Spatial And Temporal Heterogeneity Of Soil Respiration In Larix Olgensis Plantation In Northeast China

A number of studies on the soil respiration in forest communities of the world were reviewed. To find the rules in spatial and temporal variation of soil respiration, periodical measurements of soil respiration by using dynamic infrared gas absorbed method and relevant environmental factors in a Larix olgensis forest in Northeast of China were conducted from April to October in 2004. The relationships were analyzed among the soil respiration rate and temperature, soil moisture and biomass components, root respiration was extrapolated by the relation of soil respiration and root biomass. The major results were summarized as follows: (1) In diurnal variation, the highest soil respiration rate were generally observed at 19:00, and at 7:00 there was a second peak value. Soil temperature was the mainly factor controlling the diurnal variation of soil respiration.(2) Soil respiration increased steadily during spring following the increasing in temperature until July when it reached a peak of 3.27μmol.m^-2s^-1. And the lowest soil respiration rate was in April, which was averaged 0.95μmol.m^-2s^-1. The series of soil respiration was arranged: Jul>Jun>Aug>Sep>Oct>May>Apr. Soil temperature and soil volumetric water content were critical factors controlling the seasonal variation of soil respiration. Variation of soil respiration had a better positive correlation with soil temperature. Respiration rate and soil moisture are positively correlated when soil volumetric water content under 20% and negatively correlated when its content above 20%. As a result, the annual soil respiration amount was estimated as 588 gCm^-2 a^-1 for Larch forest. (3) In spatial scale, the range of respiration rate were 0.48⁵.93μmol.m^-2s^-1,1.15 9.69μmol.m^-2s^-1 and 0.85 6.06μmol.m^-2s^-1, respectively. And the mean respiration rate were 1.73μmol.m^-2s^-1, 3.25μmol.m^-2s^-1 and 2.14μmol.m^-2s^-1, respectively. Root biomass became the most important factor controlling the spatial change of soil respiration.In growing season, the coefficient of variation (CV) in spatial change were 36%, 47% and 35%, respectively. The average numbers of sampling points required to estimate the mean soil respiration in experimental plots, within 10% of its actual value at 95% probability level, were 66, 85 and 62, respectively, while within 20% of its actual value were 17,22 and 16, respectively. (4) Soil respiration was measured in four forest system (Larch, Korean pine, Scotspine and birch) by Trencbing-box method, which used to understand the difference among the components of soil respiration. It showed that the largest percentage to total soil respiration is microbial respiration( above 60%), the second one is root respiration(20-30%), and the least is litter respiration(10%).