| Climate warming affects the dynamic changes of forest soil respiration and soil carbon pool,and forest soil respiration is an effective way for the largest terrestrial organic carbon pool to input into the atmospheric carbon pool.There are positive or negative feedback effectsbetween forest soil respiration and warming,which will affect the function of forest carbon’s "sink-source".Therefore,in order to elucidate the spatial-temporal variation characteristics of soil respiration rate and its response mechanism to warming in natural secondary forests in warm temperate zone,we studied the spatial-temporal variation of soil respiration rate in the following four forests in Guandi mountain: poplar-birch forest(FB),Pinus tabulaeformis forest(PT),Larix principis Rupprecht forest(PL)and Picea asperata Mast.Forest(PF).A long-term field in-situ soil warming simulation experiment were conducted to observe the growth season variation of soil respiration under four altitude gradients,and to quantify the quantitative relationship of soil respiration components.The article will reveal the spatio-temporal variation characteristics of forest soil respiration and its response mechanism to warming,provide theoretical basis and data support for the study of forest soil respiration mechanism,and have important significance for accurately evaluating the impact of climate warming on forest soil carbon pool.The results were as follows:The results showed that there were significant differences in soil respiration rate(Rt),heterotrophic respiration rate(Rh)and autotrophic respiration rate(Ra)among four forest types,with the ranges of3.16-3.31 μmol·m-2·s-1,1.83-2.15 μmol·m-2·s-1 and 1.16-1.33 μmol·m-2·s-1,respectively.Autotrophic respiration was the main part of forest soil respiration,and its contribution rate was 57.93%-65.19%.Rt,Rh,Ra had significant seasonal variation characteristics,which a single peak curve with the peak value in August was formed.Rt and Rh decreased with the increase of altitude,while Ra of different forest types had different responses to the changes of altitude scale.Soil respiration rate decreased significantly with the depth of soil layer,but the sensitivity to temperature increased significantly.However,not all soil respiration components had significant altitudinal and annual patterns.The average soil temperature increased by 2.13℃-2.28℃,and Rs,Rh and Ra increased by7.49%-12.59%,8.43%-15.51% and 6.28%-9.75% respectively.The sensitivity of soil respiration and its components to warming decreased first and then increased in the growing season,and increased with the increase of altitude,with the highest in May and the lowest in September,and that of high altitude was more sensitive than that of low altitude.The response of different components of soil respiration to warming was different,which the components of soil heterotrophic respiration Rl,Rm,were significantly increasedby 14.15%-21.72% and 7.97%-18.15%,respectively,and the components of soil autotrophic respiration Rrs and Rrh,were significantly increased by 10.25%-14.48% and 16.54%-28.27%,respectively,and the response degree to warming had significant elevation pattern and annual variation pattern about them alike Rs,Rh and Ra.But the response of Rra to warming was not obvious.Increasing temperature decreased the contribution of autotrophic respiration Rt to total soil respiration,but increased the contribution of heterotrophic respiration and its components to total soil respiration.Increasing temperature increased the proportion of Rrh and Rrs in Ra,and decreased the proportion of Rra,but they were not significant.The sensitivity of Rl,Rm,Rrs,and Rrh to temperature increase in time and space was similar to Rt.There was a significant negative correlation between the root respiration of the arbor layer vegetation and the root respiration of the herb layer vegetation,and the correlation coefficient was significantly changed by increasing temperature.Q10 of soil respiration and its components were increased by warming,but the response degree and direction of Q10 to warming were different under different forest types and different temporal and spatial scales.The succession had the trend of decreasing soil respiration rate Rt,heterotrophic respiration rate Rh and autotrophic respiration rate Ra.Succession decreased the contribution rate of Ra to Rt,but increased the contribution rate of Rh to Rt.Succession improves the sensitivity of soil respiration and its components to warming and the value of Q10.Increasing temperature significantly affected the succession process of Rh,making Rh in late succession return to early succession,while the response degree and directionality of soil respiration and soil autotrophic respiration to increasing temperature varied with forest types.Succession and warming had different coupling effect on forest soil respirationandits components. |
