造林与间伐对东北温带弃耕地土壤温室气体排放的长期影响

Long-term effects of afforestation and thinning on greenhouse gas emissions from temperate abandoned-land soil in the Northeast of China

采用静态箱-气象色谱法,测定不同间伐强度温带弃耕地落叶松人工林(未间伐为对照、轻度间伐强度为25%、重度间伐强度为50%,林龄50年及间伐已20年)及相应立地上农田的土壤温室气体(CO_2、CH_4和N_2O)排放年通量与相关环境因子(土壤温度、湿度及养分含量等),揭示造林与间伐对弃耕地土壤温室气体排放的影响规律,以便为定量评价退耕还林工程实施效果提供依据。结果表明:1)土壤CO_2年均排放通量(149.44~204.82 mg/(m^2·h))呈现未间伐>农田>轻度间伐>重度间伐的变化趋势,未间伐较农田提高11.6%,轻、重度间伐较农田降低11.4%~18.6%,较未间伐显著降低20.6%~27.0%;2)土壤CH4吸收通量(-0.027^-0.033 mg/(m^2·h))呈现重度间伐>未间伐=农田>轻度间伐变化趋势,未间伐与农田相同,轻度间伐较农田降低12.9%,重度间伐较农田提高6.5%;3)土壤N_2O排放通量(0.025~0.037 mg/(m^2·h))呈现农田>重度间伐>轻度间伐>未间伐的变化趋势,未间伐较农田降低32.4%,轻、重度间伐较农田降低24.3%~29.7%;4)温带弃耕地造林与间伐经营并未改变土壤CO_2、CH_4、N_2O排放通量与气温和土壤温度的相关性,但改变了3种温室气体与土壤湿度的相关性;5)土壤增温潜势(13.89~18.64 t/(hm2·a))呈现未间伐>农田>轻度间伐>重度间伐的变化趋势,未间伐较农田提高9.1%,轻、重度间伐较农田降低12.1%~18.7%,两者也较未间伐降低19.4%~25.5%。因此,东北温带弃耕地营造落叶松林提高了土壤增温潜势,间伐经营较大幅度降低了土壤增温潜势,故从控制气候变暖考虑对其采取强度间伐(50%)方式比较适宜。

CO2,CH4 and N2O annual emission fluxes from larch plantations（ 50 years old） on abandoned farmland under different thinning intensities（ no thinning,contrast; mild thinning,25% and severe thinning,50%,tinning operation has been done for 20 years） and farmland on the corresponding site were measured by the static chamber method in temperate Maoershan Mountains in northeastern China to reveal the long-term effects of afforestation and thinning on greenhouse gas emissions from abandoned-land soil. The results showed that： 1） CO2 emission flux（ 149. 44-204. 82 mg/（ m2·h）） took on a trend of no thinning farmland mild thinning severe thinning,which increased by 11. 6% at no thinning site than farmland site,yet they decreased by 11. 4%-18. 6% at mild and severe thinning sites compared with farmland site,and both also decreased by 20. 6%-27. 0% significantly compared with no thinning.2） CH4 fluxes（-0. 027--0. 033 mg/（ m2·h）） showed a trend of severe thinning no thinning =farmland mild thinning,there was no significant difference between no thinning site and farmland site,but it decreased by 12. 9% at mild thinning site,and increased by 6. 5% at severe thinning site than farmland site. 3） N2 O emission fluxes（ 0. 025-0. 037 mg/（ m2·h）） presented a trend of farmland severe thinning mild thinning no thinning,which decreased by 32. 4% at no thinning site,and decreased by 24. 3%-29. 7% at mild and severe thinning sites than farmland site. 4） the correlation between CO2,CH4 and N2 O emission fluxes and the air temperature and soil temperature were not changed by afforestation and thinning,but the correlation among three kinds of greenhouse gases and soil moisture were changed. 5） The global warming potential（ GWP）（ 13. 89-18. 64 t/（ ha·yr）） showed the trend of no thinning farmland severe thinning mild thinning,which increased by 9. 1% at no thinning site,and decreased by 12. 1%-18. 7% at mild and severe thinning sites than farmland site,both also decreased by 19. 4%-25. 5% compared with no thinning site. Therefore,afforestation increased the global warming potential on the temperate abandoned land in northeastern China,thinning greatly reduced the global warming potential,so severe intensity thinning（ 50%） should be more suitable for larch plantation on temperate abandoned land to control the climate warming.