Does plant ecosystem thermoregulation occur? An extratropical assessment at different spatial and temporal scales
Zhengfei Guo, Christopher J. Still, Calvin K. F. Lee, Youngryel Ryu, Benjamin Blonder, Jing Wang, Timothy C. Bonebrake, Alice C. Hughes, Yan Li, Henry C.H. Yeung, Kun Zhang, Ying Ki Law, Ziyu Lin, Jin Wu
Abstract
Summary To what degree plant ecosystems thermoregulate their canopy temperature ( T c ) is critical to assess ecosystems' metabolisms and resilience with climate change, but remains controversial, with opinions from no to moderate thermoregulation capability. With global datasets of T c , air temperature ( T a ), and other environmental and biotic variables from FLUXNET and satellites, we tested the ‘limited homeothermy’ hypothesis (indicated by T c & T a regression slope < 1 or T c < T a around midday) across global extratropics, including temporal and spatial dimensions. Across daily to weekly and monthly timescales, over 80% of sites/ecosystems have slopes ≥1 or T c > T a around midday, rejecting the above hypothesis. For those sites unsupporting the hypothesis, their T c – T a difference (Δ T ) exhibits considerable seasonality that shows negative, partial correlations with leaf area index, implying a certain degree of thermoregulation capability. Spatially, site‐mean Δ T exhibits larger variations than the slope indicator, suggesting Δ T is a more sensitive indicator for detecting thermoregulatory differences across biomes. Furthermore, this large spatial‐wide Δ T variation (0–6°C) is primarily explained by environmental variables (38%) and secondarily by biotic factors (15%). These results demonstrate diverse thermoregulation patterns across global extratropics, with most ecosystems negating the ‘limited homeothermy’ hypothesis, but their thermoregulation still occurs, implying that slope < 1 or T c < T a are not necessary conditions for plant thermoregulation.