Tree ring δ¹⁸O reveals no long‐term change of atmospheric water demand since 1800 in the northern Great Hinggan Mountains, China

Abstract

Global warming will significantly increase transpirational water demand, which could dramatically affect plant physiology and carbon and water budgets. Tree ring δ18O is a potential index of the leaf‐to‐air vapor‐pressure deficit (VPD) and therefore has great potential for long‐term climatic reconstruction. Here we developed δ18O chronologies of two dominant native trees, Dahurian larch (Larix gmelinii Rupr.) and Mongolian pine (Pinus sylvestris var. mongolica), from a permafrost region in the Great Hinggan Mountains of northeastern China. We found that the July–August VPD and relative humidity were the dominant factors that controlled tree ring δ18O in the study region, indicating strong regulation of stomatal conductance. Based on the larch and pine tree ring δ18O chronologies, we developed a reliable summer (July–August) VPD reconstruction since 1800. Warming growing season temperatures increase transpiration and enrich cellulose 18O, but precipitation seemed to be the most important influence on VPD changes in this cold region. Periods with stronger transpirational demand occurred around the 1850s, from 1914 to 1925, and from 2005 to 2010. However, we found no overall long‐term increasing or decreasing trends for VPD since 1800, suggesting that despite the increasing temperatures and thawing permafrost throughout the region, forest transpirational demand has not increased significantly during the past two centuries. Under current climatic conditions, VPD did not limit growth of larch and pine, even during extremely drought years. Our findings will support more realistic evaluations and reliable predictions of the potential influences of ongoing climatic change on carbon and water cycles and on forest dynamics in permafrost regions.

Comparisons of the Performance of δ13C and δ18O of Fagus sylvatica, Pinus sylvestris, and Quercus petraea in the Record of Past Climate Variations

“…The strong correlations between oxygen and carbon isotopic records of Q. petrea , F. sylvatica , and P. sylvestris and summer temperature and air moisture (VPD, RH, and PET) indicated that all these climate variables are potential targets for long‐term reconstructions. While VPD plays a critical role in controlling ecosystem fluxes of water and carbon (Novick et al, ; Sulman et al, ), its long‐term changes have not been documented (to our knowledge only one reconstruction by Liu et al, ). Our results thus open the door to new VPD‐based environmental reconstructions in temperate areas.…”

Disentangling Contributions of CO2 Concentration and Climate to Changes in Intrinsic Water-Use Efficiency in the Arid Boreal Forest in China’s Altay Mountains

“…Dry air (reduced relative humidity and increased VPD) causes a strong degree of the 18 O enrichment in leaf water through transpiration, thereby producing high tree-ring δ 18 O [12,13]. Leaf δ 18 O enrichment in Larix is expected to be controlled by the water availability, which in turn is usually controlled by the VPD [46,47]. The high explained variance in VPD reconstruction at the FOD scale further illustrates the controls of VPD on tree-ring δ 18 O (Figure 8).…”

“…The high explained variance in VPD reconstruction at the FOD scale further illustrates the controls of VPD on tree-ring δ 18 O (Figure 8). Several studies have shown a positive correlation between Larix tree-ring δ 18 O and VPD [46,47], and have used this relationship to reconstruct past VPD variations [47]. In addition, Larix is sensitive to drought and soil moisture because of low drought tolerance [48].…”

A past, present and future perspective on the European summer vapour pressure deficit

“…In contrast, low VPD leads to reduced water transport into the leaves and thus a reduced supply of nutrients. This marks VPD as an important indicator for plant activity (Novick et al, 2016), which among other things notably affects plant growth (Restaino et al, 2016), forest mortality (Park Williams et al, 2013), drought occurrence (Dai, 2013), crop production (Zhao et al, 2017) and wildfire occurrence (Seager et al, 2015).…”

“…Furthermore, it is essential to investigate the independent physiological effects of VPD on large-scale vegetation dynamics, which are less explored (Grossiord et al, 2020). So far, first local reconstruction studies have shown the potential of a long-term perspective on VPD (e.g., Liu et al, 2017). For example, Churakova- Sidorova et al (2020) have shown that the recent VPD increase does not yet exceed the maximum values reconstructed during the Medieval Warm Anomaly in Siberia.…”