| Eucalyptus is one of the universal selection of plant species in South China.The fast-growing and high-yield characteristics with unscientific management show a lot of ecological problems gradually.Soil respiration plays a decisive role in the state of forest carbon budget as one of the main ways of underground carbon emissions The spatial and temporal heterogeneity of soil respiration under the control of different influencing elements will help to accurately predict the soil carbon emission regular pattern and estimate the soil carbon fluxes of plantations.At present,the study of soil respiration under different varieties of Eucalyptus is relatively lacking.In this study,five kinds of Eucalyptus plantations and one P.elliottii×caribaea plantation(Control)were selected as follows: E.urophylla plantation(EU),E.pellita plantation(EP),E.torelliana plantation(ET),E.camaldulensis plantation(EC),E.urophylla×grandis plantation(EUG)and P.elliottii×caribaea plantation(PEC).The soil respiration rate and the temperature and moisture at 10 cm were measured by Li-8100 A infrared gas analyzer from March 2016 to February 2017.Simultaneous collection of mereorological date from ecological meteorological station.Determination of physical and chemical properties of soil and litter by conventional agrochemical analysis.Determination of Leaf Area Index by HemiView image method.The purpose of this paper is to reveal the temporal and spatial characteristics of soil carbon emissions of different varieties of Eucalyptus plantation and its influencing factors.The results show that:(1)Soil respiration rate of six stands showed a significant monthly variation trend,which was similar to the soil temperature curve at 10 cm.The monthly variation was mainly driven by 10 cm temperature.Soil respiration was positively correlated with soil temperature and moisture,and both were significant or extremely significant,and could be explained by exponential and quadratic model,respectively.During the observation period,the average soil respiration rate of EU,EP,ET,EC,EUG,and PEC stands were: 3.46±0.41,2.15±0.18,3.72± 0.20,2.14 ± 0.15,2.34 ± 0.21 and 2.33 ± 0.17 μmol · m-2 · s-1.The soil respiration accumulated flux in the rainy season was significantly higher than that in the dry season,and the difference of soil carbon flux was consistent with the respiration rate.(2)The physical and chemical properties of the soil showed significant differences in the surface soil of different stands,and the differences of deep soil were not obvious.In ET stands,the correlation between soil respiration and soil bulk density was very significant(correlation coefficient was 0.713),the correlations between soil respiration and saturation moisture capacity,capillary moisture capacity,field capacity were significant(correlation coefficient was 0.689,0.635,0.597).In EUG stands,the correlations between soil respiration and capillary porosity,non-capillary porosity and field capacity were significant(correlation coefficients were 0.576,0.608,0.607).The relationship between soil respiration and soil physical properties in other stands was not significant.(3)The total phosphorus content(0.85 g?kg-1)and C/N(63.35)of EU stands were the highest,the total nitrogen content(6.68 g?kg-1)and C/P were the smallest.The standing amount of litter of EP stands(2026.85 g?m-2)was the largest.The total nitrogen content(10.78 g?kg-1)of ET stands was the largest,and C/N(39.44)was the smallest.The organic carbon content of EC stands(395.16 g?kg-1)was the smallest.The organic carbon content(501.68g?kg-1),C/P(1065.88),N/P(22.25)of PEC stands were the largest,the standing amount of litter(857.73 g?m-2)and total phosphorus content(0.53 g?kg-1)were the smallest.There was a significant positive correlation between C/N and soil respiration rate.The Leaf Area Index of EP(1.17)and ET(1.53)were significantly higher than those of the other four stands,and the Leaf Area Index of EP(1.17)was significantly higher than that of PEC(1.02).Leaf Area Index is significantly positively correlated with soil respiration and can be explained by linear equations.(4)Take EU stands as an example,the correlation between meteorological factors and soil respiration is very significant,and the relative humidity and wind speed will inhibit soil respiration.The meteorological elements can explain 12.07 ~ 57.7% of soil respiration variation,individually.The stepwise regression equation can explain 80.2% of soil respiration variation.Overall view,in estimating soil carbon fluxes in Eucalyptus plantations in South China,the immediate response of soil respiration to meteorological factors should be considered in addition to considering the soil temperature and moisture variation over time.The study of spatial variability should take into account the spatial differences in soil physical and chemical properties,especially soil organic carbon. |
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