Effects of Throughfall Exclusion on Photosynthetic Traits in Mature Japanese Cedar (Cryptomeria japonica (L. f.) D. Don.)

As climate change progresses, it is becoming more crucial to understand how timber species respond increased drought frequency and severity. Photosynthetic traits in a 40-year-old clonal Japanese cedar (Cryptomeria japonica) plantation were assessed under artificial stress using roof exclude rainfall control with no exclusion. C. japonica commercial tree that native Japan has high growth on mesic sites. The maximum carboxylation rate (Vcmax), electron transfer (Jmax), dark respiration (Rd) current-year shoots the upper canopy determined from spring autumn over two growing seasons. In addition, photosynthetic at light saturation (Pmax), stomatal conductance (gs), intrinsic water use efficiency (WUEi) measured morning afternoon during same period. Leaf mass per unit area (LMA) nitrogen concentration (N) also measured. values of Vcmax, Jmax, Rd, N, LMA did not differ between plots. By contrast, significantly lower Pmax gs higher WUEi found plot, reduction was accompanied by low values. Midday depressions pronounced plot relative related WUEi. Under conditions, mature experienced little capacity, foliar or LMA, but they tend close stomata regulate transpiration, thus avoiding drought-induced damage machinery improving