Date Published: June 29, 2017
Publisher: Public Library of Science
Author(s): Ji Young An, Byung Bae Park, Jung Hwa Chun, Akira Osawa, Luitgard Schwendenmann.
Current understanding of litterfall and fine root dynamics in temperate forests is limited, even though these are the major contributors to carbon and nutrient cycling in the ecosystems. In this study, we investigated litterfall and fine root biomass and production in five deciduous and four coniferous forests at the Gwangneung Experimental Forest in Korea. We used ingrowth cores to measure fine root production and root turnover rate. The litterfall was separated into leaves, twigs, and others, and then leaves were further separated according to species. Annual litterfall mass was not significantly different between the years, 360 to 651 g m-2 in 2011 and 300 to 656 g m-2 in 2012. Annual fine root (<5 mm) production was significantly higher in 2012 (421 to 1342 g m-2) than in 2011 (99 to 872 g m-2). Annual litterfall mass was significantly different among the stands, while fine root production did not statistically differ among the stands. The average fine root turnover rate, calculated by dividing the annual fine root production by the maximum standing fine root biomass, was 1.65 for deciduous forests and 1.97 for coniferous forests. Fine root production constituted 18–44% of NPP, where NPP was the sum of woody biomass production, litterfall production, and fine root production. Belowground production was a greater fraction of NPP in more productive forests suggesting their greater carbon allocation belowground.
Tree roots and aboveground vegetation are huge carbon and nutrient sinks, and they play an important role in the carbon and nutrient cycles of forest ecosystems. Particularly, litterfall and fine root production are major components of NPP [1,2]. However, our knowledge on the belowground sink strength of forest ecosystems is still limited due to relatively poor knowledge on the process of fine root production [2–4]. This may lead to unreliable estimates of carbon budget and uncertainties in forest simulation models [5–7].
Litterfall, fine root production, and fine root turnover rate differed across the nine stands and varied between the two sampling years as well. We confirmed that the magnitude of carbon flux in fine root turnover in these temperate forests is similar to that of litterfall. Although we could not find a significant relationship between above- and belowground production, our results contribute to the understanding of carbon allocation between above- and belowground in temperate forests: belowground production was a greater fraction of NPP where NPP was high, which indicates a greater carbon allocation belowground in more productive forests. If this finding proves to be generally true, it could be used to improve the accuracy of simulation models for carbon cycling in forest ecosystems.