Short-term Effect Of Simulated N&S Deposition On Soil Respiration In Larix Princips-rupprechtii Plantation In Taiyue

The influence of simulated nitrogen and sulfur deposition on soil respiration was studied in Larix principis-rupprechtii Plantation in Taiyue Mountain.Three litter treatment subplots including control(C),litter exlusion(B), litter and root exclusion (A) were established.According to the nitrogen and sulfur deposition in natural condition,frequency and intensity of the simulated deposition were set up as,CK(0 kg N·hm-2·a-1),LN(50 kg N·hm·2·a-1),MN(100 kg N·hm-2·a-1),HN(150 kg N·hm-2·a-1),LS(50 kg S·hm-2·a-1),MS(100 kg S·hm-2·a-1),HS(150 kg S·hm-2·a-1).The short-term effects of nitrogen deposition, sulfur deposition and combined deposition on the soil respiration of Larix principis-rupprechtii Plantation were studied, and the effects of water and heat factors such as soil temperature and moisture on soil respiration were analyzed.The results showed:1)Soil temperature and moisture mainly affected the seasonal variation of soil respiration rate,which was not changed by simulated nitrogen deposition. Simulated nitrogen deposition did not change the seasonal variation of soil temperature and soil moisture,either.During the observation period,total soil respiration was significantly enhanced by HN(P<0.05);Nitrogen deposition had no significant influence on litter respiration (P>0.05);MN significantly promoted root respiration (P< 0.05);Mineral soil respiration rate increased with the increase of N deposition.The relationship between root respiration and root temperature was not significant(P>0.05), while there was a significant relationship between other components of respiration rate and soil temperature(P<0.05).Compared with the single factor model, the double factor model (Rs=aebTWc) can better explained the seasonal variation of soil respiration.2)During the observation period,the sulfur deposition did not change the seasonal variation of soil respiration rate. The total soil respiration rate increased with the increase of sulfur deposition, and the total soil respiration rate was significantly different between CK (P<0.05) under different sulfur deposition levels.MS decreased litter respiration rate; Sulfur deposition promoted root respiration rate, HS significantly promoted root respiration rate (P<0.05); Sulfur deposition significantly promoted mineral soil respiration rate (P<0.05).The relationship between root respiration and root temperature was not significant(P>0.05),while there was a significant relationship between other components of respiration rate and soil temperature(P<0.05).Compared with the single factor model, the double factor model (Rs=aebTWc) can better explained the seasonal variation of soil respiration.3)The result showed that soil respiration had significant seasonal variation under simulated nitrogen and sulfur deposition in the growing season. Nitrogen and sulfur deposition significantly promoted the soil respiration.The greater concentration of the nitrogen and sulfur was, the stronger the CO2 emission of soil would be. Nitrogen and sulfur combined deposition improved soil respiration. Nitrogen deposition promoted the soil respiration, High nitrogen level had significant effect on soil respiration(P<0.05). Soil respiration had positive relationship with sulfur deposition level(P<0.05). Soil respiration promoted under combined depositin. The soil respiration rate of HNHS had significant difference with CK(P<0.05), while MNMS decreased the soil respiration rate, but not reaching the significant level(P>0.05).HN and HS had synergistic effect,while MN and MS had antagonism.The soil respiration of combined deposition were higher than CK under the condition of litter exclusion, and MNHS as well as HNLS significantly promoted soil respiration rate(P<0.05);LNLS、LNMS、LNHS、 MNMS、MNHS、HNMS and HNHS significantly promoted soil respiration rate(P<0.05).