Winter photosynthesis of evergreen broadleaf trees from a montane cloud forest in subtropical China

Abstract

Winter photosynthesis of trees is well studied for boreal, Mediterranean, and some temperate forests, while little is known about the forests from tropical-subtropical transition zones and subtropical areas. Evergreen broadleaf trees dominate the forests from elevation 1,000 to 2,600 m in the subtropical area of SW China, while forests in the subtropical area of SE China with similar elevations are dominated by deciduous broadleaf trees. In order to understand the winter photosynthetic performances of evergreen broadleaf trees in subtropical areas, seasonal dynamics in photosynthesis of 10 evergreen broadleaf tree species from a montane cloud forest in SW China was studied. Plant water relations and low temperature effects on photosynthetic system I and II were also studied. Although all 10 species down regulated maximum photosynthetic rate by 13% to 53% in winter, they maintained considerably high winter carbon assimilation (5.4 to 8.8 μmol m−2 s−1) during this period. Trees did not experience water deficits in the winter/dry season, and were able to tolerate the coldest winter season in history. The considerably high winter carbon assimilation of evergreen broadleaf trees in this area may help them to establish dominance and allow these forests to sequestrate carbon during the unfavorable season.