为探明东北温带森林恢复过程中土壤呼吸(RS)的变化趋势及其影响因子,在帽儿山选取皆伐后天然更新恢复的4个年龄(1a、10a、25a和56a)林分进行了1年的野外原位测定.结果表明:(1)皆伐后天然更新恢复1年、10年、25年和56年林分的年RS通量差异显著(P＜0.05),分别为686.5、639.7、733.3、762.3g C m-2 a-1;其中生长季(5月-10月)和非生长季的RS通量也存在显著差异,均呈现出随林龄增加先减后增的趋势.全年、生长季和非生长季RS随林龄变化的变异系数分别为7.6％、6.3％和21.1％,表明非生长季RS通量的变异性加大了全年RS通量的差异.(2)4个年龄林分的Rs季节变化趋势相似,且其主控因子均随季节而变:6月-8月RS与土壤含水率呈二次函数关系(R2波动在56％-79％之间),其余时段则与土壤温度呈指数函数关系(R2波动在85％-93％之间).(3)不同年龄林分生长季RS与0-20cm土层有机碳(SOC)密度呈正相关关系(R2=0.434,P＜0.05),而非生长季RS与同期土壤5cm温度呈正相关关系(R2=0.959,P＜0.01).本研究区森林皆伐导致RS降低,随皆伐后森林恢复RS不断增加,其主导驱动因子是SOC密度的增加和非生长季土壤温度的变化.%Soil respiration (RS) is the major source of CO2 efflux to the atmosphere from forest ecosystems.It plays an important role in the carbon balance of the ecosystems.The temperate forests in Northeast China are a mosaic of different aged stands resulting from various logging disturbances.The objective of the present study was to examine variations in RS and its driving factors as the forests recovered from clear cutting with a chronosequence approach.The chronosequence that included stands of four ages (i.e.,1,10,25,and 56 years since logging) was established in 2014 in the Maoershan region,Northeast China (45°24′ N,127°40′ E).The RS was measured with a LI-840 CO2/H2O analyzer from April 2014 to March 2015;and the soil temperature and water content at a depth of 5cm were measured simultaneously.Soil organic carbon (SOC) and fine root (diameter ＜ 0.5mm) biomass were also measured at the end of the growing season.The results showed that:(1) the annual RS differed significantly among the stands (P＜0.05),and averaged 686.5,639.7,733.3,and 762.3g C m-2 · a-1 for the 1-,10-,25-,and 56-year old stands,respectively.The RS in the growing and non-growing seasons differed significantly among the stands.It showed a decreasing trend immediately after the clear cutting,and subsequently increased with increasing the stand age.The coefficients of variation in RS among the stands were 7.6％,6.3％,and 21.1％ for the whole year,growing season,and non-growing season,respectively,suggesting that the variability in the RS among stands in the non-growing season amplified the variation in the annual RS.(2) The RS of all the stands followed a similar seasonal trend,but the controlling factors varied with seasons.The RS between June and August was significantly related with soil water content in a polynomial function (R2 =56％-79％),whereas the RS during the rest months was significantly related with soil temperature in an exponential function (R2=85％-93％).(3) The RS in the growing season was correlated positively with SOC content at a depth of 0-20cm in all the stands (R2 =0.434,P＜0.05),whereas that in the non-growing season was correlated positively with soil temperature at a depth of 5cm in the same season (R2 =0.959,P＜0.01).These results suggest that the RS in these forests decrease after logging disturbance and increase with increasing the stand age,driven mainly by the increased SOC content and changes in soil temperature during the non-growing season.
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