Effects Of Density Control On Carbon Budget In Larix Olgensis Plantation

This study takes the Larix olgensis plantation of Jiangshanjiao Experimental Forest Farm of Heilongjiang Academy of Forestry as research subject.Through analysis of the carbon storage,the net annual plantation carbon sequestration,and the CO₂ emission from soil respriation of four reserved densities after thinning of the same stand site:low density treatment(P₁,300³50 plants·hm^–2),medium density treatment(P₂,500⁵50 plants·hm^–2),medium-high density treatment(P₃,600⁶50·hm^–2),and high density treatment(P₄,850⁹00plants·hm^–2),according to the net ecosystem carbon balance,the impact of density control on the ecosystem carbon balance was quantitatively evaluated,and its impact mechanism was revealed to provide a scientific basis for the density control of artificial forest.?1?Density control had a significant effect on the plant carbon storage(40.94±2.34⁷5.46±5.87 t·hm^-2).Although the medium,medium-high,and high density treatments presented small impacts on the plant carbon storage of Larix olgensis plantation?p>0.05?,the low density treatment showed significant decrease than the other three stands,44.98%,44.62%and 43.96%,respectively?p<0.05?.Density control had a small impact on the carbon storage of the litter layer(0.64±0.02¹.31±0.08 t·hm^-2).The medium density treatment showed significant decrease than the other three treatments,31.18%,34.69%,and 51.15%respectively?p<0.05?,but the low,medium-high,and high density treatments had small impacts on the plant carbon storage of Larix olgensis plantation?p>0.05?.Density control had a small impact on the soil?0³0cm?carbon storage(181.38±6.92²02.94±6.98 t·hm^-2).The low density treatment showed the increase of 5.70%,11.19%and 11.89%respectively compared to the other three stands,but the difference among the density treatments was not significant?p>0.05?.Density control had a small impact on the ecosystem carbon storage of the Larix olgensis plantation(244.81±17.28²68.1±15.87 t·hm^-2).The low density treatment presented the lowest ecosystem carbon storage,8.69%,5.16%and 4.41%lower than the other three density treatments respectively,but the difference among different treatments was not significant?p>0.05?.The ecosystem carbon storage increased first and then decreased with the increase of stand density,as was consistent with the variation pattern of the carbon storage of the vegetation layer.?2?After comprehensive analysis of the distribution pattern of carbon storage of the treated stands,it showed that the low density treatment changed the distribution pattern of the ecosystem carbon storage,significantly reduced the percentage of the carbon storage of the plantation layer,while relatively increased the percentage of the carbon storage of the soil layer.The pattern presented was that the soil carbon storage in low density treatment was about 4/5and the vegetation and litter carbon storage about 1/5;and the soil carbon storage in medium,medium-high and high density treatments accounted for 3/4 while the vegetation and litter carbon storage 1/4.?3?Density control had certain effect on the annul net carbon sequestration of plantation(0.99±0.06¹.92±0.15 tC·hm^-2·a^-1).The low-density treatment showed significant decrease,46.77%,41.07%and 48.44%compared to the other three density treatments?p<0.05?,while there was no significant difference among the other three density stands?p>0.05?.Density control had a significant effect on the emission of the soil accumulative carbon in the growing season?May to October?(4.12±0.15⁵.27±0.25 tC·hm^-2).With the increase of stand density,the emission of soil accumulative carbon significantly decreased?p<0.05?,and compared with the low density treatment,the emission of the growing season soil accumulative carbon of the other three density treatments decreased by 12.90%,16.70%and 21.82%,respectively.?4?Density control had certain effect on the ecosystem carbon budget(-1.25±0.11⁰.93±0.05 tC·hm^-2·a^-1).After the density control,the carbon budget of stands has changed to a certian extent,the low density treatment after 37 years of thinning still presented the net carbon emission of the ecosystem,while the medium,medium-high,and high density treatments presented carbon sequestration.Therefore,from the consideration of maintaining China's northeast forest carbon storage,the medium,medium-high and high density treatments shall be chosen as the focus cultivating object for the first cultivation after thinning of the Larix olgensis plantation.At the same time,considering the low carbon emission factors,the emphasis should be on the selection of 850⁹00 plants·hm^-2 density stand.