关键词: 土壤呼吸速率, 时空变化, 天山云杉, 天然林

Abstract: Soil respiration is an important component of the global carbon cycle and the most important output approach of soil carbon as well as one of the largest fluxes in the global carbon cycle.Relevant researches on forest soil respiration rate have been carried out in some forest regions in China. However,few studies have been done in the Tianshan montane forest ecosystem.Xinjiang Uygur Autonomous Region located in the centre of Eurasian continent occupies a large area(about 1/6 of the total area of China)and is the biggest province in China.The Tianshan Mountains lie in the middle of the province.Picea schrenkiana var. tianschanica (Rupr.)Chen et Fu natural forest is the main forest vegetation in the Tianshan Mountains. Here,spatial and temporal patterns of soil respiration under the natural stand of P. schrenkiana var.tianschanica(Rupr.)were studied during the growing season(from June to September)in 2006. Using soil respiration chamber of LI-6400-09 and portable photosynthesis system that based on the principles of infra-red gas analyzer,we measured soil respiration rate of P. schrenkiana var. tianschanica(Rupr.)natural stand in the Tianshan montane forest ecosystem,and analyzed its variation in different elevation gradients.At the same time,we measured diurnal changes of soil respiration rate of P. schrenkiana var. tianschanica (Rupr.)natural stand at an elevation of 1956m.The objectives of the study were as follows:(1)analyzing the main factors that affect the seasonal and diurnal variability in soil respiration during the growing season; and(2)understanding the spatial variation of soil respiration along the elevation gradient in the growing season. The results showed that the soil respiration rate fluctuated along the elevation gradient. From 1950m to 2110m,soil respiration rate decreased with the increase of elevation.From 2110m to 2428m,it increased with the increase of elevation,and the highest value of soil respiration rate occurred at 2428m.From 2428m to 2620m,it decreased.The statistic test showed that the soil respiration rate was highly significantly correlated with air humidity near the soil surface(p<0.01),and significantly correlated with the 10cm soil temperature under the soil surface at different elevations(p<0.05).Changes of soil respiration rate were the unimodal form from June to September in the growing season.The maximum value(5.38±0.79μmol·m-2·s-1)occurred in July. Diurnal change of soil respiration rate in P. schrenkiana var. tianschanica(Rupr.)natural stand were mainly affected both by the soil temperature(p<0.01)and the air temperature humidity near the soil surface (p<0.05). This study demonstrates that elevation gradient could be used as an indirect environmental indicator in analyzing spatial variation of soil respiration for P. schrenkiana var. tianschanica (Rupr.)natural forest ecosystem in the Tianshan Mountains.And the temporal change of the soil respiration was mainly controlled by temperature and moisture which varied diurnally and monthly.

Key words: Picea schrenkiana var. tianschanica(Rupr.)Chen et Fu, natural forest, soil respiration rate, spatial and seasonal heterogeneity