Drought Resistance of Norway Spruce (Picea abies [L.] Karst) and European Beech (Fagus sylvatica [L.]) in Mixed vs. Monospecific Stands and on Dry vs. Wet Sites. From Evidence at the Tree Level to Relevance at the Stand Level

Abstract

Frequency of drought years is expected to increase through climate warming. Mixed stands have often shown to be more productive than monospecific stands in terms of yield and of resistance against windthrows and bark beetle attacks. Mixture of beech and spruce is of particular interest. However, little is known about its growth reaction to drought. Therefore, we investigated the drought reaction of beech and spruce in mixed vs. monospecific stands along an ecological gradient. In particular, we sought evidence for mixture-related resilience on the individual tree level. Therefore, we quantified the response of tree ring width to drought. Moreover, we attempted to explain the relevance of individual tree response on the stand level by quantifying the stand level loss of volume growth after drought. At the individual tree level, beech was found to be more resilient and resistant in pure vs. mixed stands. Spruce, in contrast, was favored by mixture, and this was especially evident on drier sites. Along the gradient, growth losses at stand level increased in both mixed and pure stands in 2015, with growth gains on the drier sites observed in the same drought year, in accordance with the Stress Gradient Hypothesis. However, the stand level difference of growth loss between mixed and pure stands was not statistically significant. Mitigating mixture effects on the level of the individual tree thus did not become evident on the level of the whole stand.

Assessing Tree Drought Resistance and Climate-Growth Relationships under Different Tree Age Classes in a Pinus nigra Arn. ssp. salzmannii Forest

“…Our study identified significant differences among tree age-classes of managed Pinus nigra forest stands in terms of basal area increment (BAI), drought resistance, and drought resilience. These results support the argument that tree age can modify the drought impact in forest stands [14,68,69]. Our results showed that younger trees (<40 years of age) were more resistant and resilient to extreme droughts which occurred in 1981, 1991, 1999, and compared to older trees (40-120 years of age) (Figures 4 and 5).…”

Distinct Responses of European Beech (Fagus sylvatica L.) to Drought Intensity and Length—A Review of the Impacts of the 2003 and 2018–2019 Drought Events in Central Europe

“…In 2003, partial or full branch diebacks, along with severe growth reductions were reported [87][88][89][90][91]. Growth recovery was often slow [3,24,92,93] and trees exhibited a significant growth decline after 2003 [3,94]. Upper branch dieback and formation of stag-headed patterns on the side branches led up to 70% loss of foliage on intermediate (height on average 10 m) and suppressed beech trees (below 10 m height) in Südbaden in Germany [92,95].…”

Traces of Local Adaptive Acclimatization Response in the Tracheid Anatomical Traits between Dry and Wet Mesic Norway Spruce (Picea abies) Forests in Moravia, Czech Republic?

“…Since 2000, parts of Central Europe have experienced persistent hot and dry periods in summer and non-summer periods [24], leading to a greater risk of precipitation deficits combined with increased temperatures and evapotranspiration [25]. Precipitation deficits can lead to a tight hydrological balance and, potentially, plant water stress [26]; thus, concerns have been raised concerning the ecological stability and adaptation of drought-sensitive Norway spruce trees [22,27,28]. Boden et al [29] indicated a loss of growth resilience and stress response to decreasing water availability and a relatively limited short-term adaptive capacity to changing climate conditions in tree-ring width (TRW) series of Norway spruce trees located in southwestern Germany in sub-mountainous and mountainous belts.…”