Inter-specific and seasonal variations in photosynthetic capacity and water use efficiency of five temperate tree species in Northeastern China

Abstract Photosynthetic capacity (P max) and water use efficiency (WUE) are useful indices for describing CO2 uptake and H2O loss of trees. Inter-specific and seasonal variations in P max and WUE of five tree species were quantified in a Chinese temperate forest. The study included pioneer (white birch), mid-successional (Amur cork-tree, Manchurian walnut, Mongolian oak), and late-successional (Amur linden) species. The P max and WUE differed significantly among species, but the inter-specific variations were smaller than previously reported. Leaf-area-based P max varied from 5.1 for linden to 11.0 µmol m−2s−1 for birch, whereas leaf-mass-based P max ranged from 154 for linden to 252 µmol kg−1s−1 for walnut. Linden had the highest WUE, whereas walnut had the lowest. The seasonal patterns of P max and WUE were significantly different between species. The P max of birch increased as the season proceeded, whereas the P max of the other four species was lowest in May, and peaked in June. The seasonality of P max was influenced by stomatal conductance, apparent carboxylation efficiency, and specific leaf area, but the determining factor varied with species and leaf development. This study suggests that a deeper understanding of inter-specific and seasonal variations of gas exchange parameters would improve our ability to predict the carbon metabolism in the temperate forests.