Seasonal changes and the driving factors of soil respiration among five typical forest types in the high-elevation-cold region, Qinghai, northwestern China.

Soil respiration, which has a great influence on global climate change, plays an important role in terrestrial ecosystem carbon cycle. Analysis of soil respiration and its response to global climate change is critical to assessment of ecosystem carbon budget.Alpine region is an important part of terrestrial ecosystem, thus the research of environmental factors influence on soil respiration in this region is contributive to understand the process of soil-carbon cycle. This paper used the method of infrared CO2 determination in closed dynamic chamber system. Taking five kinds of typical forest stand (L. principis-rupprechtii plantation, Picea asperata plantation, mixed forest of Picea asperata and L. principis-rupprechtii, mixed forest of Picea asperata and Betula platyphylla, natural forest of Betula platyphylla) in alpine region of Qinghai as the research object, the characteristics of seasonal variations of soil respiration in growing season and the relationship between soil respiration and environmental factors were studied. The results showed that the rank of soil respiration rate for five forest stands was Picea asperata forest Betula platyphylla forest mixed forest of Picea asperata and L. principis-rupprechtii L. principis-rupprechtii forest mixed forest of Picea asperata and Betula platyphylla. Soil respiration of the five forest stands showed seasonal dynamic pattern consistently, which was peaking in July. The mixed Picea asperata and L. principis-rupprechtii forest had the maximum seasonal variation, while the L. principis-rupprechtii forest had the minimum variation in soil respiration. The highest soil respiration was 17.36 and 1.83 times of the lowest soil respiration respectively. The soil respiration of L. principis-rupprechtii forest had no relationship with soil temperature, a positive correlation with air temperature(R2=0.75)and fitted a power function model, a negative correlation with soil moisture content. The soil respiration of the other four forest types had a positive correlation with the air temperature and soil temperature (R2=0.80~0.94) and fitted a power function model, which is not related to the soil moisture content. Soil respiration increased with the increasing of litter biomass. The contribution of litter respiration in mixed forest was greater than the pure forest.