Effects of spatial and temporal variability in soil moisture on widths and δ¹³C values of eastern Siberian tree rings

Abstract

[1] We studied the relationships between earlywood/latewood width, stable carbon isotope ratio (d 13 C) of cellulose, and soil moisture at a dry and a wet site in Yakutsk, eastern Siberia, which differed considerably in soil water conditions. Recharge of soil water by snowmelt in spring and subsequent drought in summer provided a marked seasonal contrast in soil water conditions between the earlywood and latewood formation period. Ring index was calculated by dividing each earlywood/latewood width by the 5-year averaged width for each individual. In order to determine whether drought influenced the ring index-d 13 C relation, the ring index time series were compared with d 13 C time series. We collected wood samples from eight Larix gmelinii (Rupr.) Rupr. and four Pinus sylvestris L. trees from the two sites and measured the earlywood and latewood widths and d 13 C of earlywood and latewood formed during the years 1996-2000. At the dry site, seasonal soil water content variation corresponded to seasonal d 13 C variation of tree rings. We found negative ring index-d 13 C correlations in latewood for both species at the dry site mainly dominated by Pinus but not in latewood of Larix at the wet site dominated by Larix. Decrease and/or early cessation of latewood growth and increase in d 13 C under drought conditions possibly explain this negative correlation. This suggests the growth limitation of trees in this region by drought and the prospects of reconstructing past drought with latewood d 13 C of the dry site.

Effect of climatic variability on δ13C and tree-ring growth in piñon pine (Pinus edulis)

“…This is consistent with field gas exchange measurements that showed the piñons at the xeric site exhibited greater changes in water-use efficiency between years relative to the mesic site (Newberry 2008). Similar results have been found in a comparison of d 13 C signal in latewood at a wet site versus a dry site in a study of conifers in Siberia (Kagawa et al 2003) where trees on the wetter site showed less seasonal variation in d 13 C in response to drought relative to the dry sites. Similarly, Adams and Kolb (2004) found a strong d 13 C leaf response to drought in ponderosa pine growing near its lower elevation range limit but not at higher elevations.…”

Warming Effects on Pinus sylvestris in the Cold–Dry Siberian Forest–Steppe: Positive or Negative Balance of Trade?

“…As with most pines, P. sylvestris is an opportunistic species highly responsive to precipitation pulses if water becomes limiting at any moment during growth [58,62]. The prevalence of drought effects over low temperature restrictions on growth suggests that warming-induced water limitation will progressively spread over areas of North Asia-having low precipitation but, also, very low temperatures (i.e., under extreme continentality)-as already observed in Yakutia [56]. Drought effects on Scots pine may not be limited to growth impairment, but they may also hamper the formation of a functional xylem structure via a reduction of cell lumen and wall thickness, as shown for the region [33,63].…”

“…Indeed, the observation that radial growth and ∆ 13 C were tightly (positively) associated at both sites is expected under frequent and intense drought episodes, since both traits are strongly influenced by water shortage in Scots pine [37,56]. P. sylvestris is a conifer with a high stomatal sensitivity to water availability [57].…”

Do centennial tree-ring and stable isotope trends of Larix gmelinii (Rupr.) Rupr. indicate increasing water shortage in the Siberian north?

“…Studies of the isotopic composition of tree rings in the northern regions of Eurasia have been primarily conducted for C (d 13 C) (Kagawa et al 2003;Gagen et al 2007;Kirdyanov et al 2008;Sidorova et al 2008) and rarely for O d 18 O (Saurer et al 2002;Sidorova et al 2008), but using both isotopes could be very helpful in improving our understanding of the forest response to environmental changes of the past century.…”