The Study Of Soil Respiration In Davurian Larch And Manchurian Ash Plantations

Soil respiration (Rs) is the process that soil releases CO₂ to atmosphere (also called soil surface CO₂ flux), is the important part of carbon cycling in terrestrial ecosystems. Studys on the soil respiration of two plantations will make further know the fine root turnover, carbon cost of two plantations and carbon cycling at stand level. In this study, we measured the soil respiration and soil temperature at 5 cm and 10 cm depths using infrared gas exchange analyzer (Li-Cor-6400) at fertilized and unfertilized plot of Davurian larch (L. gmelinii) and Manchurian ash (F. mandshurica) plantations which are in the same site. The results as follow:The average soil respirations of two plantations differed significantly: the average soil respiration of Larch plantation at growth season was 2.51 μmolCO₂·m^-2·s^-1;the average soil respiration of Ash plantation was 3.13 μmolCO₂·m^-2·s^-1, and which of Ash plantation was higher than Larch plantation about 20%. The soil respirations of two plantations had same seasonality: the soil respiration increased from May (Spring) to August (the highest in Summer), then decreased to the lowest at October (Autumn) in growth season.We found that the fertilizer influenced the soil respiration of Larch and Ash plantations differently: the soil respiration of fertilized plot was lower than control plot in Larch plantation (34.9%,p<0.05) and Ash plantation (25.8%,p<0.05). At fertilized plot, the soil respirations of two plantations also had significantly seasonality, and the average soil respiration of every mouth was lower than control plot. The average soil respiration of Larch was lower 20% than that of Ash plantation at fertilized plot. The fertilizer did not change the difference of the average soil respiration of two pangtations, But decrease the soil surface CO₂ flux of two plantations.There were significant exponent relationship (p<0.05, R²>0.93) between the soil respiration seasonality of two plantations and the seasonality of soil temperature at 5 cm and 10 cm depths, and the relevance of two species at 5 cm was higher than 10 cm. The Q₁₀ of Larch and Ash plantation was different: Q₁₀ of Larch plantation at 5 cm and 10 cm was 3.05 and 3.29 respectively;Q₁₀ of Ash plantation at 5 cm and 10 cm was 2.45 and 2.60 respectively, the Q₁₀ of Larch plantation was higher than Ash plantation. But fertilizer did not change the Q₁₀ of two plantations.The soil surface CO₂ flux of two plantations was different, annual soil surface CO₂ flux in Ash plantation was: 687.8 gC·m(-2)·a^-1 (5 cm soil temperature) and 692.0 gC·m^-2·a(-1)(10 cm soil temperature);the annual soil CO₂ flux in Larch plantation was 515.4 gC·m^-2·a^-1 (at 5 cm soil temperature) and 554.1 gC·m^-2·a^-1(at 10 cm soil temperature), we concluded that the soil surface CO₂ of conifer plantation was lower than hard-wood plantation.