Do atmospheric CO2 concentration increase, climate and forest management affect iWUE of common beech? Evidences from carbon isotope analyses in tree rings

Abstract

Beech is one of the most important forest tree species in Europe, hence possible adverse factors affecting its physiology and productivity can have strong ecological and economic impacts. In this context, four beech forests along a latitudinal gradient from southern Apennines to middle European lowlands were selected for chronological determinations of carbon isotope composition (δ13C) in tree-ring cellulose. The main objectives of this study were to assess (i) the effect of climate on the carbon signature of tree-ring cellulose (δ13C); (ii) the physiological response to recent CO2 concentration increment and to climatic variation; and (iii) the relationship between intrinsic water-use efficiency (iWUE, here the average long-term ratio of net photosynthesis to stomatal conductance) and growth of trees in different sites since 1950. Our results demonstrated that site climatic conditions peculiarly affect δ13C. In northern sites, a climatic control of summer precipitation and temperature on stomatal conductance was demonstrated by their opposite correlations with δ13C, negative and positive, respectively. Furthermore, an 'earliness effect' was suggested by a significant relationship between spring temperature and δ13C in the coldest sites and by a positive one between winter temperature and δ13C in the warmest ones. In all the study sites, during the maturity phase, a positive correlation between the increment of CO2 and iWUE was observed, due to an active response of trees to CO2 increment. This increment of CO2 was the main driver of the long term increasing trend of iWUE, resulting by an active response of trees to CO2 fertilization. Moreover, precipitation mostly influences positively and negatively the inter-annual variations of iWUE of the southernmost and northernmost sites, respectively. Overall, we observed a mean increment of 40% of iWUE. Moreover, the sensitivity of iWUE to the increase of CO2 was different between the northernmost and southernmost sites. Increasing iWUE was correlated to growth in the two sites during the release phase and we hypothesize a positive effect of silvicultural treatments.

Winter's bite: beech trees survive complete defoliation due to spring late‐frost damage by mobilizing old C reserves

“…During the period 1950–2013 the mean annual temperature was 7.4°C, and the mean annual precipitation was 1024 mm (Rezaie et al ., ), of which c . 10% falls in summer (Guidolotti et al ., ).…”

“…During the period 1950-2013 the mean annual temperature was 7.4°C, and the mean annual precipitation was 1024 mm (Rezaie et al, 2018), of which c. 10% falls in summer (Guidolotti et al, 2013). On the night between 25 and 26 April 2016 the temperature reached À6°C at the canopy level, destroying the whole stand canopy (Fig.…”

“…Five representative trees with diameters at breast height ranging from 49 to 53 cm were selected according to their similarity with site tree ring chronology (Gleichl€ aufigkeit (GLK) ranging from 70 to 85; for more information on tree selection see Rezaie et al, 2018).…”

Frost and drought: effects of extreme weather events on stem carbon dynamics in a Mediterranean beech forest

“…The measurements were carried out between 2015 and 2017 on a long-term monitored beech stand ( Fagus sylvatica L.) located at Selva Piana (41°50’58” N, 13°35’17” E, 1,560 m elevation) close to Collelongo (Abruzzi Region, Italy) in the Central Apennine. Site information regarding forest structure, climate and soil are all in depth described in previous works (Chiti et al , 2010; Guidolotti et al , 2013; Collalti et al , 2016; Rezaie et al , 2018).…”

“…In the near future, Mediterranean region is predicted to be the most vulnerable to global change between the European regions (Schröter et al , 2005). Changes in temperature and precipitation regimes may increase drought risk (Schröter et al , 2005), which can negatively affect physiological performance (Rezaie et al , 2018), growth and competitive strength (Peuke et al , 2002) of common beech, one of the most important and widespread broadleaved trees in Europe.…”