Importance of tree height and social position for drought-related stress on tree growth and mortality

Detecting the fingerprint of drought across Europe’s forests: do carbon isotope ratios and stem growth rates tell similar stories?

“…Because the extent to which trees are affected by drought is known to be size-dependent (e.g., Zang et al 2012;Bennett et al 2015;Grote et al 2016), directly relating growth and isotope values without accounting for differences in the size distribution of trees used to calculate them could affect results. To address this issue, we developed a statistical model that explicitly accounts for the effect of tree size on growth, and then used the model to estimate the stem growth of a tree of comparable size to that sampled for isotopes for each of the 26 study populations (see below for details).…”

Drought can favour the growth of small in relation to tall trees in mature stands of Norway spruce and European beech

“…Trees with inferior social positions may on the one hand benefit from being shaded in dry years, from the reduced water consumption of tall neighbours with isohydric behaviour (Goisser et al 2016), or from their rooting closer to the surface which means better access to occasional rainwater in summer (Flanagan et al 1992). On the other hand, being subdominant may mean less access to water and less stemflow in favour of the roots, limited access to ground water, or less water availability when stocking beside anisohydric neighbours which are continuously exploiting the available water supply (Wullschleger et al 1998;Grote et al 2016). So far, there is no accepted general pattern of how subdominant trees come off under drought in relation to dominant and predominant trees.…”

“…The growth partitioning in mainly light-limited environments in temperate forests is rather well explored (Pretzsch and Biber 2010), represented in models (Biging and Dobbertin 1995), and applied for silvicultural prescriptions (Kramer 1988;Pretzsch and Zenner 2017). The growth partitioning under water limited conditions is rather far from being well explored and understood (Martínez-Vilalta et al 2012;Grote et al 2016). However, there are many scientific and practical reasons for deeper exploring it in this study.…”

“…It may depend on the availability of the various resources, to what extent predominant trees can benefit from their size and privileged social position and how the resources and growth are distributed among the differently sized trees. Theory (Schwinning and Weiner 1998;Grote et al 2016) and model studies (Hara 1993) consider a wide range from completely symmetric, to sizesymmetric, and strongly size-asymmetric interindividual resource and growth distribution patterns. The resource and growth distribution pattern in a given stand may depend on the environmental conditions, and especially on the prevailing resource limitation.…”

Drought induced tree mortality – a tree‐ring isotope based conceptual model to assess mechanisms and predispositions

“…This is also crucial for simulating tree mortality in dynamic vegetation models (Meir et al ., ). Predisposing factors are assumed to be related to long‐term climatic stressors (Voltas et al ., ), prevailing long‐term nutrient supply (Gessler et al ., ), water‐use strategies (Hentschel et al ., ), tree height and interspecific and intraspecific competition (Grote et al ., ) and pests, pathogens or air pollution (Allen et al ., ).…”