Open-field warming experiments on soil carbon fluxes and pools in cool-temperate deciduous forests, Japan

Nam Jin Noh1, Masatoshi Kuribayashi1, Taku M. Saitoh1, Masahiro Nakamura2, Tatsuro Nakaji2, Tsutom Hiura2, Hiroyuki Muraoka1
1 River Basin Research Center, Gifu University
2 Field Science Center for Northern Biosphere, Hokkaido University

O 2.3 in Environmental controls on fluxes and processes in ecosystems

15.07.2014, 16:10-16:30, H18

Increasing magnitudes of climate change (global warming) considerably impact the terrestrial ecosystems. Since carbon cycle of the terrestrial ecosystems is one of the key processes governing the earth system, many studies have been conducting to clarify the potential changes in ecosystem carbon cycle processes under the future climate change. However, the reports conclude that ecosystems have different vulnerabilities depending on different places (IPCC 2014). Especially the lack of sufficient studies in forest ecosystems may cause the uncertainties in evaluation of the integrated response of terrestrial ecosystems to global climate warming. Furthermore, even in similar forest ecosystem type, clarification of site-specific difference in their temperature responses is also important for estimating future carbon dynamics in global scale. To examine the effect of temperature elevation on ecosystem functions and processes, the open-field warming experiment is now widely accepted, especially in tree species and forest ecosystems. Here, we will introduce open-field artificial soil warming experiments to investigate the possible changes in carbon cycle processes of forest ecosystems to future climate change.
This study was conducted in cool-temperate deciduous broadleaf mature forests dominated by Quercus crispula in Takayama (TKY, 36˚08’N, 137˚25’E) and Tomakomai (TOEF, 42˚40’N, 141˚36’E) in central and northern Japan, respectively. The sites are contributing to JaLTER (Japan Long-term Ecological Research network), JapanFlux and J-BON (Biodiversity Observation Network). We have been aiming to quantify the warming effects on soil respirations and belowground carbon and nitrogen pools (e.g. soil, fine root, and litter) and examine the temperature sensitivities of respirations to elevated temperature. Soil temperature was increased by heating cables at 3-5cm below the soil surface (+3˚C in TKY and +4.7˚C in TOEF). Experimental warming resulted in increases of soil respirations (about 15~35%) and in different thermal acclimation of temperature-respiration curves among soil, autotrophic and heterotrophic respirations. Temporal differences in the soil warming effects on the respiration rates were observed. Response of belowground carbon and nitrogen components to warming differed between the two sites, for example, soil organic carbon, C:N ratio, and root biomass which might be partly due to the different soil conditions and root distributions. These results would be discussed with canopy tree warming effects on aboveground carbon cycle processes (e.g. phenology and photosynthetic rate). These experimental evidences will improve our model prediction of forest carbon cycle processes under future climate change.

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last modified 2014-04-02