad. Soc. Esp. Cienc. For.