Changes in the grassland-forest boundary at Ta-Ta-Chia long term ecological research (LTER) site detected by stable isotope ratios of soil organic matter

The carbon isotope analysis [δ13C values] of organic samples can be a useful research in ecological studies because δ13C values are indicative of the plant source. This study investigated the changes in plant communities along the grassland-forest boundary in the alpine forest at Ta-Ta-Chia long term ecological research (LTER) site in central Taiwan using carbon isotope data. The aim of this study was focused on the forest fire affected the change of vegetation community. Four pedons from grassland dominated by Miscanthus transmorrisonensis (pedons 1 and 2), transition zone by Tsuga and Yushania nittakeyamensis (pedon 3), and forest zone by Tsuga and nittakeyamensis (pedon 4) were examined. Soil organic matter (SOM) δ13C values in the upper soil horizon were similar to δ13C values of the overlaying vegetation types. This indicates that the boundary between these plant communities remained the same in the past decades. The δ13C values of the grassland SOM ranged from −19.4‰ to −24.1‰, showing decrease with soil depth. This suggests that C4 plants (transmorrisonensis) have replaced C3 plants of Tsuga and nittakeyamensis. The δ13C values of the Tsuga forest area (pedon 4) range from −27.0‰ to −23.5‰ and showed only slight change with soil depth, implying that C3 plants have remained the major species in the forest.