Effects Of Fertilization And Understory Vegetation Management On Soil Greenhouse Gas Emissions In Chinese Pecan Stands

Fertilization and understory vegetation management is economic forest managementmeasures is very important, has a significant impact on the ecological system of forest soil carbonand nitrogen cycle and global climate change. Chinese pecan (Carya cathayensis) is one of themost important woody oil tree species in the world, is also very important economic forest.Zhejiang province pecan production accounted for70%of the national total output. In recent years,the farmers in order to improve the pecan yield, to eliminate understory weeds, chemical fertilizersand other management measures in production, these measures are likely to lead to the change ofsoil greenhouse gas emissions. This study provided a one-year test in Zhejiang Ling’an typicalhickory woodland, using static chamber and gas chromatography method to study differentfertilization measures: the CK, IF, OF and OIF, weed management and forest (remove weeds andkeep weeds) influence on Carya cathayensis forest soil greenhouse gas emissions and activeorganic carbon pool. The results show that:(1) Showed a significant seasonal variation of soil CO2in Chinese pecan and N2O emissionsof different fertilization treatments, is high in summer, low in winter.The single application of inorganic fertilizer on soil CO2emission flux was72.8mg C m-2h-1,significantly higher than that of CK (51.7mg C m-2h-1), OIF(47.6mg C m-2h-1) and OF(41.8mgC m-2h-1)(P<0.05). For pecan soil CO2cumulative emissions in order of different fertilization: theIF (5.07t C hm-2yr-1)> CK(3.91t C hm-2yr-1)> OIF(3.80t C hm-2yr-1)> OF (3.21t C hm-2yr-1),the IF treatment significantly promoted soil CO2emission (P<0.05), the OF and OIF had nosignificant effect on Chinese pecan forest soil CO2emission.The IF、OIF and OF treatments of soil N2O emission flux was0.020,0.025and0.016mg Nm-2h-1, were significantly higher than that of CK (0.014mg N m-2h-1)(P<0.05). For pecan soilN2O cumulative emissions in order of different fertilizer treatments: OF (2.17kg N hm-2yr-1)>IF(2.01kg N hm-2yr-1)> OIF (1.94kg N hm-2yr-1)> CK(0.94kg N hm-2yr-1), fertilizationtreatment significantly increased soil N2O emission of Chinese pecan(P<0.05), between thedifferent treatments of soil N2O emissions of no significant difference.(2) Different treatments of soil CH4emission of walnut woodland hills undulate, no obviousseasonal patterns. Chines pecan soil CH4cumulative emissions in order of different fertilizertreatments: OIF(0.21kg C hm-2yr-1)> CK(-0.21kg C hm-2yr-1)> OF (-0.30kg C hm-2yr-1)> IF (-0.994kg C hm-2yr-1), fertilization treatment had no significant effect on Carya cathayensisforest soil CH4emission.(3) To keep weeds and weed out Chinese pecan showed seasonal variation of soil CO2emissions consistent, in the weeds growing season keeping weed soil CO2emission flux wassignificantly higher than that of removing weeds, to keep weeds soil CO2emission flux was66.37mg C m-2h-1, is to eliminate weed treatment (55.34mg C m-2h-1)1.2times; soil CO2yearscumulative emissions of4.54t C hm-2yr-1, was significantly higher than that of removing weedstreatment (3.88t C hm-2yr-1)(P<0.05). To keep weeds soil N2O emission flux and cumulativeemissions for0.014mg N m-2h-1and0.96kg N hm-2yr-1, significantly lower than that ofremoving weeds treatment for0.025mg N m-2h-1and2.11kg N hm-2yr-1(P<0.05). To keepweeds soil CH4absorption and accumulation of emissions for-0.71kg C hm-2yr-1, significantlylower than that of removing weeds treatment (-1.16kg C hm-2yr-1)(P<0.05).(4) Different fertilization treatments of Chinese pecan forest soil WSOC and MBC content ofseasonal variation, high in summer, low in winter; fertilization and removal of understory weedshad no significant influence on Chinese pecan forest soil WSOC and MBC content. Control, theIF and OF treatment of soil CO2flux and WSOC content showed a significant correlation(P<0.05). Weed management under different fertilization and understory, Carya cathayensis forestsoil CO2and N2O emission and soil temperature at the depth of5cm showed significant positivecorrelation (P<0.05).(5) Different fertilization comprehensive greenhouse effect greenhouse gas emissions (GWP)in the following order: the IF (1943.4g CO2m-2)> OIF (1483.6g CO2m-2)> control (1474.6gCO-2m2)> single application of organic fertilizer (1274.0g CO-2m2); remove weeds (1512.1gCO-22m) than to keep weeds treatment (1704.3g CO22m-); indicated that the OF treatment andremoval of understory weeds is to reduce the hickory woodland soil greenhouse gas emissionsideal management measures.