Assessing the impact of current and projected climates on Douglas-Fir productivity in British Columbia, Canada, using a process-based model (3-PG)

Abstract

Predicted climate change is expected to significantly affect tree growth in many areas. We used a process-based model (Physiological Principles for Predicting Growth, 3-PG) to evaluate how climatic variation might alter growth of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.) Franco and Pseudotsuga menziesii (Mirb.) Franco var. menziesii) across biogeoclimatic zones in British Columbia. The results indicate that there will be significant changes in site index (defined as the height (in metres) of dominant trees at 50 years) over this century. In the interior, a reduction in site index is likely, particularly in stands with mid-range values of site index (25-30 m), with many of the interior bioecoclimatic zones predicted to experience a gradual mean decrease in site index by up to 10%. Individual sites may decrease by as much as 40% from current values. In contrast, site index along the coast overall is predicted to increase to a maximum of 43 m by 2080. In the Coastal Western Hemlock zone, however, mean site index is likely to increase from 26 m to only 34 m. We believe that combining process-based models with fine-spatial resolution climate forecasts offers a viable approach to assess future changes in forest productivity. Résumé :On prédit que les changements climatiques auront une influence significative sur la croissance des arbres dans plusieurs régions. Nous avons utilisé un modèle de processus (Principes physiologiques pour prédire la croissance, 3-PG) pour évaluer de quelle façon les variations climatiques pourraient modifier la croissance des douglas de Menzies bleu et typique (Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.) Franco et Pseudotsuga menziesii (Mirb.) Franco var. menziesii) dans les différentes zones biogéoclimatiques en Colombie-Britannique. Les résultats indiquent qu'il y aura des changements importants de l'indice de station (défini comme la hauteur en mètres des arbres dominants à l'âge de 50 ans) au cours de ce siècle. Il est probable que l'indice de station diminue dans la zone intérieure, particulièrement dans les peuplements dont l'indice de station se situe parmi les valeurs intermédiaires (25-30 m) et on prédit que plusieurs des zones biogéoclimatiques de l'intérieur vont subir une diminution moyenne graduelle de l'indice de station pouvant atteindre 10 %. La diminution pourrait atteindre 40 % par rapport aux valeurs actuelles dans certaines stations. À l'inverse, on pré-dit que l'indice de station le long de la côte augmentera globalement jusqu'à un maximum de 43 m vers 2080. Cependant, dans la zone côtière de la pruche de l'Ouest l'indice de station augmentera probablement de 26 m à seulement 34 m. Nous croyons que la combinaison des modèles de processus et de la prédiction du climat avec une haute résolution spatiale offre une approche viable pour évaluer les changements futurs de productivité forestière.[Traduit par la Rédaction]

Potential impacts of regional climate change on site productivity of Larix olgensis plantations in northeast China

“…Coops et al (2010) found that the site index of Douglas fir in the interior varied in an opposite manner to the variation along the coast. Weiskittel et al (2011) reported that the predominant trend from 2000 to 2090 was a 0-5 m (0-30%) increase in the average site index across forests of the western part of the United States, though the site index in some areas would decrease by approximately 30%.…”

“…There are huge differences in climate variables and modeling results among these studies, indicating that the relationship between forest site productivity and climate is still uncertain to some extent. Process-based or hybrid representations of the relationship between climate and productivity are needed (Peng et al 2002, Coops et al 2010, Bravo-Oviedo et al 2010. Using spatial and climatic variables, our empirical model could explain 72.9% of the site index variation.…”

“…In the context of global warming, the effect of rising temperatures on site productivity have been examined and both positive and negative impacts have been reported (Loustau et al 2005, Ollinger et al 2008, Kellomäki et al 2008, Chiang et al 2008, Latta et al 2009, Coops et al 2010, Kirschabum et al 2012. Quantifying such effect is still challenging, because the temperature simultaneously affects ecosystem processes (photosynthesis, respiration, transpiration, allocation, decomposition, etc.).…”

“…Because of the differences in model input, climate scenario, tree species, location and scale, the outputs of the site index change are difficult to compare. When using model outputs for the site index under future climate change, caution should be taken because of the uncertainty arising from the different climate scenarios, model errors and plant ability to acclimate and adapt to climate change (Albert & Schmidt 2009, Coops et al 2010, Medlyn et al 2011. Nonetheless, models still provide useful information for adaptive management in response to climate change despite these uncertainties.…”

Linking Climate Change and Forest Ecophysiology to Project Future Trends in Tree Growth: A Review of Forest Models

“…The model does not consider canopy complexity, does not have a water balance component, and does not attempt to be a management tool, but it contains the simulation of physiological processes which have been proven good enough to produce accurate prediction for some experimental sites (Landsberg & Waring, 1997). 3-PG is becoming an increasingly popular model for forest research, due to its capacity of being used for landscape modelling by linking it to satellite observations, and its relative lower calibration requirements (Coops et al, 2010). However, the model can be very sensitive to parameters that are very difficult to measure and are not easily related to physiological data measured in the field (Rodríguez-Suárez et al, 2010).…”