排水造林对温带小兴安岭沼泽湿地碳源/汇的影响

Effects of Wetland Drainage for Forestation on Carbon Source or Sink of Temperate Marshes Wetlands in Xiaoxing'an Mountains of China

【目的】从生态系统尺度揭示排水造林干扰对温带沼泽湿地碳源/汇功能的影响规律及其影响机制,以期为湿地碳汇管理提供科学依据。【方法】选取小兴安岭沼泽湿地排水造林后不同时期(10,30年)形成的人工兴安落叶松林及天然草丛沼泽为研究对象,采用静态箱-气相色谱法、碳/氮分析仪测定法与相对生长方程法,同步测定10,30年生人工兴安落叶松林及相应立地上天然草丛沼泽的土壤呼吸(CO_2、CH_4)碳排放量、植被净初级生产力与年净固碳量,并依据生态系统净碳收支平衡揭示排水造林对温带沼泽湿地碳源/汇的影响规律。【结果】排水造林改变了草丛沼泽CH_4排放的季节变化趋势,由单峰排放型转化为排放与吸收交替型,并使CH_4源/汇功能发生了转化,由草丛沼泽CH_4强排放源(年通量1.780 mg·m^(-2)h^(-1))转化为人工林CH_4弱吸收汇(年通量-0.006 mg·m^(-2)h^(-1));排水造林对草丛沼泽土壤CO_2排放年通量(168.07~220.43 mg·m^(-2)h^(-1))并无显著影响,10,30年生人工兴安落叶松林土壤CO_2排放年通量分别较草丛沼泽降低12.8%(P>0.05)和提高14.3%(P>0.05);排水造林改变了草丛沼泽CH_4和CO_2排放主控因子,即其CH_4主控因子由30~40 cm土壤温度转化为与土壤温度不相关,草丛沼泽土壤CO_2主控因子为气温及0~30 cm土壤温度,10和30年生人工林排水垄转化为气温及0~40 cm土层土壤温度、而排水渠转化为气温及地表温度(30年生人工林)或与气温及土壤温度均不相关(10年生人工林);10年生人工林植被净初级生产力和年净固碳量(10.51和4.68 t·hm^(-2)a^(-1))显著低于草丛沼泽(15.44和6.74 t·hm^(-2)a^(-1))31.9%和30.6%(P<0.05),而30年生人工林植被净初级生产力和年净固碳量(14.40和6.39 t·hm^(-2)a^(-1))却与草丛沼泽相近(-6.7%和-5.2%,P>0.05);10年生人工林碳汇(0.72 t·hm^(-2)a^(-1))显著低于草丛沼泽(2.08 t·hm^(-2)a^(-1))65.4%(P<0.05),30年生人工林碳汇(1.20 t·hm^(-2)a^(-1))仍低于草丛沼泽但差异性不显著(-42.3%,P>0.05)。【结论】10年生兴安落叶松人工林显著降低小兴安岭草丛沼泽湿地碳汇功能近2/3,其碳汇功能恢复至少需要30年以上时间,故应避免对温带沼泽湿地进行排水造林。

[Objective]This paper tries to reveal the impacting patterns and mechanisms of draining for forestation that affect carbon source or sink of temperate marsh wetlands at ecosystem level,in order to provide a scientific basis for carbon sink of wetlands management. [Method]The carbon （CO2 and CH4 ） emission fluxes,vegetation net primary productivity and carbon sequestration were studied by static chamber gas chromatography method and Multi N /C 3100,HT 1300 Solids Module （Analytik Jena AG,Germany） and the relative growth equation method from natural marsh wetland and Larix gmelinii plantation in the marsh wetlands under different draining treatments （10 years old,30 years old） in Xiaoxing＇an mountains of China,so as to evaluate the effects of wetland draining for forestation on carbon source or sink of temperate marshes which based on net ecosystem carbon balance.[Result]Draining for forestation changed the seasonal variation trend of CH4 emission fluxes from natural marsh wetlands which turned from approximate unimodal type into alternative emission and uptake. And it also changed the function of CH4 source or sink ,from strong CH4 emission source ,mean annual fluxes were 1. 780 mg·m - 2 h - 1 ,to weak CH4 uptake sink （ - 0. 006 mg·m - 2 h - 1 ））; Draining for forestation had no significant influence on the mean annual fluxes （168. 07 - 220. 43 mg·m - 2 h - 1 ） of CO2 emission from natural marsh wetlands; Compared with the natural marsh wetlands,mean annual fluxes of CO2 emission decreased by 12. 8% （ P 〉0. 05） from 10 years old Larix gmelinii plantation and increased by 14. 3% （P 〉 0. 05） from 30 years old Larix gmelinii plantation; Draining for forestation changed the main controlling factors of CH4 and CO2 emission from natural marsh wetlands. CH4 emission fluxes from natural marsh wetlands turned from significant positive correlation with 30 - 40 cm soil temperature,into that they were not related with 30 - 40 cm soil temperature after draining for forestation 10 or 30 years;the main controlling factors of CO2 emission fluxes from natural marsh wetlands were the air temperature and the 0 - 30 cm soil temperature,but the drainage ridge of 10 or 30 years old plantation turned into air temperature and 0 - 40 cm soil temperature,while the main controlling factors of the drainage ditches from 30 years old plantation were significantly correlated only with air temperature and 0 cm soil temperature,drainage ditches of 10 years old plantation were not related with air temperature and soil temperature; The net vegetation primary productivity （15. 44 t·hm - 2 a - 1 ） and annual net carbon sequestration （6. 74 t· hm - 2 a - 1 ） of natural marsh wetlands were significantly reduced by 31. 9% and 30. 6%（P〈0. 05） after the draining for forestation for 30 years （14. 40 and 6. 39 t·hm - 2 a - 1 ） ; The carbon sink of natural marsh wetlands （2. 08 t·hm - 2 a - 1 ） significantly decreased by 65. 4% （P〈0. 05） after the draining for forestation for 30 years.[Conclusion]The draining for forestation decreased the function of carbon sink from natural marsh wetlands by about 2 /3 significantly at first 10 years,then it needs 30 years at least for the carbon sink to be recovered to the same as natural marsh wetlands; So,draining for forestation should be avoided in the temperate marsh wetlands.