Asymmetric effects of daytime and nighttime warming on alpine treeline recruitment

Abstract

Trees at their upper range limits are highly sensitive to climate change, and thus alpine treelines worldwide have changed their recruitment patterns in response to climate warming. However, previous studies focused only on daily mean temperature, neglecting the asymmetric influences of daytime and nighttime warming on recruitments in alpine treelines. Here, based on the compiled dataset of tree recruitment series from 172 alpine treelines across the Northern Hemisphere, we quantified and compared the different effects of daytime and nighttime warming on treeline recruitment using four indices of temperature sensitivity, and assessed the responses of treeline recruitment to warming-induced drought stress. Our analyses demonstrated that even in different environmental regions, both daytime and nighttime warming could significantly promote treeline recruitment, and however, treeline recruitment was much more sensitive to nighttime warming than to daytime warming, which could be attributable to the presence of drought stress. The increasing drought stress primarily driven by daytime warming rather than by nighttime warming would likely constrain the responses of treeline recruitment to daytime warming. Our findings provided compelling evidence that nighttime warming rather than daytime warming could play a primary role in promoting the recruitment in alpine treelines, which was related to the daytime warming-induced drought stress. Thus, daytime and nighttime warming should be considered separately to improve future projections of global change impacts across alpine ecosystems.

Climate change increases net CO2assimilation in the leaves of strawberry, but not yield

“…The impact of temperature on yield can be due to higher average temperatures or short-term increases in temperatures above the optimum range (Campoy et al, 2019;Chavan et al, 2019). The effect of global warming on the changes in temperature varies across regions and ecosystems and between days and nights (Cox et al, 2020;Hou et al, 2018;Shi et al, 2023;Sun et al, 2014;Zheng et al, 2021). There can also be differences between the temperature of the canopy (T c ) and that of the air (T a ) (Guo et al, 2023).…”