Characteristics Of Soil Respiration And Carbon Balance Of Agriculture Ecosystem In Horqin Sandy Land

Researches on carbon source and carbon sink of terrestrial ecosystem have veryimportant significances to the global carbon cycle and the prediction of future globalclimate change. Soil respiration is related to global climate change and terrestrialecosystem carbon cycle and carbon balance and the structure and function ofterrestrial ecosystems. The tiny change of soil respiration will have a significantimpact on the global carbon cycle. Agri-ecosystem as an important part of terrestrialecosystem is the most active ecosystem. It’s ability of carbon source and sink, carbonstorage and the technologies and countermeasures of reduce carbon emission andincrease sequestration have become the current research focus in the carbon cycle.The carbon sequestration capacity of Agri-ecosystem will likely to have greatpotential compensation to global carbon emissions because of the human economicactivity.In order to provide basic data of carbon cycle and carbon balance of the farmlandecosystems. To explore the characteristics and response mechanism of soil respirationand its influencing factors at maize fields of Horqin Sandy Land, which located in thenorthern semi-arid farming-pastoral ecotone, the daily and seasonal variations of soilrespiration rate and environmental factors were measured, the differences of soilrespiration rate between row and inter-rows and the characteristics of the autotrophicand heterotrophic respiration were explored, and then estimated the carbon balance ofecosystem for two years, using an infrared gas analysis method (IRGA) CO2analyzer,by field observations of two growing seasons2012and2013(May toSeptember)．Results showed that:(1) The daily variations of soil respiration rate having obviously diurnal variationfollowed single peak trend at sunny day; maximum and minimum values occurred inthe period of14:00~18:00and2:00~6:00, respectively．The average daily range ofsoil respiration rate was1.49~12.69μmolCO2·m-2·s-1. The average value of soilrespiration rate in the whole growing season was5.08μmolCO2·m-2·s-1．(2) The seasonal variations of soil respiration rate were different between2012and2013. The seasonal variations of soil respiration rate in2012showed two peakcurves due to the heavy rainfall in mid-June, while it’s showed a single peak curve in2013. The maximum and the minimum value of all appeared the corn growing seasonin July and the seedlings in May, respectively. (3) There were higher consistency between daily and seasonal dynamics of soilrespiration rate and the changes of atmospheric temperature and soil temperature. Forboth daily and seasonal variations，the ex-ponential equation fitted the relationshipvery well between the soil respiration rate and temperature in2012．But there aresignificant differences in the degree of soil respiration associated with differenttemperature. The correlation coefficient R2as follows: surface air temperature>10cmsoil temperature> air temperature>15cm soil temperature>5cm soil temperature.There was strongest correlation between soil respiration rate and surface airtemperature, soil respiration rate has strongest dependence on the10cm soiltemperature in the soil temperatures. The value of Q10decreases as follows:15cmsoil temperature>10cm soil temperature> air temperature>5cm soil temperature>surface air temperature. Soil respiration rate was the most sensitive to the changes ofthe15cm soil temperature. There were related indices, quadratic, cubic, and otherlinear model fitting between the soil respiration rate and temperature of2013, but theseasonal dynamics were not showed a significant relationship of that.(4) Bio-factor played an important role in seasonal variation of soil respirationrate; root biomass showed a significant cubic correlation (R2=0.880，P<0.05) withsoil respiration rate．(5) The soil respiration of row always larger than the soil respiration inter-rowsno matter on daily or seasonal scale; there was a significant linear relationshipbetween them; There were related linear, quadratic and cubic model fitting betweenthe soil respiration rate of row and inter-rows no matter what daily or seasonaldynamics(P<0.05). Approximately largest99.8%(R2=0.998) and98.4%(R2=0.984)variations in soil respiration of inter-rows could be explained by that of row,respectively, in2012and2013.(6) There were no showed significant curve fitting between autotrophic andheterotrophic soil respiration rate and temperature of2013. The Q10values for RS, RH,and RAwere3.10,2.08and4.35, respectively, based on the surface air temperature in2012, fllowing RA> RS> RH. There was a significant difference between RSand RH, butthere was no significant difference between RAand RSas well as RAand RHin2012.There was no significant difference among RSand RHand RAin2013.(7) There were great differences in proportion between RAand RHto RSingrowing season2012and2013. The proportion range of RAto RSwere28.1%to71.1%and1%to66%, respectively. The maximum occurred at the corn stronggrowing season. The average value of RHto RSin two growing season were44.4% and59.0%, respectively．The average value of RAto RSin two growing season was47.6%．(8) The principal component factor analysis of soil respiration showed that thesoil respiration rate was decided by multiple factors to corn farmland ecosystem ofHorqin Sandy Land, but the temperature and moisture were dominant factors.(9) Maize field of Horqin Sandy Land was a carbon sink in the growth period,which could sequester carbon up to996.4and961.9g C·m-2, respectively．...