温度对湿地沉积物有机碳矿化的影响

Effects of temperature on the mineralization of organic carbon in sediment of wetland

温度是湿地沉积物有机碳积累和分解的主要影响因子。培养试验研究了 5个温度梯度下东北三江平原地区 3类典型湿地(泥炭沼泽、腐殖质沼泽和沼泽化草甸 )沉积物有机 C的矿化特征 ,以及冻融过程 (7次 )对其矿化的影响。结果表明 ,温度每升高5℃ ,泥炭沼泽、腐殖质沼泽和沼泽化草甸沉积物在 2 6 0 d培养期内有机 C矿化量分别增加 3.1%、3.3%和 1.6 %。在较低温度(10、15、2 0℃ )下 3类湿地沉积物的有机 C矿化速率基本处于稳定状态 ;但在较高温度 (2 5、30℃ )下前期 (0～ 110 d)的矿化速率明显高于后期。 3类湿地沉积物有机 C矿化温度系数 (Q1 0 )在前期较大 (2 .9～ 3.6 ) ,并出现明显的波动 ,后期逐渐趋于稳定(2 .0 )。到培养结束时 ,泥炭沼泽和腐殖质沼泽沉积物的轻组 C(比重 <1.7)占总有机 C百分比 (约占起始有机 C总量 80 % )的下降幅度与温度成正相关 ;而沼泽化草甸沉积物的轻组有机 C(仅占起始有机 C总量 5 % )的下降幅度较小 (2 .5 %～ 2 .9% )。试验结果还表明 ,在 2 0℃下培养 ,3类湿地沉积物的有机 C矿化速度明显受冻融处理的抑制 ,在

This study was aimed toward better understanding on the characteristics in the mineralization of organic C in wetland sediments affected by temperature, which is one of the most important determining the accumulation and decomposition of organic C in terestial ecosystems. Sediments from 3 types of wetlands (fen, marsh, and marshy meadow) in the San-jiang Plate region of North China were incubated for 260 d under 5 temperature regimes (10℃, 15℃, 20℃, 25℃ and 30℃) or treated with 7 cycles of freezing (at -18℃) and thawing during 150 d incubation at 10℃ or 20℃, and CO2-C evolved was measured at intervals. Results obtained indicated that, as temperature increased by each 5℃, the percentages of organic C mineralized during 260 d incubation period increased by a mean of 3.1% for the fen, 3.3% for the marsh, and 1.6% for the marshy meadow, respectively. For all of the 3 types of wetlands, the mineralization rates of organic C in the sediements incubated under lower temperature regimes (10℃, 15℃ and 20℃) were relatively stable, but much greater in the earlier phase (0～100 d) than the later phase as incubated at higher temperature regimes (25℃ and 30℃). Temperature coeffients (Q_(10)) of the mineralization of organic C were greater (2.9～3.6) and more fluctuatable in the earlier phase than those (about 2.0) in the later phase. By the end of 260 d incubation, decrease in proportion of light fraction (ρ(1.7) organic C in the fen and the marshy sediements (origninally accounting for about 80% of totol organic C) decreased by an extent positive related to temperature, but the proportion decreased were very small (2.5%～2.9%) and consistent for the marshy meadow sediement (orgninally accounting for only 5% of totol organic C). As indicated by the results obtained under incubation at 20℃, the mineralization rate of organic C in the sediments was significantly decreased by freezing and thawing treament. However, such an effect was limited at 10℃.