Comparing and evaluating process-based ecosystem model predictions of carbon and water fluxes in major European forest biomes

Morales P., Sykes M.T., Prentice I.C., Smith P., Smith B., Bugmann H., Zierl B., Friedlingstein P., Viovy N., Sabaté S., Sánchez A., Pla E., Gracia C.A., 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.
Enllaç
Doi: 10.1111/j.1365-2486.2005.01036.x

Resum:

Process-based models can be classified into: (a) terrestrial biogeochemical models (TBMs), which simulate fluxes of carbon, water and nitrogen coupled within terrestrial ecosystems, and (b) dynamic global vegetation models (DGVMs), which further couple these processes interactively with changes in slow ecosystem processes depending on resource competition, establishment, growth and mortality of different vegetation types. In this study, four models - RHESSys, GOTILWA +, LPJ-GUESS and ORCHIDEE - representing both modelling approaches were compared and evaluated against benchmarks provided by eddy-covariance measurements of carbon and water fluxes at 15 forest sites within the EUROFLUX project. Overall, model-measurement agreement varied greatly among sites. Both modelling approaches have somewhat different strengths, but there was no model among those tested that universally performed well on the two variables evaluated. Small biases and errors suggest that ORCHIDEE and GOTILWA + performed better in simulating carbon fluxes while LPJ-GUESS and RHESSys did a better job in simulating water fluxes. In general, the models can be considered as useful tools for studies of climate change impacts on carbon and water cycling in forests. However, the various sources of variation among models simulations and between models simulations and observed data described in this study place some constraints on the results and to some extent reduce their reliability. For example, at most sites in the Mediterranean region all models generally performed poorly most likely because of problems in the representation of water stress effects on both carbon uptake by photosynthesis and carbon release by heterotrophic respiration (Rh). The use of flux data as a means of assessing key processes in models of this type is an important approach to improving model performance. Our results show that the models have value but that further model development is necessary with regard to the representation of the some of the key ecosystem processes. © 2005 Blackwell Publishing Ltd.

Llegeix més

El cambio climático y la reducción de la reserva de agua en el bosque mediterráneo.

Gracia C, Sabaté S, Sánchez A (2002) El cambio climático y la reducción de la reserva de agua en el bosque mediterráneo. Ecosistemas 2002/2 (URL: http//www.aeet.org/ecosistemas/022/investigacion4.htm)

Evaluation of six process-based forest growth models using eddy-covariance measurements of CO2 and H2O fluxes at six forest sites in Europe.

Kramer K, Leinonen I, Bartelink HH, Berbigier P, Borghetti M, Bernhofer Ch, Cienciala E, Dolman AJ, Froer O, Gracia C, Granier A, Grünwald T, Hari P,Jans W, Kellomäki S, Loustau D, Magnani F, Markkanen T, Mohren GMJ, Sabaté S, Sánchez A et al (2002) Evaluation of six process-based forest growth models using eddy-covariance measurements of CO2 and H2O fluxes at six forest sites in Europe. Global Change Biology 8:213-230.

Likely effects of climate change on growth of Quercus ilex, Pinus halepensis, Pinus pinaster, Pinus sylvestris and Fagus sylvatica forests in the Mediterranean region

Sabaté S., Gracia C.A., Sánchez A. (2002) Likely effects of climate change on growth of Quercus ilex, Pinus halepensis, Pinus pinaster, Pinus sylvestris and Fagus sylvatica forests in the Mediterranean region. Forest Ecology and Management. 162: 23-37.
Enllaç
Doi: 10.1016/S0378-1127(02)00048-8

Resum:

Mediterranean forest growth is constrained by drought and high temperatures during summer. Effects of climate change on these forests depend on how changes in water availability and temperature will take place. A process-based forest growth model, growth of trees is limited by water in the Mediterranean (GOTILWA+), was applied in the Mediterranean region on Quercus ilex, Pinus halepensis, P. pinaster, P. sylvestris and Fagus sylvatica forests. The effects of climate change on growth were analysed, as well as the effect of thinning cycle length, combined with the assumption of different soil depths. Thinning cycle lengths was included because it can affect the response of stands to climatic conditions, and soil depth because this is positively related to soil water-holding capacity and consequently may change the effects of drought. The simulation period covered 140 years (1961-2100). Model results show that leaf area index (LAI) may increase, favoured by the increase of atmospheric CO2, particularly at sites where rainfall is relatively high and climatic conditions not too warm. The predicted increase in temperature significantly influenced mean leaf life span (MLLS). MLLS of F. sylvatica would increase with climate change, implying a longer growing period. Conversely, MLLS of evergreen species would be reduced, accelerating leaf turnover. In general, our results showed a higher production promoted by projected climate change in response to the increasing atmospheric CO2 concentration and rainfall in the region. Temperature increase would have different consequences for production. In F. sylvatica, the longer growing period would promote higher production, particularly when water is not limiting. On the other hand, Q. ilex and Pinus species would expend more carbon in maintaining and producing leaves to replace those lost in increased turnover rate. As expected, access of roots to deeper soil results in an increased final wood yield (FWY) due to an improved water balance that promotes higher transpiration, photosynthesis and growth. In general, the shorter the harvest cycle, the larger the FWY, because of less tree mortality between harvesting events. According to our results, temperature and rainfall may constrain growth during certain periods but if rainfall increases in the future, a positive effect on growth is likely. © 2002 Elsevier Science B.V. All rights reserved.

Llegeix més

Presente y futuro del bosque mediterráneo: balance de carbono, gestión forestal y cambio global.

Gracia C, Sabaté S, López B, Sánchez A (2001) Presente y futuro del bosque mediterráneo: balance de carbono, gestión forestal y cambio global. In Zamora R, Pugnaire FI (eds) Ecosistemas mediterráneos. Análisis funcional. Consejo Superior de Investigaciones Científicas y Asociación Española de Ecología Terrestre, Granada, pp. 351-372.