Respiration Dynamic Change Of The Qinghai-Tibet Plateau Alpine Swamp Meadow Soil And Its Response To Warming

Under the global warming, the alpine meadow ecosystem is more easily affected by climate change. To explore the change of soil respiration on Alpine meadow under climate warming, taking kobresia pygmaea meadow in Qinghai-Tibet plateau as the research object, the soil respiration change of alpine meadow and its response to warming is explored in this paper by measuring the soil respiration rate of alpine meadow in natural under warmer conditions from June 2015 to October 2015.The results of the study are as follows:1. During the whole observation, the soil temperatures in the depth of 5 cm,10 cm and 15 cm under warming condition were all higher than those in natural condition with an increase respectively of 1.289 ℃,1.297 ℃ and 1.004 ℃. Warming decreased the soil water content per unit volume in the depth of 5 cm and 10 cm, while increased that in the depth of 15 cm; the soil water content per unit volume under natural condition in the depth of 5 cm,10 cm or 15 cm was higher than that under warming condition with an increase of 0.522%,3.077% or -1.551% respectively. Warming led to an increase of the earth biomass by 36.15%; whereas it also reduced the organic matter contents of soils in the depth of 0-5 cm,5-10 cm, 10-15 cm,15-20 cm by 2.17%,5.19%,3.28%,5.12%respectively, comparing to those in natural conditions.2. During the whole observation, the soil respiration rate under warming condition (Rsw) was 3.07±0.112μmolm·-2s·-1, under natural and warming state soil respiration rate had significant difference (P<0.05); the soil respiration rate under natural condition (Rsn) was 2.273±0.097μmol·m-2·s-1. The average monthly soil respiration rate under natural and warming temperature conditions during the observation showed Rs10<Rs9<Rs6<Rs8<Rs7; the change trend of mean difference of the soil respiration rate was similar to that of the temperature under natural and warming conditions every month.3. During the whole observation, the soil temperature in the depth of 5cm played a leading role to the change of the Rs under both natural and warming conditions(P<0.01); the influence of the change of the temperature and water content per unit volume in the depth of 10 cm or 15 cm on Rs was gradually increasing with the decrease of temperature. By analyzing the partial correlation of Rs with soil temperature and water content per unit volume every month, it has been found that in June, July and August soil temperature and water content per unit volume inhibited each other of their impacts on the Rs in the depth of 5cm, while in the depth of 10cm and 15cm, soil temperatures and water contents per unit volume in the same layer mutually promoting and developing their impacts on the Rs; in September and October, soil temperatures and water contents per unit volume in the same layer in the depth of 5cm,10cm and 15cm promoted each mutually promoting and developing their impacts on the Rs.4. The minimum value of soil respiration rate under warming condition appeared earlier than that under natural condition whereas the maximum value lagged. Under the natural condition, the minimum and maximum value of soil respiration rates appeared earlier in June and July before the sunshine duration began to decline; from August on when the sunshine duration gradually became shorter and shorter, the minimum value of soil respiration rate appeared later and later, often before dawn, with an obvious regularity on time change; the change regularity of the minimum value under warming condition agreed with that under natural condition; under natural and warming conditions, the maximum value usually appeared at 13:00-15:00.5. In daytime, the Rs under warming condition was higher than that under natural condition by 1.078μmol·m-2·s-1; in the nighttime, the Rs under warming condition was higher than that under natural condition by 0.411μmol·m-2·s-1. The soil respiration rates in every month in daytime were greater than those in the nighttime under warming condition; while the soil respiration rates in every month in the nighttime were greater than those in daytime under natural conditions, except for October (on the converse). Under natural and warming conditions, the soil respiration rates contributed to the total soil respiration 52.88% and 57.93% respectively. Under natural conditions, it was in daytime that the influence to the Rs of the soil temperature and water content per unit volume was greater, while under warming condition, it was in the nighttime.6. Q10 value of daily variation of soil respiration under warming condition was mostly higher than under natural condition; Q10 value under warming condition had an significant and negative correlation with temperature(P<0.05), having a very significant and positive correlation with water content per unit volume(P<0.01); Q10 value under natural conditions had no significant correlation with temperature(P=0.3353), having very significant positive correlation with water content per unit volume(P<0.05). Q10 value of soil respiration in daytime was greater than that in the nighttime under both natural and warming conditions. On the whole observation scale, the Q10 value under natural condition was higher than that under warming condition.