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

Abstract

Background: Climate change triggered many studies showing that trends and events of environmental conditions can reduce but also accelerate growth at the stand and individual tree level. However, it is still rather unknown how climate change modifies the growth partitioning between the trees in forest stands. Methods: Based on long-term girth-tape measurements in mature monospecific and mixed-species stands of Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus sylvatica L.) we traced the effect of the severe droughts in 2003 and 2015 from the stand down to the tree level. Results: Stand growth of Norway spruce decreased by about 30% in the once-in-a-century drought 2015, while European beech was much more drought resistant. Water availability generally amplified size-asymmetric growth partitioning. Especially in case of Norway spruce water availability primarily fostered the growth of predominant trees, whereas drought favoured the growth of small trees at the expense of the predominant ones. We could not detect significant differences between mixed and monospecific stands in this regard. Conclusions: The drought-induced reallocation of growth in favour of small trees in case of spruce may result from its isohydric character. We hypothesize that as small trees are shaded, they can benefit from the reduced water consumption of their sun-exposed taller neighbours. In case of beech, as an anisohydric species, tall trees suffer less and smaller trees benefit less under drought. The discussion elaborates the consequences of the water dependent growth allocation for forest monitoring, growth modelling, and silviculture.

The effects of persistent drought and waterlogging on the dynamics of nonstructural carbohydrates of Robinia pseudoacacia L. seedlings in Northwest China

“…Note that the upper-case letter refers to the significant differences among treatments and the lower-case letter refers to the significant differences within-subject contrast, waterlogging only had moderate legacy effects on the NSC concentrations and pools, and subsequently plant growth and productivity were not significantly affected. Even some historic studies showed that higher initial NSC pools were not advantageous for resistance and survival in plants (Pretzsch et al 2018). But we observed that bigger NSC pool sizes play a key role under drought and waterlogging conditions during short-term.…”

Growth and mortality of Norway spruce and European beech in monospecific and mixed-species stands under natural episodic and experimentally extended drought. Results of the KROOF throughfall exclusion experiment

“…Meteorological data were acquired from a nearby forest weather station "Freising", which is part of the Bavarian Environmental Monitoring System (LWF 2017). For further information about the Kranzberg Forest, see Göttlein et al (2012); Häberle et al (2012), and for more details about the KROOF experiment, see Pretzsch et al (2014Pretzsch et al ( , 2018.…”

“…Collectively, there were 639-926 trees per hectare with a stand basal area of 54.0-60.1 m 2 ha −1 , standing stem volume of 802-981 m 3 ha −1 , and a mean periodic volume growth (1998-2016) of 19.4-26.3 m 3 ha −1 yr −1 . The lower values of the given ranges for tree number, stand basal area, standing volume, and volume growth of the monospecific beech stands, the upper values of the monospecific spruce stands, and the mixed species stands lie in between (for more stand information, see Pretzsch et al 2014Pretzsch et al , 2018.…”

“…Scots pine (Pinus silvestris L.) and sessile oak (Quercus petraea L.), for instance, are less susceptible to drought (Walentowski et al 2007;Zang et al 2011Zang et al , 2012 than Norway spruce and becoming more suitable for forestry in Central Europe under climate change scenarios that predict future warm and dry conditions. Possible silvicultural practices in view of climate change include down regulating stand density (D'Amato et al 2013;Sohn et al 2016), modified thinning practices (Gebhardt et al 2014;Pretzsch et al 2018;Rodríguez-Calcerrada et al 2011), and the promotion of mixed tree species plantings (Ammer 2017). The latter's efficacy, however, has yet to be assessed for drought mitigation (Grossiord 2018).…”

Site Index Models for Main Forest-Forming Tree Species in Poland

“…Another reason for the inadequacy of Schwappach's tables is because of the significant changes in growth conditions, which have greatly changed during the 100-year period since the development of the tables. Research carried out in Central Europe indicates that these changes have strongly influenced the dynamics of stand growth [19,[31][32][33]. Pretzsch [31] estimated that site productivity increased by about 30%-70%.…”