| Forest ecosystem is the largest terrestrial soil sources of greenhouse gas emissions,small changes in forest soil carbon changes will affect global greenhouse gas concentrations.Hickory(Carya cathayensis)is one of the world's most important oil woody species,the main source of income is the pecan pecan farmers in the main producing areas.However,in recent years,farmers in order to improve pecan production,the use of natural forest in the operation to remove grass,a large fertilizer business measures brought hickory forest serious water and soil water,soil organic carbon content and a series of serious ecological decline problem,carry pecan understory grass cultivation has become an important measures to mitigate the ecological problems resulting.In this study,using static tank-gas chromatography,in Zhejiang Lin'an study the effects of pecan forest grass cultivation on soil greenhouse gas emissions,set of four treatments were:blank(excluding natural forest grass),natural grass(reserved forest natural grass),rape(canola planted forest),milk vetch(understory planting milk vetch),the results show1.Different grass cultivation pecan forest soil CO2 emissions showed a significant seasonal variation,mainly in the summer and autumn,winter and spring low.Different soil CO2 emission rate of the average size of the order of:Rape(62.1mg C m-2 h-1)>milk vetch(40.4mg C m-2 h-1)>natural grass(37.4mg C m-2 h-1)>Blank(36.6mg C m-2 h-1).Different soil cumulative CO2 emissions in the order of:Rape(483.0g C m-2)>milk vetch(3 12.7 g C m-2)>natural grass(312.1g C m-2)>Blank(306.1g C m-2),rapeseed cultivation significantly increased the pecan forest soil CO2 emissions(P<0.05),milk vetch and natural grass had no significant effect on soil CO2 emissions2 seasonal variation of different grass cultivation pecan forest soil N2O emissions are basically the same,the highest N2O emission rates in July and August.Different soil N20 emissions from an average rate of processing:natural grass(7.16?g N m-2h-1)>milk vetch(2.42?g N m-2h-1)>canola(0.98?g N Blank(0.95?g N m-2h-1).Natural grass(51.8 mg N m-2)and milk vetch(39.6 mg N m-2)cumulative emissions of N2O was significantly higher than the blank(8.4 mg N m-2)and rape(9.8 mg N m-2).Natural grass and milk vetch significantly increased the pecan forest soil N2O emissions(P<0.05),rapeseed cultivation had no significant effect on soil N2O emissions.3 Blank,rape and milk vetch cultivated soil CH4 emission rate of no clear seasonal average soil CH4 emission rates were-13.2?g C m-2h-1,13.1?g C m-2h-1 and 35.7?g C m-2h-1.CH4 emissions from natural grass and other soil treatment is different in grass growing season(4-10),the soil CH4 emissions showed wavy variation of the average emission rate of soil CH4 is 91.7?g C m-2h-1.Natural grass,rape and hickory forest soil cultivation milk vetch showed the source of CH4,blank soil CH4 sink.The size of the order of cumulative emissions of CH4 soil:natural grass(806.3 mg C m-2)>milk vetch(308.5 mg C m-2)>rapeseed(137.2 mg C m-2)>Blank(-61.5 mg C m-2).Natural grass and pecan milk vetch significantly increased CH4 emissions from forest soils(P<0.05),rapeseed no significant effect on soil CH4 emissions.4 Different treatment pecan integrated forest soil greenhouse gas emissions greenhouse order:rapeseed(1788.2g CO2 m-2)>natural grass(1242.5g CO2 m-2)>milk vetch(1207.3 g CO2 m-2)>blank(1097.4 g CO2 m-2);comprehensive greenhouse rapeseed treatment was significantly higher than other treatments(P<0.05),natural grass and milk vetch cultivation had no significant effect on the consolidated greenhouse effect;This indicates that retain the natural grass and woodland understory planting two kinds of milk vetch is ideal pecan management measures. |
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