1.8 KiB
2.9.2. Introduction¶
Leaf stomatal resistance, which is needed for the water vapor flux (Chapter 2.5), is coupled to leaf photosynthesis similar to Collatz et al. (1991, 1992). These equations are solved separately for sunlit and shaded leaves using average absorbed photosynthetically active radiation for sunlit and shaded leaves [\(\phi ^{sun}\),\(\phi ^{sha}\) W m-2 (section 2.4.1)] to give sunlit and shaded stomatal resistance (\(r_{s}^{sun}\),\(r_{s}^{sha}\) s m-1) and photosynthesis (\(A^{sun}\),\(A^{sha}\) µmol CO2 m-2 s-1). Canopy photosynthesis is \(A^{sun} L^{sun} +A^{sha} L^{sha}\), where \(L^{sun}\) and \(L^{sha}\) are the sunlit and shaded leaf area indices (section 2.4.1). Canopy conductance is \(\frac{1}{r_{b} +r_{s}^{sun} } L^{sun} +\frac{1}{r_{b} +r_{s}^{sha} } L^{sha}\), where \(r_{b}\) is the leaf boundary layer resistance (section 2.5.3).