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.

摘要

在东亚地区的森林生态系统中，土壤冻融事件通常发生在田间，这可能会影响土壤碳（C）和氮（N）动态和温室气体（GHG）通量。由于亚洲季风的影响，东亚森林通常夏季降雨充足，秋季降水多变。此外，他们最有可能经历变暖背景下冬季降雪量减少引起的土壤冻融事件的变化。这会在一定程度上影响该地区森林生态系统中土壤温室气体通量和溶解有机碳（DOC）和氮淋失的年际变化。根据主要在东亚的森林土壤的实验室和现场测量，本综述总结了土壤碳和氮动态以及与冻融事件相关的温室气体通量的最新结果。在冻融干扰下，东亚森林土壤中溶解有机质（DOM）和无机氮的浓度和浸出通量大多增加，土壤微生物特性如微生物生物量和酶的活性会发生变化。可能取决于温度和冷冻持续时间、冻融频率和土壤湿度。很少有研究报道冻融扰动会影响释放到东亚森林土壤中的 DOM 的数量、成分和稳定性，这些 DOM 随土壤水分、凋落物输入和 N 添加而变化。迄今为止，在冬季气候变化条件下，东亚森林生态系统土壤温室气体通量和养分流失的现场测量相对较少。需要长期实地测量来探索冬季气候变化及其与秋季降水变化和人类活动（如氮沉降和森林管理）的相互作用对土壤年温室气体通量和东部地区年温室气体净平衡的影响。亚洲森林年降水量不同的年份。这确实有助于更准确地预测东亚地区森林生态系统中气候变化的影响和反馈。