Impacts of short-term rainfall and snowfall exclusions on hydraulic, economic and stomatal traits of Larix gmelinii in northeastern China

Abstract

Ongoing climate change has a considerable influence on the seasonality, timing, and intensity of rainfall worldwide, and is also predicted to decrease snow cover in cold ecosystems. Larch is a widely distributed tree species in boreal Eurasia, calling for a comprehensive understanding of how larch adapts to changes in both rainfall and snowfall by adjusting carbon-water physiology. Here, we conducted a short-term rainfall (− 60% ambient rainfall; three-year) and snowfall (− 73% ambient snowfall; two-year) exclusions experiment in Larix gmelinii forest in northeastern China, and aimed to explore the responses of hydraulic (leaf pressure-volume traits, leaf and branch hydraulic conductivity and embolism resistance), stomatal (stomatal closure point and stomatal safety margin), and economic (photosynthetic rate, nutrient and non-structural carbohydrates contents) traits to rainfall and snowfall reductions. Despite the weak alternation of leaf and branch hydraulic traits, both rainfall and snowfall reductions significantly led to early stomatal closure and increased stomatal safety margins (the difference between stomatal closure point and xylem embolism threshold, describing drought resistance by merging both hydraulic and stomatal strategies). Reductions in rainfall and snowfall induced water or/and low-temperature stress, resulting in more conservative leaf economic traits, including a reduced photosynthetic rate, lower leaf nitrogen concentration, and higher leaf density. In addition, larch responded to reductions in rainfall and snowfall by up-regulating non-structural carbohydrates in the xylem, which helps repair embolism or lower the freezing point acting as osmolytes. Overall, our findings reveal that larch could adapt to the drought and snowpack reduction by strict stomatal regulation and investing non-structural carbohydrates in embolism repairing, at the cost of carbon assimilation.

Keywords

Embolism resistance / Stomatal closure point / Stomatal safety margins / Non-structural carbohydrates / Larix gmelinii