小兴安岭天然森林沼泽湿地生态系统碳源/汇

采用静态箱-气相色谱法与相对生长方程法,同步测定小兴安岭7种天然沼泽湿地(草丛沼泽-C、灌丛沼泽-G、毛赤杨沼泽-M、白桦沼泽-B、落叶松苔草沼泽-L-T、落叶松藓类沼泽-L-X、落叶松泥炭藓沼泽-L-N)的土壤呼吸(CO_2、CH_4)净碳排放量、植被年净固碳量,并依据生态系统净碳收支平衡,揭示温带天然沼泽湿地的碳源/汇作用规律。结果表明:(1)7种天然沼泽CH_4年通量(0.006—7.756 mg m~(-2)h~(-1))呈M(高于其他类型1.0—1291.7倍,P0.05)C、G、B(高于针叶林沼泽17.7—649.0倍,P0.05)针叶林沼泽变化趋势,其季节动态存在3种类型(C、G单峰型、M、B多峰型及针叶林沼泽排放与吸收交替型);(2)其CO_2年通量(157.40—231.06 mg m~(-2)h~(-1))呈G(高于森林沼泽28.7%—46.8%,P0.05)C(高于森林沼泽7.4%—22.5%,P0.05)森林沼泽的变化趋势,其季节动态存在2种类型(C、G、L-X和L-N双峰型和M、B、L-T单峰型);(3)C、G、M、B、L-N CH_4排放仅受0—40 cm不同土壤层温度所控制;7种天然沼泽土壤CO_2排放均受气温及0—40 cm不同土壤层温度所控制,但B、L-X、L-N受温度与水位综合控制;(4)其植被年净固碳量((2.05±0.09)—(6.75±0.27)t C hm-2a-1)呈C(高于其他类型65.4%—229.3%,P0.05)G、B、L-T、L-X、L-N(高于M 80.0%—99.0%,P0.05)M变化趋势;(5)7种天然沼泽的碳源/汇(-2.32—2.09 t C hm-2a-1)作用不同,C、B和L-N为碳吸收汇(C强汇、B和L-N弱汇),M、G、L-T和L-X则为碳排放源(M、G强源、L-T和L-X弱源)。因此,温带小兴安岭草丛沼泽为碳强汇、灌丛沼泽为碳强源、森林沼泽基本维持碳平衡(除M外)。

Carbon source or sink of natural forested wetland ecosystem in Xiaoxing'anling region of China

Carbon (CO₂ and CH₄) emission fluxes, annual net carbon sequestration of vegetation, were studied from seven kinds of natural wetlands (Carex schmidtii marsh-C, Betula ovalifolia-C. schmidtii shrub swamp-G, Alnus sibirica-C. schmidtii swamp-M, B. platyphylla-C. schmidtii swamp-B, Larix gmelinii-C. schmidtii swamp-L-T, L. gmelinii-moss swamp-L-X, and L. gmelinii-Sphagnum spp. swamp-L-N) in Xiaoxing''anling region of China using the static chamber gas chromatography method and the relative growth equation method to evaluate the carbon source or sink of natural forested wetlands based on net ecosystem carbon balance. The results showed that: 1) seasonal dynamics of CH₄ emission fluxes from seven kinds of natural wetlands could be divided into three types (single-peak, multi-peak, and emission and absorption alternating type) and CH₄ emission flux (0.006-7.756 mg m^-2 h^-1) exhibited a different trend in M (which was 1.0-1291.7 times greater than the others, P < 0.05) > C, G, B (17.7-649.0 times greater than L-T, L-X, and L-N; P > 0.05) > L-T, L-X, and L-N; 2)seasonal dynamics of CO₂ emission fluxes from the seven kinds of natural wetlands could be divided into two types (single-peak and double peak), and CO₂ emission flux (157.40-231.06 mg m^-2 h^-1) exhibited an different trend in G (which was greater 28.7%-46.8% than forested wetlands, P < 0.05) > C(7.4%-22.5% than forested wetlands, P > 0.05) > five kinds of forested wetlands; 3)CH₄ emission fluxes from C, G, M, B, and L-N were controlled by soil temperature, but that of L-T and L-X had no significant correlation with soil temperature at 0-40 cm. CO₂ emission fluxes from C, G, M, and L-T were controlled by air temperature and soil temperature, and that of B, L-X, and L-N were controlled by air temperature, soil temperature, and the water table level; 4) the annual net carbon sequestration of vegetation ((2.05±0.09)-(6.75±0.27) tC hm^-2 a^-1) had a different trend in C (greater than the others by 65.4%-229.3%,P < 0.05)> G, B, L-T, L-X, and L-N (greater than M by 80.0%-99.0%, P < 0.05) > M; and 5) the sources and sinks of carbon were significantly different among the seven kinds of natural wetland types (-2.32-2.09 tC hm^-2 a^-1). For example, C, B, and L-N exhibited varying degrees of carbon sinks, yet M, G, L-T, and L-X exhibited varying degrees of carbon sources. Therefore, marsh wetlands were greater carbon sinks and shrub wetlands were greater carbon sources, yet forested wetlands maintained overall carbon balance (except M) in the Xiaoxing''anling region of China.