It is not just a ‘trade‐off’: indications for sink‐ and source‐limitation to vegetative and regenerative growth in an old‐growth beech forest
Martina Mund, Mathias Herbst, Alexander Knohl, Bertrand Matthäus, Jens Schumacher, Peter Schall, Lukas Siebicke, Rijan Tamrakar, Christian Ammer
Abstract
Summary Controls on tree growth are key issues in plant physiology. The hypothesis of our study was that the interannual variability of wood and fruit production are primarily controlled directly by weather conditions (sink limitation), while carbon assimilation (source limitation) plays a secondary role. We analyzed the interannual variability of weather conditions, gross primary productivity (GPP) and net primary productivity (NPP) of wood and fruits of an old‐growth, unmanaged Fagus sylvatica forest over 14 yr, including six mast years. In a multiple linear regression model, c . 71% of the annual variation in wood‐NPP could be explained by mean air temperature in May, precipitation from April to May (positive influence) and fruit‐NPP (negative influence). GPP of June to July solely explained c . 42% of the variation in wood‐NPP. Fruit‐NPP was positively related to summer precipitation 2 yr before ( R 2 = 0.85), and negatively to precipitation in May ( R 2 = 0.83) in the fruit years. GPP had no influence on fruit‐NPP. Our results suggest a complex system of sink and source limitations to tree growth driven by weather conditions and going beyond a simple carbon‐mediated ‘trade‐off’ between regenerative and vegetative growth.