Effects Of Fire Disturbances On Soil Respiration Of Larix Gmelinii Forests In The Daxing’an Mountain During Non-growing Season

Soil respiration in non-growing season, which affects the soil carbon balance of forest ecosystems observably, contributes14%to30%of the total respiratory efflux throughout the whole year. Forest fire is a major factor which influences the carbon balance of boreal forests. The Daxing’an Mountain is a key distribution area for Chinese boreal forests and is a fire-prone area, thus, understanding post-fire soil respiration, especially for the influence of the Larix gmelinii forests during non-growing season (November,2011to April,2012), is important in the study of this area’s carbon balance. We used the Li-Cor8100Automatic Measuring System for Soil Carbon Flux to detect soil respiration rate in snow-clad conditions and in snow-out conditions after different intensities of fire disturbance in the Larix gmelinii forests during non-growing season, at the time of soil respiration measurement, soil temperature at5cm depth, thickness and mass of snow were also measured. In this paper, on the basis of expounding and comparing the various methods of measuring soil respiration and reviewing the conditions of soil respiration after forest fire, we quantified the dynamic characteristics of soil respiration in the the Larix gmelinii forests throughout the non-growing season and studied the effects of different intensities of fire disturbances (Serious, Moderate and Mild) on soil respiration in the Larix gmelinii forests. What we tried to explain were as follows:(1) to quantify the dynamic characteristics of soil respiration rate in the the Larix gmelinii forests throughout the non-growing season;(2) to study the effects of different intensities of fire disturbances on soil respiration in the Larix gmelinii forests;(3) to discuss the effects of snow on soil respiration in forest ecosystems during non-growing season; and (4) to determine the relationship between soil respiration and soil temperature at5cm depth, snow water equivalent and the interaction between soil temperature at5cm depth and snow water equivalent throughout the non-growing season.The results were as follows:The seasonal dynamics of soil respiration in the Larix gmelinii forests throughout the non-growing season shows a "U" trend, the soil respiration rate fluctuated slowly from January to March, and it ranged from0.03to0.046μmolC·m-2·s-1, and the average was0.039μmolC·m-2·s-1, though the average of soil respiration in the Larix gmelinii forests throughout the non-growing season was0.39μmolC·m-2·s-1. And the soil respiration throughout the non-growing season correlated positively and significantly with environmental factors, the relationship between soil respiration and soil temperature at5cm depth or snow water equivalent was more positive than with the interaction between soil temperature at5cm depth and snow water equivalent, and the soil temperature at5cm depth affected more than other environmental factors(P<0.01). The soil temperature at5cm depth and the soil respiration rate in the burned sample plots with three burn different intensities were lower than in the unburned control areas, the soil respiration rate decreased with the three burn intensities enhanced. The soil respiration rates of control, mild, moderate and serious were0.39,0.34,0.29and0.27μmolC·m-2·s-1. The soil temperature at5cm depth ranged from-15.4to2.0℃, and the minimum temperature occurred in February, the soil temperature at5cm depth of control, mild, moderate and serious were-4.6,-4.4,-6.1and-6.5℃. The soil temperature at5cm depth in the burned sample plots with three burned different intensities were rising faster than in the unburned control areas during the thawing and the late of thawing, and the temperature was higher in the serious burned sample plots than in the mild burned sample plots. The maximum Q10occurred in the unburned control plot, was51.42, and the Ql0of serious, moderate and mild were16.71,29.17and19.87, but they were all higher than they were in growing season at the same plots.Snow had a large influence on soil respiration, it rise the soil temperature during the non-growing season, and the average soil temperature at5cm depth in snow-clad conditions was2.5℃higher than in snow-out conditions, and the maximum was6.1℃higher, the average soil respiration rate in snow-clad conditions was0.03μmolC·m-2·s-1higher than in snow-out conditions, and the maximum was0.30μmolC·m-2·s-1higher. But the soil temperature at5cm depth were rising faster in snow-out conditions than in snow-clad conditions, and it increased significantly with the fire intensity increased.