Modelling shoot respiration

Years of measurements have produced a lot of information on plant respiration. We know more or less how the respiration rate is related to the changing environmental conditions. In principle, respiration exponentially follows temperature. The temperature dependence, however, decreases in low soil water (REW).

These dependencies may be expressed in a simple and straightforward mathematical model using Hyytiälä-measured temperatures and soil water conditions:

R = Max { 0,  f(REW) * r₀ * q₁₀^(T/10) – c_r }

R means the rate of respiration (i.e. the CO₂ emission originating from respiration), T is temperature and REW, the relative extractable water. At our measuring station in Hyytiälä, r₀=1.6 µmol m^–2 s^–1, q₁₀=1.5, c_r=0.8 µmol m^–2 s^–1 and

f(REW)= Min {1,  Max { 0,  (REW+d_rew) / REW_crit } }

where d_rew=0.05 and rew_crit=0.35.