Vertical profiles of CO2 concentration and delta C-13 values in a subalpine forest of Taiwan

We investigated the vertical gradients in CO2 concentration and stable carb on isotope ratio (delta(13)Cco(2)) of the canopy air within a coniferous-ha rdwood, Chamaecyparis and Rhododendron dominated, subalpine forest in Taiwa n. The stable carbon isotope ratio of vascular plants and a epiphytic bryop hyte species (Bazzania fauriana) (delta(13)C(leaf)) from different heights within the forest were also analyzed. Results revealed that CO2 and delta(1 3)Cco(2) gradients did exist within the forest, with higher CO2 concentrati ons and more negative delta(13)Cco(2) values in air sampled from the lower canopy. The average vertical gradients in CO2 and delta(13)Cco(2) value of the CO2 of the 12 sampling dates were 28.5 +/- 6.1 ppm and 1.3 +/- 0.3 part s per thousand, respectively. Seasonal patterns of the relationship between 1/[CO2] and the corresponding delta(13)C were pronounced, with steady decr eases in the slopes and increases in the intercepts found from January to A ugust. A decreasing delta(13)C(leaf) with decreasing height was also measur ed in a bryophyte (ranging from -27.4 to -29.2 parts per thousand), canopy and understory leaves (ranging from -28.6 to -33.5 parts per thousand). It was estimated that photosynthetic physiology affected by microclimates with in the forest contributed approximately 2.8 parts per thousand of variation of the vertical gradient of vascular plant delta(13)C values.