Water Consumption by Transpiration of Landscape Trees in Beijing

A pot experiment was conducted to study the photosynthesis and the transpiration of 5 landscape trees commonly found in Beijing, Pinus bungeana, Fraxinus chinensis, Ginkgo biloba, Prunus davidiana, and Lycium chincnse. The results showed that, with ample supply of water, the rates of photosynthesis (Pn), transpiration (Tr), and stomatal conductance (Gs) on leaves of the nursery stocks in a day consistently changed in an M-shape curve with a "lunch break" at noon time. The changes on vapor pressure deficit (VPD) exhibited a single peak curve. Tr linearly correlated with Gs as well as VPD. The correlation coefficient (R²) between Tr and Gs of P. bungeana was 0.9795; and, that between Tr and VPD, 0.9884. Tr of the 5 species ranked L. chincnse (3.33 mmol·m^-2·s^-1) > F. chinensis (3.22 mmol·m^-2·s^-1) > P. davidiana (3.22 mmol·m^-2·s^-1)=G. biloba (3.21 mmol·m^-2·s^-1) > P. bungeana (2.21 mmol·m^-2·s^-1). The water consumptions for the trees were L. chincnse (0.090 g·cm^-2·d^-1) > F.chinensis (0.080 g·cm^-2·d^-1) > Prunus davidiana (0.076 g·cm^-2·d^-1)=G. biloba (0.076 g·cm^-2·d^-1)>P. bungeana (0.032 g·cm^-2·d^-1). The monthly water consumptions of F. chinensis and G. biloba exhibited in a V-shape curve; while, P. bungeana, P. davidiana and L. chincnse, an M-shape curve with twin peaks. Seasonally, the water consumptions of the trees decrease in the order of July (0.083 g·cm^-2·d^-1) > September (0.078 g·cm^-2·d^-1) > August (0.075 g·cm^-2·d^-1) > June (0.071 g·cm^-2·d^-1) > October (0.060 g·cm^-2·d^-1) > May (0.057 g·cm^-2·d^-1). And, P. bungeana consumed the greatest amount of water in autumn, while others in summer. On draught resistance, P. davidiana and G. biloba were more tolerant to the stress than L. chincnse, F. chinensis or P. bungeana.