东北东部5种温带森林的春季土壤呼吸

春季土壤解冻过程是中高纬度地区森林生态系统土壤呼吸(即土壤表面CO2通量,RS)年内变化的一个关键时期,但此期间RS的时间动态规律及其控制机理尚不清楚。以我国东北东部5种温带森林为研究对象,采用静态箱-气相色谱法测定春季土壤解冻时期RS动态及其相关的环境因子。结果表明:在土壤解冻过程中,RS受林型、解冻时期及其交互作用的显著影响。红松(Pinus koraiensis)林、落叶松(Larix gmelinii)林、硬阔叶林、杨桦(Populus davidiana-Betulaplaty phylla)林和蒙古栎(Quercus mongolica)林的RS变化范围依次为:10.0196.0mg·m-·2h-1,5.8217.1mg·m-·2h-1,9.7382.1mg·m-·2h-1,15.8-269.0mg·m-·2h-1和35.9262.5mg·m-·2h-1。RS的平均值随着解冻的进程而增大,其变化趋势大致与土壤温度的变化相吻合。土壤温度极显著地影响RS(R2=0.46-0.77),而土壤含水量对RS的影响则因林型和土壤深度而异。5种林型的土壤呼吸温度系数(Q10)依次为:落叶松林10.9,硬阔叶林7.1,红松林6.5,杨桦林4.3和蒙古栎林2.3。进一步的研究应该集中研究春季自然解冻过程中土壤呼吸的控制机制,尤其是土壤呼吸与土壤微生物种群动态及其活性之间的关系。

Vernal soil respiration of five temperate forests in Northeastern China

Spring soil thawing period is critical in the intra-annual dynamics of soil respiration (RS) in mid- and high latitudes forest ecosystems, in which the frequently occurring alternate freezing and thawing events strongly influence the availability and dynamics of soil carbon and nutrients. However the temporal changes of RS and involved mechanisms are poorly understood. Especially in situ measurements of RS in spring soil thawing process are needed. In this study, a static closed chamber-gas chromatograph technique was used to measure the vernal RS and related biophysical factors in representative temperate forests of Northeast China. The experimental design included five forest types, three random plots in each forest type, and three randomly installed static chambers in each plot. The forests were oak forest dominated by Quercus mongolica, poplar-birch forest dominated by Populus davidiana and Betula platyphylla, hardwood forest dominated by Fraxinus mandshurica, Juglans mandshurica and Phellodendron amurense, Korean pine (Pinus koraiensis) plantation, and Dahurian larch (Larix gmelinii) plantation. The RS was measured every week between March and May 2009, and 9 times in total. Soil temperature and water content were concurrently measured at 2 cm (T2, W2) and 10 cm (T10, W10) depths near each chamber. During the soil thawing period, the forest types, thawing periods and their interaction significantly affected the RS. The RS for the pine, larch, hardwood, poplar-birch, and oak forests varied from 10.0-196.0 mg?m-2?h-1, 5.8-217.1 mg?m-2?h-1, 9.7-382.1 mg?m-2?h-1, 15.8-269.0 mg?m-2?h-1, and 35.9-262.5 mg?m-2?h-1, respectively. The mean RS, T2 and W2 differed significantly among the five forest types (P < 0.001). The RS for broadleaved forests were generally higher than coniferous plantations. The mean values of RS increased as the soil thawing proceeded, and were largely consistent with the changes in soil temperature. Soil temperature significantly influenced the RS, while the effect of soil water content on the RS varied with forest types and soil depths. The RS was significantly affected by W2 for all forests except for the oak forest. The statistical models of the RS against T2 and W2 explained 60%-77% of the variability in the RS measurements. Temperature coefficients of RS (Q10) during the spring soil thawing period were much higher than those in the growing season, and changed with forest types. The Q10 for the larch, hardwood, pine, poplar-birch, and oak forests were 10.9, 7.1, 6.5, 4.3, and 2.3, respectively. Further studies should focus on the mechanisms controlling vernal soil respiration in the in situ soil thawing process, especially on temporal dynamics of soil microbial population in spring soil thawing process and the relationship between soil respiration and soil microbial activity and composition.