Effect of freeze-thaw disturbance on soil C and N dynamics and GHG fluxes of East Asia forests: review and future perspectives

Abstract

ABSTRACT In forest ecosystems of East Asia region, soil freeze-thaw events occur normally in the field, which may affect soil carbon (C) and nitrogen (N) dynamics and greenhouse gas (GHG) fluxes. Due to the influence of Asian monsoon, forests in East Asia usually have sufficient rainfall in summer and varying precipitation in autumn. In addition, they are most likely to experience the changes of soil freezing and thawing events caused by the reduction of winter snowfall under the background of warming. This can to some extent affect the interannual variations of soil GHG fluxes and dissolved organic carbon (DOC) and N leaching in forest ecosystems in this region. This review summarized recent results on soil C and N dynamics and GHG fluxes associated with freeze-thaw events, according to laboratory and field measurements of forest soils mostly in East Asia. Upon freeze-thaw disturbance, concentrations and leaching fluxes of dissolved organic matter (DOM) and inorganic N were mostly increased and soil microbial properties such as microbial biomass and the activity of enzymes would be changed in the soils of East Asia forests, which was most likely dependent on temperature and duration of freezing, freeze-thaw frequency, and soil moisture. Fewer studies reported that the freeze-thaw disturbance would affect the quantity, components, and stability of DOM released into the soils of East Asia forests, which varied with soil moisture, litter input and N addition. To date, there have been relatively fewer field measurements of soil GHG fluxes and nutrient leaching in forest ecosystems of East Asia under winter climate change conditions. Long-term field measurement should be needed to explore the effects of winter climate change and its interaction with the varying precipitation in autumn and human activity (e.g., N deposition and forest management) on soil annual GHG fluxes and the net annual GHG balance of East Asia forests during years with the varying annual precipitation. This is indeed useful to predict more precisely the effects of, and feedbacks to climate change in forest ecosystems of the East Asia region.