Woody biomass production lags stem-girth increase by over one month in coniferous forests

Henry E. Cuny and Cyrille B. K. Rathgeber and David Frank and Patrick Fonti and Harri Mäkinen and Peter Prislan and Sergio Rossi and Edurne Martinez del Castillo and Filipe Campelo and Hanuš Vavrčík and Jesus Julio Camarero and Marina V. Bryukhanova and Tuula Jyske and Jožica Gričar and Vladimír Gryc and Martin De Luis and Joana Vieira and Katarina Čufar and Alexander V. Kirdyanov and Walter Oberhuber and Vaclav Treml and Jian-Guo Huang and Li Xiaoxia and Irene Swidrak and Annie Deslauriers and Eryuan Liang and Pekka Nöjd and Andreas Gruber and Cristina Nabais and Hubert Morin and Cornelia Krause and Gregory King and Meriem Fournier (2015) Woody biomass production lags stem-girth increase by over one month in coniferous forests. Nature Plants, 1 . pp. 1-6. ISSN 2055-0278

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Abstract

Wood is the main terrestrial biotic reservoir for long-term carbon sequestration, and its formation in trees consumes around 15% of anthropogenic carbon dioxide emissions each year. However, the seasonal dynamics of woody biomass production cannot be quantified from eddy covariance or satellite observations. As such, our understanding of this key carbon cycle component, and its sensitivity to climate, remains limited. Here, we present high-resolution cellular based measurements of wood formation dynamics in three coniferous forest sites in northeastern France, performed over a period of 3 years. We show that stem woody biomass production lags behind stem-girth increase by over 1 month. We also analyse more general phenological observations of xylem tissue formation in Northern Hemisphere forests and find similar time lags in boreal, temperate, subalpine and Mediterranean forests. These time lags question the extension of the equivalence between stem size increase and woody biomass production to intra-annual time scales. They also suggest that these two growth processes exhibit differential sensitivities to local environmental conditions. Indeed, in the well-watered French sites the seasonal dynamics of stem-girth increase matched the photoperiod cycle, whereas those of woody biomass production closely followed the seasonal course of temperature. We suggest that forecasted changes in the annual cycle of climatic factors may shift the phase timing of stem size increase and woody biomass production in the future.

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