Characteristics And Temperature Sensitivity Of Soil Respiration In Degraded Peatlands In Zoige Plateau

The study of soil respiration and its temperature sensitivity(Q₁₀)has an important significance for revealing the response and its feedback mechanisms of peatland ecosystems to future climate change.Under the influence of climate change such as global warming,decrease of precipitation,increase of extreme climate and peat mining,drainage and overgrazing,peatland is seriously degraded or shrunk.However,due to very limited studies,it is impossible to predict whether the peatland is a carbon"source"or a carbon"sink"in the future climate scenarios.This study is about the soil respiration of different degradation peatland?non-degraded peatland?ND?,moderately degraded peatland?MD?and severely degraded peatland?SD??and different depth?0?20 cm,20?40 cm,40?60 cm?under different temperatures and we conducted four types of substrate addition treatments:control?CK?,glucose addition?GA?;normal litter addition?NL?and double litter addition?DL?),to identify the response of soil respiration and its temperature sensitivity(Q₁₀)to elevated temperature and substrate addition.The correlation between soil enzyme,soil properties and soil respiration was analyzed using laboratory experiment.It is of great significance for predicting regional carbon cycle in global climate change,and clarifying the response mechanism between carbon emission and degradation of peatland.The main results of this study are as follows:?1?The results showed that the cumulative emission of CO₂ decreased in the order of non-degraded peatland?ND?,moderately degraded peatland?MD?and severely degraded peatland?SD?.There was not significant difference?P>0.05?of CO₂ cumulative emission among 0?20 cm,20?40 cm and 40?60 cm depth of non-degraded peatland?ND?,accounting for 32.4%,37.4%and 30.2%of total respiration respectively.The CO₂ emission of 0?20 cm depth soil in MD and SD was higher than that of 20?40 cm and 40?60 cm depth soil,accounting for 47.5%and 68.3%of the total respiration,respectively.The difference of CO₂ emission between the moderate and severe degraded peatlands?MD and SD?was significant?P>0.05?.?2?At different temperatures,CO₂ emission increased with the increased temperature,and the soil respiration rate increased exponentially.With the increased temperature,the average CO₂ emission rate of each depth of soil increased,especially in the severely degraded peatland?SD?,the CO₂ emission rate of 0?20 cm depth soil was significantly different under varying temperatures?P<0.05?,and the CO₂emission at 15?and 25?were 135.72%and 261.25%higher than that of 5?respectively.?3?Compared with the control?CK?,the cumulative emissions of CO₂ in the soil of 20?40 cm and 40?60 cm of ND,MD and SD increased,while the cumulative emissions of CO₂ in the soil of 0?20 cm decreased,which indicated that substrate addition had an inhibitory effect on soil respiration in the soil of 0?20 cm.Compared with the treatments of GA and DL,the treatment of NL promoted the increase of soil respiration significantly.At the temperature of 5?,15?and 25?,the CO₂ emission rate of four different treatments were highest at the early stage,and decreased rapidly at the late stage,and remained at a low level.?4?The temperature sensitivity(Q₁₀)of soil respiration in MD and SD decreased with increased temperature,while the temperature sensitivity(Q₁₀)of soil respiration in ND did not change significantly with increased temperature?P>0.05?,which indicated that soil organic carbon will be more sensitive to global warming at lower temperature.The Q₁₀ values of different degrees of degraded peatland decreased in the order of SD?1.77?,MD?1.42?and ND?1.30?,which indicated that the degradation of peatland will increase the sensitivity of soil respiration to warming.Under the background of global warming,the degradation of peatland will accelerate the carbon loss of peatland,and peatland functions will change from"carbon sink"to"carbon source".Substrate addition treatment changed the temperature sensitivity of the peatland.Compared with the control treatment,substrate addition treatment increased the Q₁₀ value of the non-degraded peatland,but decreased the Q₁₀ value of the moderate degraded and severe degraded peatland.The Q₁₀ value of GA treatment was the lowest among the substrate addition treatments.?5?The correlation analysis of soil respiration and its temperature sensitivity(Q₁₀)with soil organic matter,C/N ratio and enzyme activity found that,at different temperatures,soil respiration rate was positively correlated with soil organic matter content,positively correlated with C/N ratio at 5?,negatively correlated at 15?and25?,and the correlation was not significant?P>0.05?.The correlation between Q₁₀and organic matter content was significant at 5?15??P<0.05?.The sucrase and catalase activities increased under the combined treatment of warming and substrate addition.The soil respiration rate was significantly correlated with sucrase and catalase activities in the NL and DL?P<0.05?,but not with catalase activities?P>0.05?.The differences of soil respiration and its temperature sensitivity(Q₁₀)at different degradation degrees and depths were the results of the combined interactions of soil enzyme activities,soil organic matter content and C/N ratio.