青藏高原若尔盖沼泽潜在CH_4氧化与生成的分布特征

SPATIAL DISTRIBUTION OF POTENTIAL CH_4 OXIDATION AND PRODUCTION IN ZOIG MARSH OF QINGHAI-TIBET PLATEAU

该实验采集若尔盖草本沼泽 3种生境 (洼地、草坪、微丘草地 )中的 4个层位 (0～ 5、5～ 15、15～ 30、30～ 5 0cm)的土壤样品 ,在实验室培养条件下 ,测定潜在CH4氧化与生成 ,分析其分布特征。草坪泥炭层与矿质层分明 ,两层都表现出显著的CH4氧化能力 ,与高、低亲合力CH4氧化菌跟随地下水位、CH4源在两层之间的迁移变化有关。然而 ,草坪CH4生成不明显。洼地土壤剖面缺乏层次性 ,但CH4氧化呈现明显的梯度特征 ,表层 (0～ 5cm)土壤CH4生成率显著高于其它层位。洼地表层土壤是CH4氧化菌与CH4生成菌的共聚层位 ,在它们各自适宜条件下贡献着CH4氧化与生成。微丘草地的土壤也缺乏层次性 ,CH4生成不明显 ,CH4氧化弱。土壤理化因子、通气状况以及植被条件是影响若尔盖沼泽CH4氧化与生成分布的重要因素。需在不同季节测定CH4氧化与生成 。

In a temperate marsh in Qinghai_Tibet plateau, the potential CH 4 oxidation and production were investigated by field sampling and lab incubation experiments. The potential CH 4 oxidation and production rates were measured for four horizons (0-5, 5-15, 15-30, 30-50 cm) at three typical sites (hill_sod, drained, waterlogged). General soil factors usually showed a significant difference between the upper peat horizon (0-15 cm) and the underlying mineral horizon (15-50 cm) at the drained site and little distinct values for horizons at the hill_sod site and the waterlogged site. At the hill_sod site, CH 4 oxidation and production were weak. At the drained site, the subsurface peat showed much greater CH 4 oxidation rates than the other soil horizons, with a maximal rate of 20.9 ng CH 4·g -1 DW·h -1 at initial 20 mL CH 4·L -1. The underlying mineral also showed a very strong CH 4 oxidation capacity at an initially high CH 4 concentration. However, at the drained site, CH 4 production was weak. At the waterlogged site, the surface soil (0-5 cm) was a most active co_horizon with the maximal CH 4 oxidation and production rates in aerobic and anaerobic incubations, respectively; CH 4 production of 29 ng CH 4·g -1 DW·h -1 was much greater than CH 4 oxidation of 7.8 ng CH 4·g -1 DW·h -1, suggesting a net CH 4 efflux from this site. The spatial distribution of CH 4 oxidation and production was influenced by soil physico_chemical factors, soil air status, and vegetation in Zoigê marsh. The hill_sod site and the drained site were probably CH 4 sinks, but the waterlogged site was probably a CH 4 source. However, it is unclear whether or not the whole marsh is a CH 4 source or CH 4 sink. Further work is required to measure and evaluate CH 4 oxidation and production in the various seasons in this plateau marsh. It is anticipated that our preliminary investigation will increase interest in studies of C cycling in plateau wetland.