Slow growth, branch dieback and scarce acorn yield are visible symptoms of decay in abandoned Quercus pyrenaica coppices. A hypothetical root-to-shoot (R:S) imbalance provoked by historical coppicing is investigated as the underlying driver of stand degradation. After stem genotyping, 12 stems belonging to two clones covering 81 and 16m2 were harvested and excavated to measure above- and below-ground biomass and nonstructural carbohydrate (NSC) pools. To study root system functionality, root connections and root longevity were assessed by radiocarbon analysis. Seasonality of NSC was monitored on five additional clones. NSC pools, R:S biomass ratio and fine roots-to-foliage ratio were higher in the large clone, whose centennial root system, estimated to be 550years old, maintained large amounts of sapwood (51.8%) for NSC storage. 248 root connections were observed within the large clone, whereas the small clone showed comparatively simpler root structure (26 connections). NSC concentrations were higher in spring (before bud burst) and autumn (before leaf fall), and lower in summer (after complete leaf expansion); they were always higher in roots than in stems or twigs. The persistence of massive and highly inter-connected root systems after coppicing may lead to increasing R:S biomass ratios and root NSC pools over time. We highlight the need of surveying belowground organs to understand aboveground dynamics of Q. pyrenaica, and suggest that enhanced belowground NSC storage and consumption reflect a trade-off between clonal vegetative resilience and aboveground performance.
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We are grateful to Javier Donés, director of the Centro de Montes y Aserradero de Valsaín, for economic and logistic support. We thank Manuel Iglesias for Fig. 6 and his inestimable support in the field and lab work together with César Otero, Guillermo González, Eva Miranda, Paula Guzman, Alfredo Cabranes and Andrés Sanz. We also thank to Drs. Fabio Marzaioli and Filippo Terrasi of the Center for Isotopic Research on the Cultural and Environmental Heritage for radiocarbon dating. Roberto Salomón was supported by a Ph.D. scholarship from the Universidad Politécnica de Madrid . César Morales-Molino holds a Swiss Government Excellent Postdoctoral Scholarship for Foreign Researchers (Ref.: 2014.0386 ). This work was funded by the CAM P2009/AMB-1668 and P2013/MAE-2760 projects and the Transnational Access to Research Infrastructures activity in the Seventh Framework Programme of the European Union under the Trees4Future project ( 284181 ).
- Biomass partitioning
- Forest decline
- Multi-stemmed tree
- Vegetative regeneration