Climatic significance of D/H ratios in the cellulose of late wood in tree rings from spruce (Picea abies L.)

Abstract

Natural variations in the deuterium composition of carbon bound hydrogen of late wood cellulose from rings of five trees were measured. The δ2H values in annual late wood of the spruce trees (Picea abies L.) from Middle Franconia (Germany) show a good correlation with both temperature and relative humidity of July and August (period of late wood formation). This isotope pattern results from the isotopic composition of precipitation and perhaps soil water used during (summer) photosynthesis. The δ2H values of summer precipitation reflect mean temperatures of July and August at the growth site, and hence a certain δ2Hcellulose-temperature relationship is reasonable. Furthermore, it is assumed that changes in summer relative humidity may cause changes in δ2H values of tree ring late wood due to evapotranspiration effects. A negative relationship between ring widths and tree ring late wood δ2H values was observed. This is interpreted as a climatic signal, since tree ring widths reflect climate to some extent, especially in dry and warm, and in cool and moist years ('signature' years having weather anomalies).