天山云杉天然林分土壤呼吸速率的时空变化规律分析

天山云杉(Picea schrenkiana var.tianschanica(Rupr.)Chen et Fu)是构成天山山地森林生态系统的主体。在天山中部,从天山云杉在此区域分布的底线开始,结合天山云杉自然分布特征,沿每隔约100m的海拔梯度选择典型地段设置样地。根据远红外气体分析原理,采用LI-6400-09土壤呼吸室和LI-6400便携式光合作用测量系统,于2006年6-9月,测定了天山云杉天然林分在生长季内土壤呼吸速率随海拔高度和时间的变化规律。在空间上,林分的土壤呼吸速率并非随海拔高度呈线性增加或减少的关系,而是有规律的波动,在海拔1950～2110m之间,土壤呼吸速率是随着海拔高度的增加而降低,在2110～2428m之间是随着海拔高度的增加而升高,在海拔2428m处达到最大的呼吸速率值后又降低。不同海拔高度林分的土壤呼吸速率主要受土壤表面空气相对湿度及土壤温度的影响。在时间上,林分的土壤呼吸速率在生长季内随不同月份的变化为单峰曲线,其最大值出现在7月份;生长季内土壤呼吸速率与土壤温度呈显著负相关,与土壤表面空气相对湿度呈极显著正相关。而林分土壤呼吸速率的日变化在各时间点上的大小排序为7月>6月>8月>9月。它的变化与土壤温度具有极显著的正相关性,与土壤表面空气相对湿度具有显著的负相关性。

Spatial and Temporal Variation in Soil Respiration of Picea. schrenkiana.var tianschanica (Rupr.) Chen et Fu Natural Stand in the Tianshan Mountains

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.