Seasonal variations and influencing factors of dissolved organic carbon in pore water from the Dajiuhu peatland in Shennongjia
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摘要: 亚热带泥炭地在水源涵养、碳储存和生物多样性等方面有着重要的保护价值。溶解有机碳(DOC)是泥炭地中容易受到外界扰动的一部分碳，在气候变化和人类活动的双重影响下，DOC可能通过降解或横向迁移从泥炭地中流失，潜在地威胁了泥炭地的碳储存功能。然而，目前对于亚热带泥炭地DOC如何响应季节性尺度的环境变化还缺乏深入的认识。以位于北亚热带的神农架大九湖泥炭地为研究对象，开展了季节尺度的泥炭孔隙水DOC浓度和紫外-可见吸收光谱特征以及环境参数的监测。结果显示，在大九湖泥炭地中，表层0~10 cm的泥炭孔隙水DOC浓度和光谱参数具有明显的季节差异性，DOC浓度和光谱参数还表现出明显的深度差异性。相关性分析显示，DOC浓度及紫外-可见吸收光谱参数直接受控于泥炭孔隙水的电导率和氨态氮浓度，可能还间接受到泥炭地水位和孔隙水硝态氮浓度等因素的影响。以上结果表明，在亚热带季风气候条件下，季节性水位波动引起的泥炭水化学参数和营养盐的变化，可能显著改变表层泥炭DOC动态，需要重视这种季节性波动对亚热带泥炭地碳储存能力以及生态功能的影响。Abstract: Subtropical peatlands are an important component of the global peatlands and play essential roles in water regulation, carbon storage, and biodiversity.These peatlands are being subjected to the influences of global climate changes and human disturbances.Thus, it is vital to explore how the carbon dynamics of these subtropical peatlands respond to climate changes and human activities.Dissolved organic carbon (DOC) exits as labile carbon pools that are susceptive to external environmental disturbance.Under both impacts of climate change and human activities, DOC may be lost from peatlands through degradation or horizontal migration, potentially threatening the carbon storage function of peatlands.However, knowledge about the response of DOC to seasonal environmental changes in subtropical peatlands remains poor.In this study, the seasonal variations of DOC extracted from the peat porewater along a depth profile were investigated in the Dajiuhu peatland, a typical subalpine peatland in the subtropical China.Both DOC concentration and its ultra-visible (UV-Vis) spectral indices show apparently seasonal fluctuations, while some indices also display differences among depths.Correlation analysis reveals that the DOC concentration and UV-Vis indices correlate closely with the porewater conductivity and the concentration of ammoniacal nitrogen.This study demonstrates that seasonal variation is an essential phenomenon of the carbon dynamics in the Chinese subtropical peatlands.It is urgent to quantitatively evaluate how the seasonal changes affect the carbon uptake capacity and ecosystem services of the Chinese subtropical peatlands.
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图 1 神农架大九湖盆地地图(a)和采样点分布图(b)
Figure 1. Maps of Dajiuhu Basin (a) and the sampling sites (b)
图 3 大九湖泥炭不同深度孔隙水水化学参数季节变化
Figure 3. Seasonal variations of porewater chemistry parameters in peat pore water collected from the Dajiuhu peatland
图 4 大九湖泥炭不同深度孔隙水营养盐浓度季节变化
Figure 4. Seasonal variations of nutrient concentration of peat pore water at different depth in the Dajiuhu peatland
图 5 大九湖泥炭不同深度孔隙水DOC质量浓度(a)及UV-Vis参数(b~d)季节变化
Figure 5. Seasonal variations of DOC concentration (a) and UV-Vis ratios (b~d) in peat pore water collected from the Dajiuhu peatland
图 6 2016年大九湖泥炭孔隙水DOC与环境参数PCA分析
Figure 6. PCA analysis of environmental parameters and DOC indices in the peat pore water collected from different peat depths during 2016
表 1 泥炭孔隙水DOC质量浓度和E2/E3比值与环境参数相关性
Table 1. Correlation results among DOC concentration, E2/E3 parameters and environmental factors
DOC α254 E2/E3 SUVA254 pH ORP Cond Fe2+ NH3-N NO3-N Temp RH α254 0.96** E2/E3 -0.66** -0.62** SUVA254 -0.24 -0.10 0.14 pH -0.01 -0.09 0.20 0.16 ORP -0.32 -0.30 0.21 -0.08 -0.20 Cond 0.50** 0.38* -0.48** -0.33 0.41* -0.06 Fe2+ 0.20 0.19 -0.14 -0.08 -0.13 -0.36 0.06 NH3-N 0.46** 0.44** -0.43** -0.02 -0.10 -0.84** 0.03 0.55** NO3-N -0.19 -0.12 -0.06 0.17 -0.14 -0.55** -0.40* -0.10 0.33 Temp -0.19 -0.16 0.09 0.07 -0.22 0.92** -0.06 -0.12 -0.62** -0.51** RH 0.23 0.23 -0.26 -0.27 -0.22 -0.82** -0.01 0.14 0.50** 0.28 -0.78** DWT -0.29 -0.25 0.06 0.01 -0.14 0.86** 0.03 -0.42* -0.86** -0.26 0.73** -0.51** 注：**为p < 0.01; *为p < 0.05；ORP.氧化还原电位；Cond.电导率；Temp.气温；RH.相对湿度；DWT.沼泽水位埋深 
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