Design and performance of an ecosystem-scale forest soil warming experiment with infrared heater arrays

How forest ecosystems respond to climate warming will determine forest
trajectories over the next 100 years. However, the potential effects of
elevated temperature on forests remain unclear, primarily because of the
absence of long-term and large-size field warming experiments in forests,
especially in Asia. Here, we present the design and performance of an
ecosystem-scale warming experiment using an infrared (IR) heater array in
a 60-year-old temperate mixed forest at Qingyuan Forest CERN in
northeastern China. In paired 108 m2 plots (n = 3), the surface soils were
constantly elevated 2 degrees above control plots with a feedback control
system over four years (2018-2021). Subsoils down to 60 cm depth were
warmed 1.2-2 degrees. Soil warming did not affect soil moisture either in
surface soils or subsoils. Turn-off time due to weather extremes (heavy
rains, snow) and power outages only accounted for 2.5% of the total
warming period. In conclusion, we provide a proof-of-principle setup that
allows long-term analysis of forest response to warming temperatures in
large-size field plots. Importantly, our warming experiment demonstrated
the feasibility of IR heater arrays for soil warming in tall-statured
forest ecosystems.