Biology subjects

Piedallu, C.

Publications and source records attributed to Piedallu, C..

2 recordsLinked to original sources

bioRxiv2024

Turning point in forest productivity revealed from 40 years of national forest inventory data

Aim: Global changes, such as changing climate or disruption in biogeochemical cycles, are affecting forest productivity worldwide. Trends in productivity are depending on the focal spatial scale and on the considered time window, stable trends at large spatial scale can mask divergence at smaller scale while short time windows limit the capacity to reveal non-linear trends such as turning points. Capitalizing on 40 years of national forest inventory data from more than 100 tree species we explored trends in forest productivity at the regional level across 4 biogeographical regions. Location: France Time period: 1978-2022 Major taxa studied: 146 tree species Methods: We fitted two classes of models, a first one explicitly estimating temporal trends and a second one including no temporal components but climatic variables reflecting changing temperature and water availability. Results: We find a decrease in productivity in 95% of the regions and a high contrast in trend shapes between regions over the period studied: lowland regions with average temperature above 11.9{degrees}C showed linear negative trends in productivity since 1985 while colder lowland regions showed hump-shaped trends with turning points between 1985 and 2005, followed by declines in productivity. In mountainous regions, average climate did not appear to be a strong mediator of trend shapes. The temporal trends were reconstituted with high fidelity from the model including only climatic variables implying that changes in temperature and water availability are likely drivers of the reported trends. Main conclusion: These results illustrate the progression during the last decades of the adverse effects of climate change on forest productivity over the European forests. They suggest the expected changes over the 21st century that will put further pressure on forest productivity, impacting forest carbon sink potential and reducing sustainable rate of timber extraction.

ecology↗

bioRxiv2020

Tree diversity and the temporal stability of mountain forest productivity: testing the effect of species composition, through asynchrony and overyielding

Climate change modifies ecosystem processes directly through its effect on environmental conditions, but also indirectly by changing community composition. Theoretical studies and grassland experiments suggest that diversity may increase and stabilize communities productivity over time. Few recent studies on forest ecosystems suggested the same pattern but with a larger variability between the results. In this paper, we aimed to test stabilizing diversity effect for two kinds of mixtures (Fagus sylvatica - Quercus pubescens and Fagus sylvatica - Abies alba), and to assess how climate may affect the patterns. We used tree ring data from forest plots distributed along a latitudinal gradient across French Alps. We found that diversity effect on stability in productivity varies with stand composition. Most beech-fir stands showed a greater stability in productivity over time than monocultures, while beech-oak stands showed a less stable productivity. Considering non-additive effects, no significant trends were found, regardless the type of mixed stands considered. We further highlighted that these patterns could be partially explained by asynchrony between species responses to annual climatic conditions (notably to variation in temperature or precipitation), overyielding, and climatic conditions. We also showed that the intensity of the diversity effect on stability varies along the ecological gradient, consistently with the stress gradient hypothesis for beech-oak forests, but not for beech-fir forests. This study showed the importance of the species identity on the relationships between diversity, climate and stability of forest productivity. Better depicting diversity and composition effects on forest ecosystem functioning appears to be crucial for forest managers to promote forest adaptation and maintain timber resource in the context of on-going climate change.

ecology↗