Effects of forest fires on soil carbon and nitrogen storages in the permafrost region in the Da Xing'anling Mountains,NE China
In the boreal permafrost region,forest fires not only affect the soil properties of forest ecosystems,but also the permafrost environment,soil organic carbon (SOC) and total nitrogen (TN) contents and storages. The permafrost region in Northeast China is located at the southern margin of Eurasia permafrost zone,which is undergoing extensive degradation under the influence of climate change and human activities. This affects car-bon emissions,carbon and nitrogen storages in permafrost region,creating a positive feedback effect on climate warming. In this study,we selected the burned area in 2009 in Alongshan,northern Da Xing'anling Moun-tains,and the unburned site as a control to study the effects of different fire severity (light and severe burn) on the SOC and TN contents and storages in the permafrost region. The results showed that:(1) SOC and TN con-tents and storages varied significantly at different fire severities sites,and gradually decreased with increasing fire severity. Compared with the unburned site,SOC contents decreased by 9.78％ and 65.11％,respectively;SOC stocks decreased by 9.29％ and 68.48％,respectively;TN contents decreased by 1.99％ and 52.49％,re-spectively;and TN stocks decreased by 3.23％ and 51.61％ at the light and severe burned sites,respectively. With the increase of soil depth,SOC and TN content gradually decreased;SOC storages showed a fluctuation pattern at burned site,increased first and then decreased at light burned site,and gradually decreased at severe burned site;TN storages showed a fluctuation pattern at unburned and light burned sites,and gradually de-creased at severe burned site. (2) Soil temperature increased gradually with increasing fire severity. At depths of 0～100 cm,compared with the unburned sites,soil temperatures increased by (0.87±0.18) ℃ and (9.09±0.37) ℃ at light and severe burned sites,respectively;soil moisture contents (SMC) increased by (17.79±3.36)％ at light burned site and decreased by (16.71±2.92)％ at the severe burned site. Soil temperature and SMC decreased with increasing soil depth. (3) Redundancy analysis (RDA) showed that soil microbial biomass nitrogen (MBN) was the key factor affecting post-fire soil carbon and nitrogen contents and storages,with an ex-planatory rate of 65.6％ (P=0.002). SOC and TN contents were significantly positively correlated with soil tem-perature,SMC,NH4+-N,microbial biomass carbon (MBC) and MBN,and significantly negatively correlated with fire severity,soil depth,and pH. SOC and TN storages were significantly negatively correlated with fire se-verity,soil depth,soil temperature,soil bulk density,and NO3--N. In summary,forest fire has a significant ef-fect on SOC and TN storages,resulting in the loss of SOC and TN storages,altering the distribution pattern of carbon and nitrogen pools,and reducing the stability of soil carbon and nitrogen pools. The study of forest fires on SOC and TN contents and storages is of great significance to the ecosystem carbon balance and the manage-ment of ecological environment in the cold region,and it can provide important data references for the SOC and TN storages in the boreal permafrost region.
permafrostDa Xing'anling Mountainssoil organic carbon storagessoil total nitrogen storagesfire severity
万方数据
维普
