若尔盖高原沼泽湿地CO2排放时空变化特征

为了更好理解若尔盖高原不同微生境下沼泽湿地生态系统CO₂排放通量的变化特征，以若尔盖高原湿地自然保护区为研究对象，2013和2014年生长季期间，采用了静态箱和快速温室气体法原位观测了3种湿地5种微生境下沼泽湿地CO₂排放通量时空变化规律。结果表明：长期淹水微地貌草丘区湿地（PHK）和洼地区湿地（PHW） CO₂排放通量变化范围分别为38.99-1731.74 mg m^-2 h^-1和46.69-335.22 mg m^-2 h^-1，季节性淹水区微地貌草丘区湿地（SHK）和洼地区湿地（SHW） CO₂排放通量变化范围分别为193.90-2575.60 mg m^-2 h^-1和49.93-1467.45 mg m^-2 h^-1，而两者过渡区的无淹水区沼泽湿地（Lawn） CO₂排放通量变化范围194.20-898.75 mg m^-2 h^-1。相关性分析表明5种微地貌区沼泽湿地CO₂排放通量季节性变化与不同深度土壤温度均存在显著正相关，与水位存在显著负相关（PHW、SHW、SHK、Lawn）或不相关（PHK），并且水位和温度（5 cm）共同解释了CO₂排放通量季节性变化的87%。3种湿地5种微生境下沼泽湿地CO₂排放通量存在空间变化规律，主要受水位影响，但植物也影响沼泽湿地CO₂排放通量空间变化规律，并且表明沼泽湿地CO₂排放通量与水位平均值存在显著负相关。

Temporal and spatial variability of ecosystems CO2 emissions in the Zoigê Plateau marsh

The objective of this study is to better understand the CO₂ emission flux characteristics in different microtopographic marshes of the Zoigê Plateau. The temporal and spatial variability of CO₂ emission flux in five sampling sites among three marshes were measured by the dark static chamber method and Fast Greenhouse Gas Analyzer during the growing seasons in 2013 and 2014. The three typical marshes were the permanently flooded zone, the seasonally flooded zone, and the transition zone between them. The results showed that the seasonal CO₂ emission fluxes of the permanently flooded hummock zone (PHK) and hollow zone (PHW) in the Zoigê Plateau marsh ranged from 38.99 to 1731.74 mg m^-2 h^-1 and 46.69 to 335.22 mg m^-2 h^-1, respectively. In addition, the seasonal CO₂ emission fluxes of the seasonally flooded hummock zone (SHK) and hollow zone (SHW) in the Zoigê Plateau marsh varied from 193.90 to 2575.60 mg m^-2 h^-1 and 49.93 to 1467.45 mg m^-2 h^-1, respectively. The non-flooded zone (Lawn) was located in the transition zone. The seasonal CO₂ emission flux in the Lawn changed from 194.20 to 898.75 mg m^-2 h^-1. During the growing seasons, the mean CO₂ emission fluxes in the PHW, PHK, Lawn, SHW and SHK zones in the Zoigê Plateau marsh were 143.73, 443.55, 522.86, 552.60, and 946.95 mg m^-2 h^-1, respectively. In general, the peak value of the CO₂ emission flux in the Zoigê Plateau marsh was achieved between July and August, while the low value of the CO₂ emission flux occurred in the early Spring and/or late Autumn. The results indicated that there was a significant and positive correlation between the seasonal CO₂ emission flux and soil temperatures at the 5-45 cm depth in the PHK, PHW, and SHK zones in the Zoigê Plateau marsh. Meanwhile, the seasonal CO₂ emission flux was also positively correlated with the soil temperature at 5 and 15 cm depth in the Lawn zone in the Zoigê Plateau marsh. Besides, the seasonal CO₂ emission flux in the SHW zone in the Zoigê Plateau marsh was positively correlated with the soil temperature at 5-30 cm depth. Additionally, the seasonal CO₂ emission flux was negatively correlated with water table depth in the PHW, SHW, SHK, and Lawn zones, while not correlated with water table depth in the PHK. Overall, about 87% of the seasonal variation of CO₂ emission flux could be explained by the changes of soil temperature (5 cm depth) and water table depth (CO₂ emission flux=56.479 T₅-11.170 WT-156.617, R²=0.874, P<0.001). Our results revealed that the CO₂ emission flux in five sampling sites among three marshes in the Zoigê Plateau exhibited an obvious spatial variability. The spatial variability of the CO₂ emission flux in the Zoigê Plateau marsh was mainly controlled by water table depth, and could be affected by the type of plant. In addition, the results also exhibited that the mean CO₂ emission flux was negatively correlated with the mean water table depth.